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sqlcipher/src/select.c
Stephen Lombardo 92bc32215d track 3.7.2
2010-08-28 08:35:57 -04:00

4311 lines
151 KiB
C
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/*
** 2001 September 15
**
** The author disclaims copyright to this source code. In place of
** a legal notice, here is a blessing:
**
** May you do good and not evil.
** May you find forgiveness for yourself and forgive others.
** May you share freely, never taking more than you give.
**
*************************************************************************
** This file contains C code routines that are called by the parser
** to handle SELECT statements in SQLite.
*/
#include "sqliteInt.h"
/*
** Delete all the content of a Select structure but do not deallocate
** the select structure itself.
*/
static void clearSelect(sqlite3 *db, Select *p){
sqlite3ExprListDelete(db, p->pEList);
sqlite3SrcListDelete(db, p->pSrc);
sqlite3ExprDelete(db, p->pWhere);
sqlite3ExprListDelete(db, p->pGroupBy);
sqlite3ExprDelete(db, p->pHaving);
sqlite3ExprListDelete(db, p->pOrderBy);
sqlite3SelectDelete(db, p->pPrior);
sqlite3ExprDelete(db, p->pLimit);
sqlite3ExprDelete(db, p->pOffset);
}
/*
** Initialize a SelectDest structure.
*/
void sqlite3SelectDestInit(SelectDest *pDest, int eDest, int iParm){
pDest->eDest = (u8)eDest;
pDest->iParm = iParm;
pDest->affinity = 0;
pDest->iMem = 0;
pDest->nMem = 0;
}
/*
** Allocate a new Select structure and return a pointer to that
** structure.
*/
Select *sqlite3SelectNew(
Parse *pParse, /* Parsing context */
ExprList *pEList, /* which columns to include in the result */
SrcList *pSrc, /* the FROM clause -- which tables to scan */
Expr *pWhere, /* the WHERE clause */
ExprList *pGroupBy, /* the GROUP BY clause */
Expr *pHaving, /* the HAVING clause */
ExprList *pOrderBy, /* the ORDER BY clause */
int isDistinct, /* true if the DISTINCT keyword is present */
Expr *pLimit, /* LIMIT value. NULL means not used */
Expr *pOffset /* OFFSET value. NULL means no offset */
){
Select *pNew;
Select standin;
sqlite3 *db = pParse->db;
pNew = sqlite3DbMallocZero(db, sizeof(*pNew) );
assert( db->mallocFailed || !pOffset || pLimit ); /* OFFSET implies LIMIT */
if( pNew==0 ){
pNew = &standin;
memset(pNew, 0, sizeof(*pNew));
}
if( pEList==0 ){
pEList = sqlite3ExprListAppend(pParse, 0, sqlite3Expr(db,TK_ALL,0));
}
pNew->pEList = pEList;
pNew->pSrc = pSrc;
pNew->pWhere = pWhere;
pNew->pGroupBy = pGroupBy;
pNew->pHaving = pHaving;
pNew->pOrderBy = pOrderBy;
pNew->selFlags = isDistinct ? SF_Distinct : 0;
pNew->op = TK_SELECT;
pNew->pLimit = pLimit;
pNew->pOffset = pOffset;
assert( pOffset==0 || pLimit!=0 );
pNew->addrOpenEphm[0] = -1;
pNew->addrOpenEphm[1] = -1;
pNew->addrOpenEphm[2] = -1;
if( db->mallocFailed ) {
clearSelect(db, pNew);
if( pNew!=&standin ) sqlite3DbFree(db, pNew);
pNew = 0;
}
return pNew;
}
/*
** Delete the given Select structure and all of its substructures.
*/
void sqlite3SelectDelete(sqlite3 *db, Select *p){
if( p ){
clearSelect(db, p);
sqlite3DbFree(db, p);
}
}
/*
** Given 1 to 3 identifiers preceeding the JOIN keyword, determine the
** type of join. Return an integer constant that expresses that type
** in terms of the following bit values:
**
** JT_INNER
** JT_CROSS
** JT_OUTER
** JT_NATURAL
** JT_LEFT
** JT_RIGHT
**
** A full outer join is the combination of JT_LEFT and JT_RIGHT.
**
** If an illegal or unsupported join type is seen, then still return
** a join type, but put an error in the pParse structure.
*/
int sqlite3JoinType(Parse *pParse, Token *pA, Token *pB, Token *pC){
int jointype = 0;
Token *apAll[3];
Token *p;
/* 0123456789 123456789 123456789 123 */
static const char zKeyText[] = "naturaleftouterightfullinnercross";
static const struct {
u8 i; /* Beginning of keyword text in zKeyText[] */
u8 nChar; /* Length of the keyword in characters */
u8 code; /* Join type mask */
} aKeyword[] = {
/* natural */ { 0, 7, JT_NATURAL },
/* left */ { 6, 4, JT_LEFT|JT_OUTER },
/* outer */ { 10, 5, JT_OUTER },
/* right */ { 14, 5, JT_RIGHT|JT_OUTER },
/* full */ { 19, 4, JT_LEFT|JT_RIGHT|JT_OUTER },
/* inner */ { 23, 5, JT_INNER },
/* cross */ { 28, 5, JT_INNER|JT_CROSS },
};
int i, j;
apAll[0] = pA;
apAll[1] = pB;
apAll[2] = pC;
for(i=0; i<3 && apAll[i]; i++){
p = apAll[i];
for(j=0; j<ArraySize(aKeyword); j++){
if( p->n==aKeyword[j].nChar
&& sqlite3StrNICmp((char*)p->z, &zKeyText[aKeyword[j].i], p->n)==0 ){
jointype |= aKeyword[j].code;
break;
}
}
testcase( j==0 || j==1 || j==2 || j==3 || j==4 || j==5 || j==6 );
if( j>=ArraySize(aKeyword) ){
jointype |= JT_ERROR;
break;
}
}
if(
(jointype & (JT_INNER|JT_OUTER))==(JT_INNER|JT_OUTER) ||
(jointype & JT_ERROR)!=0
){
const char *zSp = " ";
assert( pB!=0 );
if( pC==0 ){ zSp++; }
sqlite3ErrorMsg(pParse, "unknown or unsupported join type: "
"%T %T%s%T", pA, pB, zSp, pC);
jointype = JT_INNER;
}else if( (jointype & JT_OUTER)!=0
&& (jointype & (JT_LEFT|JT_RIGHT))!=JT_LEFT ){
sqlite3ErrorMsg(pParse,
"RIGHT and FULL OUTER JOINs are not currently supported");
jointype = JT_INNER;
}
return jointype;
}
/*
** Return the index of a column in a table. Return -1 if the column
** is not contained in the table.
*/
static int columnIndex(Table *pTab, const char *zCol){
int i;
for(i=0; i<pTab->nCol; i++){
if( sqlite3StrICmp(pTab->aCol[i].zName, zCol)==0 ) return i;
}
return -1;
}
/*
** Search the first N tables in pSrc, from left to right, looking for a
** table that has a column named zCol.
**
** When found, set *piTab and *piCol to the table index and column index
** of the matching column and return TRUE.
**
** If not found, return FALSE.
*/
static int tableAndColumnIndex(
SrcList *pSrc, /* Array of tables to search */
int N, /* Number of tables in pSrc->a[] to search */
const char *zCol, /* Name of the column we are looking for */
int *piTab, /* Write index of pSrc->a[] here */
int *piCol /* Write index of pSrc->a[*piTab].pTab->aCol[] here */
){
int i; /* For looping over tables in pSrc */
int iCol; /* Index of column matching zCol */
assert( (piTab==0)==(piCol==0) ); /* Both or neither are NULL */
for(i=0; i<N; i++){
iCol = columnIndex(pSrc->a[i].pTab, zCol);
if( iCol>=0 ){
if( piTab ){
*piTab = i;
*piCol = iCol;
}
return 1;
}
}
return 0;
}
/*
** This function is used to add terms implied by JOIN syntax to the
** WHERE clause expression of a SELECT statement. The new term, which
** is ANDed with the existing WHERE clause, is of the form:
**
** (tab1.col1 = tab2.col2)
**
** where tab1 is the iSrc'th table in SrcList pSrc and tab2 is the
** (iSrc+1)'th. Column col1 is column iColLeft of tab1, and col2 is
** column iColRight of tab2.
*/
static void addWhereTerm(
Parse *pParse, /* Parsing context */
SrcList *pSrc, /* List of tables in FROM clause */
int iLeft, /* Index of first table to join in pSrc */
int iColLeft, /* Index of column in first table */
int iRight, /* Index of second table in pSrc */
int iColRight, /* Index of column in second table */
int isOuterJoin, /* True if this is an OUTER join */
Expr **ppWhere /* IN/OUT: The WHERE clause to add to */
){
sqlite3 *db = pParse->db;
Expr *pE1;
Expr *pE2;
Expr *pEq;
assert( iLeft<iRight );
assert( pSrc->nSrc>iRight );
assert( pSrc->a[iLeft].pTab );
assert( pSrc->a[iRight].pTab );
pE1 = sqlite3CreateColumnExpr(db, pSrc, iLeft, iColLeft);
pE2 = sqlite3CreateColumnExpr(db, pSrc, iRight, iColRight);
pEq = sqlite3PExpr(pParse, TK_EQ, pE1, pE2, 0);
if( pEq && isOuterJoin ){
ExprSetProperty(pEq, EP_FromJoin);
assert( !ExprHasAnyProperty(pEq, EP_TokenOnly|EP_Reduced) );
ExprSetIrreducible(pEq);
pEq->iRightJoinTable = (i16)pE2->iTable;
}
*ppWhere = sqlite3ExprAnd(db, *ppWhere, pEq);
}
/*
** Set the EP_FromJoin property on all terms of the given expression.
** And set the Expr.iRightJoinTable to iTable for every term in the
** expression.
**
** The EP_FromJoin property is used on terms of an expression to tell
** the LEFT OUTER JOIN processing logic that this term is part of the
** join restriction specified in the ON or USING clause and not a part
** of the more general WHERE clause. These terms are moved over to the
** WHERE clause during join processing but we need to remember that they
** originated in the ON or USING clause.
**
** The Expr.iRightJoinTable tells the WHERE clause processing that the
** expression depends on table iRightJoinTable even if that table is not
** explicitly mentioned in the expression. That information is needed
** for cases like this:
**
** SELECT * FROM t1 LEFT JOIN t2 ON t1.a=t2.b AND t1.x=5
**
** The where clause needs to defer the handling of the t1.x=5
** term until after the t2 loop of the join. In that way, a
** NULL t2 row will be inserted whenever t1.x!=5. If we do not
** defer the handling of t1.x=5, it will be processed immediately
** after the t1 loop and rows with t1.x!=5 will never appear in
** the output, which is incorrect.
*/
static void setJoinExpr(Expr *p, int iTable){
while( p ){
ExprSetProperty(p, EP_FromJoin);
assert( !ExprHasAnyProperty(p, EP_TokenOnly|EP_Reduced) );
ExprSetIrreducible(p);
p->iRightJoinTable = (i16)iTable;
setJoinExpr(p->pLeft, iTable);
p = p->pRight;
}
}
/*
** This routine processes the join information for a SELECT statement.
** ON and USING clauses are converted into extra terms of the WHERE clause.
** NATURAL joins also create extra WHERE clause terms.
**
** The terms of a FROM clause are contained in the Select.pSrc structure.
** The left most table is the first entry in Select.pSrc. The right-most
** table is the last entry. The join operator is held in the entry to
** the left. Thus entry 0 contains the join operator for the join between
** entries 0 and 1. Any ON or USING clauses associated with the join are
** also attached to the left entry.
**
** This routine returns the number of errors encountered.
*/
static int sqliteProcessJoin(Parse *pParse, Select *p){
SrcList *pSrc; /* All tables in the FROM clause */
int i, j; /* Loop counters */
struct SrcList_item *pLeft; /* Left table being joined */
struct SrcList_item *pRight; /* Right table being joined */
pSrc = p->pSrc;
pLeft = &pSrc->a[0];
pRight = &pLeft[1];
for(i=0; i<pSrc->nSrc-1; i++, pRight++, pLeft++){
Table *pLeftTab = pLeft->pTab;
Table *pRightTab = pRight->pTab;
int isOuter;
if( NEVER(pLeftTab==0 || pRightTab==0) ) continue;
isOuter = (pRight->jointype & JT_OUTER)!=0;
/* When the NATURAL keyword is present, add WHERE clause terms for
** every column that the two tables have in common.
*/
if( pRight->jointype & JT_NATURAL ){
if( pRight->pOn || pRight->pUsing ){
sqlite3ErrorMsg(pParse, "a NATURAL join may not have "
"an ON or USING clause", 0);
return 1;
}
for(j=0; j<pRightTab->nCol; j++){
char *zName; /* Name of column in the right table */
int iLeft; /* Matching left table */
int iLeftCol; /* Matching column in the left table */
zName = pRightTab->aCol[j].zName;
if( tableAndColumnIndex(pSrc, i+1, zName, &iLeft, &iLeftCol) ){
addWhereTerm(pParse, pSrc, iLeft, iLeftCol, i+1, j,
isOuter, &p->pWhere);
}
}
}
/* Disallow both ON and USING clauses in the same join
*/
if( pRight->pOn && pRight->pUsing ){
sqlite3ErrorMsg(pParse, "cannot have both ON and USING "
"clauses in the same join");
return 1;
}
/* Add the ON clause to the end of the WHERE clause, connected by
** an AND operator.
*/
if( pRight->pOn ){
if( isOuter ) setJoinExpr(pRight->pOn, pRight->iCursor);
p->pWhere = sqlite3ExprAnd(pParse->db, p->pWhere, pRight->pOn);
pRight->pOn = 0;
}
/* Create extra terms on the WHERE clause for each column named
** in the USING clause. Example: If the two tables to be joined are
** A and B and the USING clause names X, Y, and Z, then add this
** to the WHERE clause: A.X=B.X AND A.Y=B.Y AND A.Z=B.Z
** Report an error if any column mentioned in the USING clause is
** not contained in both tables to be joined.
*/
if( pRight->pUsing ){
IdList *pList = pRight->pUsing;
for(j=0; j<pList->nId; j++){
char *zName; /* Name of the term in the USING clause */
int iLeft; /* Table on the left with matching column name */
int iLeftCol; /* Column number of matching column on the left */
int iRightCol; /* Column number of matching column on the right */
zName = pList->a[j].zName;
iRightCol = columnIndex(pRightTab, zName);
if( iRightCol<0
|| !tableAndColumnIndex(pSrc, i+1, zName, &iLeft, &iLeftCol)
){
sqlite3ErrorMsg(pParse, "cannot join using column %s - column "
"not present in both tables", zName);
return 1;
}
addWhereTerm(pParse, pSrc, iLeft, iLeftCol, i+1, iRightCol,
isOuter, &p->pWhere);
}
}
}
return 0;
}
/*
** Insert code into "v" that will push the record on the top of the
** stack into the sorter.
*/
static void pushOntoSorter(
Parse *pParse, /* Parser context */
ExprList *pOrderBy, /* The ORDER BY clause */
Select *pSelect, /* The whole SELECT statement */
int regData /* Register holding data to be sorted */
){
Vdbe *v = pParse->pVdbe;
int nExpr = pOrderBy->nExpr;
int regBase = sqlite3GetTempRange(pParse, nExpr+2);
int regRecord = sqlite3GetTempReg(pParse);
sqlite3ExprCacheClear(pParse);
sqlite3ExprCodeExprList(pParse, pOrderBy, regBase, 0);
sqlite3VdbeAddOp2(v, OP_Sequence, pOrderBy->iECursor, regBase+nExpr);
sqlite3ExprCodeMove(pParse, regData, regBase+nExpr+1, 1);
sqlite3VdbeAddOp3(v, OP_MakeRecord, regBase, nExpr + 2, regRecord);
sqlite3VdbeAddOp2(v, OP_IdxInsert, pOrderBy->iECursor, regRecord);
sqlite3ReleaseTempReg(pParse, regRecord);
sqlite3ReleaseTempRange(pParse, regBase, nExpr+2);
if( pSelect->iLimit ){
int addr1, addr2;
int iLimit;
if( pSelect->iOffset ){
iLimit = pSelect->iOffset+1;
}else{
iLimit = pSelect->iLimit;
}
addr1 = sqlite3VdbeAddOp1(v, OP_IfZero, iLimit);
sqlite3VdbeAddOp2(v, OP_AddImm, iLimit, -1);
addr2 = sqlite3VdbeAddOp0(v, OP_Goto);
sqlite3VdbeJumpHere(v, addr1);
sqlite3VdbeAddOp1(v, OP_Last, pOrderBy->iECursor);
sqlite3VdbeAddOp1(v, OP_Delete, pOrderBy->iECursor);
sqlite3VdbeJumpHere(v, addr2);
pSelect->iLimit = 0;
}
}
/*
** Add code to implement the OFFSET
*/
static void codeOffset(
Vdbe *v, /* Generate code into this VM */
Select *p, /* The SELECT statement being coded */
int iContinue /* Jump here to skip the current record */
){
if( p->iOffset && iContinue!=0 ){
int addr;
sqlite3VdbeAddOp2(v, OP_AddImm, p->iOffset, -1);
addr = sqlite3VdbeAddOp1(v, OP_IfNeg, p->iOffset);
sqlite3VdbeAddOp2(v, OP_Goto, 0, iContinue);
VdbeComment((v, "skip OFFSET records"));
sqlite3VdbeJumpHere(v, addr);
}
}
/*
** Add code that will check to make sure the N registers starting at iMem
** form a distinct entry. iTab is a sorting index that holds previously
** seen combinations of the N values. A new entry is made in iTab
** if the current N values are new.
**
** A jump to addrRepeat is made and the N+1 values are popped from the
** stack if the top N elements are not distinct.
*/
static void codeDistinct(
Parse *pParse, /* Parsing and code generating context */
int iTab, /* A sorting index used to test for distinctness */
int addrRepeat, /* Jump to here if not distinct */
int N, /* Number of elements */
int iMem /* First element */
){
Vdbe *v;
int r1;
v = pParse->pVdbe;
r1 = sqlite3GetTempReg(pParse);
sqlite3VdbeAddOp4Int(v, OP_Found, iTab, addrRepeat, iMem, N);
sqlite3VdbeAddOp3(v, OP_MakeRecord, iMem, N, r1);
sqlite3VdbeAddOp2(v, OP_IdxInsert, iTab, r1);
sqlite3ReleaseTempReg(pParse, r1);
}
/*
** Generate an error message when a SELECT is used within a subexpression
** (example: "a IN (SELECT * FROM table)") but it has more than 1 result
** column. We do this in a subroutine because the error occurs in multiple
** places.
*/
static int checkForMultiColumnSelectError(
Parse *pParse, /* Parse context. */
SelectDest *pDest, /* Destination of SELECT results */
int nExpr /* Number of result columns returned by SELECT */
){
int eDest = pDest->eDest;
if( nExpr>1 && (eDest==SRT_Mem || eDest==SRT_Set) ){
sqlite3ErrorMsg(pParse, "only a single result allowed for "
"a SELECT that is part of an expression");
return 1;
}else{
return 0;
}
}
/*
** This routine generates the code for the inside of the inner loop
** of a SELECT.
**
** If srcTab and nColumn are both zero, then the pEList expressions
** are evaluated in order to get the data for this row. If nColumn>0
** then data is pulled from srcTab and pEList is used only to get the
** datatypes for each column.
*/
static void selectInnerLoop(
Parse *pParse, /* The parser context */
Select *p, /* The complete select statement being coded */
ExprList *pEList, /* List of values being extracted */
int srcTab, /* Pull data from this table */
int nColumn, /* Number of columns in the source table */
ExprList *pOrderBy, /* If not NULL, sort results using this key */
int distinct, /* If >=0, make sure results are distinct */
SelectDest *pDest, /* How to dispose of the results */
int iContinue, /* Jump here to continue with next row */
int iBreak /* Jump here to break out of the inner loop */
){
Vdbe *v = pParse->pVdbe;
int i;
int hasDistinct; /* True if the DISTINCT keyword is present */
int regResult; /* Start of memory holding result set */
int eDest = pDest->eDest; /* How to dispose of results */
int iParm = pDest->iParm; /* First argument to disposal method */
int nResultCol; /* Number of result columns */
assert( v );
if( NEVER(v==0) ) return;
assert( pEList!=0 );
hasDistinct = distinct>=0;
if( pOrderBy==0 && !hasDistinct ){
codeOffset(v, p, iContinue);
}
/* Pull the requested columns.
