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-rw-r--r--src/btree.c24
-rw-r--r--src/btree.h1
-rw-r--r--src/build.c14
-rw-r--r--src/resolve.c5
-rw-r--r--src/select.c125
-rw-r--r--src/shell.c.in1
-rw-r--r--src/sqliteInt.h4
-rw-r--r--src/vdbe.c26
-rw-r--r--src/vdbeInt.h2
-rw-r--r--src/where.c11
-rw-r--r--src/wherecode.c6
-rw-r--r--src/whereexpr.c2
12 files changed, 203 insertions, 18 deletions
diff --git a/src/btree.c b/src/btree.c
index 00cdc9760..a931b0d12 100644
--- a/src/btree.c
+++ b/src/btree.c
@@ -5667,6 +5667,30 @@ int sqlite3BtreeFirst(BtCursor *pCur, int *pRes){
return rc;
}
+/* Set *pRes to 1 (true) if the BTree pointed to by cursor pCur contains zero
+** rows of content. Set *pRes to 0 (false) if the table contains content.
+** Return SQLITE_OK on success or some error code (ex: SQLITE_NOMEM) if
+** something goes wrong.
+*/
+int sqlite3BtreeIsEmpty(BtCursor *pCur, int *pRes){
+ int rc;
+
+ assert( cursorOwnsBtShared(pCur) );
+ assert( sqlite3_mutex_held(pCur->pBtree->db->mutex) );
+ if( pCur->eState==CURSOR_VALID ){
+ *pRes = 0;
+ return SQLITE_OK;
+ }
+ rc = moveToRoot(pCur);
+ if( rc==SQLITE_EMPTY ){
+ *pRes = 1;
+ rc = SQLITE_OK;
+ }else{
+ *pRes = 0;
+ }
+ return rc;
+}
+
#ifdef SQLITE_DEBUG
/* The cursors is CURSOR_VALID and has BTCF_AtLast set. Verify that
** this flags are true for a consistent database.
diff --git a/src/btree.h b/src/btree.h
index 241261dc6..96f4c4c60 100644
--- a/src/btree.h
+++ b/src/btree.h
@@ -317,6 +317,7 @@ struct BtreePayload {
int sqlite3BtreeInsert(BtCursor*, const BtreePayload *pPayload,
int flags, int seekResult);
int sqlite3BtreeFirst(BtCursor*, int *pRes);
+int sqlite3BtreeIsEmpty(BtCursor *pCur, int *pRes);
int sqlite3BtreeLast(BtCursor*, int *pRes);
int sqlite3BtreeNext(BtCursor*, int flags);
int sqlite3BtreeEof(BtCursor*);
diff --git a/src/build.c b/src/build.c
index 27d7b499d..5495cef18 100644
--- a/src/build.c
+++ b/src/build.c
@@ -5137,16 +5137,22 @@ void sqlite3SrcListIndexedBy(Parse *pParse, SrcList *p, Token *pIndexedBy){
