Disable the skip-scan optimization for DISTINCT queries.

Fix for ticket [ced41c7c7d6b4d36]
timerz98 · Jul 30, 2019 · 4e64819 · 4e64819
1 parent 496878e
commit 4e64819
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diff --git a/src/where.c b/src/where.c
@@ -2723,6 +2723,7 @@ static int whereLoopAddBtreeIndex(
    && pProbe->noSkipScan==0
    && OptimizationEnabled(db, SQLITE_SkipScan)
    && pProbe->aiRowLogEst[saved_nEq+1]>=42  /* TUNING: Minimum for skip-scan */
+   && (pWInfo->wctrlFlags & (WHERE_WANT_DISTINCT|WHERE_DISTINCTBY))==0
    && (rc = whereLoopResize(db, pNew, pNew->nLTerm+1))==SQLITE_OK
   ){
     LogEst nIter;

diff --git a/test/skipscan1.test b/test/skipscan1.test
@@ -373,4 +373,21 @@ do_execsql_test skipscan1-2.3 {
   SELECT a,b,c,d,'|' FROM t6 WHERE d<>99 AND b=345 ORDER BY a DESC;
 } {}
 
+# 2019-07-29 Ticket ced41c7c7d6b4d36
+# Skip-scan is disabled for DISTINCT queries
+#
+db close
+sqlite3 db :memory:
+do_execsql_test skipscan1-3.1 {
+  CREATE TABLE t1 (c1, c2, c3, c4, PRIMARY KEY(c4, c3));
+  INSERT INTO t1 VALUES(NULL,0,1,NULL);
+  INSERT INTO t1 VALUES(0,NULL,1,NULL);
+  INSERT INTO t1 VALUES(NULL,NULL,1,NULL);
+  ANALYZE sqlite_master;
+  INSERT INTO sqlite_stat1 VALUES('t1','sqlite_autoindex_t1_1','18 18 6');
+  ANALYZE sqlite_master;
+  SELECT DISTINCT quote(c1), quote(c2), quote(c3), quote(c4), '|'
+    FROM t1 WHERE t1.c3 = 1;
+} {NULL 0 1 NULL | 0 NULL 1 NULL | NULL NULL 1 NULL |}
+
 finish_test