*/
if( nColumn>0 ){
nResultCol = nColumn;
}else{
nResultCol = pEList->nExpr;
}
if( pDest->iMem==0 ){
pDest->iMem = pParse->nMem+1;
pDest->nMem = nResultCol;
pParse->nMem += nResultCol;
}else{
assert( pDest->nMem==nResultCol );
}
regResult = pDest->iMem;
if( nColumn>0 ){
for(i=0; i<nColumn; i++){
sqlite3VdbeAddOp3(v, OP_Column, srcTab, i, regResult+i);
}
}else if( eDest!=SRT_Exists ){
/* If the destination is an EXISTS(...) expression, the actual
** values returned by the SELECT are not required.
*/
sqlite3ExprCacheClear(pParse);
sqlite3ExprCodeExprList(pParse, pEList, regResult, eDest==SRT_Output);
}
nColumn = nResultCol;
/* If the DISTINCT keyword was present on the SELECT statement
** and this row has been seen before, then do not make this row
** part of the result.
*/
if( hasDistinct ){
assert( pEList!=0 );
assert( pEList->nExpr==nColumn );
codeDistinct(pParse, distinct, iContinue, nColumn, regResult);
if( pOrderBy==0 ){
codeOffset(v, p, iContinue);
}
}
if( checkForMultiColumnSelectError(pParse, pDest, pEList->nExpr) ){
return;
}
switch( eDest ){
/* In this mode, write each query result to the key of the temporary
** table iParm.
*/
#ifndef SQLITE_OMIT_COMPOUND_SELECT
case SRT_Union: {
int r1;
r1 = sqlite3GetTempReg(pParse);
sqlite3VdbeAddOp3(v, OP_MakeRecord, regResult, nColumn, r1);
sqlite3VdbeAddOp2(v, OP_IdxInsert, iParm, r1);
sqlite3ReleaseTempReg(pParse, r1);
break;
}
/* Construct a record from the query result, but instead of
** saving that record, use it as a key to delete elements from
** the temporary table iParm.
*/
case SRT_Except: {
sqlite3VdbeAddOp3(v, OP_IdxDelete, iParm, regResult, nColumn);
break;
}
#endif
/* Store the result as data using a unique key.
*/
case SRT_Table:
case SRT_EphemTab: {
int r1 = sqlite3GetTempReg(pParse);
testcase( eDest==SRT_Table );
testcase( eDest==SRT_EphemTab );
sqlite3VdbeAddOp3(v, OP_MakeRecord, regResult, nColumn, r1);
if( pOrderBy ){
pushOntoSorter(pParse, pOrderBy, p, r1);
}else{
int r2 = sqlite3GetTempReg(pParse);
sqlite3VdbeAddOp2(v, OP_NewRowid, iParm, r2);
sqlite3VdbeAddOp3(v, OP_Insert, iParm, r1, r2);
sqlite3VdbeChangeP5(v, OPFLAG_APPEND);
sqlite3ReleaseTempReg(pParse, r2);
}
sqlite3ReleaseTempReg(pParse, r1);
break;
}
#ifndef SQLITE_OMIT_SUBQUERY
/* If we are creating a set for an "expr IN (SELECT ...)" construct,
** then there should be a single item on the stack. Write this
** item into the set table with bogus data.
*/
case SRT_Set: {
assert( nColumn==1 );
p->affinity = sqlite3CompareAffinity(pEList->a[0].pExpr, pDest->affinity);
if( pOrderBy ){
/* At first glance you would think we could optimize out the
** ORDER BY in this case since the order of entries in the set
** does not matter. But there might be a LIMIT clause, in which
** case the order does matter */
pushOntoSorter(pParse, pOrderBy, p, regResult);
}else{
int r1 = sqlite3GetTempReg(pParse);
sqlite3VdbeAddOp4(v, OP_MakeRecord, regResult, 1, r1, &p->affinity, 1);
sqlite3ExprCacheAffinityChange(pParse, regResult, 1);
sqlite3VdbeAddOp2(v, OP_IdxInsert, iParm, r1);
sqlite3ReleaseTempReg(pParse, r1);
}
break;
}
/* If any row exist in the result set, record that fact and abort.
*/
case SRT_Exists: {
sqlite3VdbeAddOp2(v, OP_Integer, 1, iParm);
/* The LIMIT clause will terminate the loop for us */
break;
}
/* If this is a scalar select that is part of an expression, then
** store the results in the appropriate memory cell and break out
** of the scan loop.
*/
case SRT_Mem: {
assert( nColumn==1 );
if( pOrderBy ){
pushOntoSorter(pParse, pOrderBy, p, regResult);
}else{
sqlite3ExprCodeMove(pParse, regResult, iParm, 1);
/* The LIMIT clause will jump out of the loop for us */
}
break;
}
#endif /* #ifndef SQLITE_OMIT_SUBQUERY */
/* Send the data to the callback function or to a subroutine. In the
** case of a subroutine, the subroutine itself is responsible for
** popping the data from the stack.
*/
case SRT_Coroutine:
case SRT_Output: {
testcase( eDest==SRT_Coroutine );
testcase( eDest==SRT_Output );
if( pOrderBy ){
int r1 = sqlite3GetTempReg(pParse);
sqlite3VdbeAddOp3(v, OP_MakeRecord, regResult, nColumn, r1);
pushOntoSorter(pParse, pOrderBy, p, r1);
sqlite3ReleaseTempReg(pParse, r1);
}else if( eDest==SRT_Coroutine ){
sqlite3VdbeAddOp1(v, OP_Yield, pDest->iParm);
}else{
sqlite3VdbeAddOp2(v, OP_ResultRow, regResult, nColumn);
sqlite3ExprCacheAffinityChange(pParse, regResult, nColumn);
}
break;
}
#if !defined(SQLITE_OMIT_TRIGGER)
/* Discard the results. This is used for SELECT statements inside
** the body of a TRIGGER. The purpose of such selects is to call
** user-defined functions that have side effects. We do not care
** about the actual results of the select.
*/
default: {
assert( eDest==SRT_Discard );
break;
}
#endif
}
/* Jump to the end of the loop if the LIMIT is reached.
*/
if( p->iLimit ){
assert( pOrderBy==0 ); /* If there is an ORDER BY, the call to
** pushOntoSorter() would have cleared p->iLimit */
sqlite3VdbeAddOp3(v, OP_IfZero, p->iLimit, iBreak, -1);
}
}
/*
** Given an expression list, generate a KeyInfo structure that records
** the collating sequence for each expression in that expression list.
**
** If the ExprList is an ORDER BY or GROUP BY clause then the resulting
** KeyInfo structure is appropriate for initializing a virtual index to
** implement that clause. If the ExprList is the result set of a SELECT
** then the KeyInfo structure is appropriate for initializing a virtual
** index to implement a DISTINCT test.
**
** Space to hold the KeyInfo structure is obtain from malloc. The calling
** function is responsible for seeing that this structure is eventually
** freed. Add the KeyInfo structure to the P4 field of an opcode using
** P4_KEYINFO_HANDOFF is the usual way of dealing with this.
*/
static KeyInfo *keyInfoFromExprList(Parse *pParse, ExprList *pList){
sqlite3 *db = pParse->db;
int nExpr;
KeyInfo *pInfo;
struct ExprList_item *pItem;
int i;
nExpr = pList->nExpr;
pInfo = sqlite3DbMallocZero(db, sizeof(*pInfo) + nExpr*(sizeof(CollSeq*)+1) );
if( pInfo ){
pInfo->aSortOrder = (u8*)&pInfo->aColl[nExpr];
pInfo->nField = (u16)nExpr;
pInfo->enc = ENC(db);
pInfo->db = db;
for(i=0, pItem=pList->a; i<nExpr; i++, pItem++){
CollSeq *pColl;
pColl = sqlite3ExprCollSeq(pParse, pItem->pExpr);
if( !pColl ){
pColl = db->pDfltColl;
}
pInfo->aColl[i] = pColl;
pInfo->aSortOrder[i] = pItem->sortOrder;
}
}
return pInfo;
}
/*
** If the inner loop was generated using a non-null pOrderBy argument,
** then the results were placed in a sorter. After the loop is terminated
** we need to run the sorter and output the results. The following
** routine generates the code needed to do that.
*/
static void generateSortTail(
Parse *pParse, /* Parsing context */
Select *p, /* The SELECT statement */
Vdbe *v, /* Generate code into this VDBE */
int nColumn, /* Number of columns of data */
SelectDest *pDest /* Write the sorted results here */
){
int addrBreak = sqlite3VdbeMakeLabel(v); /* Jump here to exit loop */
int addrContinue = sqlite3VdbeMakeLabel(v); /* Jump here for next cycle */
int addr;
int iTab;
int pseudoTab = 0;
ExprList *pOrderBy = p->pOrderBy;
int eDest = pDest->eDest;
int iParm = pDest->iParm;
int regRow;
int regRowid;
iTab = pOrderBy->iECursor;
regRow = sqlite3GetTempReg(pParse);
if( eDest==SRT_Output || eDest==SRT_Coroutine ){
pseudoTab = pParse->nTab++;
sqlite3VdbeAddOp3(v, OP_OpenPseudo, pseudoTab, regRow, nColumn);
regRowid = 0;
}else{
regRowid = sqlite3GetTempReg(pParse);
}
addr = 1 + sqlite3VdbeAddOp2(v, OP_Sort, iTab, addrBreak);
codeOffset(v, p, addrContinue);
sqlite3VdbeAddOp3(v, OP_Column, iTab, pOrderBy->nExpr + 1, regRow);
switch( eDest ){
case SRT_Table:
case SRT_EphemTab: {
testcase( eDest==SRT_Table );
testcase( eDest==SRT_EphemTab );
sqlite3VdbeAddOp2(v, OP_NewRowid, iParm, regRowid);
sqlite3VdbeAddOp3(v, OP_Insert, iParm, regRow, regRowid);
sqlite3VdbeChangeP5(v, OPFLAG_APPEND);
break;
}
#ifndef SQLITE_OMIT_SUBQUERY
case SRT_Set: {
assert( nColumn==1 );
sqlite3VdbeAddOp4(v, OP_MakeRecord, regRow, 1, regRowid, &p->affinity, 1);
sqlite3ExprCacheAffinityChange(pParse, regRow, 1);
sqlite3VdbeAddOp2(v, OP_IdxInsert, iParm, regRowid);
break;
}
case SRT_Mem: {
assert( nColumn==1 );
sqlite3ExprCodeMove(pParse, regRow, iParm, 1);
/* The LIMIT clause will terminate the loop for us */
break;
}
#endif
default: {
int i;
assert( eDest==SRT_Output || eDest==SRT_Coroutine );
testcase( eDest==SRT_Output );
testcase( eDest==SRT_Coroutine );
for(i=0; i<nColumn; i++){
assert( regRow!=pDest->iMem+i );
sqlite3VdbeAddOp3(v, OP_Column, pseudoTab, i, pDest->iMem+i);
if( i==0 ){
sqlite3VdbeChangeP5(v, OPFLAG_CLEARCACHE);
}
}
if( eDest==SRT_Output ){
sqlite3VdbeAddOp2(v, OP_ResultRow, pDest->iMem, nColumn);
sqlite3ExprCacheAffinityChange(pParse, pDest->iMem, nColumn);
}else{
sqlite3VdbeAddOp1(v, OP_Yield, pDest->iParm);
}
break;
}
}
sqlite3ReleaseTempReg(pParse, regRow);
sqlite3ReleaseTempReg(pParse, regRowid);
/* LIMIT has been implemented by the pushOntoSorter() routine.
*/
assert( p->iLimit==0 );
/* The bottom of the loop
*/
sqlite3VdbeResolveLabel(v, addrContinue);
sqlite3VdbeAddOp2(v, OP_Next, iTab, addr);
sqlite3VdbeResolveLabel(v, addrBreak);
if( eDest==SRT_Output || eDest==SRT_Coroutine ){
sqlite3VdbeAddOp2(v, OP_Close, pseudoTab, 0);
}
}
/*
** Return a pointer to a string containing the 'declaration type' of the
** expression pExpr. The string may be treated as static by the caller.
**
** The declaration type is the exact datatype definition extracted from the
** original CREATE TABLE statement if the expression is a column. The
** declaration type for a ROWID field is INTEGER. Exactly when an expression
** is considered a column can be complex in the presence of subqueries. The
** result-set expression in all of the following SELECT statements is
** considered a column by this function.
**
** SELECT col FROM tbl;
** SELECT (SELECT col FROM tbl;
** SELECT (SELECT col FROM tbl);
** SELECT abc FROM (SELECT col AS abc FROM tbl);
**
** The declaration type for any expression other than a column is NULL.
*/
static const char *columnType(
NameContext *pNC,
Expr *pExpr,
const char **pzOriginDb,
const char **pzOriginTab,
const char **pzOriginCol
){
char const *zType = 0;
char const *zOriginDb = 0;
char const *zOriginTab = 0;
char const *zOriginCol = 0;
int j;
if( NEVER(pExpr==0) || pNC->pSrcList==0 ) return 0;
switch( pExpr->op ){
case TK_AGG_COLUMN:
case TK_COLUMN: {
/* The expression is a column. Locate the table the column is being
** extracted from in NameContext.pSrcList. This table may be real
** database table or a subquery.
*/
Table *pTab = 0; /* Table structure column is extracted from */
Select *pS = 0; /* Select the column is extracted from */
int iCol = pExpr->iColumn; /* Index of column in pTab */
testcase( pExpr->op==TK_AGG_COLUMN );
testcase( pExpr->op==TK_COLUMN );
while( pNC && !pTab ){
SrcList *pTabList = pNC->pSrcList;
for(j=0;j<pTabList->nSrc && pTabList->a[j].iCursor!=pExpr->iTable;j++);
if( j<pTabList->nSrc ){
pTab = pTabList->a[j].pTab;
pS = pTabList->a[j].pSelect;
}else{
pNC = pNC->pNext;
}
}
if( pTab==0 ){
/* At one time, code such as "SELECT new.x" within a trigger would
** cause this condition to run. Since then, we have restructured how
** trigger code is generated and so this condition is no longer
** possible. However, it can still be true for statements like
** the following:
**
** CREATE TABLE t1(col INTEGER);
** SELECT (SELECT t1.col) FROM FROM t1;
**
** when columnType() is called on the expression "t1.col" in the
** sub-select. In this case, set the column type to NULL, even
** though it should really be "INTEGER".
**
** This is not a problem, as the column type of "t1.col" is never
** used. When columnType() is called on the expression
** "(SELECT t1.col)", the correct type is returned (see the TK_SELECT
** branch below. */
break;
}
assert( pTab && pExpr->pTab==pTab );
if( pS ){
/* The "table" is actually a sub-select or a view in the FROM clause
** of the SELECT statement. Return the declaration type and origin
** data for the result-set column of the sub-select.
*/
if( iCol>=0 && ALWAYS(iCol<pS->pEList->nExpr) ){
/* If iCol is less than zero, then the expression requests the
** rowid of the sub-select or view. This expression is legal (see
** test case misc2.2.2) - it always evaluates to NULL.
*/
NameContext sNC;
Expr *p = pS->pEList->a[iCol].pExpr;
sNC.pSrcList = pS->pSrc;
sNC.pNext = pNC;
sNC.pParse = pNC->pParse;
zType = columnType(&sNC, p, &zOriginDb, &zOriginTab, &zOriginCol);
}
}else if( ALWAYS(pTab->pSchema) ){
/* A real table */
assert( !pS );
if( iCol<0 ) iCol = pTab->iPKey;
assert( iCol==-1 || (iCol>=0 && iCol<pTab->nCol) );
if( iCol<0 ){
zType = "INTEGER";
zOriginCol = "rowid";
}else{
zType = pTab->aCol[iCol].zType;
zOriginCol = pTab->aCol[iCol].zName;
}
zOriginTab = pTab->zName;
if( pNC->pParse ){
int iDb = sqlite3SchemaToIndex(pNC->pParse->db, pTab->pSchema);
zOriginDb = pNC->pParse->db->aDb[iDb].zName;
}
}
break;
}
#ifndef SQLITE_OMIT_SUBQUERY
case TK_SELECT: {
/* The expression is a sub-select. Return the declaration type and
** origin info for the single column in the result set of the SELECT
** statement.
*/
NameContext sNC;
Select *pS = pExpr->x.pSelect;
Expr *p = pS->pEList->a[0].pExpr;
assert( ExprHasProperty(pExpr, EP_xIsSelect) );
sNC.pSrcList = pS->pSrc;
sNC.pNext = pNC;
sNC.pParse = pNC->pParse;
zType = columnType(&sNC, p, &zOriginDb, &zOriginTab, &zOriginCol);
break;
}
#endif
}
if( pzOriginDb ){
assert( pzOriginTab && pzOriginCol );
*pzOriginDb = zOriginDb;
*pzOriginTab = zOriginTab;
*pzOriginCol = zOriginCol;
}
return zType;
}
/*
** Generate code that will tell the VDBE the declaration types of columns
** in the result set.
*/
static void generateColumnTypes(
Parse *pParse, /* Parser context */
SrcList *pTabList, /* List of tables */
ExprList *pEList /* Expressions defining the result set */
){
#ifndef SQLITE_OMIT_DECLTYPE
Vdbe *v = pParse->pVdbe;
int i;
NameContext sNC;
sNC.pSrcList = pTabList;
sNC.pParse = pParse;
for(i=0; i<pEList->nExpr; i++){
Expr *p = pEList->a[i].pExpr;
const char *zType;
#ifdef SQLITE_ENABLE_COLUMN_METADATA
const char *zOrigDb = 0;
const char *zOrigTab = 0;
const char *zOrigCol = 0;
zType = columnType(&sNC, p, &zOrigDb, &zOrigTab, &zOrigCol);
/* The vdbe must make its own copy of the column-type and other
** column specific strings, in case the schema is reset before this
** virtual machine is deleted.
*/
sqlite3VdbeSetColName(v, i, COLNAME_DATABASE, zOrigDb, SQLITE_TRANSIENT);
sqlite3VdbeSetColName(v, i, COLNAME_TABLE, zOrigTab, SQLITE_TRANSIENT);
sqlite3VdbeSetColName(v, i, COLNAME_COLUMN, zOrigCol, SQLITE_TRANSIENT);
#else
zType = columnType(&sNC, p, 0, 0, 0);
#endif
sqlite3VdbeSetColName(v, i, COLNAME_DECLTYPE, zType, SQLITE_TRANSIENT);
}
#endif /* SQLITE_OMIT_DECLTYPE */
}
/*
** Generate code that will tell the VDBE the names of columns
** in the result set. This information is used to provide the
** azCol[] values in the callback.
*/
static void generateColumnNames(
Parse *pParse, /* Parser context */
SrcList *pTabList, /* List of tables */
ExprList *pEList /* Expressions defining the result set */
){
Vdbe *v = pParse->pVdbe;
int i, j;
sqlite3 *db = pParse->db;
int fullNames, shortNames;
#ifndef SQLITE_OMIT_EXPLAIN
/* If this is an EXPLAIN, skip this step */
if( pParse->explain ){
return;
}
#endif
if( pParse->colNamesSet || NEVER(v==0) || db->mallocFailed ) return;
pParse->colNamesSet = 1;
fullNames = (db->flags & SQLITE_FullColNames)!=0;
shortNames = (db->flags & SQLITE_ShortColNames)!=0;
sqlite3VdbeSetNumCols(v, pEList->nExpr);
for(i=0; i<pEList->nExpr; i++){
Expr *p;
p = pEList->a[i].pExpr;
if( NEVER(p==0) ) continue;
if( pEList->a[i].zName ){
char *zName = pEList->a[i].zName;
sqlite3VdbeSetColName(v, i, COLNAME_NAME, zName, SQLITE_TRANSIENT);
}else if( (p->op==TK_COLUMN || p->op==TK_AGG_COLUMN) && pTabList ){
Table *pTab;
char *zCol;
int iCol = p->iColumn;
for(j=0; ALWAYS(j<pTabList->nSrc); j++){
if( pTabList->a[j].iCursor==p->iTable ) break;
}
assert( j<pTabList->nSrc );
pTab = pTabList->a[j].pTab;
if( iCol<0 ) iCol = pTab->iPKey;
assert( iCol==-1 || (iCol>=0 && iCol<pTab->nCol) );
if( iCol<0 ){
zCol = "rowid";
}else{
zCol = pTab->aCol[iCol].zName;
}
if( !shortNames && !fullNames ){
sqlite3VdbeSetColName(v, i, COLNAME_NAME,
sqlite3DbStrDup(db, pEList->a[i].zSpan), SQLITE_DYNAMIC);
}else if( fullNames ){
char *zName = 0;
zName = sqlite3MPrintf(db, "%s.%s", pTab->zName, zCol);
sqlite3VdbeSetColName(v, i, COLNAME_NAME, zName, SQLITE_DYNAMIC);
}else{
sqlite3VdbeSetColName(v, i, COLNAME_NAME, zCol, SQLITE_TRANSIENT);
}
}else{
sqlite3VdbeSetColName(v, i, COLNAME_NAME,
sqlite3DbStrDup(db, pEList->a[i].zSpan), SQLITE_DYNAMIC);
}
}
generateColumnTypes(pParse, pTabList, pEList);