** are deleted by this function.
*/
SrcList *sqlite3SrcListAppendList(Parse *pParse, SrcList *p1, SrcList *p2){
- assert( p1 && p1->nSrc==1 );
+ assert( p1 );
+ assert( p2 || pParse->nErr );
+ assert( p2==0 || p2->nSrc>=1 );
+ testcase( p1->nSrc==0 );
if( p2 ){
- SrcList *pNew = sqlite3SrcListEnlarge(pParse, p1, p2->nSrc, 1);
+ int nOld = p1->nSrc;
+ SrcList *pNew = sqlite3SrcListEnlarge(pParse, p1, p2->nSrc, nOld);
if( pNew==0 ){
sqlite3SrcListDelete(pParse->db, p2);
}else{
p1 = pNew;
- memcpy(&p1->a[1], p2->a, p2->nSrc*sizeof(SrcItem));
+ memcpy(&p1->a[nOld], p2->a, p2->nSrc*sizeof(SrcItem));
+ assert( nOld==1 || (p2->a[0].fg.jointype & JT_LTORJ)==0 );
+ assert( p1->nSrc>=1 );
+ p1->a[0].fg.jointype |= (JT_LTORJ & p2->a[0].fg.jointype);
sqlite3DbFree(pParse->db, p2);
- p1->a[0].fg.jointype |= (JT_LTORJ & p1->a[1].fg.jointype);
}
}
return p1;
diff --git a/src/resolve.c b/src/resolve.c
index 3961a2009..57ccd0c07 100644
--- a/src/resolve.c
+++ b/src/resolve.c
@@ -1358,11 +1358,13 @@ static int resolveExprStep(Walker *pWalker, Expr *pExpr){
return WRC_Prune;
}
#ifndef SQLITE_OMIT_SUBQUERY
+ case TK_EXISTS:
case TK_SELECT:
- case TK_EXISTS: testcase( pExpr->op==TK_EXISTS );
#endif
case TK_IN: {
testcase( pExpr->op==TK_IN );
+ testcase( pExpr->op==TK_EXISTS );
+ testcase( pExpr->op==TK_SELECT );
if( ExprUseXSelect(pExpr) ){
int nRef = pNC->nRef;
testcase( pNC->ncFlags & NC_IsCheck );
@@ -1370,6 +1372,7 @@ static int resolveExprStep(Walker *pWalker, Expr *pExpr){
testcase( pNC->ncFlags & NC_IdxExpr );
testcase( pNC->ncFlags & NC_GenCol );
assert( pExpr->x.pSelect );
+ if( pExpr->op==TK_EXISTS ) pParse->bHasExists = 1;
if( pNC->ncFlags & NC_SelfRef ){
notValidImpl(pParse, pNC, "subqueries", pExpr, pExpr);
}else{
diff --git a/src/select.c b/src/select.c
index 1e54747fc..1b1266313 100644
--- a/src/select.c
+++ b/src/select.c
@@ -384,7 +384,7 @@ static int tableAndColumnIndex(
int iEnd, /* Last member of pSrc->a[] to check */
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 *piCol, /* Write index of pSrc->a[*piTab].pSTab->aCol[] here */
int bIgnoreHidden /* Ignore hidden columns */
){
int i; /* For looping over tables in pSrc */
@@ -3036,7 +3036,9 @@ static int multiSelect(
int priorOp; /* The SRT_ operation to apply to prior selects */
Expr *pLimit; /* Saved values of p->nLimit */
int addr;
+ int emptyBypass = 0; /* IfEmpty opcode to bypass RHS */
SelectDest uniondest;
+
testcase( p->op==TK_EXCEPT );
testcase( p->op==TK_UNION );
@@ -3075,6 +3077,8 @@ static int multiSelect(
*/
if( p->op==TK_EXCEPT ){
op = SRT_Except;
+ emptyBypass = sqlite3VdbeAddOp1(v, OP_IfEmpty, unionTab);
+ VdbeCoverage(v);
}else{
assert( p->op==TK_UNION );
op = SRT_Union;
@@ -3095,6 +3099,7 @@ static int multiSelect(
if( p->op==TK_UNION ){
p->nSelectRow = sqlite3LogEstAdd(p->nSelectRow, pPrior->nSelectRow);
}
+ if( emptyBypass ) sqlite3VdbeJumpHere(v, emptyBypass);
sqlite3ExprDelete(db, p->pLimit);
p->pLimit = pLimit;
p->iLimit = 0;
@@ -3125,9 +3130,10 @@ static int multiSelect(
int tab1, tab2;
int iCont, iBreak, iStart;
Expr *pLimit;
- int addr;
+ int addr, iLimit, iOffset;
SelectDest intersectdest;
int r1;
+ int emptyBypass;
/* INTERSECT is different from the others since it requires
** two temporary tables. Hence it has its own case. Begin
@@ -3151,15 +3157,29 @@ static int multiSelect(
if( rc ){
goto multi_select_end;
}
+
+ /* Initialize LIMIT counters before checking to see if the LHS
+ ** is empty, in case the jump is taken */
+ iBreak = sqlite3VdbeMakeLabel(pParse);
+ computeLimitRegisters(pParse, p, iBreak);
+ emptyBypass = sqlite3VdbeAddOp1(v, OP_IfEmpty, tab1); VdbeCoverage(v);
/* 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;
+
+ /* Disable prior SELECTs and the LIMIT counters during the computation
+ ** of the RHS select */
pLimit = p->pLimit;
+ iLimit = p->iLimit;
+ iOffset = p->iOffset;
+ p->pPrior = 0;
p->pLimit = 0;
+ p->iLimit = 0;
+ p->iOffset = 0;
+
intersectdest.iSDParm = tab2;
ExplainQueryPlan((pParse, 1, "%s USING TEMP B-TREE",
sqlite3SelectOpName(p->op)));
@@ -3172,19 +3192,21 @@ static int multiSelect(
p->nSelectRow = pPrior->nSelectRow;
}
sqlite3ExprDelete(db, p->pLimit);
+
+ /* Reinstate the LIMIT counters prior to running the final intersect */
p->pLimit = pLimit;
+ p->iLimit = iLimit;
+ p->iOffset = iOffset;
