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Improved comments on the new co-routine logic. Fix a C++-ism in the code.

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Update test cases to accommodate the more aggressive use of co-routines.

FossilOrigin-Name: 9243e850ae656d16adc8f0e5c4dcf3dcf476312cee192c39c38685fc437ccbbd
This commit is contained in:
drh
2022-12-08 16:47:16 +00:00
parent 05cb9d881e
commit a60d61bf14
7 changed files with 53 additions and 48 deletions
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45
src/select.c
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@@ -6713,8 +6713,8 @@ static SrcItem *isSelfJoinView(
assert( pThis->pSelect!=0 );
if( pThis->pSelect->selFlags & SF_PushDown ) return 0;
while( iFirst<iEnd ){
pItem = &pTabList->a[iFirst++];
Select *pS1;
pItem = &pTabList->a[iFirst++];
if( pItem->pSelect==0 ) continue;
if( pItem->fg.viaCoroutine ) continue;
if( pItem->zName==0 ) continue;
@@ -6867,44 +6867,49 @@ static int sameSrcAlias(SrcItem *p0, SrcList *pSrc){
** The subquery is implemented as a co-routine if all of the following are
** true:
**
** (1) Either of the following are true:
** (1a) The subquery must be the outer loop because it is either
** (i) the only term in the FROM clause, or because (ii) it
** is the left-most term and a CROSS JOIN or similar requires
** it to be the outer loop. subquery and there is nothing
** (1b) There is nothing that would prevent the subquery from
** being an outer loop and the SQLITE_PREPARE_SAFESQL flag
** is not set.
** (2) The subquery is not a CTE that should be materialized
** (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 SQLITE_PREPARE_SAFEOPT flag is not set
** (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 */
Parse *pParse, /* Parsing context */
SrcList *pTabList, /* FROM clause */
int i /* Which term of the FROM clause holds the subquery */
){
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) */
return 0; /* (5) */
}
if( i==0 ){
if( pTabList->nSrc==1 ) return 1; /* (1a-i) */
if( pTabList->a[1].fg.jointype & JT_CROSS ) return 1; /* (1a-ii) */
if( pParse->prepFlags & SQLITE_PREPARE_SAFEOPT ) return 0;
if( pTabList->nSrc==1 ) return 1; /* (1a) */
if( pTabList->a[1].fg.jointype & JT_CROSS ) return 1; /* (1b) */
if( pParse->prepFlags & SQLITE_PREPARE_SAFEOPT ) return 0; /* (1c-iii) */
return 1;
}
if( pParse->prepFlags & SQLITE_PREPARE_SAFEOPT ) return 0;
if( pParse->prepFlags & SQLITE_PREPARE_SAFEOPT ) return 0; /* (1c-iii) */
while( 1 /*exit-by-break*/ ){
if( pItem->fg.jointype & (JT_OUTER|JT_CROSS) ) return 0;
if( pItem->fg.jointype & (JT_OUTER|JT_CROSS) ) return 0; /* (1c-ii) */
if( i==0 ) break;
i--;
pItem--;
if( pItem->pSelect!=0 ) return 0;
if( pItem->pSelect!=0 ) return 0; /* (1c-i) */
}
return 1;
}