Enhancements to covering-index prediction. In particular, avoid the

false-positive prediction described by
[forum:/forumpost/e60e4c295d22f8ce|forum post e60e4c295d22f8ce].
Add early detection of over-prediction of covering-indexes so that
sqlite3_prepare() will return an error rather than just generate bad
bytecode.

FossilOrigin-Name: f0b671183f44d0ae294956e7651a1653f47bd6219f9636872d15993f30f28dfb

1 files changed, 18 insertions, 40 deletions

diff --git a/src/where.c b/src/where.c
index c850121c3..15f5fe7d9 100644
--- a/src/where.c
+++ b/src/where.c
@@ -4047,7 +4047,9 @@ static int whereLoopAddBtree(
                   " according to whereIsCoveringIndex()\n", pProbe->zName));
             }
           }
-        }else if( m==0 ){
+        }else if( m==0 
+           && (HasRowid(pTab) || pWInfo->pSelect!=0 || sqlite3FaultSim(700))
+        ){
           WHERETRACE(0x200,
              ("-> %s a covering index according to bitmasks\n",
              pProbe->zName, m==0 ? "is" : "is not"));
@@ -7078,26 +7080,6 @@ whereBeginError:
   }
 #endif
 
-#ifdef SQLITE_DEBUG
-/*
-** Return true if cursor iCur is opened by instruction k of the
-** bytecode.  Used inside of assert() only.
-*/
-static int cursorIsOpen(Vdbe *v, int iCur, int k){
-  while( k>=0 ){
-    VdbeOp *pOp = sqlite3VdbeGetOp(v,k--);
-    if( pOp->p1!=iCur ) continue;
-    if( pOp->opcode==OP_Close ) return 0;
-    if( pOp->opcode==OP_OpenRead ) return 1;
-    if( pOp->opcode==OP_OpenWrite ) return 1;
-    if( pOp->opcode==OP_OpenDup ) return 1;
-    if( pOp->opcode==OP_OpenAutoindex ) return 1;
-    if( pOp->opcode==OP_OpenEphemeral ) return 1;
-  }
-  return 0;
-}
-#endif /* SQLITE_DEBUG */
-
 /*
 ** Generate the end of the WHERE loop.  See comments on
 ** sqlite3WhereBegin() for additional information.
@@ -7376,18 +7358,20 @@ void sqlite3WhereEnd(WhereInfo *pWInfo){
           assert( pIdx->pTable==pTab );
 #ifdef SQLITE_ENABLE_OFFSET_SQL_FUNC
           if( pOp->opcode==OP_Offset ){
-            /* Do not need to translate the column number */
+            x = 0;
           }else
 #endif
-          if( !HasRowid(pTab) ){
-            Index *pPk = sqlite3PrimaryKeyIndex(pTab);
-            x = pPk->aiColumn[x];
-            assert( x>=0 );
-          }else{
-            testcase( x!=sqlite3StorageColumnToTable(pTab,x) );
-            x = sqlite3StorageColumnToTable(pTab,x);
+          {
+            if( !HasRowid(pTab) ){
+              Index *pPk = sqlite3PrimaryKeyIndex(pTab);
+              x = pPk->aiColumn[x];
+              assert( x>=0 );
+            }else{
+              testcase( x!=sqlite3StorageColumnToTable(pTab,x) );
+              x = sqlite3StorageColumnToTable(pTab,x);
+            }
+            x = sqlite3TableColumnToIndex(pIdx, x);
           }
-          x = sqlite3TableColumnToIndex(pIdx, x);
           if( x>=0 ){
             pOp->p2 = x;
             pOp->p1 = pLevel->iIdxCur;
@@ -7397,16 +7381,10 @@ void sqlite3WhereEnd(WhereInfo *pWInfo){
             ** reference.  Verify that this is harmless - that the
             ** table being referenced really is open.
             */
-#ifdef SQLITE_ENABLE_OFFSET_SQL_FUNC
-            assert( (pLoop->wsFlags & WHERE_IDX_ONLY)==0
-                 || cursorIsOpen(v,pOp->p1,k)
-                 || pOp->opcode==OP_Offset
-            );
-#else
-            assert( (pLoop->wsFlags & WHERE_IDX_ONLY)==0
-                 || cursorIsOpen(v,pOp->p1,k)
-            );
-#endif
+            if( pLoop->wsFlags & WHERE_IDX_ONLY ){
+              sqlite3ErrorMsg(pParse, "internal query planner error");
+              pParse->rc = SQLITE_INTERNAL;
+            }
           }
         }else if( pOp->opcode==OP_Rowid ){
           pOp->p1 = pLevel->iIdxCur;