nimbus-eth1/nimbus/db/kvt/kvt_tx.nim

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Nim

# nimbus-eth1
# Copyright (c) 2023-2024 Status Research & Development GmbH
# Licensed under either of
# * Apache License, version 2.0, ([LICENSE-APACHE](LICENSE-APACHE) or
# http://www.apache.org/licenses/LICENSE-2.0)
# * MIT license ([LICENSE-MIT](LICENSE-MIT) or
# http://opensource.org/licenses/MIT)
# at your option. This file may not be copied, modified, or distributed
# except according to those terms.
## Kvt DB -- Transaction interface
## ===============================
##
{.push raises: [].}
import
std/[sequtils, tables],
eth/common,
results,
./kvt_desc/desc_backend,
"."/[kvt_desc, kvt_layers]
func isTop*(tx: KvtTxRef): bool {.gcsafe.}
proc txBegin*(db: KvtDbRef): Result[KvtTxRef,KvtError] {.gcsafe.}
# ------------------------------------------------------------------------------
# Private helpers
# ------------------------------------------------------------------------------
func getDbDescFromTopTx(tx: KvtTxRef): Result[KvtDbRef,KvtError] =
if not tx.isTop():
return err(TxNotTopTx)
let db = tx.db
if tx.level != db.stack.len:
return err(TxStackUnderflow)
ok db
proc getTxUid(db: KvtDbRef): uint =
if db.txUidGen == high(uint):
db.txUidGen = 0
db.txUidGen.inc
db.txUidGen
# ------------------------------------------------------------------------------
# Public functions, getters
# ------------------------------------------------------------------------------
func txTop*(db: KvtDbRef): Result[KvtTxRef,KvtError] =
## Getter, returns top level transaction if there is any.
if db.txRef.isNil:
err(TxNoPendingTx)
else:
ok(db.txRef)
func isTop*(tx: KvtTxRef): bool =
## Getter, returns `true` if the argument `tx` referes to the current top
## level transaction.
tx.db.txRef == tx and tx.db.top.txUid == tx.txUid
func level*(tx: KvtTxRef): int =
## Getter, positive nesting level of transaction argument `tx`
tx.level
func level*(db: KvtDbRef): int =
## Getter, non-negative nesting level (i.e. number of pending transactions)
if not db.txRef.isNil:
result = db.txRef.level
# ------------------------------------------------------------------------------
# Public functions
# ------------------------------------------------------------------------------
func to*(tx: KvtTxRef; T: type[KvtDbRef]): T =
## Getter, retrieves the parent database descriptor from argument `tx`
tx.db
proc forkTx*(tx: KvtTxRef): Result[KvtDbRef,KvtError] =
## Clone a transaction into a new DB descriptor accessing the same backend
## (if any) database as the argument `db`. The new descriptor is linked to
## the transaction parent and is fully functional as a forked instance (see
## comments on `kvt_desc.reCentre()` for details.)
##
## The new DB descriptor will contain a copy of the argument transaction
## `tx` as top layer of level 1 (i.e. this is he only transaction.) Rolling
## back will end up at the backend layer (incl. backend filter.)
##
## Use `kvt_desc.forget()` to clean up this descriptor.
##
let db = tx.db
# Verify `tx` argument
if db.txRef == tx:
if db.top.txUid != tx.txUid:
return err(TxArgStaleTx)
elif db.stack.len <= tx.level:
return err(TxArgStaleTx)
elif db.stack[tx.level].txUid != tx.txUid:
return err(TxArgStaleTx)
# Set up clone associated to `db`
let txClone = ? db.fork()
txClone.top = db.layersCc tx.level
txClone.stack = @[LayerRef()] # Provide tx level 1 stack
txClone.top.txUid = 1
txClone.txUidGen = 1 # Used value of `txClone.top.txUid`
# Install transaction similar to `tx` on clone
txClone.txRef = KvtTxRef(
db: txClone,
txUid: 1,
level: 1)
ok(txClone)
