Bug#37074489 stored procedure is producing different results in different attempts

The error occurs also in the recursive CTE query if used in a prepared statement;
in the first execution the result is correct, but wrong in subsequent executions.

Tracing revealed that the creation of the materialized tmp table
during optimization was made using the wrong key, so execution found
no row matching its where clause againt the constant in this part of
the query:

   SELECT type,
              COUNT(*) AS count
   FROM t
   WHERE batch_uid = 549285

where t is the recursive cte.

The second execution uses index on "type" instead of on "batch_uid"
for materialized table "t" (and also wrong index for materialized
"tran": "refguid' instead of "batch_uid".

This happens because TABLE::s->key_parts is not reset when the tmp
table is cleaned up in 'cleanup_tmp_tables'. s->keys is reset to 0,
but s->key_parts is not touched. This upsets the logic in
TABLE::add_tmp_key, so we end up with the wrong index (the value for
s->key_parts ends up one too high in the second execution).

Solution: reset TABLE_SHARE::key_parts as well in 'cleanup_tmp_tables'.

Change-Id: I556f041f4476817208a6b8beb179ddaa44fd712f

Author: Dag Wanvik

mysql-test/r/with_recursive_bugs.result

@@ -247,3 +247,94 @@ SELECT 2 FROM cte1 WHERE FALSE
 SELECT * FROM cte1;
 1
 DROP TABLE t1;
+#
+# Bug#37074489 stored procedure is producing different results in different attempts
+#              The error also reproduces with prepared statement in 2..n executions
+PREPARE p FROM "WITH RECURSIVE
+tran(batch_uid, guid, type, trantime, refguid) AS (
+SELECT 549285, 'W5PT9A5F3D2WF57', 13, '2023-04-07 09:19:04', NULL
+UNION ALL
+SELECT 549286, 'W5PTVYU84715VJ7', 13, '2023-04-07 09:31:20', 'W5PT9A5F3D2WF57'
+        )
+,t(init_dataset, batch_uid, guid, type, trantime) AS (
+SELECT TRUE AS init_dataset,
+batch_uid,
+guid,
+type,
+trantime
+FROM tran
+WHERE batch_uid = 549285
+UNION ALL
+SELECT FALSE,
+wt.batch_uid,
+wt.guid,
+wt.type,
+wt.trantime
+FROM tran wt
+JOIN
+t ts
+ON wt.refguid = ts.guid
+WHERE wt.batch_uid != 549285 AND init_dataset
+)
+SELECT t2.count
+FROM t
+LEFT JOIN
+( SELECT type,
+COUNT(*) AS count
+FROM t /* t2 */
+WHERE batch_uid = 549285
+GROUP BY type
+) t2 ON t2.type = t.type
+";
+EXECUTE p;
+count
+1
+1
+# This used to yield two NULL rows
+EXECUTE p;
+count
+1
+1
+DROP PREPARE p;
+# Original repro
+CREATE PROCEDURE cte_bug() BEGIN WITH RECURSIVE
+tran(batch_uid, guid, type, trantime, refguid) AS (
+SELECT 549285, 'W5PT9A5F3D2WF57', 13, '2023-04-07 09:19:04', NULL
+UNION ALL
+SELECT 549286, 'W5PTVYU84715VJ7', 13, '2023-04-07 09:31:20', 'W5PT9A5F3D2WF57'
+        )
+,t(init_dataset, batch_uid, guid, type, trantime) AS (
+SELECT TRUE AS init_dataset,
+batch_uid,
+guid,
+type,
+trantime
+FROM tran
+WHERE batch_uid = 549285
+UNION ALL
+SELECT FALSE,
+wt.batch_uid,
+wt.guid,
+wt.type,
+wt.trantime
+FROM tran wt
+JOIN
+t ts
+ON wt.refguid = ts.guid
+WHERE wt.batch_uid != 549285 AND init_dataset
+)
+SELECT t2.count
+FROM t
+LEFT JOIN
+( SELECT type,
+COUNT(*) AS count
+FROM t /* t2 */
+WHERE batch_uid = 549285
+GROUP BY type
+) t2 ON t2.type = t.type
+; END $$
+CALL cte_bug();
+count
+1
+1
+DROP PROCEDURE cte_bug;

mysql-test/t/with_recursive_bugs.test

@@ -264,3 +264,63 @@ WITH RECURSIVE cte1 AS
 SELECT * FROM cte1;
 
 DROP TABLE t1;
+
+--echo #
+--echo # Bug#37074489 stored procedure is producing different results in different attempts
+--echo #              The error also reproduces with prepared statement in 2..n executions
+
+let $query =
+WITH RECURSIVE
+        tran(batch_uid, guid, type, trantime, refguid) AS (
+          SELECT 549285, 'W5PT9A5F3D2WF57', 13, '2023-04-07 09:19:04', NULL
+          UNION ALL
+          SELECT 549286, 'W5PTVYU84715VJ7', 13, '2023-04-07 09:31:20', 'W5PT9A5F3D2WF57'
+        )
+        ,t(init_dataset, batch_uid, guid, type, trantime) AS (
+          SELECT TRUE AS init_dataset,
+               batch_uid,
+               guid,
+               type,
+               trantime
+          FROM tran
+          WHERE batch_uid = 549285
+          UNION ALL
+          SELECT FALSE,
+                 wt.batch_uid,
+                 wt.guid,
+                 wt.type,
+                 wt.trantime
+          FROM tran wt
+               JOIN
+               t ts
+               ON wt.refguid = ts.guid
+          WHERE wt.batch_uid != 549285 AND init_dataset
+        )
+SELECT t2.count
+FROM t
+     LEFT JOIN
+     ( SELECT type,
+              COUNT(*) AS count
+       FROM t /* t2 */
+       WHERE batch_uid = 549285
+       GROUP BY type
+     ) t2 ON t2.type = t.type
+;
+
+eval PREPARE p FROM "$query";
+
+EXECUTE p;
+--echo # This used to yield two NULL rows
+EXECUTE p;
+
+DROP PREPARE p;
+
+--echo # Original repro
+DELIMITER $$;
+
+eval CREATE PROCEDURE cte_bug() BEGIN $query; END $$
+DELIMITER ;$$
+
+CALL cte_bug();
+
+DROP PROCEDURE cte_bug;

sql/sql_union.cc

@@ -1382,6 +1382,8 @@ static void cleanup_tmp_tables(Table_ref *list) {
         // Clear indexes added during optimization, keep possible unique index
         TABLE *t = tl->table;
         t->s->keys = t->s->is_distinct ? 1 : 0;
+        t->s->key_parts =
+            t->s->is_distinct ? t->s->key_info[0].user_defined_key_parts : 0;
         t->s->first_unused_tmp_key = 0;
         t->keys_in_use_for_query.clear_all();
         t->keys_in_use_for_group_by.clear_all();