diff options
Diffstat (limited to 'src/select.c')
| -rw-r--r-- | src/select.c | 22 |
1 files changed, 15 insertions, 7 deletions
diff --git a/src/select.c b/src/select.c index 750de5e8f..b15300237 100644 --- a/src/select.c +++ b/src/select.c @@ -7418,11 +7418,17 @@ static int fromClauseTermCanBeCoroutine( ** ** 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, - Select *p, - Expr *pWhere + Parse *pParse, /* Parsing context */ + Select *p, /* The SELECT statement being optimized */ + Expr *pWhere /* part of the WHERE clause currently being examined */ ){ if( pWhere && !ExprHasProperty(pWhere, EP_OuterON|EP_InnerON) @@ -7437,9 +7443,9 @@ static SQLITE_NOINLINE void existsToJoin( } 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->pWhere && !pSub->pSrc->a[0].fg.isSubquery ){ memset(pWhere, 0, sizeof(*pWhere)); @@ -7451,9 +7457,10 @@ static SQLITE_NOINLINE void existsToJoin( pSub->pSrc->a[0].fg.fromExists = 1; pSub->pSrc->a[0].fg.jointype |= JT_CROSS; p->pSrc = sqlite3SrcListAppendList(pParse, p->pSrc, pSub->pSrc); - p->pWhere = sqlite3PExpr(pParse, TK_AND, p->pWhere, pSub->pWhere); - - pSub->pWhere = 0; + if( pSubWhere ){ + p->pWhere = sqlite3PExpr(pParse, TK_AND, p->pWhere, pSubWhere); + pSub->pWhere = 0; + } pSub->pSrc = 0; sqlite3ParserAddCleanup(pParse, sqlite3SelectDeleteGeneric, pSub); #if TREETRACE_ENABLED @@ -7463,6 +7470,7 @@ static SQLITE_NOINLINE void existsToJoin( sqlite3TreeViewSelect(0, p, 0); } #endif + existsToJoin(pParse, p, pSubWhere); } } } |