proc forkTop*(db: KvtDbRef): Result[KvtDbRef,KvtError] =
## Variant of `forkTx()` for the top transaction if there is any. Otherwise
## the top layer is cloned, and an empty transaction is set up. After
## successful fork the returned descriptor has transaction level 1.
##
## Use `kvt_desc.forget()` to clean up this descriptor.
##
if db.txRef.isNil:
let dbClone = ? db.fork()
dbClone.top = db.layersCc
discard dbClone.txBegin
return ok(dbClone)
db.txRef.forkTx()
# ------------------------------------------------------------------------------
# Public functions: Transaction frame
# ------------------------------------------------------------------------------
proc txBegin*(db: KvtDbRef): Result[KvtTxRef,KvtError] =
## Starts a new transaction.
##
## Example:
## ::
## proc doSomething(db: KvtDbRef) =
## let tx = db.begin
## defer: tx.rollback()
## ... continue using db ...
## tx.commit()
##
if db.level != db.stack.len:
return err(TxStackGarbled)
db.stack.add db.top
db.top = LayerRef(txUid: db.getTxUid)
db.txRef = KvtTxRef(
db: db,
txUid: db.top.txUid,
parent: db.txRef,
level: db.stack.len)
ok db.txRef
proc rollback*(
tx: KvtTxRef; # Top transaction on database
): Result[void,KvtError] =
## Given a *top level* handle, this function discards all database operations
## performed for this transactio. The previous transaction is returned if
## there was any.
##
let db = ? tx.getDbDescFromTopTx()
# Roll back to previous layer.
db.top = db.stack[^1]
db.stack.setLen(db.stack.len-1)
db.txRef = tx.parent
ok()
proc commit*(
tx: KvtTxRef; # Top transaction on database
): Result[void,KvtError] =
## Given a *top level* handle, this function accepts all database operations
## performed through this handle and merges it to the previous layer. The
## previous transaction is returned if there was any.
##
let db = ? tx.getDbDescFromTopTx()
# Replace the top two layers by its merged version
let merged = db.stack[^1]
for (key,val) in db.top.delta.sTab.pairs:
merged.delta.sTab[key] = val
# Install `merged` layer
db.top = merged
db.stack.setLen(db.stack.len-1)
db.txRef = tx.parent
if 0 < db.stack.len:
db.txRef.txUid = db.getTxUid
db.top.txUid = db.txRef.txUid
ok()
proc collapse*(
tx: KvtTxRef; # Top transaction on database
commit: bool; # Commit if `true`, otherwise roll back
): Result[void,KvtError] =
## Iterated application of `commit()` or `rollback()` performing the
## something similar to
## ::
## while true:
## discard tx.commit() # ditto for rollback()
## if db.topTx.isErr: break
## tx = db.topTx.value
##
let db = ? tx.getDbDescFromTopTx()
if commit:
db.top = db.layersCc
else:
db.top = db.stack[0]
db.top.txUid = 0
# Clean up
db.stack.setLen(0)
db.txRef = KvtTxRef(nil)
ok()
# ------------------------------------------------------------------------------
# Public functions: save database
# ------------------------------------------------------------------------------
proc stow*(
db: KvtDbRef; # Database
): Result[void,KvtError] =
## The function saves the data from the top layer cache into the
## backend database.
##
## If there is no backend the function returns immediately with an error.
## The same happens if there is a pending transaction.
##
if not db.txRef.isNil:
return err(TxPendingTx)
if 0 < db.stack.len:
return err(TxStackGarbled)
let be = db.backend
if be.isNil:
return err(TxBackendNotWritable)
# Save structural and other table entries
let txFrame = be.putBegFn()
be.putKvpFn(txFrame, db.top.delta.sTab.pairs.toSeq)
? be.putEndFn txFrame
# Clean up
db.top.delta.sTab.clear
ok()
# ------------------------------------------------------------------------------
# End
# ------------------------------------------------------------------------------