}
#ifndef SQLITE_OMIT_COMPOUND_SELECT
/*
** Name of the connection operator, used for error messages.
*/
static const char *selectOpName(int id){
char *z;
switch( id ){
case TK_ALL: z = "UNION ALL"; break;
case TK_INTERSECT: z = "INTERSECT"; break;
case TK_EXCEPT: z = "EXCEPT"; break;
default: z = "UNION"; break;
}
return z;
}
#endif /* SQLITE_OMIT_COMPOUND_SELECT */
/*
** Given a an expression list (which is really the list of expressions
** that form the result set of a SELECT statement) compute appropriate
** column names for a table that would hold the expression list.
**
** All column names will be unique.
**
** Only the column names are computed. Column.zType, Column.zColl,
** and other fields of Column are zeroed.
**
** Return SQLITE_OK on success. If a memory allocation error occurs,
** store NULL in *paCol and 0 in *pnCol and return SQLITE_NOMEM.
*/
static int selectColumnsFromExprList(
Parse *pParse, /* Parsing context */
ExprList *pEList, /* Expr list from which to derive column names */
int *pnCol, /* Write the number of columns here */
Column **paCol /* Write the new column list here */
){
sqlite3 *db = pParse->db; /* Database connection */
int i, j; /* Loop counters */
int cnt; /* Index added to make the name unique */
Column *aCol, *pCol; /* For looping over result columns */
int nCol; /* Number of columns in the result set */
Expr *p; /* Expression for a single result column */
char *zName; /* Column name */
int nName; /* Size of name in zName[] */
*pnCol = nCol = pEList->nExpr;
aCol = *paCol = sqlite3DbMallocZero(db, sizeof(aCol[0])*nCol);
if( aCol==0 ) return SQLITE_NOMEM;
for(i=0, pCol=aCol; i<nCol; i++, pCol++){
/* Get an appropriate name for the column
*/
p = pEList->a[i].pExpr;
assert( p->pRight==0 || ExprHasProperty(p->pRight, EP_IntValue)
|| p->pRight->u.zToken==0 || p->pRight->u.zToken[0]!=0 );
if( (zName = pEList->a[i].zName)!=0 ){
/* If the column contains an "AS <name>" phrase, use <name> as the name */
zName = sqlite3DbStrDup(db, zName);
}else{
Expr *pColExpr = p; /* The expression that is the result column name */
Table *pTab; /* Table associated with this expression */
while( pColExpr->op==TK_DOT ) pColExpr = pColExpr->pRight;
if( pColExpr->op==TK_COLUMN && ALWAYS(pColExpr->pTab!=0) ){
/* For columns use the column name name */
int iCol = pColExpr->iColumn;
pTab = pColExpr->pTab;
if( iCol<0 ) iCol = pTab->iPKey;
zName = sqlite3MPrintf(db, "%s",
iCol>=0 ? pTab->aCol[iCol].zName : "rowid");
}else if( pColExpr->op==TK_ID ){
assert( !ExprHasProperty(pColExpr, EP_IntValue) );
zName = sqlite3MPrintf(db, "%s", pColExpr->u.zToken);
}else{
/* Use the original text of the column expression as its name */
zName = sqlite3MPrintf(db, "%s", pEList->a[i].zSpan);
}
}
if( db->mallocFailed ){
sqlite3DbFree(db, zName);
break;
}
/* Make sure the column name is unique. If the name is not unique,
** append a integer to the name so that it becomes unique.
*/
nName = sqlite3Strlen30(zName);
for(j=cnt=0; j<i; j++){
if( sqlite3StrICmp(aCol[j].zName, zName)==0 ){
char *zNewName;
zName[nName] = 0;
zNewName = sqlite3MPrintf(db, "%s:%d", zName, ++cnt);
sqlite3DbFree(db, zName);
zName = zNewName;
j = -1;
if( zName==0 ) break;
}
}
pCol->zName = zName;
}
if( db->mallocFailed ){
for(j=0; j<i; j++){
sqlite3DbFree(db, aCol[j].zName);
}
sqlite3DbFree(db, aCol);
*paCol = 0;
*pnCol = 0;
return SQLITE_NOMEM;
}
return SQLITE_OK;
}
/*
** Add type and collation information to a column list based on
** a SELECT statement.
**
** The column list presumably came from selectColumnNamesFromExprList().
** The column list has only names, not types or collations. This
** routine goes through and adds the types and collations.
**
** This routine requires that all identifiers in the SELECT
** statement be resolved.
*/
static void selectAddColumnTypeAndCollation(
Parse *pParse, /* Parsing contexts */
int nCol, /* Number of columns */
Column *aCol, /* List of columns */
Select *pSelect /* SELECT used to determine types and collations */
){
sqlite3 *db = pParse->db;
NameContext sNC;
Column *pCol;
CollSeq *pColl;
int i;
Expr *p;
struct ExprList_item *a;
assert( pSelect!=0 );
assert( (pSelect->selFlags & SF_Resolved)!=0 );
assert( nCol==pSelect->pEList->nExpr || db->mallocFailed );
if( db->mallocFailed ) return;
memset(&sNC, 0, sizeof(sNC));
sNC.pSrcList = pSelect->pSrc;
a = pSelect->pEList->a;
for(i=0, pCol=aCol; i<nCol; i++, pCol++){
p = a[i].pExpr;
pCol->zType = sqlite3DbStrDup(db, columnType(&sNC, p, 0, 0, 0));
pCol->affinity = sqlite3ExprAffinity(p);
if( pCol->affinity==0 ) pCol->affinity = SQLITE_AFF_NONE;
pColl = sqlite3ExprCollSeq(pParse, p);
if( pColl ){
pCol->zColl = sqlite3DbStrDup(db, pColl->zName);
}
}
}
/*
** Given a SELECT statement, generate a Table structure that describes
** the result set of that SELECT.
*/
Table *sqlite3ResultSetOfSelect(Parse *pParse, Select *pSelect){
Table *pTab;
sqlite3 *db = pParse->db;
int savedFlags;
savedFlags = db->flags;
db->flags &= ~SQLITE_FullColNames;
db->flags |= SQLITE_ShortColNames;
sqlite3SelectPrep(pParse, pSelect, 0);
if( pParse->nErr ) return 0;
while( pSelect->pPrior ) pSelect = pSelect->pPrior;
db->flags = savedFlags;
pTab = sqlite3DbMallocZero(db, sizeof(Table) );
if( pTab==0 ){
return 0;
}
/* The sqlite3ResultSetOfSelect() is only used n contexts where lookaside
** is disabled */
assert( db->lookaside.bEnabled==0 );
pTab->nRef = 1;
pTab->zName = 0;
selectColumnsFromExprList(pParse, pSelect->pEList, &pTab->nCol, &pTab->aCol);
selectAddColumnTypeAndCollation(pParse, pTab->nCol, pTab->aCol, pSelect);
pTab->iPKey = -1;
if( db->mallocFailed ){
sqlite3DeleteTable(db, pTab);
return 0;
}
return pTab;
}
/*
** Get a VDBE for the given parser context. Create a new one if necessary.
** If an error occurs, return NULL and leave a message in pParse.
*/
Vdbe *sqlite3GetVdbe(Parse *pParse){
Vdbe *v = pParse->pVdbe;
if( v==0 ){
v = pParse->pVdbe = sqlite3VdbeCreate(pParse->db);
#ifndef SQLITE_OMIT_TRACE
if( v ){
sqlite3VdbeAddOp0(v, OP_Trace);
}
#endif
}
return v;
}
/*
** Compute the iLimit and iOffset fields of the SELECT based on the
** pLimit and pOffset expressions. pLimit and pOffset hold the expressions
** that appear in the original SQL statement after the LIMIT and OFFSET
** keywords. Or NULL if those keywords are omitted. iLimit and iOffset
** are the integer memory register numbers for counters used to compute
** the limit and offset. If there is no limit and/or offset, then
** iLimit and iOffset are negative.
**
** This routine changes the values of iLimit and iOffset only if
** a limit or offset is defined by pLimit and pOffset. iLimit and
** iOffset should have been preset to appropriate default values
** (usually but not always -1) prior to calling this routine.
** Only if pLimit!=0 or pOffset!=0 do the limit registers get
** redefined. The UNION ALL operator uses this property to force
** the reuse of the same limit and offset registers across multiple
** SELECT statements.
*/
static void computeLimitRegisters(Parse *pParse, Select *p, int iBreak){
Vdbe *v = 0;
int iLimit = 0;
int iOffset;
int addr1, n;
if( p->iLimit ) return;
/*
** "LIMIT -1" always shows all rows. There is some
** contraversy about what the correct behavior should be.
** The current implementation interprets "LIMIT 0" to mean
** no rows.
*/
sqlite3ExprCacheClear(pParse);
assert( p->pOffset==0 || p->pLimit!=0 );
if( p->pLimit ){
p->iLimit = iLimit = ++pParse->nMem;
v = sqlite3GetVdbe(pParse);
if( NEVER(v==0) ) return; /* VDBE should have already been allocated */
if( sqlite3ExprIsInteger(p->pLimit, &n) ){
sqlite3VdbeAddOp2(v, OP_Integer, n, iLimit);
VdbeComment((v, "LIMIT counter"));
if( n==0 ){
sqlite3VdbeAddOp2(v, OP_Goto, 0, iBreak);
}
}else{
sqlite3ExprCode(pParse, p->pLimit, iLimit);
sqlite3VdbeAddOp1(v, OP_MustBeInt, iLimit);
VdbeComment((v, "LIMIT counter"));
sqlite3VdbeAddOp2(v, OP_IfZero, iLimit, iBreak);
}
if( p->pOffset ){
p->iOffset = iOffset = ++pParse->nMem;
pParse->nMem++; /* Allocate an extra register for limit+offset */
sqlite3ExprCode(pParse, p->pOffset, iOffset);
sqlite3VdbeAddOp1(v, OP_MustBeInt, iOffset);
VdbeComment((v, "OFFSET counter"));
addr1 = sqlite3VdbeAddOp1(v, OP_IfPos, iOffset);
sqlite3VdbeAddOp2(v, OP_Integer, 0, iOffset);
sqlite3VdbeJumpHere(v, addr1);
sqlite3VdbeAddOp3(v, OP_Add, iLimit, iOffset, iOffset+1);
VdbeComment((v, "LIMIT+OFFSET"));
addr1 = sqlite3VdbeAddOp1(v, OP_IfPos, iLimit);
sqlite3VdbeAddOp2(v, OP_Integer, -1, iOffset+1);
sqlite3VdbeJumpHere(v, addr1);
}
}
}
#ifndef SQLITE_OMIT_COMPOUND_SELECT
/*
** Return the appropriate collating sequence for the iCol-th column of
** the result set for the compound-select statement "p". Return NULL if
** the column has no default collating sequence.
**
** The collating sequence for the compound select is taken from the
** left-most term of the select that has a collating sequence.
*/
static CollSeq *multiSelectCollSeq(Parse *pParse, Select *p, int iCol){
CollSeq *pRet;
if( p->pPrior ){
pRet = multiSelectCollSeq(pParse, p->pPrior, iCol);
}else{
pRet = 0;
}
assert( iCol>=0 );
if( pRet==0 && iCol<p->pEList->nExpr ){
pRet = sqlite3ExprCollSeq(pParse, p->pEList->a[iCol].pExpr);
}
return pRet;
}
#endif /* SQLITE_OMIT_COMPOUND_SELECT */
/* Forward reference */
static int multiSelectOrderBy(
Parse *pParse, /* Parsing context */
Select *p, /* The right-most of SELECTs to be coded */
SelectDest *pDest /* What to do with query results */
);
#ifndef SQLITE_OMIT_COMPOUND_SELECT
/*
** This routine is called to process a compound query form from
** two or more separate queries using UNION, UNION ALL, EXCEPT, or
** INTERSECT
**
** "p" points to the right-most of the two queries. the query on the
** left is p->pPrior. The left query could also be a compound query
** in which case this routine will be called recursively.
**
** The results of the total query are to be written into a destination
** of type eDest with parameter iParm.
**
** Example 1: Consider a three-way compound SQL statement.
**
** SELECT a FROM t1 UNION SELECT b FROM t2 UNION SELECT c FROM t3
**
** This statement is parsed up as follows:
**
** SELECT c FROM t3
** |
** `-----> SELECT b FROM t2
** |
** `------> SELECT a FROM t1
**
** The arrows in the diagram above represent the Select.pPrior pointer.
** So if this routine is called with p equal to the t3 query, then
** pPrior will be the t2 query. p->op will be TK_UNION in this case.
**
** Notice that because of the way SQLite parses compound SELECTs, the
** individual selects always group from left to right.
*/
static int multiSelect(
Parse *pParse, /* Parsing context */
Select *p, /* The right-most of SELECTs to be coded */
SelectDest *pDest /* What to do with query results */
){
int rc = SQLITE_OK; /* Success code from a subroutine */
Select *pPrior; /* Another SELECT immediately to our left */
Vdbe *v; /* Generate code to this VDBE */
SelectDest dest; /* Alternative data destination */
Select *pDelete = 0; /* Chain of simple selects to delete */
sqlite3 *db; /* Database connection */
/* Make sure there is no ORDER BY or LIMIT clause on prior SELECTs. Only
** the last (right-most) SELECT in the series may have an ORDER BY or LIMIT.
*/
assert( p && p->pPrior ); /* Calling function guarantees this much */
db = pParse->db;
pPrior = p->pPrior;
assert( pPrior->pRightmost!=pPrior );
assert( pPrior->pRightmost==p->pRightmost );
dest = *pDest;
if( pPrior->pOrderBy ){
sqlite3ErrorMsg(pParse,"ORDER BY clause should come after %s not before",
selectOpName(p->op));
rc = 1;
goto multi_select_end;
}
if( pPrior->pLimit ){
sqlite3ErrorMsg(pParse,"LIMIT clause should come after %s not before",
selectOpName(p->op));
rc = 1;
goto multi_select_end;
}
v = sqlite3GetVdbe(pParse);
assert( v!=0 ); /* The VDBE already created by calling function */
/* Create the destination temporary table if necessary
*/
if( dest.eDest==SRT_EphemTab ){
assert( p->pEList );
sqlite3VdbeAddOp2(v, OP_OpenEphemeral, dest.iParm, p->pEList->nExpr);
dest.eDest = SRT_Table;
}
/* Make sure all SELECTs in the statement have the same number of elements
** in their result sets.
*/
assert( p->pEList && pPrior->pEList );
if( p->pEList->nExpr!=pPrior->pEList->nExpr ){
sqlite3ErrorMsg(pParse, "SELECTs to the left and right of %s"
" do not have the same number of result columns", selectOpName(p->op));
rc = 1;
goto multi_select_end;
}
/* Compound SELECTs that have an ORDER BY clause are handled separately.
*/
if( p->pOrderBy ){
return multiSelectOrderBy(pParse, p, pDest);
}
/* Generate code for the left and right SELECT statements.
*/
switch( p->op ){
case TK_ALL: {
int addr = 0;
assert( !pPrior->pLimit );
pPrior->pLimit = p->pLimit;
pPrior->pOffset = p->pOffset;
rc = sqlite3Select(pParse, pPrior, &dest);
p->pLimit = 0;
p->pOffset = 0;
if( rc ){
goto multi_select_end;
}
p->pPrior = 0;
p->iLimit = pPrior->iLimit;
p->iOffset = pPrior->iOffset;
if( p->iLimit ){
addr = sqlite3VdbeAddOp1(v, OP_IfZero, p->iLimit);
VdbeComment((v, "Jump ahead if LIMIT reached"));
}
rc = sqlite3Select(pParse, p, &dest);
testcase( rc!=SQLITE_OK );
pDelete = p->pPrior;
p->pPrior = pPrior;
if( addr ){
sqlite3VdbeJumpHere(v, addr);
}
break;
}
case TK_EXCEPT:
case TK_UNION: {
int unionTab; /* Cursor number of the temporary table holding result */
u8 op = 0; /* One of the SRT_ operations to apply to self */
int priorOp; /* The SRT_ operation to apply to prior selects */
Expr *pLimit, *pOffset; /* Saved values of p->nLimit and p->nOffset */
int addr;
SelectDest uniondest;
testcase( p->op==TK_EXCEPT );
testcase( p->op==TK_UNION );
priorOp = SRT_Union;
if( dest.eDest==priorOp && ALWAYS(!p->pLimit &&!p->pOffset) ){
/* We can reuse a temporary table generated by a SELECT to our
** right.
*/
assert( p->pRightmost!=p ); /* Can only happen for leftward elements
** of a 3-way or more compound */
assert( p->pLimit==0 ); /* Not allowed on leftward elements */
assert( p->pOffset==0 ); /* Not allowed on leftward elements */
unionTab = dest.iParm;
}else{
/* We will need to create our own temporary table to hold the
** intermediate results.
*/
unionTab = pParse->nTab++;
assert( p->pOrderBy==0 );
addr = sqlite3VdbeAddOp2(v, OP_OpenEphemeral, unionTab, 0);
assert( p->addrOpenEphm[0] == -1 );
p->addrOpenEphm[0] = addr;
p->pRightmost->selFlags |= SF_UsesEphemeral;
assert( p->pEList );
}
/* Code the SELECT statements to our left
*/
assert( !pPrior->pOrderBy );
sqlite3SelectDestInit(&uniondest, priorOp, unionTab);
rc = sqlite3Select(pParse, pPrior, &uniondest);
if( rc ){
goto multi_select_end;
}
/* Code the current SELECT statement
*/
if( p->op==TK_EXCEPT ){
op = SRT_Except;
}else{
assert( p->op==TK_UNION );
op = SRT_Union;
}
p->pPrior = 0;
pLimit = p->pLimit;
p->pLimit = 0;
pOffset = p->pOffset;
p->pOffset = 0;
uniondest.eDest = op;
rc = sqlite3Select(pParse, p, &uniondest);
testcase( rc!=SQLITE_OK );
/* Query flattening in sqlite3Select() might refill p->pOrderBy.
** Be sure to delete p->pOrderBy, therefore, to avoid a memory leak. */
sqlite3ExprListDelete(db, p->pOrderBy);
pDelete = p->pPrior;
p->pPrior = pPrior;
p->pOrderBy = 0;
sqlite3ExprDelete(db, p->pLimit);
p->pLimit = pLimit;
p->pOffset = pOffset;
p->iLimit = 0;
p->iOffset = 0;
/* Convert the data in the temporary table into whatever form
** it is that we currently need.
*/
assert( unionTab==dest.iParm || dest.eDest!=priorOp );
if( dest.eDest!=priorOp ){
int iCont, iBreak, iStart;
assert( p->pEList );
if( dest.eDest==SRT_Output ){
Select *pFirst = p;
while( pFirst->pPrior ) pFirst = pFirst->pPrior;
generateColumnNames(pParse, 0, pFirst->pEList);
}
iBreak = sqlite3VdbeMakeLabel(v);
iCont = sqlite3VdbeMakeLabel(v);
computeLimitRegisters(pParse, p, iBreak);
sqlite3VdbeAddOp2(v, OP_Rewind, unionTab, iBreak);
iStart = sqlite3VdbeCurrentAddr(v);
selectInnerLoop(pParse, p, p->pEList, unionTab, p->pEList->nExpr,
0, -1, &dest, iCont, iBreak);
sqlite3VdbeResolveLabel(v, iCont);
sqlite3VdbeAddOp2(v, OP_Next, unionTab, iStart);
sqlite3VdbeResolveLabel(v, iBreak);
sqlite3VdbeAddOp2(v, OP_Close, unionTab, 0);
}
break;
}
default: assert( p->op==TK_INTERSECT ); {
int tab1, tab2;
int iCont, iBreak, iStart;
Expr *pLimit, *pOffset;
int addr;
SelectDest intersectdest;
int r1;
/* INTERSECT is different from the others since it requires
** two temporary tables. Hence it has its own case. Begin
** by allocating the tables we will need.
*/
tab1 = pParse->nTab++;
tab2 = pParse->nTab++;
assert( p->pOrderBy==0 );
addr = sqlite3VdbeAddOp2(v, OP_OpenEphemeral, tab1, 0);
assert( p->addrOpenEphm[0] == -1 );
p->addrOpenEphm[0] = addr;
p->pRightmost->selFlags |= SF_UsesEphemeral;
assert( p->pEList );
/* Code the SELECTs to our left into temporary table "tab1".
