Avoid an OP_Next in cases where an IN(...) query against a UNIQUE index may return at most 1 row.

FossilOrigin-Name: d7648e21605a0b381b1935a47e5a77bdfacc4cc96f03d6bb7956f8f4e6a40648

1 files changed, 24 insertions, 1 deletions

diff --git a/src/wherecode.c b/src/wherecode.c
index d95eae279..a895d3935 100644
--- a/src/wherecode.c
+++ b/src/wherecode.c
@@ -1338,6 +1338,27 @@ static SQLITE_NOINLINE void filterPullDown(
 }
 
 /*
+** Loop pLoop is a WHERE_INDEXED level that uses at least one IN(...) 
+** operator. Return true if level pLoop is guaranteed to visit only one 
+** row for each key generated for the index.
+*/
+static int whereLoopIsOneRow(WhereLoop *pLoop){
+  if( pLoop->u.btree.pIndex->onError 
+   && pLoop->nSkip==0 
+   && pLoop->u.btree.nEq==pLoop->u.btree.pIndex->nKeyCol 
+  ){
+    int ii;
+    for(ii=0; ii<pLoop->u.btree.nEq; ii++){
+      if( pLoop->aLTerm[ii]->eOperator & (WO_IS|WO_ISNULL) ){
+        return 0;
+      }
+    }
+    return 1;
+  }
+  return 0;
+}
+
+/*
 ** Generate code for the start of the iLevel-th loop in the WHERE clause
 ** implementation described by pWInfo.
 */
@@ -2084,7 +2105,9 @@ Bitmask sqlite3WhereCodeOneLoopStart(
     }
  
     /* Record the instruction used to terminate the loop. */
-    if( pLoop->wsFlags & WHERE_ONEROW ){
+    if( (pLoop->wsFlags & WHERE_ONEROW)
+     || (pLevel->u.in.nIn && whereLoopIsOneRow(pLoop))
+    ){
       pLevel->op = OP_Noop;
     }else if( bRev ){
       pLevel->op = OP_Prev;