/* Generate code to take the intersection of the two temporary
** tables.
*/
if( rc ) break;
assert( p->pEList );
- iBreak = sqlite3VdbeMakeLabel(pParse);
- iCont = sqlite3VdbeMakeLabel(pParse);
- computeLimitRegisters(pParse, p, iBreak);
- sqlite3VdbeAddOp2(v, OP_Rewind, tab1, iBreak); VdbeCoverage(v);
+ sqlite3VdbeAddOp1(v, OP_Rewind, tab1);
r1 = sqlite3GetTempReg(pParse);
iStart = sqlite3VdbeAddOp2(v, OP_RowData, tab1, r1);
+ iCont = sqlite3VdbeMakeLabel(pParse);
sqlite3VdbeAddOp4Int(v, OP_NotFound, tab2, iCont, r1, 0);
VdbeCoverage(v);
sqlite3ReleaseTempReg(pParse, r1);
@@ -3194,6 +3216,7 @@ static int multiSelect(
sqlite3VdbeAddOp2(v, OP_Next, tab1, iStart); VdbeCoverage(v);
sqlite3VdbeResolveLabel(v, iBreak);
sqlite3VdbeAddOp2(v, OP_Close, tab2, 0);
+ sqlite3VdbeJumpHere(v, emptyBypass);
sqlite3VdbeAddOp2(v, OP_Close, tab1, 0);
break;
}
@@ -4650,7 +4673,7 @@ static int flattenSubquery(
** 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.
+ ** pSubitem->pSTab is always non-NULL by test restrictions and tests above.
*/
if( ALWAYS(pSubitem->pSTab!=0) ){
Table *pTabToDel = pSubitem->pSTab;
@@ -5764,7 +5787,7 @@ With *sqlite3WithPush(Parse *pParse, With *pWith, u8 bFree){
** CTE expression, through routine checks to see if the reference is
** a recursive reference to the CTE.
**
-** If pFrom matches a CTE according to either of these two above, pFrom->pTab
+** If pFrom matches a CTE according to either of these two above, pFrom->pSTab
** and other fields are populated accordingly.
**
** Return 0 if no match is found.
@@ -7392,6 +7415,83 @@ static int fromClauseTermCanBeCoroutine(
}
/*
+** Argument pWhere is the WHERE clause belonging to SELECT statement p. This
+** function attempts to transform expressions of the form:
+**
+** EXISTS (SELECT ...)
+**
+** into joins. For example, given
+**
+** CREATE TABLE sailors(sid INTEGER PRIMARY KEY, name TEXT);
+** CREATE TABLE reserves(sid INT, day DATE, PRIMARY KEY(sid, day));
+**
+** SELECT name FROM sailors AS S WHERE EXISTS (
+** SELECT * FROM reserves AS R WHERE S.sid = R.sid AND R.day = '2022-10-25'
+** );
+**
+** the SELECT statement may be transformed as follows:
+**
+** SELECT name FROM sailors AS S, reserves AS R
+** WHERE S.sid = R.sid AND R.day = '2022-10-25';
+**
+** **Approximately**. Really, we have to ensure that the FROM-clause term
+** that was formerly inside the EXISTS is only executed once. This is handled
+** by setting the SrcItem.fg.fromExists flag, which then causes code in
+** the where.c file to exit the corresponding loop after the first successful
+** match (if any).
