Bug#36918913 INCORRECT QUERY RESULT FOR INDEX_SUBQUERY TYPE

                          IN NULL SUBQUERY

The filter condition in the subquery was getting ignored when a query
uses indexsubquery-engine for subquery execution and the subquery
table uses materialization in the plan. The derived table access path
was replacing the filter condition resulting a final plan without the
filter layer. Updated the code to add derived table access path along
with the filter access path instead of replacing.

Change-Id: I26b14f033c35fb8aa2cafab2c9dec5dda2070baa

Author: Ajo Robert

mysql-test/r/condition_filter.result

@@ -105,3 +105,37 @@ OK
 1
 SET optimizer_trace="enabled=off";
 DROP TABLE t1, t2;
+#
+# Bug#36918913 INCORRECT QUERY RESULT FOR INDEX_SUBQUERY TYPE IN NULL
+#              SUBQUERY
+#
+SET @save_optimizer_switch= @@optimizer_switch;
+SET @@optimizer_switch= 'semijoin=off';
+CREATE TABLE t1 (a INT);
+INSERT INTO t1 VALUES (1), (2), (3);
+CREATE TABLE t2 (b INT);
+INSERT INTO t2 VALUES (1), (2), (3);
+ANALYZE TABLE t1, t2;
+Table	Op	Msg_type	Msg_text
+test.t1	analyze	status	OK
+test.t2	analyze	status	OK
+SELECT * FROM t1 WHERE a IN (SELECT * FROM (
+SELECT b FROM t2 ORDER BY b LIMIT 2) x where b > 1);
+a
+2
+EXPLAIN FORMAT=TREE SELECT * FROM t1 WHERE a IN (SELECT * FROM (
+SELECT b FROM t2 ORDER BY b LIMIT 2) x where b > 1);
+EXPLAIN
+-> Filter: <in_optimizer>(t1.a,<exists>(select #2))  (rows=3)
+    -> Table scan on t1  (rows=3)
+    -> Select #2 (subquery in condition; dependent)
+        -> Limit: 1 row(s)  (rows=1)
+            -> Filter: (x.b > 1)  (rows=2)
+                -> Covering index lookup on x using <auto_key0> (b=<cache>(t1.a))  (rows=2)
+                    -> Materialize  (rows=2)
+                        -> Limit: 2 row(s)  (rows=2)
+                            -> Sort: t2.b, limit input to 2 row(s) per chunk  (rows=3)
+                                -> Table scan on t2  (rows=3)
+
+DROP TABLE t1,t2;
+SET @@optimizer_switch= @save_optimizer_switch;

mysql-test/r/explain_tree.result

@@ -868,13 +868,14 @@ EXPLAIN
 -> Group (no aggregates)  (cost=0.45 rows=1)
     -> Table scan on t1  (cost=0.35 rows=1)
 -> Select #2 (subquery in projection; dependent)
-    -> Limit: 1 row(s)  (cost=1.85..1.85 rows=1)
-        -> Filter: <if>(outer_field_is_not_null, <is_not_null_test>(d.a), true)  (cost=1.85..1.85 rows=1)
-            -> Alternative plans for IN subquery: Index lookup unless a IS NULL  (cost=0.8..1.85 rows=4)
-                -> Covering index lookup on d using <auto_key0> (a=<cache>(t1.a) or NULL)  (cost=1.4 rows=4)
-                    -> Materialize  (cost=0.45..0.45 rows=1)
-                        -> Table scan on t1  (cost=0.35 rows=1)
-                -> Table scan on d  (cost=2.52 rows=2)
+    -> Limit: 1 row(s)  (cost=1.95..1.95 rows=1)
+        -> Filter: <if>(outer_field_is_not_null, <is_not_null_test>(d.a), true)  (cost=1.95..1.95 rows=1)
+            -> Filter: <if>(outer_field_is_not_null, ((<cache>(t1.a) = d.a) or (d.a is null)), true)  (cost=1.95..1.95 rows=1)
+                -> Alternative plans for IN subquery: Index lookup unless a IS NULL  (cost=0.8..1.85 rows=4)
+                    -> Covering index lookup on d using <auto_key0> (a=<cache>(t1.a) or NULL)  (cost=1.4 rows=4)
+                        -> Materialize  (cost=0.45..0.45 rows=1)
+                            -> Table scan on t1  (cost=0.35 rows=1)
+                    -> Table scan on d  (cost=2.52 rows=2)
 
 Warnings:
 Warning	1287	Setting user variables within expressions is deprecated and will be removed in a future release. Consider alternatives: 'SET variable=expression, ...', or 'SELECT expression(s) INTO variables(s)'.

mysql-test/t/condition_filter.test

@@ -1,3 +1,5 @@
+--source include/elide_costs.inc
+
 --echo #
 --echo # Bug 20219846: EXPLAIN FOR LIMIT QUERY SHOWS FILESORT BUT EXECUTION
 --echo #               IS DONE WITH INDEX ONLY
@@ -81,3 +83,23 @@ SELECT TRACE NOT RLIKE '"final_filtering_effect": 1' AS OK
 SET optimizer_trace="enabled=off";
 
 DROP TABLE t1, t2;
+
+--echo #
+--echo # Bug#36918913 INCORRECT QUERY RESULT FOR INDEX_SUBQUERY TYPE IN NULL
+--echo #              SUBQUERY
+--echo #
+SET @save_optimizer_switch= @@optimizer_switch;
+SET @@optimizer_switch= 'semijoin=off';
+CREATE TABLE t1 (a INT);
+INSERT INTO t1 VALUES (1), (2), (3);
+CREATE TABLE t2 (b INT);
+INSERT INTO t2 VALUES (1), (2), (3);
+ANALYZE TABLE t1, t2;
+SELECT * FROM t1 WHERE a IN (SELECT * FROM (
+    SELECT b FROM t2 ORDER BY b LIMIT 2) x where b > 1);
+--skip_if_hypergraph  # Depends on the query plan.
+--replace_regex $elide_costs
+EXPLAIN FORMAT=TREE SELECT * FROM t1 WHERE a IN (SELECT * FROM (
+                  SELECT b FROM t2 ORDER BY b LIMIT 2) x where b > 1);
+DROP TABLE t1,t2;
+SET @@optimizer_switch= @save_optimizer_switch;

sql/sql_executor.cc

@@ -3405,8 +3405,7 @@ void JOIN::create_access_paths_for_index_subquery() {
       path = NewMaterializedTableFunctionAccessPath(thd, first_qep_tab->table(),
                                                     tl->table_function, path);
     } else {
-      path = GetAccessPathForDerivedTable(thd, first_qep_tab,
-                                          first_qep_tab->access_path());
+      path = GetAccessPathForDerivedTable(thd, first_qep_tab, path);
     }
   }