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Just because a CTE is used more than once, does not mean it should be

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tagged with M10d_Yes and thereby prohibited from participating in the
query flattening optimization.  See
[forum:/forumpost/1d571c02963355ed|forum thread 1d571c02963].

FossilOrigin-Name: 66f29c403d28630bfaea9124bd63ee4a047b1fe4a7e27dc5d10d67d1601b15e0
This commit is contained in:
drh
2023-02-01 15:41:07 +00:00
parent 288409d731
commit 54725efd80
4 changed files with 71 additions and 17 deletions
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19
src/select.c
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@@ -5626,9 +5626,6 @@ static int resolveFromTermToCte(
pFrom->fg.isCte = 1;
pFrom->u2.pCteUse = pCteUse;
pCteUse->nUse++;
if( pCteUse->nUse>=2 && pCteUse->eM10d==M10d_Any ){
pCteUse->eM10d = M10d_Yes;
}
/* Check if this is a recursive CTE. */
pRecTerm = pSel = pFrom->pSelect;
@@ -6911,8 +6908,10 @@ static int sameSrcAlias(SrcItem *p0, SrcList *pSrc){
** 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
** (2) The subquery is not a CTE that should be materialized because
** (a) the AS MATERIALIZED keyword is used, or
** (b) the CTE is used multiple times and does not have the
** NOT MATERIALIZED keyword
** (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
@@ -6924,9 +6923,13 @@ static int fromClauseTermCanBeCoroutine(
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( pItem->fg.isCte ){
const CteUse *pCteUse = pItem->u2.pCteUse;
if( pCteUse->eM10d==M10d_Yes ) return 0; /* (2a) */
if( pCteUse->nUse>=2 && pCteUse->eM10d!=M10d_No ) return 0; /* (2b) */
}
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) */
}