*/
sqlite3SelectDestInit(&intersectdest, SRT_Union, tab1);
rc = sqlite3Select(pParse, pPrior, &intersectdest);
if( rc ){
goto multi_select_end;
}
/* Code the current SELECT into temporary table "tab2"
*/
addr = sqlite3VdbeAddOp2(v, OP_OpenEphemeral, tab2, 0);
assert( p->addrOpenEphm[1] == -1 );
p->addrOpenEphm[1] = addr;
p->pPrior = 0;
pLimit = p->pLimit;
p->pLimit = 0;
pOffset = p->pOffset;
p->pOffset = 0;
intersectdest.iParm = tab2;
rc = sqlite3Select(pParse, p, &intersectdest);
testcase( rc!=SQLITE_OK );
pDelete = p->pPrior;
p->pPrior = pPrior;
sqlite3ExprDelete(db, p->pLimit);
p->pLimit = pLimit;
p->pOffset = pOffset;
/* Generate code to take the intersection of the two temporary
** tables.
*/
assert( p->pEList );
if( dest.eDest==SRT_Output ){
Select *pFirst = p;
while( pFirst->pPrior ) pFirst = pFirst->pPrior;
generateColumnNames(pParse, 0, pFirst->pEList);
}
iBreak = sqlite3VdbeMakeLabel(v);
iCont = sqlite3VdbeMakeLabel(v);
computeLimitRegisters(pParse, p, iBreak);
sqlite3VdbeAddOp2(v, OP_Rewind, tab1, iBreak);
r1 = sqlite3GetTempReg(pParse);
iStart = sqlite3VdbeAddOp2(v, OP_RowKey, tab1, r1);
sqlite3VdbeAddOp4Int(v, OP_NotFound, tab2, iCont, r1, 0);
sqlite3ReleaseTempReg(pParse, r1);
selectInnerLoop(pParse, p, p->pEList, tab1, p->pEList->nExpr,
0, -1, &dest, iCont, iBreak);
sqlite3VdbeResolveLabel(v, iCont);
sqlite3VdbeAddOp2(v, OP_Next, tab1, iStart);
sqlite3VdbeResolveLabel(v, iBreak);
sqlite3VdbeAddOp2(v, OP_Close, tab2, 0);
sqlite3VdbeAddOp2(v, OP_Close, tab1, 0);
break;
}
}
/* Compute collating sequences used by
** temporary tables needed to implement the compound select.
** Attach the KeyInfo structure to all temporary tables.
**
** This section is run by the right-most SELECT statement only.
** SELECT statements to the left always skip this part. The right-most
** SELECT might also skip this part if it has no ORDER BY clause and
** no temp tables are required.
*/
if( p->selFlags & SF_UsesEphemeral ){
int i; /* Loop counter */
KeyInfo *pKeyInfo; /* Collating sequence for the result set */
Select *pLoop; /* For looping through SELECT statements */
CollSeq **apColl; /* For looping through pKeyInfo->aColl[] */
int nCol; /* Number of columns in result set */
assert( p->pRightmost==p );
nCol = p->pEList->nExpr;
pKeyInfo = sqlite3DbMallocZero(db,
sizeof(*pKeyInfo)+nCol*(sizeof(CollSeq*) + 1));
if( !pKeyInfo ){
rc = SQLITE_NOMEM;
goto multi_select_end;
}
pKeyInfo->enc = ENC(db);
pKeyInfo->nField = (u16)nCol;
for(i=0, apColl=pKeyInfo->aColl; i<nCol; i++, apColl++){
*apColl = multiSelectCollSeq(pParse, p, i);
if( 0==*apColl ){
*apColl = db->pDfltColl;
}
}
for(pLoop=p; pLoop; pLoop=pLoop->pPrior){
for(i=0; i<2; i++){
int addr = pLoop->addrOpenEphm[i];
if( addr<0 ){
/* If [0] is unused then [1] is also unused. So we can
** always safely abort as soon as the first unused slot is found */
assert( pLoop->addrOpenEphm[1]<0 );
break;
}
sqlite3VdbeChangeP2(v, addr, nCol);
sqlite3VdbeChangeP4(v, addr, (char*)pKeyInfo, P4_KEYINFO);
pLoop->addrOpenEphm[i] = -1;
}
}
sqlite3DbFree(db, pKeyInfo);
}
multi_select_end:
pDest->iMem = dest.iMem;
pDest->nMem = dest.nMem;
sqlite3SelectDelete(db, pDelete);
return rc;
}
#endif /* SQLITE_OMIT_COMPOUND_SELECT */
/*
** Code an output subroutine for a coroutine implementation of a
** SELECT statment.
**
** The data to be output is contained in pIn->iMem. There are
** pIn->nMem columns to be output. pDest is where the output should
** be sent.
**
** regReturn is the number of the register holding the subroutine
** return address.
**
** If regPrev>0 then it is the first register in a vector that
** records the previous output. mem[regPrev] is a flag that is false
** if there has been no previous output. If regPrev>0 then code is
** generated to suppress duplicates. pKeyInfo is used for comparing
** keys.
**
** If the LIMIT found in p->iLimit is reached, jump immediately to
** iBreak.
*/
static int generateOutputSubroutine(
Parse *pParse, /* Parsing context */
Select *p, /* The SELECT statement */
SelectDest *pIn, /* Coroutine supplying data */
SelectDest *pDest, /* Where to send the data */
int regReturn, /* The return address register */
int regPrev, /* Previous result register. No uniqueness if 0 */
KeyInfo *pKeyInfo, /* For comparing with previous entry */
int p4type, /* The p4 type for pKeyInfo */
int iBreak /* Jump here if we hit the LIMIT */
){
Vdbe *v = pParse->pVdbe;
int iContinue;
int addr;
addr = sqlite3VdbeCurrentAddr(v);
iContinue = sqlite3VdbeMakeLabel(v);
/* Suppress duplicates for UNION, EXCEPT, and INTERSECT
*/
if( regPrev ){
int j1, j2;
j1 = sqlite3VdbeAddOp1(v, OP_IfNot, regPrev);
j2 = sqlite3VdbeAddOp4(v, OP_Compare, pIn->iMem, regPrev+1, pIn->nMem,
(char*)pKeyInfo, p4type);
sqlite3VdbeAddOp3(v, OP_Jump, j2+2, iContinue, j2+2);
sqlite3VdbeJumpHere(v, j1);
sqlite3ExprCodeCopy(pParse, pIn->iMem, regPrev+1, pIn->nMem);
sqlite3VdbeAddOp2(v, OP_Integer, 1, regPrev);
}
if( pParse->db->mallocFailed ) return 0;
/* Suppress the the first OFFSET entries if there is an OFFSET clause
*/
codeOffset(v, p, iContinue);
switch( pDest->eDest ){
/* Store the result as data using a unique key.
*/
case SRT_Table:
case SRT_EphemTab: {
int r1 = sqlite3GetTempReg(pParse);
int r2 = sqlite3GetTempReg(pParse);
testcase( pDest->eDest==SRT_Table );
testcase( pDest->eDest==SRT_EphemTab );
sqlite3VdbeAddOp3(v, OP_MakeRecord, pIn->iMem, pIn->nMem, r1);
sqlite3VdbeAddOp2(v, OP_NewRowid, pDest->iParm, r2);
sqlite3VdbeAddOp3(v, OP_Insert, pDest->iParm, r1, r2);
sqlite3VdbeChangeP5(v, OPFLAG_APPEND);
sqlite3ReleaseTempReg(pParse, r2);
sqlite3ReleaseTempReg(pParse, r1);
break;
}
#ifndef SQLITE_OMIT_SUBQUERY
/* If we are creating a set for an "expr IN (SELECT ...)" construct,
** then there should be a single item on the stack. Write this
** item into the set table with bogus data.
*/
case SRT_Set: {
int r1;
assert( pIn->nMem==1 );
p->affinity =
sqlite3CompareAffinity(p->pEList->a[0].pExpr, pDest->affinity);
r1 = sqlite3GetTempReg(pParse);
sqlite3VdbeAddOp4(v, OP_MakeRecord, pIn->iMem, 1, r1, &p->affinity, 1);
sqlite3ExprCacheAffinityChange(pParse, pIn->iMem, 1);
sqlite3VdbeAddOp2(v, OP_IdxInsert, pDest->iParm, r1);
sqlite3ReleaseTempReg(pParse, r1);
break;
}
#if 0 /* Never occurs on an ORDER BY query */
/* If any row exist in the result set, record that fact and abort.
*/
case SRT_Exists: {
sqlite3VdbeAddOp2(v, OP_Integer, 1, pDest->iParm);
/* The LIMIT clause will terminate the loop for us */
break;
}
#endif
/* If this is a scalar select that is part of an expression, then
** store the results in the appropriate memory cell and break out
** of the scan loop.
*/
case SRT_Mem: {
assert( pIn->nMem==1 );
sqlite3ExprCodeMove(pParse, pIn->iMem, pDest->iParm, 1);
/* The LIMIT clause will jump out of the loop for us */
break;
}
#endif /* #ifndef SQLITE_OMIT_SUBQUERY */
/* The results are stored in a sequence of registers
** starting at pDest->iMem. Then the co-routine yields.
*/
case SRT_Coroutine: {
if( pDest->iMem==0 ){
pDest->iMem = sqlite3GetTempRange(pParse, pIn->nMem);
pDest->nMem = pIn->nMem;
}
sqlite3ExprCodeMove(pParse, pIn->iMem, pDest->iMem, pDest->nMem);
sqlite3VdbeAddOp1(v, OP_Yield, pDest->iParm);
break;
}
/* If none of the above, then the result destination must be
** SRT_Output. This routine is never called with any other
** destination other than the ones handled above or SRT_Output.
**
** For SRT_Output, results are stored in a sequence of registers.
** Then the OP_ResultRow opcode is used to cause sqlite3_step() to
** return the next row of result.
*/
default: {
assert( pDest->eDest==SRT_Output );
sqlite3VdbeAddOp2(v, OP_ResultRow, pIn->iMem, pIn->nMem);
sqlite3ExprCacheAffinityChange(pParse, pIn->iMem, pIn->nMem);
break;
}
}
/* Jump to the end of the loop if the LIMIT is reached.
*/
if( p->iLimit ){
sqlite3VdbeAddOp3(v, OP_IfZero, p->iLimit, iBreak, -1);
}
/* Generate the subroutine return
*/
sqlite3VdbeResolveLabel(v, iContinue);
sqlite3VdbeAddOp1(v, OP_Return, regReturn);
return addr;
}
/*
** Alternative compound select code generator for cases when there
** is an ORDER BY clause.
**
** We assume a query of the following form:
**
** <selectA> <operator> <selectB> ORDER BY <orderbylist>
**
** <operator> is one of UNION ALL, UNION, EXCEPT, or INTERSECT. The idea
** is to code both <selectA> and <selectB> with the ORDER BY clause as
** co-routines. Then run the co-routines in parallel and merge the results
** into the output. In addition to the two coroutines (called selectA and
** selectB) there are 7 subroutines:
**
** outA: Move the output of the selectA coroutine into the output
** of the compound query.
**
** outB: Move the output of the selectB coroutine into the output
** of the compound query. (Only generated for UNION and
** UNION ALL. EXCEPT and INSERTSECT never output a row that
** appears only in B.)
**
** AltB: Called when there is data from both coroutines and A<B.
**
** AeqB: Called when there is data from both coroutines and A==B.
**
** AgtB: Called when there is data from both coroutines and A>B.
**
** EofA: Called when data is exhausted from selectA.
**
** EofB: Called when data is exhausted from selectB.
**
** The implementation of the latter five subroutines depend on which
** <operator> is used:
**
**
** UNION ALL UNION EXCEPT INTERSECT
** ------------- ----------------- -------------- -----------------
** AltB: outA, nextA outA, nextA outA, nextA nextA
**
** AeqB: outA, nextA nextA nextA outA, nextA
**
** AgtB: outB, nextB outB, nextB nextB nextB
**
** EofA: outB, nextB outB, nextB halt halt
**
** EofB: outA, nextA outA, nextA outA, nextA halt
**
** In the AltB, AeqB, and AgtB subroutines, an EOF on A following nextA
** causes an immediate jump to EofA and an EOF on B following nextB causes
** an immediate jump to EofB. Within EofA and EofB, and EOF on entry or
** following nextX causes a jump to the end of the select processing.
**
** Duplicate removal in the UNION, EXCEPT, and INTERSECT cases is handled
** within the output subroutine. The regPrev register set holds the previously
** output value. A comparison is made against this value and the output
** is skipped if the next results would be the same as the previous.
**
** The implementation plan is to implement the two coroutines and seven
** subroutines first, then put the control logic at the bottom. Like this:
**
** goto Init
** coA: coroutine for left query (A)
** coB: coroutine for right query (B)
** outA: output one row of A
** outB: output one row of B (UNION and UNION ALL only)
** EofA: ...
** EofB: ...
** AltB: ...
** AeqB: ...
** AgtB: ...
** Init: initialize coroutine registers
** yield coA
** if eof(A) goto EofA
** yield coB
** if eof(B) goto EofB
** Cmpr: Compare A, B
** Jump AltB, AeqB, AgtB
** End: ...
**
** We call AltB, AeqB, AgtB, EofA, and EofB "subroutines" but they are not
** actually called using Gosub and they do not Return. EofA and EofB loop
** until all data is exhausted then jump to the "end" labe. AltB, AeqB,
** and AgtB jump to either L2 or to one of EofA or EofB.
*/
#ifndef SQLITE_OMIT_COMPOUND_SELECT
static int multiSelectOrderBy(
Parse *pParse, /* Parsing context */
Select *p, /* The right-most of SELECTs to be coded */
SelectDest *pDest /* What to do with query results */
){
int i, j; /* Loop counters */
Select *pPrior; /* Another SELECT immediately to our left */
Vdbe *v; /* Generate code to this VDBE */
SelectDest destA; /* Destination for coroutine A */
SelectDest destB; /* Destination for coroutine B */
int regAddrA; /* Address register for select-A coroutine */
int regEofA; /* Flag to indicate when select-A is complete */
int regAddrB; /* Address register for select-B coroutine */
int regEofB; /* Flag to indicate when select-B is complete */
int addrSelectA; /* Address of the select-A coroutine */
int addrSelectB; /* Address of the select-B coroutine */
int regOutA; /* Address register for the output-A subroutine */
int regOutB; /* Address register for the output-B subroutine */
int addrOutA; /* Address of the output-A subroutine */
int addrOutB = 0; /* Address of the output-B subroutine */
int addrEofA; /* Address of the select-A-exhausted subroutine */
int addrEofB; /* Address of the select-B-exhausted subroutine */
int addrAltB; /* Address of the A<B subroutine */
int addrAeqB; /* Address of the A==B subroutine */
int addrAgtB; /* Address of the A>B subroutine */
int regLimitA; /* Limit register for select-A */
int regLimitB; /* Limit register for select-A */
int regPrev; /* A range of registers to hold previous output */
int savedLimit; /* Saved value of p->iLimit */
int savedOffset; /* Saved value of p->iOffset */
int labelCmpr; /* Label for the start of the merge algorithm */
int labelEnd; /* Label for the end of the overall SELECT stmt */
int j1; /* Jump instructions that get retargetted */
int op; /* One of TK_ALL, TK_UNION, TK_EXCEPT, TK_INTERSECT */
KeyInfo *pKeyDup = 0; /* Comparison information for duplicate removal */
KeyInfo *pKeyMerge; /* Comparison information for merging rows */
sqlite3 *db; /* Database connection */
ExprList *pOrderBy; /* The ORDER BY clause */
int nOrderBy; /* Number of terms in the ORDER BY clause */
int *aPermute; /* Mapping from ORDER BY terms to result set columns */
assert( p->pOrderBy!=0 );
assert( pKeyDup==0 ); /* "Managed" code needs this. Ticket #3382. */
db = pParse->db;
v = pParse->pVdbe;
assert( v!=0 ); /* Already thrown the error if VDBE alloc failed */
labelEnd = sqlite3VdbeMakeLabel(v);
labelCmpr = sqlite3VdbeMakeLabel(v);
/* Patch up the ORDER BY clause
*/
op = p->op;
pPrior = p->pPrior;
assert( pPrior->pOrderBy==0 );
pOrderBy = p->pOrderBy;
assert( pOrderBy );
nOrderBy = pOrderBy->nExpr;
/* For operators other than UNION ALL we have to make sure that
** the ORDER BY clause covers every term of the result set. Add
** terms to the ORDER BY clause as necessary.
*/
if( op!=TK_ALL ){
for(i=1; db->mallocFailed==0 && i<=p->pEList->nExpr; i++){
struct ExprList_item *pItem;
for(j=0, pItem=pOrderBy->a; j<nOrderBy; j++, pItem++){
assert( pItem->iCol>0 );
if( pItem->iCol==i ) break;
}
if( j==nOrderBy ){
Expr *pNew = sqlite3Expr(db, TK_INTEGER, 0);
if( pNew==0 ) return SQLITE_NOMEM;
pNew->flags |= EP_IntValue;
pNew->u.iValue = i;
pOrderBy = sqlite3ExprListAppend(pParse, pOrderBy, pNew);
pOrderBy->a[nOrderBy++].iCol = (u16)i;
}
}
}
/* Compute the comparison permutation and keyinfo that is used with
** the permutation used to determine if the next
** row of results comes from selectA or selectB. Also add explicit
** collations to the ORDER BY clause terms so that when the subqueries
** to the right and the left are evaluated, they use the correct
** collation.
*/
aPermute = sqlite3DbMallocRaw(db, sizeof(int)*nOrderBy);
if( aPermute ){
struct ExprList_item *pItem;
for(i=0, pItem=pOrderBy->a; i<nOrderBy; i++, pItem++){
assert( pItem->iCol>0 && pItem->iCol<=p->pEList->nExpr );
aPermute[i] = pItem->iCol - 1;
}
pKeyMerge =
sqlite3DbMallocRaw(db, sizeof(*pKeyMerge)+nOrderBy*(sizeof(CollSeq*)+1));
if( pKeyMerge ){
pKeyMerge->aSortOrder = (u8*)&pKeyMerge->aColl[nOrderBy];
pKeyMerge->nField = (u16)nOrderBy;
pKeyMerge->enc = ENC(db);
for(i=0; i<nOrderBy; i++){
CollSeq *pColl;
Expr *pTerm = pOrderBy->a[i].pExpr;
if( pTerm->flags & EP_ExpCollate ){
pColl = pTerm->pColl;
}else{
pColl = multiSelectCollSeq(pParse, p, aPermute[i]);
pTerm->flags |= EP_ExpCollate;
pTerm->pColl = pColl;
}
pKeyMerge->aColl[i] = pColl;
pKeyMerge->aSortOrder[i] = pOrderBy->a[i].sortOrder;
}
}
}else{
pKeyMerge = 0;
}
/* Reattach the ORDER BY clause to the query.
