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Revisit [f84b2beca7197589]: disallow co-routine implementations of tables

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that are to the left of a RIGHT JOIN, to avoid other complications.

FossilOrigin-Name: cf00ebfc4b77f45ec466b0d57d7c22c7f48acab19e4e55b168eb4b53f390d887
This commit is contained in:
drh
2022-04-10 23:01:20 +00:00
parent 62ed36bb5d
commit 9debb58e48
4 changed files with 155 additions and 108 deletions
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12
src/select.c
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@@ -6727,18 +6727,19 @@ int sqlite3Select(
/* Generate code to implement the subquery
**
** The subquery is implemented as a co-routine if:
** The subquery is implemented as a co-routine 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
**
** TODO: Are there other reasons beside (1) and (2) to use a co-routine
** implementation?
** (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) */
){
/* Implement a co-routine that will return a single row of the result
** set on each invocation.
@@ -6755,9 +6756,6 @@ int sqlite3Select(
pItem->pTab->nRowLogEst = pSub->nSelectRow;
pItem->fg.viaCoroutine = 1;
pItem->regResult = dest.iSdst;
if( pItem->fg.jointype & JT_LTORJ ){
sqlite3VdbeAddOp3(v, OP_Null, 0, dest.iSdst, dest.iSdst+dest.nSdst-1);
}
sqlite3VdbeEndCoroutine(v, pItem->regReturn);
sqlite3VdbeJumpHere(v, addrTop-1);
sqlite3ClearTempRegCache(pParse);