aboutsummaryrefslogtreecommitdiff
path: root/src/select.c
diff options
context:
space:
mode:
Diffstat (limited to 'src/select.c')
-rw-r--r--src/select.c101
1 files changed, 70 insertions, 31 deletions
diff --git a/src/select.c b/src/select.c
index f2441e490..b4d57f489 100644
--- a/src/select.c
+++ b/src/select.c
@@ -6731,19 +6731,24 @@ static void havingToWhere(Parse *pParse, Select *p){
}
/*
-** Check to see if the pThis entry of pTabList is a self-join of a prior view.
-** If it is, then return the SrcItem for the prior view. If it is not,
-** then return 0.
+** Check to see if the pThis entry of pTabList is a self-join of another view.
+** Search FROM-clause entries in the range of iFirst..iEnd, including iFirst
+** but stopping before iEnd.
+**
+** If pThis is a self-join, then return the SrcItem for the first other
+** instance of that view found. If pThis is not a self-join then return 0.
*/
static SrcItem *isSelfJoinView(
SrcList *pTabList, /* Search for self-joins in this FROM clause */
- SrcItem *pThis /* Search for prior reference to this subquery */
+ SrcItem *pThis, /* Search for prior reference to this subquery */
+ int iFirst, int iEnd /* Range of FROM-clause entries to search. */
){
SrcItem *pItem;
assert( pThis->pSelect!=0 );
if( pThis->pSelect->selFlags & SF_PushDown ) return 0;
- for(pItem = pTabList->a; pItem<pThis; pItem++){
+ while( iFirst<iEnd ){
Select *pS1;
+ pItem = &pTabList->a[iFirst++];
if( pItem->pSelect==0 ) continue;
if( pItem->fg.viaCoroutine ) continue;
if( pItem->zName==0 ) continue;
@@ -6889,6 +6894,62 @@ static int sameSrcAlias(SrcItem *p0, SrcList *pSrc){
}
/*
+** Return TRUE (non-zero) if the i-th entry in the pTabList SrcList can
+** be implemented as a co-routine. The i-th entry is guaranteed to be
+** a subquery.
+**
+** The subquery is implemented as a co-routine if all of the following are
+** true:
+**
+** (1) The subquery will likely be implemented in the outer loop of
+** the query. This will be the case if any one of the following
+** conditions hold:
+** (a) The subquery is the only term in the FROM clause
+** (b) The subquery is the left-most term and a CROSS JOIN or similar
+** requires it to be the outer loop
+** (c) All of the following are true:
+** (i) The subquery is the left-most subquery in the FROM clause
+** (ii) There is nothing that would prevent the subquery from
+** being used as the outer loop if the sqlite3WhereBegin()
+** routine nominates it to that position.
+** (iii) The query is not a UPDATE ... FROM
+** (2) The subquery is not a CTE that should be materialized because of
+** the AS MATERIALIZED keywords
+** (3) The subquery is not part of a left operand for a RIGHT JOIN
+** (4) The SQLITE_Coroutine optimization disable flag is not set
+** (5) The subquery is not self-joined
+*/
+static int fromClauseTermCanBeCoroutine(
+ Parse *pParse, /* Parsing context */
+ SrcList *pTabList, /* FROM clause */
+ int i, /* Which term of the FROM clause holds the subquery */
+ int selFlags /* Flags on the SELECT statement */
+){
+ SrcItem *pItem = &pTabList->a[i];
+ if( pItem->fg.isCte && pItem->u2.pCteUse->eM10d==M10d_Yes ) return 0;/* (2) */
+ if( pTabList->a[0].fg.jointype & JT_LTORJ ) return 0; /* (3) */
+ if( OptimizationDisabled(pParse->db, SQLITE_Coroutines) ) return 0; /* (4) */
+ if( isSelfJoinView(pTabList, pItem, i+1, pTabList->nSrc)!=0 ){
+ return 0; /* (5) */
+ }
+ if( i==0 ){
+ if( pTabList->nSrc==1 ) return 1; /* (1a) */
+ if( pTabList->a[1].fg.jointype & JT_CROSS ) return 1; /* (1b) */
+ if( selFlags & SF_UpdateFrom ) return 0; /* (1c-iii) */
+ return 1;
+ }
+ if( selFlags & SF_UpdateFrom ) return 0; /* (1c-iii) */
+ while( 1 /*exit-by-break*/ ){
+ if( pItem->fg.jointype & (JT_OUTER|JT_CROSS) ) return 0; /* (1c-ii) */
+ if( i==0 ) break;
+ i--;
+ pItem--;
+ if( pItem->pSelect!=0 ) return 0; /* (1c-i) */
+ }
+ return 1;