*/
p->pOrderBy = pOrderBy;
pPrior->pOrderBy = sqlite3ExprListDup(pParse->db, pOrderBy, 0);
/* Allocate a range of temporary registers and the KeyInfo needed
** for the logic that removes duplicate result rows when the
** operator is UNION, EXCEPT, or INTERSECT (but not UNION ALL).
*/
if( op==TK_ALL ){
regPrev = 0;
}else{
int nExpr = p->pEList->nExpr;
assert( nOrderBy>=nExpr || db->mallocFailed );
regPrev = sqlite3GetTempRange(pParse, nExpr+1);
sqlite3VdbeAddOp2(v, OP_Integer, 0, regPrev);
pKeyDup = sqlite3DbMallocZero(db,
sizeof(*pKeyDup) + nExpr*(sizeof(CollSeq*)+1) );
if( pKeyDup ){
pKeyDup->aSortOrder = (u8*)&pKeyDup->aColl[nExpr];
pKeyDup->nField = (u16)nExpr;
pKeyDup->enc = ENC(db);
for(i=0; i<nExpr; i++){
pKeyDup->aColl[i] = multiSelectCollSeq(pParse, p, i);
pKeyDup->aSortOrder[i] = 0;
}
}
}
/* Separate the left and the right query from one another
*/
p->pPrior = 0;
pPrior->pRightmost = 0;
sqlite3ResolveOrderGroupBy(pParse, p, p->pOrderBy, "ORDER");
if( pPrior->pPrior==0 ){
sqlite3ResolveOrderGroupBy(pParse, pPrior, pPrior->pOrderBy, "ORDER");
}
/* Compute the limit registers */
computeLimitRegisters(pParse, p, labelEnd);
if( p->iLimit && op==TK_ALL ){
regLimitA = ++pParse->nMem;
regLimitB = ++pParse->nMem;
sqlite3VdbeAddOp2(v, OP_Copy, p->iOffset ? p->iOffset+1 : p->iLimit,
regLimitA);
sqlite3VdbeAddOp2(v, OP_Copy, regLimitA, regLimitB);
}else{
regLimitA = regLimitB = 0;
}
sqlite3ExprDelete(db, p->pLimit);
p->pLimit = 0;
sqlite3ExprDelete(db, p->pOffset);
p->pOffset = 0;
regAddrA = ++pParse->nMem;
regEofA = ++pParse->nMem;
regAddrB = ++pParse->nMem;
regEofB = ++pParse->nMem;
regOutA = ++pParse->nMem;
regOutB = ++pParse->nMem;
sqlite3SelectDestInit(&destA, SRT_Coroutine, regAddrA);
sqlite3SelectDestInit(&destB, SRT_Coroutine, regAddrB);
/* Jump past the various subroutines and coroutines to the main
** merge loop
*/
j1 = sqlite3VdbeAddOp0(v, OP_Goto);
addrSelectA = sqlite3VdbeCurrentAddr(v);
/* Generate a coroutine to evaluate the SELECT statement to the
** left of the compound operator - the "A" select.
*/
VdbeNoopComment((v, "Begin coroutine for left SELECT"));
pPrior->iLimit = regLimitA;
sqlite3Select(pParse, pPrior, &destA);
sqlite3VdbeAddOp2(v, OP_Integer, 1, regEofA);
sqlite3VdbeAddOp1(v, OP_Yield, regAddrA);
VdbeNoopComment((v, "End coroutine for left SELECT"));
/* Generate a coroutine to evaluate the SELECT statement on
** the right - the "B" select
*/
addrSelectB = sqlite3VdbeCurrentAddr(v);
VdbeNoopComment((v, "Begin coroutine for right SELECT"));
savedLimit = p->iLimit;
savedOffset = p->iOffset;
p->iLimit = regLimitB;
p->iOffset = 0;
sqlite3Select(pParse, p, &destB);
p->iLimit = savedLimit;
p->iOffset = savedOffset;
sqlite3VdbeAddOp2(v, OP_Integer, 1, regEofB);
sqlite3VdbeAddOp1(v, OP_Yield, regAddrB);
VdbeNoopComment((v, "End coroutine for right SELECT"));
/* Generate a subroutine that outputs the current row of the A
** select as the next output row of the compound select.
*/
VdbeNoopComment((v, "Output routine for A"));
addrOutA = generateOutputSubroutine(pParse,
p, &destA, pDest, regOutA,
regPrev, pKeyDup, P4_KEYINFO_HANDOFF, labelEnd);
/* Generate a subroutine that outputs the current row of the B
** select as the next output row of the compound select.
*/
if( op==TK_ALL || op==TK_UNION ){
VdbeNoopComment((v, "Output routine for B"));
addrOutB = generateOutputSubroutine(pParse,
p, &destB, pDest, regOutB,
regPrev, pKeyDup, P4_KEYINFO_STATIC, labelEnd);
}
/* Generate a subroutine to run when the results from select A
** are exhausted and only data in select B remains.
*/
VdbeNoopComment((v, "eof-A subroutine"));
if( op==TK_EXCEPT || op==TK_INTERSECT ){
addrEofA = sqlite3VdbeAddOp2(v, OP_Goto, 0, labelEnd);
}else{
addrEofA = sqlite3VdbeAddOp2(v, OP_If, regEofB, labelEnd);
sqlite3VdbeAddOp2(v, OP_Gosub, regOutB, addrOutB);
sqlite3VdbeAddOp1(v, OP_Yield, regAddrB);
sqlite3VdbeAddOp2(v, OP_Goto, 0, addrEofA);
}
/* Generate a subroutine to run when the results from select B
** are exhausted and only data in select A remains.
*/
if( op==TK_INTERSECT ){
addrEofB = addrEofA;
}else{
VdbeNoopComment((v, "eof-B subroutine"));
addrEofB = sqlite3VdbeAddOp2(v, OP_If, regEofA, labelEnd);
sqlite3VdbeAddOp2(v, OP_Gosub, regOutA, addrOutA);
sqlite3VdbeAddOp1(v, OP_Yield, regAddrA);
sqlite3VdbeAddOp2(v, OP_Goto, 0, addrEofB);
}
/* Generate code to handle the case of A<B
*/
VdbeNoopComment((v, "A-lt-B subroutine"));
addrAltB = sqlite3VdbeAddOp2(v, OP_Gosub, regOutA, addrOutA);
sqlite3VdbeAddOp1(v, OP_Yield, regAddrA);
sqlite3VdbeAddOp2(v, OP_If, regEofA, addrEofA);
sqlite3VdbeAddOp2(v, OP_Goto, 0, labelCmpr);
/* Generate code to handle the case of A==B
*/
if( op==TK_ALL ){
addrAeqB = addrAltB;
}else if( op==TK_INTERSECT ){
addrAeqB = addrAltB;
addrAltB++;
}else{
VdbeNoopComment((v, "A-eq-B subroutine"));
addrAeqB =
sqlite3VdbeAddOp1(v, OP_Yield, regAddrA);
sqlite3VdbeAddOp2(v, OP_If, regEofA, addrEofA);
sqlite3VdbeAddOp2(v, OP_Goto, 0, labelCmpr);
}
/* Generate code to handle the case of A>B
*/
VdbeNoopComment((v, "A-gt-B subroutine"));
addrAgtB = sqlite3VdbeCurrentAddr(v);
if( op==TK_ALL || op==TK_UNION ){
sqlite3VdbeAddOp2(v, OP_Gosub, regOutB, addrOutB);
}
sqlite3VdbeAddOp1(v, OP_Yield, regAddrB);
sqlite3VdbeAddOp2(v, OP_If, regEofB, addrEofB);
sqlite3VdbeAddOp2(v, OP_Goto, 0, labelCmpr);
/* This code runs once to initialize everything.
*/
sqlite3VdbeJumpHere(v, j1);
sqlite3VdbeAddOp2(v, OP_Integer, 0, regEofA);
sqlite3VdbeAddOp2(v, OP_Integer, 0, regEofB);
sqlite3VdbeAddOp2(v, OP_Gosub, regAddrA, addrSelectA);
sqlite3VdbeAddOp2(v, OP_Gosub, regAddrB, addrSelectB);
sqlite3VdbeAddOp2(v, OP_If, regEofA, addrEofA);
sqlite3VdbeAddOp2(v, OP_If, regEofB, addrEofB);
/* Implement the main merge loop
*/
sqlite3VdbeResolveLabel(v, labelCmpr);
sqlite3VdbeAddOp4(v, OP_Permutation, 0, 0, 0, (char*)aPermute, P4_INTARRAY);
sqlite3VdbeAddOp4(v, OP_Compare, destA.iMem, destB.iMem, nOrderBy,
(char*)pKeyMerge, P4_KEYINFO_HANDOFF);
sqlite3VdbeAddOp3(v, OP_Jump, addrAltB, addrAeqB, addrAgtB);
/* Release temporary registers
*/
if( regPrev ){
sqlite3ReleaseTempRange(pParse, regPrev, nOrderBy+1);
}
/* Jump to the this point in order to terminate the query.
*/
sqlite3VdbeResolveLabel(v, labelEnd);
/* Set the number of output columns
*/
if( pDest->eDest==SRT_Output ){
Select *pFirst = pPrior;
while( pFirst->pPrior ) pFirst = pFirst->pPrior;
generateColumnNames(pParse, 0, pFirst->pEList);
}
/* Reassembly the compound query so that it will be freed correctly
** by the calling function */
if( p->pPrior ){
sqlite3SelectDelete(db, p->pPrior);
}
p->pPrior = pPrior;
/*** TBD: Insert subroutine calls to close cursors on incomplete
**** subqueries ****/
return SQLITE_OK;
}
#endif
#if !defined(SQLITE_OMIT_SUBQUERY) || !defined(SQLITE_OMIT_VIEW)
/* Forward Declarations */
static void substExprList(sqlite3*, ExprList*, int, ExprList*);
static void substSelect(sqlite3*, Select *, int, ExprList *);
/*
** Scan through the expression pExpr. Replace every reference to
** a column in table number iTable with a copy of the iColumn-th
** entry in pEList. (But leave references to the ROWID column
** unchanged.)
**
** This routine is part of the flattening procedure. A subquery
** whose result set is defined by pEList appears as entry in the
** FROM clause of a SELECT such that the VDBE cursor assigned to that
** FORM clause entry is iTable. This routine make the necessary
** changes to pExpr so that it refers directly to the source table
** of the subquery rather the result set of the subquery.
*/
static Expr *substExpr(
sqlite3 *db, /* Report malloc errors to this connection */
Expr *pExpr, /* Expr in which substitution occurs */
int iTable, /* Table to be substituted */
ExprList *pEList /* Substitute expressions */
){
if( pExpr==0 ) return 0;
if( pExpr->op==TK_COLUMN && pExpr->iTable==iTable ){
if( pExpr->iColumn<0 ){
pExpr->op = TK_NULL;
}else{
Expr *pNew;
assert( pEList!=0 && pExpr->iColumn<pEList->nExpr );
assert( pExpr->pLeft==0 && pExpr->pRight==0 );
pNew = sqlite3ExprDup(db, pEList->a[pExpr->iColumn].pExpr, 0);
if( pNew && pExpr->pColl ){
pNew->pColl = pExpr->pColl;
}
sqlite3ExprDelete(db, pExpr);
pExpr = pNew;
}
}else{
pExpr->pLeft = substExpr(db, pExpr->pLeft, iTable, pEList);
pExpr->pRight = substExpr(db, pExpr->pRight, iTable, pEList);
if( ExprHasProperty(pExpr, EP_xIsSelect) ){
substSelect(db, pExpr->x.pSelect, iTable, pEList);
}else{
substExprList(db, pExpr->x.pList, iTable, pEList);
}
}
return pExpr;
}
static void substExprList(
sqlite3 *db, /* Report malloc errors here */
ExprList *pList, /* List to scan and in which to make substitutes */
int iTable, /* Table to be substituted */
ExprList *pEList /* Substitute values */
){
int i;
if( pList==0 ) return;
for(i=0; i<pList->nExpr; i++){
pList->a[i].pExpr = substExpr(db, pList->a[i].pExpr, iTable, pEList);
}
}
static void substSelect(
sqlite3 *db, /* Report malloc errors here */
Select *p, /* SELECT statement in which to make substitutions */
int iTable, /* Table to be replaced */
ExprList *pEList /* Substitute values */
){
SrcList *pSrc;
struct SrcList_item *pItem;
int i;
if( !p ) return;
substExprList(db, p->pEList, iTable, pEList);
substExprList(db, p->pGroupBy, iTable, pEList);
substExprList(db, p->pOrderBy, iTable, pEList);
p->pHaving = substExpr(db, p->pHaving, iTable, pEList);
p->pWhere = substExpr(db, p->pWhere, iTable, pEList);
substSelect(db, p->pPrior, iTable, pEList);
pSrc = p->pSrc;
assert( pSrc ); /* Even for (SELECT 1) we have: pSrc!=0 but pSrc->nSrc==0 */
if( ALWAYS(pSrc) ){
for(i=pSrc->nSrc, pItem=pSrc->a; i>0; i--, pItem++){
substSelect(db, pItem->pSelect, iTable, pEList);
}
}
}
#endif /* !defined(SQLITE_OMIT_SUBQUERY) || !defined(SQLITE_OMIT_VIEW) */
#if !defined(SQLITE_OMIT_SUBQUERY) || !defined(SQLITE_OMIT_VIEW)
/*
** This routine attempts to flatten subqueries in order to speed
** execution. It returns 1 if it makes changes and 0 if no flattening
** occurs.
**
** To understand the concept of flattening, consider the following
** query:
**
** SELECT a FROM (SELECT x+y AS a FROM t1 WHERE z<100) WHERE a>5
**
** The default way of implementing this query is to execute the
** subquery first and store the results in a temporary table, then
** run the outer query on that temporary table. This requires two
** passes over the data. Furthermore, because the temporary table
** has no indices, the WHERE clause on the outer query cannot be
** optimized.
**
** This routine attempts to rewrite queries such as the above into
** a single flat select, like this:
**
** SELECT x+y AS a FROM t1 WHERE z<100 AND a>5
**
** The code generated for this simpification gives the same result
** but only has to scan the data once. And because indices might
** exist on the table t1, a complete scan of the data might be
** avoided.
**
** Flattening is only attempted if all of the following are true:
**
** (1) The subquery and the outer query do not both use aggregates.
**
** (2) The subquery is not an aggregate or the outer query is not a join.
**
** (3) The subquery is not the right operand of a left outer join
** (Originally ticket #306. Strengthened by ticket #3300)
**
** (4) The subquery is not DISTINCT.
**
** (**) At one point restrictions (4) and (5) defined a subset of DISTINCT
** sub-queries that were excluded from this optimization. Restriction
** (4) has since been expanded to exclude all DISTINCT subqueries.
**
** (6) The subquery does not use aggregates or the outer query is not
** DISTINCT.
**
** (7) The subquery has a FROM clause.
**
** (8) The subquery does not use LIMIT or the outer query is not a join.
**
** (9) The subquery does not use LIMIT or the outer query does not use
** aggregates.
**
** (10) The subquery does not use aggregates or the outer query does not
** use LIMIT.
**
** (11) The subquery and the outer query do not both have ORDER BY clauses.
**
** (**) Not implemented. Subsumed into restriction (3). Was previously
** a separate restriction deriving from ticket #350.
**
** (13) The subquery and outer query do not both use LIMIT.
**
** (14) The subquery does not use OFFSET.
**
** (15) The outer query is not part of a compound select or the
** subquery does not have a LIMIT clause.
** (See ticket #2339 and ticket [02a8e81d44]).
**
** (16) The outer query is not an aggregate or the subquery does
** not contain ORDER BY. (Ticket #2942) This used to not matter
** until we introduced the group_concat() function.
**
** (17) The sub-query is not a compound select, or it is a UNION ALL
** compound clause made up entirely of non-aggregate queries, and
** the parent query:
**
** * is not itself part of a compound select,
** * is not an aggregate or DISTINCT query, and
** * has no other tables or sub-selects in the FROM clause.
**
** The parent and sub-query may contain WHERE clauses. Subject to
** rules (11), (13) and (14), they may also contain ORDER BY,
** LIMIT and OFFSET clauses.
**
** (18) If the sub-query is a compound select, then all terms of the
** ORDER by clause of the parent must be simple references to
** columns of the sub-query.
**
** (19) The subquery does not use LIMIT or the outer query does not
** have a WHERE clause.
**
** (20) If the sub-query is a compound select, then it must not use
** an ORDER BY clause. Ticket #3773. We could relax this constraint
** somewhat by saying that the terms of the ORDER BY clause must
** appear as unmodified result columns in the outer query. But
** have other optimizations in mind to deal with that case.
**
** In this routine, the "p" parameter is a pointer to the outer query.
** The subquery is p->pSrc->a[iFrom]. isAgg is true if the outer query
** uses aggregates and subqueryIsAgg is true if the subquery uses aggregates.
**
** If flattening is not attempted, this routine is a no-op and returns 0.
** If flattening is attempted this routine returns 1.
**
** All of the expression analysis must occur on both the outer query and
** the subquery before this routine runs.
*/
static int flattenSubquery(
Parse *pParse, /* Parsing context */
Select *p, /* The parent or outer SELECT statement */
int iFrom, /* Index in p->pSrc->a[] of the inner subquery */
int isAgg, /* True if outer SELECT uses aggregate functions */
int subqueryIsAgg /* True if the subquery uses aggregate functions */
){
const char *zSavedAuthContext = pParse->zAuthContext;
Select *pParent;
Select *pSub; /* The inner query or "subquery" */
Select *pSub1; /* Pointer to the rightmost select in sub-query */
SrcList *pSrc; /* The FROM clause of the outer query */
SrcList *pSubSrc; /* The FROM clause of the subquery */
ExprList *pList; /* The result set of the outer query */
int iParent; /* VDBE cursor number of the pSub result set temp table */
int i; /* Loop counter */
Expr *pWhere; /* The WHERE clause */
struct SrcList_item *pSubitem; /* The subquery */
sqlite3 *db = pParse->db;
/* Check to see if flattening is permitted. Return 0 if not.
*/
assert( p!=0 );
assert( p->pPrior==0 ); /* Unable to flatten compound queries */
if( db->flags & SQLITE_QueryFlattener ) return 0;
pSrc = p->pSrc;
assert( pSrc && iFrom>=0 && iFrom<pSrc->nSrc );
pSubitem = &pSrc->a[iFrom];
iParent = pSubitem->iCursor;
pSub = pSubitem->pSelect;
assert( pSub!=0 );
if( isAgg && subqueryIsAgg ) return 0; /* Restriction (1) */
if( subqueryIsAgg && pSrc->nSrc>1 ) return 0; /* Restriction (2) */
pSubSrc = pSub->pSrc;
assert( pSubSrc );
/* Prior to version 3.1.2, when LIMIT and OFFSET had to be simple constants,
** not arbitrary expresssions, we allowed some combining of LIMIT and OFFSET
** because they could be computed at compile-time. But when LIMIT and OFFSET
** became arbitrary expressions, we were forced to add restrictions (13)
** and (14). */
if( pSub->pLimit && p->pLimit ) return 0; /* Restriction (13) */
if( pSub->pOffset ) return 0; /* Restriction (14) */
if( p->pRightmost && pSub->pLimit ){
return 0; /* Restriction (15) */
}
if( pSubSrc->nSrc==0 ) return 0; /* Restriction (7) */
if( pSub->selFlags & SF_Distinct ) return 0; /* Restriction (5) */
if( pSub->pLimit && (pSrc->nSrc>1 || isAgg) ){
return 0; /* Restrictions (8)(9) */
}
if( (p->selFlags & SF_Distinct)!=0 && subqueryIsAgg ){
return 0; /* Restriction (6) */
}
if( p->pOrderBy && pSub->pOrderBy ){
return 0; /* Restriction (11) */
}
if( isAgg && pSub->pOrderBy ) return 0; /* Restriction (16) */
if( pSub->pLimit && p->pWhere ) return 0; /* Restriction (19) */
/* OBSOLETE COMMENT 1:
** Restriction 3: If the subquery is a join, make sure the subquery is
** not used as the right operand of an outer join. Examples of why this
** is not allowed:
**
** t1 LEFT OUTER JOIN (t2 JOIN t3)
**
** If we flatten the above, we would get
**
** (t1 LEFT OUTER JOIN t2) JOIN t3
**
** which is not at all the same thing.
**
** OBSOLETE COMMENT 2:
** Restriction 12: If the subquery is the right operand of a left outer
** join, make sure the subquery has no WHERE clause.
** An examples of why this is not allowed:
**
** t1 LEFT OUTER JOIN (SELECT * FROM t2 WHERE t2.x>0)
**
** If we flatten the above, we would get
**
** (t1 LEFT OUTER JOIN t2) WHERE t2.x>0
**
** But the t2.x>0 test will always fail on a NULL row of t2, which
** effectively converts the OUTER JOIN into an INNER JOIN.
**
** THIS OVERRIDES OBSOLETE COMMENTS 1 AND 2 ABOVE:
** Ticket #3300 shows that flattening the right term of a LEFT JOIN
** is fraught with danger. Best to avoid the whole thing. If the
** subquery is the right term of a LEFT JOIN, then do not flatten.
*/
if( (pSubitem->jointype & JT_OUTER)!=0 ){
return 0;
}
/* Restriction 17: If the sub-query is a compound SELECT, then it must
** use only the UNION ALL operator. And none of the simple select queries
** that make up the compound SELECT are allowed to be aggregate or distinct
** queries.
*/
if( pSub->pPrior ){
if( pSub->pOrderBy ){
return 0; /* Restriction 20 */
}
if( isAgg || (p->selFlags & SF_Distinct)!=0 || pSrc->nSrc!=1 ){
return 0;
}
for(pSub1=pSub; pSub1; pSub1=pSub1->pPrior){
testcase( (pSub1->selFlags & (SF_Distinct|SF_Aggregate))==SF_Distinct );
testcase( (pSub1->selFlags & (SF_Distinct|SF_Aggregate))==SF_Aggregate );
if( (pSub1->selFlags & (SF_Distinct|SF_Aggregate))!=0
|| (pSub1->pPrior && pSub1->op!=TK_ALL)
|| NEVER(pSub1->pSrc==0) || pSub1->pSrc->nSrc!=1
){
return 0;
}
}
/* Restriction 18. */
if( p->pOrderBy ){
int ii;
for(ii=0; ii<p->pOrderBy->nExpr; ii++){
if( p->pOrderBy->a[ii].iCol==0 ) return 0;
}
}
}
/***** If we reach this point, flattening is permitted. *****/
/* Authorize the subquery */
pParse->zAuthContext = pSubitem->zName;
sqlite3AuthCheck(pParse, SQLITE_SELECT, 0, 0, 0);
pParse->zAuthContext = zSavedAuthContext;
