avoid computing state root just to know if storage is empty (#2380)

The state root computation here is one of the major hotspots in block
processing - in the cases the code only needs to know if it's empty or
not, it can be done a lot faster.

Adding a separate function for this looks fragile and should probably be
revisited.

nimbus/db/core_db/backend/aristo_db.nim

@@ -150,6 +150,9 @@ proc baseMethods(db: AristoCoreDbRef): CoreDbBaseFns =
     levelFn: proc(): int =
       aBase.getLevel,
 
+    colStateEmptyFn: proc(col: CoreDbColRef): CoreDbRc[bool] =
+      aBase.rootHashEmpty(col, "rootHashFn()"),
+
     colStateFn: proc(col: CoreDbColRef): CoreDbRc[Hash256] =
       aBase.rootHash(col, "rootHashFn()"),
 

nimbus/db/core_db/backend/aristo_db/handlers_aristo.nim

@@ -645,6 +645,20 @@ proc colPrint*(
     result &= "$?"
 
 
+proc rootHashEmpty*(
+    base: AristoBaseRef;
+    col: CoreDbColRef;
+    info: static[string];
+      ): CoreDbRc[bool] =
+  let col = AristoColRef(col)
+  if not col.isValid:
+    return err(TrieInvalid.toError(base, info, HashNotAvailable))
+
+  let root = col.to(VertexID)
+  if not root.isValid:
+    return ok(true)
+  return ok(false)
+
 proc rootHash*(
     base: AristoBaseRef;
     col: CoreDbColRef;

nimbus/db/core_db/base.nim

@@ -445,6 +445,23 @@ proc `$$`*(col: CoreDbColRef): string =
   result = col.prettyText()
   #col.ifTrackNewApi: debug newApiTxt, api, elapsed, result
 
+proc stateEmpty*(col: CoreDbColRef): CoreDbRc[bool] =
+  ## Getter (well, sort of). It retrieves the column state hash for the
+  ## argument `col` descriptor. The function might fail unless the current
+  ## state is available (e.g. on `Aristo`.)
+  ##
+  ## The value `EMPTY_ROOT_HASH` is returned on the void `col` descriptor
+  ## argument `CoreDbColRef(nil)`.
+  ##
+  col.setTrackNewApi BaseColStateEmptyFn
+  result = block:
+    if not col.isNil and col.ready:
+      col.parent.methods.colStateEmptyFn col
+    else:
+      ok true
+  # Note: tracker will be silent if `vid` is NIL
+  col.ifTrackNewApi: debug newApiTxt, api, elapsed, col, result
+
 proc state*(col: CoreDbColRef): CoreDbRc[Hash256] =
   ## Getter (well, sort of). It retrieves the column state hash for the
   ## argument `col` descriptor. The function might fail unless the current

nimbus/db/core_db/base/api_tracking.nim

@@ -41,6 +41,7 @@ type
     AnyBackendFn        = "any/backend"
 
     BaseColPrintFn      = "$$"
+    BaseColStateEmptyFn = "stateEmpty"
     BaseColStateFn      = "state"
     BaseDbTypeFn        = "dbType"
     BaseFinishFn        = "finish"

nimbus/db/core_db/base/base_desc.nim

@@ -92,6 +92,8 @@ type
   CoreDbBaseDestroyFn* = proc(eradicate = true) {.noRaise.}
   CoreDbBaseColStateFn* = proc(
     col: CoreDbColRef): CoreDbRc[Hash256] {.noRaise.}
+  CoreDbBaseColStateEmptyFn* = proc(
+    col: CoreDbColRef): CoreDbRc[bool] {.noRaise.}
   CoreDbBaseColPrintFn* = proc(vid: CoreDbColRef): string {.noRaise.}
   CoreDbBaseErrorPrintFn* = proc(e: CoreDbErrorRef): string {.noRaise.}
   CoreDbBaseLevelFn* = proc(): int {.noRaise.}
@@ -110,6 +112,7 @@ type
   CoreDbBaseFns* = object
     destroyFn*:      CoreDbBaseDestroyFn
     colStateFn*:     CoreDbBaseColStateFn
+    colStateEmptyFn*: CoreDbBaseColStateEmptyFn
     colPrintFn*:     CoreDbBaseColPrintFn
     errorPrintFn*:   CoreDbBaseErrorPrintFn
     levelFn*:        CoreDbBaseLevelFn

nimbus/db/ledger/accounts_ledger.nim

@@ -376,9 +376,9 @@ proc persistStorage(acc: AccountRef, ac: AccountsLedgerRef) =
   acc.statement.storage = storageLedger.getColumn()
 
   # No need to hold descriptors for longer than needed
-  let state = acc.statement.storage.state.valueOr:
+  let stateEmpty = acc.statement.storage.stateEmpty.valueOr:
     raiseAssert "Storage column state error: " & $$error
-  if state == EMPTY_ROOT_HASH:
+  if stateEmpty:
     acc.statement.storage = CoreDbColRef(nil)
 
 
@@ -540,8 +540,8 @@ proc clearStorage*(ac: AccountsLedgerRef, address: EthAddress) =
   let acc = ac.getAccount(address)
   acc.flags.incl {Alive, NewlyCreated}
 
-  let accHash = acc.statement.storage.state.valueOr: return
+  let empty = acc.statement.storage.stateEmpty.valueOr: return
-  if accHash != EMPTY_ROOT_HASH:
+  if not empty:
     # need to clear the storage from the database first
     let acc = ac.makeDirty(address, cloneStorage = false)
     ac.ledger.freeStorage address
@@ -613,7 +613,7 @@ proc clearEmptyAccounts(ac: AccountsLedgerRef) =
     ac.ripemdSpecial = false
 
 proc persist*(ac: AccountsLedgerRef,
-              clearEmptyAccount: bool = false) =
+              clearEmptyAccount: bool = false) {.deprecated.} =
   # make sure all savepoint already committed
   doAssert(ac.savePoint.parentSavepoint.isNil)