Use a mini Bloom filter to help reduce the number of pointless searches for

prior SubrtnSig objects when generating code for IN operators with subqueries
as their right operand.

Author: D. Richard Hipp

src/expr.c

@@ -3436,7 +3436,7 @@ static int findCompatibleInRhsSubrtn(
   Vdbe *v;
 
   if( pNewSig==0 ) return 0;
-  if( pParse->bHasSubrtn==0 ) return 0;
+  if( (pParse->mSubrtnSig & (1<<(pNewSig->selId&7)))==0 ) return 0;
   assert( pExpr->op==TK_IN );
   assert( !ExprUseYSub(pExpr) );
   assert( ExprUseXSelect(pExpr) );
@@ -3564,7 +3564,7 @@ void sqlite3CodeRhsOfIN(
       pSig->regReturn = pExpr->y.sub.regReturn;
       pSig->iTable = iTab;
       sqlite3VdbeChangeP4(v, -1, (const char*)pSig, P4_SUBRTNSIG);
-      pParse->bHasSubrtn = 1;
+      pParse->mSubrtnSig = 1 << (pSig->selId&7);
     }
     addrOnce = sqlite3VdbeAddOp0(v, OP_Once); VdbeCoverage(v);
   }

src/sqliteInt.h

@@ -3834,7 +3834,7 @@ struct Parse {
   u8 prepFlags;        /* SQLITE_PREPARE_* flags */
   u8 withinRJSubrtn;   /* Nesting level for RIGHT JOIN body subroutines */
   u8 bHasWith;         /* True if statement contains WITH */
-  u8 bHasSubrtn;       /* True if any P4_SUBRTNSIG has been set */
+  u8 mSubrtnSig;       /* mini Bloom filter on available SubrtnSig.selId */
 #if defined(SQLITE_DEBUG) || defined(SQLITE_COVERAGE_TEST)
   u8 earlyCleanup;     /* OOM inside sqlite3ParserAddCleanup() */
 #endif