Invert the meaning of the regBignull flag so that it is 1 when doing the

normal scan and 1 when scanning nulls.  This enables the re-do jump at the
bottom of the loop to be coded with a single OP_IfNotZero opcode, rather
than a sequence of OP_If, OP_Integer, OP_Goto.

FossilOrigin-Name: bf875e1a259a4167694e06349458452dc36c1d38aa6843518d9ae46ce74e5559

3 files changed, 8 insertions, 14 deletions

diff --git a/src/where.c b/src/where.c
index 00aa5f366..1dbeb0e06 100644
--- a/src/where.c
+++ b/src/where.c
@@ -5218,13 +5218,7 @@ void sqlite3WhereEnd(WhereInfo *pWInfo){
       VdbeCoverageIf(v, pLevel->op==OP_VNext);
       if( pLevel->regBignull ){
         sqlite3VdbeResolveLabel(v, pLevel->addrBignull);
-        addr = sqlite3VdbeAddOp1(v, OP_If, pLevel->regBignull);
-        VdbeComment((v, "If NULL-scan done"));
-        VdbeCoverage(v);
-        sqlite3VdbeAddOp2(v, OP_Integer, 1, pLevel->regBignull);
-        sqlite3VdbeAddOp2(v, OP_Goto, 0, pLevel->p2-1);
-        VdbeComment((v, "Do the NULL-scan"));
-        sqlite3VdbeJumpHere(v, addr);
+        sqlite3VdbeAddOp2(v, OP_IfNotZero, pLevel->regBignull, pLevel->p2-1);
       }
 #ifndef SQLITE_DISABLE_SKIPAHEAD_DISTINCT
       if( addrSeek ) sqlite3VdbeJumpHere(v, addrSeek);
diff --git a/src/whereInt.h b/src/whereInt.h
index d1fc3515a..e63ca46d5 100644
--- a/src/whereInt.h
+++ b/src/whereInt.h
@@ -71,7 +71,7 @@ struct WhereLevel {
   int addrCont;         /* Jump here to continue with the next loop cycle */
   int addrFirst;        /* First instruction of interior of the loop */
   int addrBody;         /* Beginning of the body of this loop */
-  int regBignull;       /* big-null flag reg. True if NULLs not yet scanned */
+  int regBignull;       /* big-null flag reg. True if a NULL-scan is needed */
   int addrBignull;      /* Jump here for next part of big-null scan */
 #ifndef SQLITE_LIKE_DOESNT_MATCH_BLOBS
   u32 iLikeRepCntr;     /* LIKE range processing counter register (times 2) */
diff --git a/src/wherecode.c b/src/wherecode.c
index 12ed0d7af..2aff70554 100644
--- a/src/wherecode.c
+++ b/src/wherecode.c
@@ -1690,8 +1690,8 @@ Bitmask sqlite3WhereCodeOneLoopStart(
         sqlite3VdbeAddOp1(v, OP_SeekHit, iIdxCur);
       }
       if( regBignull ){
-        sqlite3VdbeAddOp2(v, OP_Integer, 0, regBignull);
-        VdbeComment((v, "NULL-scan flag"));
+        sqlite3VdbeAddOp2(v, OP_Integer, 1, regBignull);
+        VdbeComment((v, "NULL-scan needed flag"));
       }
 
       op = aStartOp[(start_constraints<<2) + (startEq<<1) + bRev];
@@ -1776,8 +1776,8 @@ Bitmask sqlite3WhereCodeOneLoopStart(
     /* Check if the index cursor is past the end of the range. */
     if( nConstraint ){
       if( regBignull ){
-        sqlite3VdbeAddOp2(v, OP_If, regBignull, sqlite3VdbeCurrentAddr(v)+3);
-        VdbeComment((v, "If in NULL-scan"));
+        sqlite3VdbeAddOp2(v, OP_IfNot, regBignull, sqlite3VdbeCurrentAddr(v)+3);
+        VdbeComment((v, "If NULL-scan active"));
         VdbeCoverage(v);
       }
       op = aEndOp[bRev*2 + endEq];
@@ -1788,8 +1788,8 @@ Bitmask sqlite3WhereCodeOneLoopStart(
       testcase( op==OP_IdxLE );  VdbeCoverageIf(v, op==OP_IdxLE );
     }
     if( regBignull ){
-      sqlite3VdbeAddOp2(v, OP_IfNot, regBignull, sqlite3VdbeCurrentAddr(v)+2);
-      VdbeComment((v, "If not in NULL-scan"));
+      sqlite3VdbeAddOp2(v, OP_If, regBignull, sqlite3VdbeCurrentAddr(v)+2);
+      VdbeComment((v, "If NULL-scan pending"));
       VdbeCoverage(v);
       if( bStopAtNull ){
         op = aEndOp[bRev*2 + 0];