Back out the "low-quality index" query planner hack of check-in

[bcac937526d9a6ef].  Subsequent query planner enhancements for dealing
with star-queries make that change unnecessary and the change was recently
found to cause a performance regression in an unrelated query.
Also fix a typo in a debugging message.

FossilOrigin-Name: e7dcf25efae364b7cdf9eb8265803c816c8b8557e4a7684da428badc6ffb3875

3 files changed, 3 insertions, 17 deletions

diff --git a/src/analyze.c b/src/analyze.c
index 8ca0e3e74..2721f2523 100644
--- a/src/analyze.c
+++ b/src/analyze.c
@@ -1576,16 +1576,6 @@ static void decodeIntArray(
       while( z[0]!=0 && z[0]!=' ' ) z++;
       while( z[0]==' ' ) z++;
     }
-
-    /* Set the bLowQual flag if the peak number of rows obtained
-    ** from a full equality match is so large that a full table scan
-    ** seems likely to be faster than using the index.
-    */
-    if( aLog[0] > 66              /* Index has more than 100 rows */
-     && aLog[0] <= aLog[nOut-1]   /* And only a single value seen */
-    ){
-      pIndex->bLowQual = 1;
-    }
   }
 }
 
diff --git a/src/sqliteInt.h b/src/sqliteInt.h
index edf925964..af7ed4a4c 100644
--- a/src/sqliteInt.h
+++ b/src/sqliteInt.h
@@ -2789,7 +2789,6 @@ struct Index {
   unsigned isCovering:1;   /* True if this is a covering index */
   unsigned noSkipScan:1;   /* Do not try to use skip-scan if true */
   unsigned hasStat1:1;     /* aiRowLogEst values come from sqlite_stat1 */
-  unsigned bLowQual:1;     /* sqlite_stat1 says this is a low-quality index */
   unsigned bNoQuery:1;     /* Do not use this index to optimize queries */
   unsigned bAscKeyBug:1;   /* True if the bba7b69f9849b5bf bug applies */
   unsigned bIdxRowid:1;    /* One or more of the index keys is the ROWID */
diff --git a/src/where.c b/src/where.c
index c51d1ba81..0103db5e8 100644
--- a/src/where.c
+++ b/src/where.c
@@ -3159,11 +3159,8 @@ static int whereLoopAddBtreeIndex(
     assert( pNew->u.btree.nBtm==0 );
     opMask = WO_EQ|WO_IN|WO_GT|WO_GE|WO_LT|WO_LE|WO_ISNULL|WO_IS;
   }
-  if( pProbe->bUnordered || pProbe->bLowQual ){
-    if( pProbe->bUnordered ) opMask &= ~(WO_GT|WO_GE|WO_LT|WO_LE);
-    if( pProbe->bLowQual && pSrc->fg.isIndexedBy==0 ){ 
-      opMask &= ~(WO_EQ|WO_IN|WO_IS);
-    }
+  if( pProbe->bUnordered ){
+    opMask &= ~(WO_GT|WO_GE|WO_LT|WO_LE);
   }
 
   assert( pNew->u.btree.nEq<pProbe->nColumn );
@@ -4100,7 +4097,7 @@ static int whereLoopAddBtree(
            && (HasRowid(pTab) || pWInfo->pSelect!=0 || sqlite3FaultSim(700))
         ){
           WHERETRACE(0x200,
-             ("-> %s a covering index according to bitmasks\n",
+             ("-> %s is a covering index according to bitmasks\n",
              pProbe->zName, m==0 ? "is" : "is not"));
           pNew->wsFlags = WHERE_IDX_ONLY | WHERE_INDEXED;
         }