+*/
+static SQLITE_NOINLINE void existsToJoin(
+ Parse *pParse, /* Parsing context */
+ Select *p, /* The SELECT statement being optimized */
+ Expr *pWhere /* part of the WHERE clause currently being examined */
+){
+ if( pParse->nErr==0
+ && pWhere!=0
+ && !ExprHasProperty(pWhere, EP_OuterON|EP_InnerON)
+ && ALWAYS(p->pSrc!=0)
+ && p->pSrc->nSrc<BMS
+ ){
+ if( pWhere->op==TK_AND ){
+ Expr *pRight = pWhere->pRight;
+ existsToJoin(pParse, p, pWhere->pLeft);
+ existsToJoin(pParse, p, pRight);
+ }
+ else if( pWhere->op==TK_EXISTS ){
+ Select *pSub = pWhere->x.pSelect;
+ Expr *pSubWhere = pSub->pWhere;
+ if( pSub->pSrc->nSrc==1
+ && (pSub->selFlags & SF_Aggregate)==0
+ && !pSub->pSrc->a[0].fg.isSubquery
+ ){
+ memset(pWhere, 0, sizeof(*pWhere));
+ pWhere->op = TK_INTEGER;
+ pWhere->u.iValue = 1;
+ ExprSetProperty(pWhere, EP_IntValue);
+
+ assert( p->pWhere!=0 );
+ pSub->pSrc->a[0].fg.fromExists = 1;
+ pSub->pSrc->a[0].fg.jointype |= JT_CROSS;
+ p->pSrc = sqlite3SrcListAppendList(pParse, p->pSrc, pSub->pSrc);
+ if( pSubWhere ){
+ p->pWhere = sqlite3PExpr(pParse, TK_AND, p->pWhere, pSubWhere);
+ pSub->pWhere = 0;
+ }
+ pSub->pSrc = 0;
+ sqlite3ParserAddCleanup(pParse, sqlite3SelectDeleteGeneric, pSub);
+#if TREETRACE_ENABLED
+ if( sqlite3TreeTrace & 0x100000 ){
+ TREETRACE(0x100000,pParse,p,
+ ("After EXISTS-to-JOIN optimization:\n"));
+ sqlite3TreeViewSelect(0, p, 0);
+ }
+#endif
+ existsToJoin(pParse, p, pSubWhere);
+ }
+ }
+ }
+}
+
+/*
** Generate byte-code for the SELECT statement given in the p argument.
**
** The results are returned according to the SelectDest structure.
@@ -7759,6 +7859,13 @@ int sqlite3Select(
}
#endif
+ /* If there may be an "EXISTS (SELECT ...)" in the WHERE clause, attempt
+ ** to change it into a join. */
+ if( pParse->bHasExists && OptimizationEnabled(db,SQLITE_ExistsToJoin) ){
+ existsToJoin(pParse, p, p->pWhere);
+ pTabList = p->pSrc;
+ }
+
/* Do the WHERE-clause constant propagation optimization if this is
** a join. No need to spend time on this operation for non-join queries
** as the equivalent optimization will be handled by query planner in
diff --git a/src/shell.c.in b/src/shell.c.in
index 33dd30697..5cda6a1a1 100644
--- a/src/shell.c.in
+++ b/src/shell.c.in
@@ -11710,6 +11710,7 @@ static int do_meta_command(char *zLine, ShellState *p){
{ 0x08000000, 1, "OnePass" },
{ 0x10000000, 1, "OrderBySubq" },
{ 0x20000000, 1, "StarQuery" },
+ { 0x40000000, 1, "ExistsToJoin" },
{ 0xffffffff, 0, "All" },
};
unsigned int curOpt;
diff --git a/src/sqliteInt.h b/src/sqliteInt.h
index a05cf75ad..7b914d958 100644
--- a/src/sqliteInt.h
+++ b/src/sqliteInt.h
@@ -1154,6 +1154,7 @@ extern u32 sqlite3TreeTrace;