/* If the sub-query is a compound SELECT statement, then (by restrictions
** 17 and 18 above) it must be a UNION ALL and the parent query must
** be of the form:
**
** SELECT <expr-list> FROM (<sub-query>) <where-clause>
**
** followed by any ORDER BY, LIMIT and/or OFFSET clauses. This block
** creates N-1 copies of the parent query without any ORDER BY, LIMIT or
** OFFSET clauses and joins them to the left-hand-side of the original
** using UNION ALL operators. In this case N is the number of simple
** select statements in the compound sub-query.
**
** Example:
**
** SELECT a+1 FROM (
** SELECT x FROM tab
** UNION ALL
** SELECT y FROM tab
** UNION ALL
** SELECT abs(z*2) FROM tab2
** ) WHERE a!=5 ORDER BY 1
**
** Transformed into:
**
** SELECT x+1 FROM tab WHERE x+1!=5
** UNION ALL
** SELECT y+1 FROM tab WHERE y+1!=5
** UNION ALL
** SELECT abs(z*2)+1 FROM tab2 WHERE abs(z*2)+1!=5
** ORDER BY 1
**
** We call this the "compound-subquery flattening".
*/
for(pSub=pSub->pPrior; pSub; pSub=pSub->pPrior){
Select *pNew;
ExprList *pOrderBy = p->pOrderBy;
Expr *pLimit = p->pLimit;
Select *pPrior = p->pPrior;
p->pOrderBy = 0;
p->pSrc = 0;
p->pPrior = 0;
p->pLimit = 0;
pNew = sqlite3SelectDup(db, p, 0);
p->pLimit = pLimit;
p->pOrderBy = pOrderBy;
p->pSrc = pSrc;
p->op = TK_ALL;
p->pRightmost = 0;
if( pNew==0 ){
pNew = pPrior;
}else{
pNew->pPrior = pPrior;
pNew->pRightmost = 0;
}
p->pPrior = pNew;
if( db->mallocFailed ) return 1;
}
/* Begin flattening the iFrom-th entry of the FROM clause
** in the outer query.
*/
pSub = pSub1 = pSubitem->pSelect;
/* Delete the transient table structure associated with the
** subquery
*/
sqlite3DbFree(db, pSubitem->zDatabase);
sqlite3DbFree(db, pSubitem->zName);
sqlite3DbFree(db, pSubitem->zAlias);
pSubitem->zDatabase = 0;
pSubitem->zName = 0;
pSubitem->zAlias = 0;
pSubitem->pSelect = 0;
/* Defer deleting the Table object associated with the
** subquery until code generation is
** complete, since there may still exist Expr.pTab entries that
** refer to the subquery even after flattening. Ticket #3346.
**
** pSubitem->pTab is always non-NULL by test restrictions and tests above.
*/
if( ALWAYS(pSubitem->pTab!=0) ){
Table *pTabToDel = pSubitem->pTab;
if( pTabToDel->nRef==1 ){
Parse *pToplevel = sqlite3ParseToplevel(pParse);
pTabToDel->pNextZombie = pToplevel->pZombieTab;
pToplevel->pZombieTab = pTabToDel;
}else{
pTabToDel->nRef--;
}
pSubitem->pTab = 0;
}
/* The following loop runs once for each term in a compound-subquery
** flattening (as described above). If we are doing a different kind
** of flattening - a flattening other than a compound-subquery flattening -
** then this loop only runs once.
**
** This loop moves all of the FROM elements of the subquery into the
** the FROM clause of the outer query. Before doing this, remember
** the cursor number for the original outer query FROM element in
** iParent. The iParent cursor will never be used. Subsequent code
** will scan expressions looking for iParent references and replace
** those references with expressions that resolve to the subquery FROM
** elements we are now copying in.
*/
for(pParent=p; pParent; pParent=pParent->pPrior, pSub=pSub->pPrior){
int nSubSrc;
u8 jointype = 0;
pSubSrc = pSub->pSrc; /* FROM clause of subquery */
nSubSrc = pSubSrc->nSrc; /* Number of terms in subquery FROM clause */
pSrc = pParent->pSrc; /* FROM clause of the outer query */
if( pSrc ){
assert( pParent==p ); /* First time through the loop */
jointype = pSubitem->jointype;
}else{
assert( pParent!=p ); /* 2nd and subsequent times through the loop */
pSrc = pParent->pSrc = sqlite3SrcListAppend(db, 0, 0, 0);
if( pSrc==0 ){
assert( db->mallocFailed );
break;
}
}
/* The subquery uses a single slot of the FROM clause of the outer
** query. If the subquery has more than one element in its FROM clause,
** then expand the outer query to make space for it to hold all elements
** of the subquery.
**
** Example:
**
** SELECT * FROM tabA, (SELECT * FROM sub1, sub2), tabB;
**
** The outer query has 3 slots in its FROM clause. One slot of the
** outer query (the middle slot) is used by the subquery. The next
** block of code will expand the out query to 4 slots. The middle
** slot is expanded to two slots in order to make space for the
** two elements in the FROM clause of the subquery.
*/
if( nSubSrc>1 ){
pParent->pSrc = pSrc = sqlite3SrcListEnlarge(db, pSrc, nSubSrc-1,iFrom+1);
if( db->mallocFailed ){
break;
}
}
/* Transfer the FROM clause terms from the subquery into the
** outer query.
*/
for(i=0; i<nSubSrc; i++){
sqlite3IdListDelete(db, pSrc->a[i+iFrom].pUsing);
pSrc->a[i+iFrom] = pSubSrc->a[i];
memset(&pSubSrc->a[i], 0, sizeof(pSubSrc->a[i]));
}
pSrc->a[iFrom].jointype = jointype;
/* Now begin substituting subquery result set expressions for
** references to the iParent in the outer query.
**
** Example:
**
** SELECT a+5, b*10 FROM (SELECT x*3 AS a, y+10 AS b FROM t1) WHERE a>b;
** \ \_____________ subquery __________/ /
** \_____________________ outer query ______________________________/
**
** We look at every expression in the outer query and every place we see
** "a" we substitute "x*3" and every place we see "b" we substitute "y+10".
*/
pList = pParent->pEList;
for(i=0; i<pList->nExpr; i++){
if( pList->a[i].zName==0 ){
const char *zSpan = pList->a[i].zSpan;
if( ALWAYS(zSpan) ){
pList->a[i].zName = sqlite3DbStrDup(db, zSpan);
}
}
}
substExprList(db, pParent->pEList, iParent, pSub->pEList);
if( isAgg ){
substExprList(db, pParent->pGroupBy, iParent, pSub->pEList);
pParent->pHaving = substExpr(db, pParent->pHaving, iParent, pSub->pEList);
}
if( pSub->pOrderBy ){
assert( pParent->pOrderBy==0 );
pParent->pOrderBy = pSub->pOrderBy;
pSub->pOrderBy = 0;
}else if( pParent->pOrderBy ){
substExprList(db, pParent->pOrderBy, iParent, pSub->pEList);
}
if( pSub->pWhere ){
pWhere = sqlite3ExprDup(db, pSub->pWhere, 0);
}else{
pWhere = 0;
}
if( subqueryIsAgg ){
assert( pParent->pHaving==0 );
pParent->pHaving = pParent->pWhere;
pParent->pWhere = pWhere;
pParent->pHaving = substExpr(db, pParent->pHaving, iParent, pSub->pEList);
pParent->pHaving = sqlite3ExprAnd(db, pParent->pHaving,
sqlite3ExprDup(db, pSub->pHaving, 0));
assert( pParent->pGroupBy==0 );
pParent->pGroupBy = sqlite3ExprListDup(db, pSub->pGroupBy, 0);
}else{
pParent->pWhere = substExpr(db, pParent->pWhere, iParent, pSub->pEList);
pParent->pWhere = sqlite3ExprAnd(db, pParent->pWhere, pWhere);
}
/* The flattened query is distinct if either the inner or the
** outer query is distinct.
*/
pParent->selFlags |= pSub->selFlags & SF_Distinct;
/*
** SELECT ... FROM (SELECT ... LIMIT a OFFSET b) LIMIT x OFFSET y;
**
** One is tempted to try to add a and b to combine the limits. But this
** does not work if either limit is negative.
*/
if( pSub->pLimit ){
pParent->pLimit = pSub->pLimit;
pSub->pLimit = 0;
}
}
/* Finially, delete what is left of the subquery and return
** success.
*/
sqlite3SelectDelete(db, pSub1);
return 1;
}
#endif /* !defined(SQLITE_OMIT_SUBQUERY) || !defined(SQLITE_OMIT_VIEW) */
/*
** Analyze the SELECT statement passed as an argument to see if it
** is a min() or max() query. Return WHERE_ORDERBY_MIN or WHERE_ORDERBY_MAX if
** it is, or 0 otherwise. At present, a query is considered to be
** a min()/max() query if:
**
** 1. There is a single object in the FROM clause.
**
** 2. There is a single expression in the result set, and it is
** either min(x) or max(x), where x is a column reference.
*/
static u8 minMaxQuery(Select *p){
Expr *pExpr;
ExprList *pEList = p->pEList;
if( pEList->nExpr!=1 ) return WHERE_ORDERBY_NORMAL;
pExpr = pEList->a[0].pExpr;
if( pExpr->op!=TK_AGG_FUNCTION ) return 0;
if( NEVER(ExprHasProperty(pExpr, EP_xIsSelect)) ) return 0;
pEList = pExpr->x.pList;
if( pEList==0 || pEList->nExpr!=1 ) return 0;
if( pEList->a[0].pExpr->op!=TK_AGG_COLUMN ) return WHERE_ORDERBY_NORMAL;
assert( !ExprHasProperty(pExpr, EP_IntValue) );
if( sqlite3StrICmp(pExpr->u.zToken,"min")==0 ){
return WHERE_ORDERBY_MIN;
}else if( sqlite3StrICmp(pExpr->u.zToken,"max")==0 ){
return WHERE_ORDERBY_MAX;
}
return WHERE_ORDERBY_NORMAL;
}
/*
** The select statement passed as the first argument is an aggregate query.
** The second argment is the associated aggregate-info object. This
** function tests if the SELECT is of the form:
**
** SELECT count(*) FROM <tbl>
**
** where table is a database table, not a sub-select or view. If the query
** does match this pattern, then a pointer to the Table object representing
** <tbl> is returned. Otherwise, 0 is returned.
*/
static Table *isSimpleCount(Select *p, AggInfo *pAggInfo){
Table *pTab;
Expr *pExpr;
assert( !p->pGroupBy );
if( p->pWhere || p->pEList->nExpr!=1
|| p->pSrc->nSrc!=1 || p->pSrc->a[0].pSelect
){
return 0;
}
pTab = p->pSrc->a[0].pTab;
pExpr = p->pEList->a[0].pExpr;
assert( pTab && !pTab->pSelect && pExpr );
if( IsVirtual(pTab) ) return 0;
if( pExpr->op!=TK_AGG_FUNCTION ) return 0;
if( (pAggInfo->aFunc[0].pFunc->flags&SQLITE_FUNC_COUNT)==0 ) return 0;
if( pExpr->flags&EP_Distinct ) return 0;
return pTab;
}
/*
** If the source-list item passed as an argument was augmented with an
** INDEXED BY clause, then try to locate the specified index. If there
** was such a clause and the named index cannot be found, return
** SQLITE_ERROR and leave an error in pParse. Otherwise, populate
** pFrom->pIndex and return SQLITE_OK.
*/
int sqlite3IndexedByLookup(Parse *pParse, struct SrcList_item *pFrom){
if( pFrom->pTab && pFrom->zIndex ){
Table *pTab = pFrom->pTab;
char *zIndex = pFrom->zIndex;
Index *pIdx;
for(pIdx=pTab->pIndex;
pIdx && sqlite3StrICmp(pIdx->zName, zIndex);
pIdx=pIdx->pNext
);
if( !pIdx ){
sqlite3ErrorMsg(pParse, "no such index: %s", zIndex, 0);
pParse->checkSchema = 1;
return SQLITE_ERROR;
}
pFrom->pIndex = pIdx;
}
return SQLITE_OK;
}
/*
** This routine is a Walker callback for "expanding" a SELECT statement.
** "Expanding" means to do the following:
**
** (1) Make sure VDBE cursor numbers have been assigned to every
** element of the FROM clause.
**
** (2) Fill in the pTabList->a[].pTab fields in the SrcList that
** defines FROM clause. When views appear in the FROM clause,
** fill pTabList->a[].pSelect with a copy of the SELECT statement
** that implements the view. A copy is made of the view's SELECT
** statement so that we can freely modify or delete that statement
** without worrying about messing up the presistent representation
** of the view.
**
** (3) Add terms to the WHERE clause to accomodate the NATURAL keyword
** on joins and the ON and USING clause of joins.
**
** (4) Scan the list of columns in the result set (pEList) looking
** for instances of the "*" operator or the TABLE.* operator.
** If found, expand each "*" to be every column in every table
** and TABLE.* to be every column in TABLE.
**
*/
static int selectExpander(Walker *pWalker, Select *p){
Parse *pParse = pWalker->pParse;
int i, j, k;
SrcList *pTabList;
ExprList *pEList;
struct SrcList_item *pFrom;
sqlite3 *db = pParse->db;
if( db->mallocFailed ){
return WRC_Abort;
}
if( NEVER(p->pSrc==0) || (p->selFlags & SF_Expanded)!=0 ){
return WRC_Prune;
}
p->selFlags |= SF_Expanded;
pTabList = p->pSrc;
pEList = p->pEList;
/* Make sure cursor numbers have been assigned to all entries in
** the FROM clause of the SELECT statement.
*/
sqlite3SrcListAssignCursors(pParse, pTabList);
/* Look up every table named in the FROM clause of the select. If
** an entry of the FROM clause is a subquery instead of a table or view,
** then create a transient table structure to describe the subquery.
*/
for(i=0, pFrom=pTabList->a; i<pTabList->nSrc; i++, pFrom++){
Table *pTab;
if( pFrom->pTab!=0 ){
/* This statement has already been prepared. There is no need
** to go further. */
assert( i==0 );
return WRC_Prune;
}
if( pFrom->zName==0 ){
#ifndef SQLITE_OMIT_SUBQUERY
Select *pSel = pFrom->pSelect;
/* A sub-query in the FROM clause of a SELECT */
assert( pSel!=0 );
assert( pFrom->pTab==0 );
sqlite3WalkSelect(pWalker, pSel);
pFrom->pTab = pTab = sqlite3DbMallocZero(db, sizeof(Table));
if( pTab==0 ) return WRC_Abort;
pTab->nRef = 1;
pTab->zName = sqlite3MPrintf(db, "sqlite_subquery_%p_", (void*)pTab);
while( pSel->pPrior ){ pSel = pSel->pPrior; }
selectColumnsFromExprList(pParse, pSel->pEList, &pTab->nCol, &pTab->aCol);
pTab->iPKey = -1;
pTab->tabFlags |= TF_Ephemeral;
#endif
}else{
/* An ordinary table or view name in the FROM clause */
assert( pFrom->pTab==0 );
pFrom->pTab = pTab =
sqlite3LocateTable(pParse,0,pFrom->zName,pFrom->zDatabase);
if( pTab==0 ) return WRC_Abort;
pTab->nRef++;
#if !defined(SQLITE_OMIT_VIEW) || !defined (SQLITE_OMIT_VIRTUALTABLE)
if( pTab->pSelect || IsVirtual(pTab) ){
/* We reach here if the named table is a really a view */
if( sqlite3ViewGetColumnNames(pParse, pTab) ) return WRC_Abort;
assert( pFrom->pSelect==0 );
pFrom->pSelect = sqlite3SelectDup(db, pTab->pSelect, 0);
sqlite3WalkSelect(pWalker, pFrom->pSelect);
}
#endif
}
/* Locate the index named by the INDEXED BY clause, if any. */
if( sqlite3IndexedByLookup(pParse, pFrom) ){
return WRC_Abort;
}
}
/* Process NATURAL keywords, and ON and USING clauses of joins.
*/
if( db->mallocFailed || sqliteProcessJoin(pParse, p) ){
return WRC_Abort;
}
/* For every "*" that occurs in the column list, insert the names of
** all columns in all tables. And for every TABLE.* insert the names
** of all columns in TABLE. The parser inserted a special expression
** with the TK_ALL operator for each "*" that it found in the column list.
** The following code just has to locate the TK_ALL expressions and expand
** each one to the list of all columns in all tables.
**
** The first loop just checks to see if there are any "*" operators
** that need expanding.
*/
for(k=0; k<pEList->nExpr; k++){
Expr *pE = pEList->a[k].pExpr;
if( pE->op==TK_ALL ) break;
assert( pE->op!=TK_DOT || pE->pRight!=0 );
assert( pE->op!=TK_DOT || (pE->pLeft!=0 && pE->pLeft->op==TK_ID) );
if( pE->op==TK_DOT && pE->pRight->op==TK_ALL ) break;
}
if( k<pEList->nExpr ){
/*
** If we get here it means the result set contains one or more "*"
** operators that need to be expanded. Loop through each expression
** in the result set and expand them one by one.
*/
struct ExprList_item *a = pEList->a;
ExprList *pNew = 0;
int flags = pParse->db->flags;
int longNames = (flags & SQLITE_FullColNames)!=0
&& (flags & SQLITE_ShortColNames)==0;
for(k=0; k<pEList->nExpr; k++){
Expr *pE = a[k].pExpr;
assert( pE->op!=TK_DOT || pE->pRight!=0 );
if( pE->op!=TK_ALL && (pE->op!=TK_DOT || pE->pRight->op!=TK_ALL) ){
/* This particular expression does not need to be expanded.
*/
pNew = sqlite3ExprListAppend(pParse, pNew, a[k].pExpr);
if( pNew ){
pNew->a[pNew->nExpr-1].zName = a[k].zName;
pNew->a[pNew->nExpr-1].zSpan = a[k].zSpan;
a[k].zName = 0;
a[k].zSpan = 0;
}
a[k].pExpr = 0;
}else{
/* This expression is a "*" or a "TABLE.*" and needs to be
** expanded. */
int tableSeen = 0; /* Set to 1 when TABLE matches */
char *zTName; /* text of name of TABLE */
if( pE->op==TK_DOT ){
assert( pE->pLeft!=0 );
assert( !ExprHasProperty(pE->pLeft, EP_IntValue) );
zTName = pE->pLeft->u.zToken;
}else{
zTName = 0;
}
for(i=0, pFrom=pTabList->a; i<pTabList->nSrc; i++, pFrom++){
Table *pTab = pFrom->pTab;
char *zTabName = pFrom->zAlias;
if( zTabName==0 ){
zTabName = pTab->zName;
}
if( db->mallocFailed ) break;
if( zTName && sqlite3StrICmp(zTName, zTabName)!=0 ){
continue;
}
tableSeen = 1;
for(j=0; j<pTab->nCol; j++){
Expr *pExpr, *pRight;
char *zName = pTab->aCol[j].zName;
char *zColname; /* The computed column name */
char *zToFree; /* Malloced string that needs to be freed */
Token sColname; /* Computed column name as a token */
/* If a column is marked as 'hidden' (currently only possible
** for virtual tables), do not include it in the expanded
** result-set list.
*/
if( IsHiddenColumn(&pTab->aCol[j]) ){
assert(IsVirtual(pTab));
continue;
}
if( i>0 && zTName==0 ){
if( (pFrom->jointype & JT_NATURAL)!=0
&& tableAndColumnIndex(pTabList, i, zName, 0, 0)
){
/* In a NATURAL join, omit the join columns from the
** table to the right of the join */
continue;
}
if( sqlite3IdListIndex(pFrom->pUsing, zName)>=0 ){
/* In a join with a USING clause, omit columns in the
** using clause from the table on the right. */
continue;
}
}
pRight = sqlite3Expr(db, TK_ID, zName);
zColname = zName;
zToFree = 0;
if( longNames || pTabList->nSrc>1 ){
Expr *pLeft;
pLeft = sqlite3Expr(db, TK_ID, zTabName);
pExpr = sqlite3PExpr(pParse, TK_DOT, pLeft, pRight, 0);
if( longNames ){
zColname = sqlite3MPrintf(db, "%s.%s", zTabName, zName);
zToFree = zColname;
}
}else{
pExpr = pRight;
}
pNew = sqlite3ExprListAppend(pParse, pNew, pExpr);
sColname.z = zColname;
sColname.n = sqlite3Strlen30(zColname);
sqlite3ExprListSetName(pParse, pNew, &sColname, 0);
sqlite3DbFree(db, zToFree);
}
}
if( !tableSeen ){
if( zTName ){
sqlite3ErrorMsg(pParse, "no such table: %s", zTName);
}else{
sqlite3ErrorMsg(pParse, "no tables specified");
}
}
}
}
sqlite3ExprListDelete(db, pEList);
p->pEList = pNew;
}
#if SQLITE_MAX_COLUMN
if( p->pEList && p->pEList->nExpr>db->aLimit[SQLITE_LIMIT_COLUMN] ){
sqlite3ErrorMsg(pParse, "too many columns in result set");
}
#endif
return WRC_Continue;
