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

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

FossilOrigin-Name: cf00ebfc4b77f45ec466b0d57d7c22c7f48acab19e4e55b168eb4b53f390d887

1 files changed, 5 insertions, 7 deletions

diff --git a/src/select.c b/src/select.c
index 3672a7c0f..80b488777 100644
--- a/src/select.c
+++ b/src/select.c
@@ -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);