+}
+
+/*
** Generate code for the SELECT statement given in the p argument.
**
** The results are returned according to the SelectDest structure.
@@ -7275,35 +7336,19 @@ int sqlite3Select(
pParse->zAuthContext = pItem->zName;
/* Generate code to implement the subquery
- **
- ** The subquery is implemented as a co-routine if all of the following are
- ** true:
- **
- ** (1) the subquery is guaranteed to be the outer loop (so that
- ** it does not need to be computed more than once), and
- ** (2) the subquery is not a CTE that should be materialized
- ** (3) the subquery is not part of a left operand for a RIGHT JOIN
*/
- if( i==0
- && (pTabList->nSrc==1
- || (pTabList->a[1].fg.jointype&(JT_OUTER|JT_CROSS))!=0) /* (1) */
- && (pItem->fg.isCte==0 || pItem->u2.pCteUse->eM10d!=M10d_Yes) /* (2) */
- && (pTabList->a[0].fg.jointype & JT_LTORJ)==0 /* (3) */
- ){
+ if( fromClauseTermCanBeCoroutine(pParse, pTabList, i, p->selFlags) ){
/* Implement a co-routine that will return a single row of the result
** set on each invocation.
*/
int addrTop = sqlite3VdbeCurrentAddr(v)+1;
-#ifdef SQLITE_ENABLE_STMT_SCANSTATUS
- int addrExplain;
-#endif
pItem->regReturn = ++pParse->nMem;
sqlite3VdbeAddOp3(v, OP_InitCoroutine, pItem->regReturn, 0, addrTop);
VdbeComment((v, "%!S", pItem));
pItem->addrFillSub = addrTop;
sqlite3SelectDestInit(&dest, SRT_Coroutine, pItem->regReturn);
- ExplainQueryPlan2(addrExplain, (pParse, 1, "CO-ROUTINE %!S", pItem));
+ ExplainQueryPlan((pParse, 1, "CO-ROUTINE %!S", pItem));
sqlite3Select(pParse, pSub, &dest);
pItem->pTab->nRowLogEst = pSub->nSelectRow;
pItem->fg.viaCoroutine = 1;
@@ -7311,10 +7356,6 @@ int sqlite3Select(
sqlite3VdbeEndCoroutine(v, pItem->regReturn);
sqlite3VdbeJumpHere(v, addrTop-1);
sqlite3ClearTempRegCache(pParse);
- /* For SQLITE_SCANSTAT_NCYCLE, all instructions from the
- ** OP_InitCoroutine coded above until this point are attributed to
- ** the CO-ROUTINE query element. */
- sqlite3VdbeScanStatusRange(v, addrExplain, addrExplain-1, -1);
}else if( pItem->fg.isCte && pItem->u2.pCteUse->addrM9e>0 ){
/* This is a CTE for which materialization code has already been
** generated. Invoke the subroutine to compute the materialization,
@@ -7327,7 +7368,7 @@ int sqlite3Select(
VdbeComment((v, "%!S", pItem));
}
pSub->nSelectRow = pCteUse->nRowEst;
- }else if( (pPrior = isSelfJoinView(pTabList, pItem))!=0 ){
+ }else if( (pPrior = isSelfJoinView(pTabList, pItem, 0, i))!=0 ){
/* This view has already been materialized by a prior entry in
** this same FROM clause. Reuse it. */
if( pPrior->addrFillSub ){
@@ -7366,6 +7407,7 @@ int sqlite3Select(
if( onceAddr ) sqlite3VdbeJumpHere(v, onceAddr);
sqlite3VdbeAddOp2(v, OP_Return, pItem->regReturn, topAddr+1);
VdbeComment((v, "end %!S", pItem));
+ sqlite3VdbeScanStatusRange(v, addrExplain, addrExplain, -1);
sqlite3VdbeJumpHere(v, topAddr);
sqlite3ClearTempRegCache(pParse);
if( pItem->fg.isCte && pItem->fg.isCorrelated==0 ){
@@ -7375,9 +7417,6 @@ int sqlite3Select(
pCteUse->iCur = pItem->iCursor;
pCteUse->nRowEst = pSub->nSelectRow;
}
- /* For SQLITE_SCANSTAT_NCYCLE, all instructions from the
- ** OP_Explain to here are attibuted to the MATERIALIZE element. */
- sqlite3VdbeScanStatusRange(v, addrExplain, addrExplain, -1);
}
if( db->mallocFailed ) goto select_end;
pParse->nHeight -= sqlite3SelectExprHeight(p);
generated by cgit v1.2.3 (git 2.25.1) at 2025-07-19 10:27:07 +0000