}
/*
** No-op routine for the parse-tree walker.
**
** When this routine is the Walker.xExprCallback then expression trees
** are walked without any actions being taken at each node. Presumably,
** when this routine is used for Walker.xExprCallback then
** Walker.xSelectCallback is set to do something useful for every
** subquery in the parser tree.
*/
static int exprWalkNoop(Walker *NotUsed, Expr *NotUsed2){
UNUSED_PARAMETER2(NotUsed, NotUsed2);
return WRC_Continue;
}
/*
** This routine "expands" a SELECT statement and all of its subqueries.
** For additional information on what it means to "expand" a SELECT
** statement, see the comment on the selectExpand worker callback above.
**
** Expanding a SELECT statement is the first step in processing a
** SELECT statement. The SELECT statement must be expanded before
** name resolution is performed.
**
** If anything goes wrong, an error message is written into pParse.
** The calling function can detect the problem by looking at pParse->nErr
** and/or pParse->db->mallocFailed.
*/
static void sqlite3SelectExpand(Parse *pParse, Select *pSelect){
Walker w;
w.xSelectCallback = selectExpander;
w.xExprCallback = exprWalkNoop;
w.pParse = pParse;
sqlite3WalkSelect(&w, pSelect);
}
#ifndef SQLITE_OMIT_SUBQUERY
/*
** This is a Walker.xSelectCallback callback for the sqlite3SelectTypeInfo()
** interface.
**
** For each FROM-clause subquery, add Column.zType and Column.zColl
** information to the Table structure that represents the result set
** of that subquery.
**
** The Table structure that represents the result set was constructed
** by selectExpander() but the type and collation information was omitted
** at that point because identifiers had not yet been resolved. This
** routine is called after identifier resolution.
*/
static int selectAddSubqueryTypeInfo(Walker *pWalker, Select *p){
Parse *pParse;
int i;
SrcList *pTabList;
struct SrcList_item *pFrom;
assert( p->selFlags & SF_Resolved );
if( (p->selFlags & SF_HasTypeInfo)==0 ){
p->selFlags |= SF_HasTypeInfo;
pParse = pWalker->pParse;
pTabList = p->pSrc;
for(i=0, pFrom=pTabList->a; i<pTabList->nSrc; i++, pFrom++){
Table *pTab = pFrom->pTab;
if( ALWAYS(pTab!=0) && (pTab->tabFlags & TF_Ephemeral)!=0 ){
/* A sub-query in the FROM clause of a SELECT */
Select *pSel = pFrom->pSelect;
assert( pSel );
while( pSel->pPrior ) pSel = pSel->pPrior;
selectAddColumnTypeAndCollation(pParse, pTab->nCol, pTab->aCol, pSel);
}
}
}
return WRC_Continue;
}
#endif
/*
** This routine adds datatype and collating sequence information to
** the Table structures of all FROM-clause subqueries in a
** SELECT statement.
**
** Use this routine after name resolution.
*/
static void sqlite3SelectAddTypeInfo(Parse *pParse, Select *pSelect){
#ifndef SQLITE_OMIT_SUBQUERY
Walker w;
w.xSelectCallback = selectAddSubqueryTypeInfo;
w.xExprCallback = exprWalkNoop;
w.pParse = pParse;
sqlite3WalkSelect(&w, pSelect);
#endif
}
/*
** This routine sets of a SELECT statement for processing. The
** following is accomplished:
**
** * VDBE Cursor numbers are assigned to all FROM-clause terms.
** * Ephemeral Table objects are created for all FROM-clause subqueries.
** * ON and USING clauses are shifted into WHERE statements
** * Wildcards "*" and "TABLE.*" in result sets are expanded.
** * Identifiers in expression are matched to tables.
**
** This routine acts recursively on all subqueries within the SELECT.
*/
void sqlite3SelectPrep(
Parse *pParse, /* The parser context */
Select *p, /* The SELECT statement being coded. */
NameContext *pOuterNC /* Name context for container */
){
sqlite3 *db;
if( NEVER(p==0) ) return;
db = pParse->db;
if( p->selFlags & SF_HasTypeInfo ) return;
sqlite3SelectExpand(pParse, p);
if( pParse->nErr || db->mallocFailed ) return;
sqlite3ResolveSelectNames(pParse, p, pOuterNC);
if( pParse->nErr || db->mallocFailed ) return;
sqlite3SelectAddTypeInfo(pParse, p);
}
/*
** Reset the aggregate accumulator.
**
** The aggregate accumulator is a set of memory cells that hold
** intermediate results while calculating an aggregate. This
** routine simply stores NULLs in all of those memory cells.
*/
static void resetAccumulator(Parse *pParse, AggInfo *pAggInfo){
Vdbe *v = pParse->pVdbe;
int i;
struct AggInfo_func *pFunc;
if( pAggInfo->nFunc+pAggInfo->nColumn==0 ){
return;
}
for(i=0; i<pAggInfo->nColumn; i++){
sqlite3VdbeAddOp2(v, OP_Null, 0, pAggInfo->aCol[i].iMem);
}
for(pFunc=pAggInfo->aFunc, i=0; i<pAggInfo->nFunc; i++, pFunc++){
sqlite3VdbeAddOp2(v, OP_Null, 0, pFunc->iMem);
if( pFunc->iDistinct>=0 ){
Expr *pE = pFunc->pExpr;
assert( !ExprHasProperty(pE, EP_xIsSelect) );
if( pE->x.pList==0 || pE->x.pList->nExpr!=1 ){
sqlite3ErrorMsg(pParse, "DISTINCT aggregates must have exactly one "
"argument");
pFunc->iDistinct = -1;
}else{
KeyInfo *pKeyInfo = keyInfoFromExprList(pParse, pE->x.pList);
sqlite3VdbeAddOp4(v, OP_OpenEphemeral, pFunc->iDistinct, 0, 0,
(char*)pKeyInfo, P4_KEYINFO_HANDOFF);
}
}
}
}
/*
** Invoke the OP_AggFinalize opcode for every aggregate function
** in the AggInfo structure.
*/
static void finalizeAggFunctions(Parse *pParse, AggInfo *pAggInfo){
Vdbe *v = pParse->pVdbe;
int i;
struct AggInfo_func *pF;
for(i=0, pF=pAggInfo->aFunc; i<pAggInfo->nFunc; i++, pF++){
ExprList *pList = pF->pExpr->x.pList;
assert( !ExprHasProperty(pF->pExpr, EP_xIsSelect) );
sqlite3VdbeAddOp4(v, OP_AggFinal, pF->iMem, pList ? pList->nExpr : 0, 0,
(void*)pF->pFunc, P4_FUNCDEF);
}
}
/*
** Update the accumulator memory cells for an aggregate based on
** the current cursor position.
*/
static void updateAccumulator(Parse *pParse, AggInfo *pAggInfo){
Vdbe *v = pParse->pVdbe;
int i;
struct AggInfo_func *pF;
struct AggInfo_col *pC;
pAggInfo->directMode = 1;
sqlite3ExprCacheClear(pParse);
for(i=0, pF=pAggInfo->aFunc; i<pAggInfo->nFunc; i++, pF++){
int nArg;
int addrNext = 0;
int regAgg;
ExprList *pList = pF->pExpr->x.pList;
assert( !ExprHasProperty(pF->pExpr, EP_xIsSelect) );
if( pList ){
nArg = pList->nExpr;
regAgg = sqlite3GetTempRange(pParse, nArg);
sqlite3ExprCodeExprList(pParse, pList, regAgg, 0);
}else{
nArg = 0;
regAgg = 0;
}
if( pF->iDistinct>=0 ){
addrNext = sqlite3VdbeMakeLabel(v);
assert( nArg==1 );
codeDistinct(pParse, pF->iDistinct, addrNext, 1, regAgg);
}
if( pF->pFunc->flags & SQLITE_FUNC_NEEDCOLL ){
CollSeq *pColl = 0;
struct ExprList_item *pItem;
int j;
assert( pList!=0 ); /* pList!=0 if pF->pFunc has NEEDCOLL */
for(j=0, pItem=pList->a; !pColl && j<nArg; j++, pItem++){
pColl = sqlite3ExprCollSeq(pParse, pItem->pExpr);
}
if( !pColl ){
pColl = pParse->db->pDfltColl;
}
sqlite3VdbeAddOp4(v, OP_CollSeq, 0, 0, 0, (char *)pColl, P4_COLLSEQ);
}
sqlite3VdbeAddOp4(v, OP_AggStep, 0, regAgg, pF->iMem,
(void*)pF->pFunc, P4_FUNCDEF);
sqlite3VdbeChangeP5(v, (u8)nArg);
sqlite3ExprCacheAffinityChange(pParse, regAgg, nArg);
sqlite3ReleaseTempRange(pParse, regAgg, nArg);
if( addrNext ){
sqlite3VdbeResolveLabel(v, addrNext);
sqlite3ExprCacheClear(pParse);
}
}
/* Before populating the accumulator registers, clear the column cache.
** Otherwise, if any of the required column values are already present
** in registers, sqlite3ExprCode() may use OP_SCopy to copy the value
** to pC->iMem. But by the time the value is used, the original register
** may have been used, invalidating the underlying buffer holding the
** text or blob value. See ticket [883034dcb5].
**
** Another solution would be to change the OP_SCopy used to copy cached
** values to an OP_Copy.
*/
sqlite3ExprCacheClear(pParse);
for(i=0, pC=pAggInfo->aCol; i<pAggInfo->nAccumulator; i++, pC++){
sqlite3ExprCode(pParse, pC->pExpr, pC->iMem);
}
pAggInfo->directMode = 0;
sqlite3ExprCacheClear(pParse);
}
/*
** Generate code for the SELECT statement given in the p argument.
**
** The results are distributed in various ways depending on the
** contents of the SelectDest structure pointed to by argument pDest
** as follows:
**
** pDest->eDest Result
** ------------ -------------------------------------------
** SRT_Output Generate a row of output (using the OP_ResultRow
** opcode) for each row in the result set.
**
** SRT_Mem Only valid if the result is a single column.
** Store the first column of the first result row
** in register pDest->iParm then abandon the rest
** of the query. This destination implies "LIMIT 1".
**
** SRT_Set The result must be a single column. Store each
** row of result as the key in table pDest->iParm.
** Apply the affinity pDest->affinity before storing
** results. Used to implement "IN (SELECT ...)".
**
** SRT_Union Store results as a key in a temporary table pDest->iParm.
**
** SRT_Except Remove results from the temporary table pDest->iParm.
**
** SRT_Table Store results in temporary table pDest->iParm.
** This is like SRT_EphemTab except that the table
** is assumed to already be open.
**
** SRT_EphemTab Create an temporary table pDest->iParm and store
** the result there. The cursor is left open after
** returning. This is like SRT_Table except that
** this destination uses OP_OpenEphemeral to create
** the table first.
**
** SRT_Coroutine Generate a co-routine that returns a new row of
** results each time it is invoked. The entry point
** of the co-routine is stored in register pDest->iParm.
**
** SRT_Exists Store a 1 in memory cell pDest->iParm if the result
** set is not empty.
**
** SRT_Discard Throw the results away. This is used by SELECT
** statements within triggers whose only purpose is
** the side-effects of functions.
**
** This routine returns the number of errors. If any errors are
** encountered, then an appropriate error message is left in
** pParse->zErrMsg.
**
** This routine does NOT free the Select structure passed in. The
** calling function needs to do that.
*/
int sqlite3Select(
Parse *pParse, /* The parser context */
Select *p, /* The SELECT statement being coded. */
SelectDest *pDest /* What to do with the query results */
){
int i, j; /* Loop counters */
WhereInfo *pWInfo; /* Return from sqlite3WhereBegin() */
Vdbe *v; /* The virtual machine under construction */
int isAgg; /* True for select lists like "count(*)" */
ExprList *pEList; /* List of columns to extract. */
SrcList *pTabList; /* List of tables to select from */
Expr *pWhere; /* The WHERE clause. May be NULL */
ExprList *pOrderBy; /* The ORDER BY clause. May be NULL */
ExprList *pGroupBy; /* The GROUP BY clause. May be NULL */
Expr *pHaving; /* The HAVING clause. May be NULL */
int isDistinct; /* True if the DISTINCT keyword is present */
int distinct; /* Table to use for the distinct set */
int rc = 1; /* Value to return from this function */
int addrSortIndex; /* Address of an OP_OpenEphemeral instruction */
AggInfo sAggInfo; /* Information used by aggregate queries */
int iEnd; /* Address of the end of the query */
sqlite3 *db; /* The database connection */
db = pParse->db;
if( p==0 || db->mallocFailed || pParse->nErr ){
return 1;
}
if( sqlite3AuthCheck(pParse, SQLITE_SELECT, 0, 0, 0) ) return 1;
memset(&sAggInfo, 0, sizeof(sAggInfo));
if( IgnorableOrderby(pDest) ){
assert(pDest->eDest==SRT_Exists || pDest->eDest==SRT_Union ||
pDest->eDest==SRT_Except || pDest->eDest==SRT_Discard);
/* If ORDER BY makes no difference in the output then neither does
** DISTINCT so it can be removed too. */
sqlite3ExprListDelete(db, p->pOrderBy);
p->pOrderBy = 0;
p->selFlags &= ~SF_Distinct;
}
sqlite3SelectPrep(pParse, p, 0);
pOrderBy = p->pOrderBy;
pTabList = p->pSrc;
pEList = p->pEList;
if( pParse->nErr || db->mallocFailed ){
goto select_end;
}
isAgg = (p->selFlags & SF_Aggregate)!=0;
assert( pEList!=0 );
/* Begin generating code.
*/
v = sqlite3GetVdbe(pParse);
if( v==0 ) goto select_end;
/* Generate code for all sub-queries in the FROM clause
*/
#if !defined(SQLITE_OMIT_SUBQUERY) || !defined(SQLITE_OMIT_VIEW)
for(i=0; !p->pPrior && i<pTabList->nSrc; i++){
struct SrcList_item *pItem = &pTabList->a[i];
SelectDest dest;
Select *pSub = pItem->pSelect;
int isAggSub;
if( pSub==0 || pItem->isPopulated ) continue;
/* Increment Parse.nHeight by the height of the largest expression
** tree refered to by this, the parent select. The child select
** may contain expression trees of at most
** (SQLITE_MAX_EXPR_DEPTH-Parse.nHeight) height. This is a bit
** more conservative than necessary, but much easier than enforcing
** an exact limit.
*/
pParse->nHeight += sqlite3SelectExprHeight(p);
/* Check to see if the subquery can be absorbed into the parent. */
isAggSub = (pSub->selFlags & SF_Aggregate)!=0;
if( flattenSubquery(pParse, p, i, isAgg, isAggSub) ){
if( isAggSub ){
isAgg = 1;
p->selFlags |= SF_Aggregate;
}
i = -1;
}else{
sqlite3SelectDestInit(&dest, SRT_EphemTab, pItem->iCursor);
assert( pItem->isPopulated==0 );
sqlite3Select(pParse, pSub, &dest);
pItem->isPopulated = 1;
}
if( /*pParse->nErr ||*/ db->mallocFailed ){
goto select_end;
}
pParse->nHeight -= sqlite3SelectExprHeight(p);
pTabList = p->pSrc;
if( !IgnorableOrderby(pDest) ){
pOrderBy = p->pOrderBy;
}
}
pEList = p->pEList;
#endif
pWhere = p->pWhere;
pGroupBy = p->pGroupBy;
pHaving = p->pHaving;
isDistinct = (p->selFlags & SF_Distinct)!=0;
#ifndef SQLITE_OMIT_COMPOUND_SELECT
/* If there is are a sequence of queries, do the earlier ones first.
*/
if( p->pPrior ){
if( p->pRightmost==0 ){
Select *pLoop, *pRight = 0;
int cnt = 0;
int mxSelect;
for(pLoop=p; pLoop; pLoop=pLoop->pPrior, cnt++){
pLoop->pRightmost = p;
pLoop->pNext = pRight;
pRight = pLoop;
}
mxSelect = db->aLimit[SQLITE_LIMIT_COMPOUND_SELECT];
if( mxSelect && cnt>mxSelect ){
sqlite3ErrorMsg(pParse, "too many terms in compound SELECT");
return 1;
}
}
return multiSelect(pParse, p, pDest);
}
#endif
/* If writing to memory or generating a set
** only a single column may be output.
*/
#ifndef SQLITE_OMIT_SUBQUERY
if( checkForMultiColumnSelectError(pParse, pDest, pEList->nExpr) ){
goto select_end;
}
#endif
/* If possible, rewrite the query to use GROUP BY instead of DISTINCT.
** GROUP BY might use an index, DISTINCT never does.
*/
assert( p->pGroupBy==0 || (p->selFlags & SF_Aggregate)!=0 );
if( (p->selFlags & (SF_Distinct|SF_Aggregate))==SF_Distinct ){
p->pGroupBy = sqlite3ExprListDup(db, p->pEList, 0);
pGroupBy = p->pGroupBy;
p->selFlags &= ~SF_Distinct;
isDistinct = 0;
}
/* If there is both a GROUP BY and an ORDER BY clause and they are
** identical, then disable the ORDER BY clause since the GROUP BY
** will cause elements to come out in the correct order. This is
** an optimization - the correct answer should result regardless.
** Use the SQLITE_GroupByOrder flag with SQLITE_TESTCTRL_OPTIMIZER
** to disable this optimization for testing purposes.
*/
if( sqlite3ExprListCompare(p->pGroupBy, pOrderBy)==0
&& (db->flags & SQLITE_GroupByOrder)==0 ){
pOrderBy = 0;
}
/* If there is an ORDER BY clause, then this sorting
** index might end up being unused if the data can be
** extracted in pre-sorted order. If that is the case, then the
** OP_OpenEphemeral instruction will be changed to an OP_Noop once
** we figure out that the sorting index is not needed. The addrSortIndex
** variable is used to facilitate that change.
*/
if( pOrderBy ){
KeyInfo *pKeyInfo;
pKeyInfo = keyInfoFromExprList(pParse, pOrderBy);
pOrderBy->iECursor = pParse->nTab++;
p->addrOpenEphm[2] = addrSortIndex =
sqlite3VdbeAddOp4(v, OP_OpenEphemeral,
pOrderBy->iECursor, pOrderBy->nExpr+2, 0,
(char*)pKeyInfo, P4_KEYINFO_HANDOFF);
}else{
addrSortIndex = -1;
}
/* If the output is destined for a temporary table, open that table.
*/
if( pDest->eDest==SRT_EphemTab ){
sqlite3VdbeAddOp2(v, OP_OpenEphemeral, pDest->iParm, pEList->nExpr);
}
/* Set the limiter.
*/
iEnd = sqlite3VdbeMakeLabel(v);
computeLimitRegisters(pParse, p, iEnd);
/* Open a virtual index to use for the distinct set.
*/
if( isDistinct ){
KeyInfo *pKeyInfo;
assert( isAgg || pGroupBy );
distinct = pParse->nTab++;
pKeyInfo = keyInfoFromExprList(pParse, p->pEList);
sqlite3VdbeAddOp4(v, OP_OpenEphemeral, distinct, 0, 0,
(char*)pKeyInfo, P4_KEYINFO_HANDOFF);
}else{
distinct = -1;
}
/* Aggregate and non-aggregate queries are handled differently */
if( !isAgg && pGroupBy==0 ){
/* This case is for non-aggregate queries
** Begin the database scan
*/
pWInfo = sqlite3WhereBegin(pParse, pTabList, pWhere, &pOrderBy, 0);
if( pWInfo==0 ) goto select_end;
/* If sorting index that was created by a prior OP_OpenEphemeral
** instruction ended up not being needed, then change the OP_OpenEphemeral
** into an OP_Noop.
*/
if( addrSortIndex>=0 && pOrderBy==0 ){
sqlite3VdbeChangeToNoop(v, addrSortIndex, 1);
p->addrOpenEphm[2] = -1;
}
/* Use the standard inner loop
*/
assert(!isDistinct);
selectInnerLoop(pParse, p, pEList, 0, 0, pOrderBy, -1, pDest,
pWInfo->iContinue, pWInfo->iBreak);
/* End the database scan loop.
