Fix a problem causing the planner to generate sub-optimal plans for some queries

that use recursive WITH sub-queries with LIMIT clauses.

FossilOrigin-Name: 053a149cc8244a7f85137129cfcb8622efe90306

1 files changed, 56 insertions, 0 deletions

diff --git a/test/with3.test b/test/with3.test
index 62e88441a..5540a7fca 100644
--- a/test/with3.test
+++ b/test/with3.test
@@ -61,4 +61,60 @@ do_execsql_test 2.1 {
   SELECT * FROM t1;
 } {200}
 
+#-------------------------------------------------------------------------
+# Test that the planner notices LIMIT clauses on recursive WITH queries.
+#
+
+ifcapable analyze {
+  do_execsql_test 3.1.1 {
+    CREATE TABLE y1(a, b);
+    CREATE INDEX y1a ON y1(a);
+
+    WITH cnt(i) AS ( SELECT 1 UNION ALL SELECT i+1 FROM cnt LIMIT 1000)
+      INSERT INTO y1 SELECT i%10, i FROM cnt;
+    ANALYZE;
+
+  }
+
+  do_eqp_test 3.1.2 {
+    WITH cnt(i) AS ( SELECT 1 UNION ALL SELECT i+1 FROM cnt LIMIT 1)
+    SELECT * FROM cnt, y1 WHERE i=a
+  } {
+    3 0 0 {SCAN TABLE cnt} 
+    1 0 0 {COMPOUND SUBQUERIES 0 AND 0 (UNION ALL)}
+    0 0 0 {SCAN SUBQUERY 1} 
+    0 1 1 {SEARCH TABLE y1 USING INDEX y1a (a=?)}
+  }
+
+  do_eqp_test 3.1.3 {
+    WITH cnt(i) AS ( SELECT 1 UNION ALL SELECT i+1 FROM cnt LIMIT 1000000)
+    SELECT * FROM cnt, y1 WHERE i=a
+  } {
+    3 0 0 {SCAN TABLE cnt} 
+    1 0 0 {COMPOUND SUBQUERIES 0 AND 0 (UNION ALL)}
+    0 0 1 {SCAN TABLE y1} 
+    0 1 0 {SEARCH SUBQUERY 1 USING AUTOMATIC COVERING INDEX (i=?)}
+  }
+}
+
+do_execsql_test 3.2.1 {
+  CREATE TABLE w1(pk INTEGER PRIMARY KEY, x INTEGER);
+  CREATE TABLE w2(pk INTEGER PRIMARY KEY);
+}
+
+do_eqp_test 3.2.2 {
+  WITH RECURSIVE c(w,id) AS (SELECT 0, (SELECT pk FROM w2 LIMIT 1)
+     UNION ALL SELECT c.w + 1, x FROM w1, c LIMIT 1)
+     SELECT * FROM c, w2, w1
+     WHERE c.id=w2.pk AND c.id=w1.pk;
+} {
+  2 0 0 {EXECUTE SCALAR SUBQUERY 3} 
+  3 0 0 {SCAN TABLE w2} 
+  4 0 0 {SCAN TABLE w1}
+  4 1 1 {SCAN TABLE c} 
+  1 0 0 {COMPOUND SUBQUERIES 0 AND 0 (UNION ALL)} 0 0 0 {SCAN SUBQUERY 1}
+  0 1 1 {SEARCH TABLE w2 USING INTEGER PRIMARY KEY (rowid=?)} 
+  0 2 2 {SEARCH TABLE w1 USING INTEGER PRIMARY KEY (rowid=?)}
+}
+
 finish_test