** 0x00040000 SELECT tree dump after all code has been generated
** 0x00080000 NOT NULL strength reduction
** 0x00100000 Pointers are all shown as zero
+** 0x00200000 EXISTS-to-JOIN optimization
*/
/*
@@ -1926,6 +1927,7 @@ struct sqlite3 {
#define SQLITE_OnePass 0x08000000 /* Single-pass DELETE and UPDATE */
#define SQLITE_OrderBySubq 0x10000000 /* ORDER BY in subquery helps outer */
#define SQLITE_StarQuery 0x20000000 /* Heurists for star queries */
+#define SQLITE_ExistsToJoin 0x40000000 /* The EXISTS-to-JOIN optimization */
#define SQLITE_AllOpts 0xffffffff /* All optimizations */
/*
@@ -3369,6 +3371,7 @@ struct SrcItem {
unsigned rowidUsed :1; /* The ROWID of this table is referenced */
unsigned fixedSchema :1; /* Uses u4.pSchema, not u4.zDatabase */
unsigned hadSchema :1; /* Had u4.zDatabase before u4.pSchema */
+ unsigned fromExists :1; /* Comes from WHERE EXISTS(...) */
} fg;
int iCursor; /* The VDBE cursor number used to access this table */
Bitmask colUsed; /* Bit N set if column N used. Details above for N>62 */
@@ -3899,6 +3902,7 @@ struct Parse {
u8 disableLookaside; /* Number of times lookaside has been disabled */
u8 prepFlags; /* SQLITE_PREPARE_* flags */
u8 withinRJSubrtn; /* Nesting level for RIGHT JOIN body subroutines */
+ u8 bHasExists; /* Has a correlated "EXISTS (SELECT ....)" expression */
u8 mSubrtnSig; /* mini Bloom filter on available SubrtnSig.selId */
u8 eTriggerOp; /* TK_UPDATE, TK_INSERT or TK_DELETE */
u8 bReturning; /* Coding a RETURNING trigger */
diff --git a/src/vdbe.c b/src/vdbe.c
index 0020b52bf..9e456a1cd 100644
--- a/src/vdbe.c
+++ b/src/vdbe.c
@@ -6398,6 +6398,32 @@ case OP_Rewind: { /* jump0, ncycle */
break;
}
+/* Opcode: IfEmpty P1 P2 * * *
+** Synopsis: if( empty(P1) ) goto P2
+**
+** Check to see if the b-tree table that cursor P1 references is empty
+** and jump to P2 if it is.
+*/
+case OP_IfEmpty: { /* jump */
+ VdbeCursor *pC;
+ BtCursor *pCrsr;
+ int res;
+
+ assert( pOp->p1>=0 && pOp->p1<p->nCursor );
+ assert( pOp->p2>=0 && pOp->p2<p->nOp );
+
+ pC = p->apCsr[pOp->p1];
+ assert( pC!=0 );
+ assert( pC->eCurType==CURTYPE_BTREE );
+ pCrsr = pC->uc.pCursor;
+ assert( pCrsr );
+ rc = sqlite3BtreeIsEmpty(pCrsr, &res);
+ if( rc ) goto abort_due_to_error;
+ VdbeBranchTaken(res!=0,2);
+ if( res ) goto jump_to_p2;
+ break;
+}
+
/* Opcode: Next P1 P2 P3 * P5
**
** Advance cursor P1 so that it points to the next key/data pair in its
diff --git a/src/vdbeInt.h b/src/vdbeInt.h
index 0faa32747..07160f590 100644
--- a/src/vdbeInt.h
+++ b/src/vdbeInt.h
@@ -288,7 +288,7 @@ struct sqlite3_value {
** MEM_Int, MEM_Real, and MEM_IntReal.
**
** * MEM_Blob|MEM_Zero A blob in Mem.z of length Mem.n plus
-** MEM.u.i extra 0x00 bytes at the end.
+** Mem.u.nZero extra 0x00 bytes at the end.