*/
sqlite3WhereEnd(pWInfo);
}else{
/* This is the processing for aggregate queries */
NameContext sNC; /* Name context for processing aggregate information */
int iAMem; /* First Mem address for storing current GROUP BY */
int iBMem; /* First Mem address for previous GROUP BY */
int iUseFlag; /* Mem address holding flag indicating that at least
** one row of the input to the aggregator has been
** processed */
int iAbortFlag; /* Mem address which causes query abort if positive */
int groupBySort; /* Rows come from source in GROUP BY order */
int addrEnd; /* End of processing for this SELECT */
/* Remove any and all aliases between the result set and the
** GROUP BY clause.
*/
if( pGroupBy ){
int k; /* Loop counter */
struct ExprList_item *pItem; /* For looping over expression in a list */
for(k=p->pEList->nExpr, pItem=p->pEList->a; k>0; k--, pItem++){
pItem->iAlias = 0;
}
for(k=pGroupBy->nExpr, pItem=pGroupBy->a; k>0; k--, pItem++){
pItem->iAlias = 0;
}
}
/* Create a label to jump to when we want to abort the query */
addrEnd = sqlite3VdbeMakeLabel(v);
/* Convert TK_COLUMN nodes into TK_AGG_COLUMN and make entries in
** sAggInfo for all TK_AGG_FUNCTION nodes in expressions of the
** SELECT statement.
*/
memset(&sNC, 0, sizeof(sNC));
sNC.pParse = pParse;
sNC.pSrcList = pTabList;
sNC.pAggInfo = &sAggInfo;
sAggInfo.nSortingColumn = pGroupBy ? pGroupBy->nExpr+1 : 0;
sAggInfo.pGroupBy = pGroupBy;
sqlite3ExprAnalyzeAggList(&sNC, pEList);
sqlite3ExprAnalyzeAggList(&sNC, pOrderBy);
if( pHaving ){
sqlite3ExprAnalyzeAggregates(&sNC, pHaving);
}
sAggInfo.nAccumulator = sAggInfo.nColumn;
for(i=0; i<sAggInfo.nFunc; i++){
assert( !ExprHasProperty(sAggInfo.aFunc[i].pExpr, EP_xIsSelect) );
sqlite3ExprAnalyzeAggList(&sNC, sAggInfo.aFunc[i].pExpr->x.pList);
}
if( db->mallocFailed ) goto select_end;
/* Processing for aggregates with GROUP BY is very different and
** much more complex than aggregates without a GROUP BY.
*/
if( pGroupBy ){
KeyInfo *pKeyInfo; /* Keying information for the group by clause */
int j1; /* A-vs-B comparision jump */
int addrOutputRow; /* Start of subroutine that outputs a result row */
int regOutputRow; /* Return address register for output subroutine */
int addrSetAbort; /* Set the abort flag and return */
int addrTopOfLoop; /* Top of the input loop */
int addrSortingIdx; /* The OP_OpenEphemeral for the sorting index */
int addrReset; /* Subroutine for resetting the accumulator */
int regReset; /* Return address register for reset subroutine */
/* If there is a GROUP BY clause we might need a sorting index to
** implement it. Allocate that sorting index now. If it turns out
** that we do not need it after all, the OpenEphemeral instruction
** will be converted into a Noop.
*/
sAggInfo.sortingIdx = pParse->nTab++;
pKeyInfo = keyInfoFromExprList(pParse, pGroupBy);
addrSortingIdx = sqlite3VdbeAddOp4(v, OP_OpenEphemeral,
sAggInfo.sortingIdx, sAggInfo.nSortingColumn,
0, (char*)pKeyInfo, P4_KEYINFO_HANDOFF);
/* Initialize memory locations used by GROUP BY aggregate processing
*/
iUseFlag = ++pParse->nMem;
iAbortFlag = ++pParse->nMem;
regOutputRow = ++pParse->nMem;
addrOutputRow = sqlite3VdbeMakeLabel(v);
regReset = ++pParse->nMem;
addrReset = sqlite3VdbeMakeLabel(v);
iAMem = pParse->nMem + 1;
pParse->nMem += pGroupBy->nExpr;
iBMem = pParse->nMem + 1;
pParse->nMem += pGroupBy->nExpr;
sqlite3VdbeAddOp2(v, OP_Integer, 0, iAbortFlag);
VdbeComment((v, "clear abort flag"));
sqlite3VdbeAddOp2(v, OP_Integer, 0, iUseFlag);
VdbeComment((v, "indicate accumulator empty"));
/* Begin a loop that will extract all source rows in GROUP BY order.
** This might involve two separate loops with an OP_Sort in between, or
** it might be a single loop that uses an index to extract information
** in the right order to begin with.
*/
sqlite3VdbeAddOp2(v, OP_Gosub, regReset, addrReset);
pWInfo = sqlite3WhereBegin(pParse, pTabList, pWhere, &pGroupBy, 0);
if( pWInfo==0 ) goto select_end;
if( pGroupBy==0 ){
/* The optimizer is able to deliver rows in group by order so
** we do not have to sort. The OP_OpenEphemeral table will be
** cancelled later because we still need to use the pKeyInfo
*/
pGroupBy = p->pGroupBy;
groupBySort = 0;
}else{
/* Rows are coming out in undetermined order. We have to push
** each row into a sorting index, terminate the first loop,
** then loop over the sorting index in order to get the output
** in sorted order
*/
int regBase;
int regRecord;
int nCol;
int nGroupBy;
groupBySort = 1;
nGroupBy = pGroupBy->nExpr;
nCol = nGroupBy + 1;
j = nGroupBy+1;
for(i=0; i<sAggInfo.nColumn; i++){
if( sAggInfo.aCol[i].iSorterColumn>=j ){
nCol++;
j++;
}
}
regBase = sqlite3GetTempRange(pParse, nCol);
sqlite3ExprCacheClear(pParse);
sqlite3ExprCodeExprList(pParse, pGroupBy, regBase, 0);
sqlite3VdbeAddOp2(v, OP_Sequence, sAggInfo.sortingIdx,regBase+nGroupBy);
j = nGroupBy+1;
for(i=0; i<sAggInfo.nColumn; i++){
struct AggInfo_col *pCol = &sAggInfo.aCol[i];
if( pCol->iSorterColumn>=j ){
int r1 = j + regBase;
int r2;
r2 = sqlite3ExprCodeGetColumn(pParse,
pCol->pTab, pCol->iColumn, pCol->iTable, r1);
if( r1!=r2 ){
sqlite3VdbeAddOp2(v, OP_SCopy, r2, r1);
}
j++;
}
}
regRecord = sqlite3GetTempReg(pParse);
sqlite3VdbeAddOp3(v, OP_MakeRecord, regBase, nCol, regRecord);
sqlite3VdbeAddOp2(v, OP_IdxInsert, sAggInfo.sortingIdx, regRecord);
sqlite3ReleaseTempReg(pParse, regRecord);
sqlite3ReleaseTempRange(pParse, regBase, nCol);
sqlite3WhereEnd(pWInfo);
sqlite3VdbeAddOp2(v, OP_Sort, sAggInfo.sortingIdx, addrEnd);
VdbeComment((v, "GROUP BY sort"));
sAggInfo.useSortingIdx = 1;
sqlite3ExprCacheClear(pParse);
}
/* Evaluate the current GROUP BY terms and store in b0, b1, b2...
** (b0 is memory location iBMem+0, b1 is iBMem+1, and so forth)
** Then compare the current GROUP BY terms against the GROUP BY terms
** from the previous row currently stored in a0, a1, a2...
*/
addrTopOfLoop = sqlite3VdbeCurrentAddr(v);
sqlite3ExprCacheClear(pParse);
for(j=0; j<pGroupBy->nExpr; j++){
if( groupBySort ){
sqlite3VdbeAddOp3(v, OP_Column, sAggInfo.sortingIdx, j, iBMem+j);
}else{
sAggInfo.directMode = 1;
sqlite3ExprCode(pParse, pGroupBy->a[j].pExpr, iBMem+j);
}
}
sqlite3VdbeAddOp4(v, OP_Compare, iAMem, iBMem, pGroupBy->nExpr,
(char*)pKeyInfo, P4_KEYINFO);
j1 = sqlite3VdbeCurrentAddr(v);
sqlite3VdbeAddOp3(v, OP_Jump, j1+1, 0, j1+1);
/* Generate code that runs whenever the GROUP BY changes.
** Changes in the GROUP BY are detected by the previous code
** block. If there were no changes, this block is skipped.
**
** This code copies current group by terms in b0,b1,b2,...
** over to a0,a1,a2. It then calls the output subroutine
** and resets the aggregate accumulator registers in preparation
** for the next GROUP BY batch.
*/
sqlite3ExprCodeMove(pParse, iBMem, iAMem, pGroupBy->nExpr);
sqlite3VdbeAddOp2(v, OP_Gosub, regOutputRow, addrOutputRow);
VdbeComment((v, "output one row"));
sqlite3VdbeAddOp2(v, OP_IfPos, iAbortFlag, addrEnd);
VdbeComment((v, "check abort flag"));
sqlite3VdbeAddOp2(v, OP_Gosub, regReset, addrReset);
VdbeComment((v, "reset accumulator"));
/* Update the aggregate accumulators based on the content of
** the current row
*/
sqlite3VdbeJumpHere(v, j1);
updateAccumulator(pParse, &sAggInfo);
sqlite3VdbeAddOp2(v, OP_Integer, 1, iUseFlag);
VdbeComment((v, "indicate data in accumulator"));
/* End of the loop
*/
if( groupBySort ){
sqlite3VdbeAddOp2(v, OP_Next, sAggInfo.sortingIdx, addrTopOfLoop);
}else{
sqlite3WhereEnd(pWInfo);
sqlite3VdbeChangeToNoop(v, addrSortingIdx, 1);
}
/* Output the final row of result
*/
sqlite3VdbeAddOp2(v, OP_Gosub, regOutputRow, addrOutputRow);
VdbeComment((v, "output final row"));
/* Jump over the subroutines
*/
sqlite3VdbeAddOp2(v, OP_Goto, 0, addrEnd);
/* Generate a subroutine that outputs a single row of the result
** set. This subroutine first looks at the iUseFlag. If iUseFlag
** is less than or equal to zero, the subroutine is a no-op. If
** the processing calls for the query to abort, this subroutine
** increments the iAbortFlag memory location before returning in
** order to signal the caller to abort.
*/
addrSetAbort = sqlite3VdbeCurrentAddr(v);
sqlite3VdbeAddOp2(v, OP_Integer, 1, iAbortFlag);
VdbeComment((v, "set abort flag"));
sqlite3VdbeAddOp1(v, OP_Return, regOutputRow);
sqlite3VdbeResolveLabel(v, addrOutputRow);
addrOutputRow = sqlite3VdbeCurrentAddr(v);
sqlite3VdbeAddOp2(v, OP_IfPos, iUseFlag, addrOutputRow+2);
VdbeComment((v, "Groupby result generator entry point"));
sqlite3VdbeAddOp1(v, OP_Return, regOutputRow);
finalizeAggFunctions(pParse, &sAggInfo);
sqlite3ExprIfFalse(pParse, pHaving, addrOutputRow+1, SQLITE_JUMPIFNULL);
selectInnerLoop(pParse, p, p->pEList, 0, 0, pOrderBy,
distinct, pDest,
addrOutputRow+1, addrSetAbort);
sqlite3VdbeAddOp1(v, OP_Return, regOutputRow);
VdbeComment((v, "end groupby result generator"));
/* Generate a subroutine that will reset the group-by accumulator
*/
sqlite3VdbeResolveLabel(v, addrReset);
resetAccumulator(pParse, &sAggInfo);
sqlite3VdbeAddOp1(v, OP_Return, regReset);
} /* endif pGroupBy. Begin aggregate queries without GROUP BY: */
else {
ExprList *pDel = 0;
#ifndef SQLITE_OMIT_BTREECOUNT
Table *pTab;
if( (pTab = isSimpleCount(p, &sAggInfo))!=0 ){
/* If isSimpleCount() returns a pointer to a Table structure, then
** the SQL statement is of the form:
**
** SELECT count(*) FROM <tbl>
**
** where the Table structure returned represents table <tbl>.
**
** This statement is so common that it is optimized specially. The
** OP_Count instruction is executed either on the intkey table that
** contains the data for table <tbl> or on one of its indexes. It
** is better to execute the op on an index, as indexes are almost
** always spread across less pages than their corresponding tables.
*/
const int iDb = sqlite3SchemaToIndex(pParse->db, pTab->pSchema);
const int iCsr = pParse->nTab++; /* Cursor to scan b-tree */
Index *pIdx; /* Iterator variable */
KeyInfo *pKeyInfo = 0; /* Keyinfo for scanned index */
Index *pBest = 0; /* Best index found so far */
int iRoot = pTab->tnum; /* Root page of scanned b-tree */
sqlite3CodeVerifySchema(pParse, iDb);
sqlite3TableLock(pParse, iDb, pTab->tnum, 0, pTab->zName);
/* Search for the index that has the least amount of columns. If
** there is such an index, and it has less columns than the table
** does, then we can assume that it consumes less space on disk and
** will therefore be cheaper to scan to determine the query result.
** In this case set iRoot to the root page number of the index b-tree
** and pKeyInfo to the KeyInfo structure required to navigate the
** index.
**
** In practice the KeyInfo structure will not be used. It is only
** passed to keep OP_OpenRead happy.
*/
for(pIdx=pTab->pIndex; pIdx; pIdx=pIdx->pNext){
if( !pBest || pIdx->nColumn<pBest->nColumn ){
pBest = pIdx;
}
}
if( pBest && pBest->nColumn<pTab->nCol ){
iRoot = pBest->tnum;
pKeyInfo = sqlite3IndexKeyinfo(pParse, pBest);
}
/* Open a read-only cursor, execute the OP_Count, close the cursor. */
sqlite3VdbeAddOp3(v, OP_OpenRead, iCsr, iRoot, iDb);
if( pKeyInfo ){
sqlite3VdbeChangeP4(v, -1, (char *)pKeyInfo, P4_KEYINFO_HANDOFF);
}
sqlite3VdbeAddOp2(v, OP_Count, iCsr, sAggInfo.aFunc[0].iMem);
sqlite3VdbeAddOp1(v, OP_Close, iCsr);
}else
#endif /* SQLITE_OMIT_BTREECOUNT */
{
/* Check if the query is of one of the following forms:
**
** SELECT min(x) FROM ...
** SELECT max(x) FROM ...
**
** If it is, then ask the code in where.c to attempt to sort results
** as if there was an "ORDER ON x" or "ORDER ON x DESC" clause.
** If where.c is able to produce results sorted in this order, then
** add vdbe code to break out of the processing loop after the
** first iteration (since the first iteration of the loop is
** guaranteed to operate on the row with the minimum or maximum
** value of x, the only row required).
**
** A special flag must be passed to sqlite3WhereBegin() to slightly
** modify behaviour as follows:
**
** + If the query is a "SELECT min(x)", then the loop coded by
** where.c should not iterate over any values with a NULL value
** for x.
**
** + The optimizer code in where.c (the thing that decides which
** index or indices to use) should place a different priority on
** satisfying the 'ORDER BY' clause than it does in other cases.
** Refer to code and comments in where.c for details.
*/
ExprList *pMinMax = 0;
u8 flag = minMaxQuery(p);
if( flag ){
assert( !ExprHasProperty(p->pEList->a[0].pExpr, EP_xIsSelect) );
pMinMax = sqlite3ExprListDup(db, p->pEList->a[0].pExpr->x.pList,0);
pDel = pMinMax;
if( pMinMax && !db->mallocFailed ){
pMinMax->a[0].sortOrder = flag!=WHERE_ORDERBY_MIN ?1:0;
pMinMax->a[0].pExpr->op = TK_COLUMN;
}
}
/* This case runs if the aggregate has no GROUP BY clause. The
** processing is much simpler since there is only a single row
** of output.
*/
resetAccumulator(pParse, &sAggInfo);
pWInfo = sqlite3WhereBegin(pParse, pTabList, pWhere, &pMinMax, flag);
if( pWInfo==0 ){
sqlite3ExprListDelete(db, pDel);
goto select_end;
}
updateAccumulator(pParse, &sAggInfo);
if( !pMinMax && flag ){
sqlite3VdbeAddOp2(v, OP_Goto, 0, pWInfo->iBreak);
VdbeComment((v, "%s() by index",
(flag==WHERE_ORDERBY_MIN?"min":"max")));
}
sqlite3WhereEnd(pWInfo);
finalizeAggFunctions(pParse, &sAggInfo);
}
pOrderBy = 0;
sqlite3ExprIfFalse(pParse, pHaving, addrEnd, SQLITE_JUMPIFNULL);
selectInnerLoop(pParse, p, p->pEList, 0, 0, 0, -1,
pDest, addrEnd, addrEnd);
sqlite3ExprListDelete(db, pDel);
}
sqlite3VdbeResolveLabel(v, addrEnd);
} /* endif aggregate query */
/* If there is an ORDER BY clause, then we need to sort the results
** and send them to the callback one by one.
*/
if( pOrderBy ){
generateSortTail(pParse, p, v, pEList->nExpr, pDest);
}
/* Jump here to skip this query
*/
sqlite3VdbeResolveLabel(v, iEnd);
/* The SELECT was successfully coded. Set the return code to 0
** to indicate no errors.
*/
rc = 0;
/* Control jumps to here if an error is encountered above, or upon
** successful coding of the SELECT.
*/
select_end:
/* Identify column names if results of the SELECT are to be output.
*/
if( rc==SQLITE_OK && pDest->eDest==SRT_Output ){
generateColumnNames(pParse, pTabList, pEList);
}
sqlite3DbFree(db, sAggInfo.aCol);
sqlite3DbFree(db, sAggInfo.aFunc);
return rc;
}
#if defined(SQLITE_DEBUG)
/*
*******************************************************************************
** The following code is used for testing and debugging only. The code
** that follows does not appear in normal builds.
**
** These routines are used to print out the content of all or part of a
** parse structures such as Select or Expr. Such printouts are useful
** for helping to understand what is happening inside the code generator
** during the execution of complex SELECT statements.
**
** These routine are not called anywhere from within the normal
** code base. Then are intended to be called from within the debugger
** or from temporary "printf" statements inserted for debugging.
*/
void sqlite3PrintExpr(Expr *p){
if( !ExprHasProperty(p, EP_IntValue) && p->u.zToken ){
sqlite3DebugPrintf("(%s", p->u.zToken);
}else{
sqlite3DebugPrintf("(%d", p->op);
}
if( p->pLeft ){
sqlite3DebugPrintf(" ");
sqlite3PrintExpr(p->pLeft);
}
if( p->pRight ){
sqlite3DebugPrintf(" ");
sqlite3PrintExpr(p->pRight);
}
sqlite3DebugPrintf(")");
}
void sqlite3PrintExprList(ExprList *pList){
int i;
for(i=0; i<pList->nExpr; i++){
sqlite3PrintExpr(pList->a[i].pExpr);
if( i<pList->nExpr-1 ){
sqlite3DebugPrintf(", ");
}
}
}
void sqlite3PrintSelect(Select *p, int indent){
sqlite3DebugPrintf("%*sSELECT(%p) ", indent, "", p);
sqlite3PrintExprList(p->pEList);
sqlite3DebugPrintf("\n");
if( p->pSrc ){
char *zPrefix;
int i;
zPrefix = "FROM";
for(i=0; i<p->pSrc->nSrc; i++){
struct SrcList_item *pItem = &p->pSrc->a[i];
sqlite3DebugPrintf("%*s ", indent+6, zPrefix);
zPrefix = "";
if( pItem->pSelect ){
sqlite3DebugPrintf("(\n");
sqlite3PrintSelect(pItem->pSelect, indent+10);
sqlite3DebugPrintf("%*s)", indent+8, "");
}else if( pItem->zName ){
sqlite3DebugPrintf("%s", pItem->zName);
}
if( pItem->pTab ){
sqlite3DebugPrintf("(table: %s)", pItem->pTab->zName);
}
if( pItem->zAlias ){
sqlite3DebugPrintf(" AS %s", pItem->zAlias);
}
if( i<p->pSrc->nSrc-1 ){
sqlite3DebugPrintf(",");
}
sqlite3DebugPrintf("\n");
}
}
if( p->pWhere ){
sqlite3DebugPrintf("%*s WHERE ", indent, "");
sqlite3PrintExpr(p->pWhere);
sqlite3DebugPrintf("\n");
}
if( p->pGroupBy ){
sqlite3DebugPrintf("%*s GROUP BY ", indent, "");
sqlite3PrintExprList(p->pGroupBy);
sqlite3DebugPrintf("\n");
}
if( p->pHaving ){
sqlite3DebugPrintf("%*s HAVING ", indent, "");
sqlite3PrintExpr(p->pHaving);
sqlite3DebugPrintf("\n");
}
if( p->pOrderBy ){
sqlite3DebugPrintf("%*s ORDER BY ", indent, "");
sqlite3PrintExprList(p->pOrderBy);
sqlite3DebugPrintf("\n");
}
}
/* End of the structure debug printing code
*****************************************************************************/
#endif /* defined(SQLITE_TEST) || defined(SQLITE_DEBUG) */
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