**
** * MEM_Int Integer stored in Mem.u.i.
**
diff --git a/src/where.c b/src/where.c
index 5d80dd3d6..ab1b419a2 100644
--- a/src/where.c
+++ b/src/where.c
@@ -3532,6 +3532,7 @@ static int whereLoopAddBtreeIndex(
&& pProbe->hasStat1!=0
&& OptimizationEnabled(db, SQLITE_SkipScan)
&& pProbe->aiRowLogEst[saved_nEq+1]>=42 /* TUNING: Minimum for skip-scan */
+ && pSrc->fg.fromExists==0
&& (rc = whereLoopResize(db, pNew, pNew->nLTerm+1))==SQLITE_OK
){
LogEst nIter;
@@ -7148,6 +7149,13 @@ WhereInfo *sqlite3WhereBegin(
sqlite3VdbeAddOp4Dup8(v, OP_ColumnsUsed, pTabItem->iCursor, 0, 0,
(const u8*)&pTabItem->colUsed, P4_INT64);
#endif
+ if( ii>=2
+ && (pTabItem[0].fg.jointype & (JT_LTORJ|JT_LEFT))==0
+ && pLevel->addrHalt==pWInfo->a[0].addrHalt
+ ){
+ sqlite3VdbeAddOp2(v, OP_IfEmpty, pTabItem->iCursor, pWInfo->iBreak);
+ VdbeCoverage(v);
+ }
}else{
sqlite3TableLock(pParse, iDb, pTab->tnum, 0, pTab->zName);
}
@@ -7404,6 +7412,9 @@ void sqlite3WhereEnd(WhereInfo *pWInfo){
sqlite3VdbeAddOp2(v, OP_Goto, 1, pLevel->p2);
}
#endif /* SQLITE_DISABLE_SKIPAHEAD_DISTINCT */
+ if( pTabList->a[pLevel->iFrom].fg.fromExists ){
+ sqlite3VdbeAddOp2(v, OP_Goto, 0, sqlite3VdbeCurrentAddr(v)+2);
+ }
/* The common case: Advance to the next row */
if( pLevel->addrCont ) sqlite3VdbeResolveLabel(v, pLevel->addrCont);
sqlite3VdbeAddOp3(v, pLevel->op, pLevel->p1, pLevel->p2, pLevel->p3);
diff --git a/src/wherecode.c b/src/wherecode.c
index 839304c11..43a669d81 100644
--- a/src/wherecode.c
+++ b/src/wherecode.c
@@ -126,7 +126,6 @@ void sqlite3WhereAddExplainText(
#endif
{
VdbeOp *pOp = sqlite3VdbeGetOp(pParse->pVdbe, addr);
-
SrcItem *pItem = &pTabList->a[pLevel->iFrom];
sqlite3 *db = pParse->db; /* Database handle */
int isSearch; /* True for a SEARCH. False for SCAN. */
@@ -149,7 +148,10 @@ void sqlite3WhereAddExplainText(
sqlite3StrAccumInit(&str, db, zBuf, sizeof(zBuf), SQLITE_MAX_LENGTH);
str.printfFlags = SQLITE_PRINTF_INTERNAL;
- sqlite3_str_appendf(&str, "%s %S", isSearch ? "SEARCH" : "SCAN", pItem);
+ sqlite3_str_appendf(&str, "%s %S%s",
+ isSearch ? "SEARCH" : "SCAN",
+ pItem,
+ pItem->fg.fromExists ? " EXISTS" : "");
if( (flags & (WHERE_IPK|WHERE_VIRTUALTABLE))==0 ){
const char *zFmt = 0;
Index *pIdx;
diff --git a/src/whereexpr.c b/src/whereexpr.c
index e4be8d9d6..e9fa4a143 100644
--- a/src/whereexpr.c
+++ b/src/whereexpr.c
@@ -948,7 +948,7 @@ static int termIsEquivalence(Parse *pParse, Expr *pExpr, SrcList *pSrc){
if( ExprHasProperty(pExpr, EP_OuterON) ) return 0; /* (3) */
assert( pSrc!=0 );
if( pExpr->op==TK_IS
- && pSrc->nSrc
+ && pSrc->nSrc>=2
&& (pSrc->a[0].fg.jointype & JT_LTORJ)!=0
){
return 0; /* (4) */
generated by cgit v1.2.3 (git 2.25.1) at 2025-07-10 20:02:52 +0000