From 1e31d74833d56609f8711022394c1eb2eb25a19a Mon Sep 17 00:00:00 2001
From: Varun Gupta <varun.gupta@mariadb.com>
Date: Thu, 23 Jul 2020 14:17:05 +0530
Subject: MDEV-17066: Bytes lost or Assertion `status_var.local_memory_used ==
 0 after DELETE with subquery with ROLLUP

The issue here is when records are read from the temporary file
(filesort result in this case) via a cache(rr_from_cache).
The cache is initialized with init_rr_cache.
For correlated subquery the cache allocation is happening at each execution
of the subquery but the deallocation happens only once and that was
when the query execution was done.

So generally for subqueries we do two types of cleanup

1) Full cleanup: we should free all resources of the query(like temp tables).
   This is done generally when the query execution is complete or the subquery
   re-execution is not needed (case with uncorrelated subquery)

2) Partial cleanup: Minor cleanup that is required if
   the subquery needs recalculation. This is done for all the structures that
   need to be allocated for each execution (example SORT_INFO for filesort
   is allocated for each execution of the correlated subquery).

The fix here would be free the cache used by rr_from_cache in the partial
cleanup phase.
---
 sql/sql_select.cc | 53 +++++++++++++++++++++++++++++++++++------------------
 1 file changed, 35 insertions(+), 18 deletions(-)

(limited to 'sql/sql_select.cc')

diff --git a/sql/sql_select.cc b/sql/sql_select.cc
index 379a109c57c..96e9602d77d 100644
--- a/sql/sql_select.cc
+++ b/sql/sql_select.cc
@@ -12391,24 +12391,7 @@ void JOIN::cleanup(bool full)
       for (tab= first_linear_tab(this, WITH_BUSH_ROOTS, WITH_CONST_TABLES); tab;
            tab= next_linear_tab(this, tab, WITH_BUSH_ROOTS))
       {
-        if (!tab->table)
-          continue;
-        DBUG_PRINT("info", ("close index: %s.%s  alias: %s",
-                            tab->table->s->db.str,
-                            tab->table->s->table_name.str,
-                            tab->table->alias.c_ptr()));
-	if (tab->table->is_created())
-        {
-          tab->table->file->ha_index_or_rnd_end();
-          if (tab->aggr)
-          {
-            int tmp= 0;
-            if ((tmp= tab->table->file->extra(HA_EXTRA_NO_CACHE)))
-              tab->table->file->print_error(tmp, MYF(0));
-          }
-        }
-        delete tab->filesort_result;
-        tab->filesort_result= NULL;
+        tab->partial_cleanup();
       }
     }
   }
@@ -26982,6 +26965,40 @@ void JOIN::handle_implicit_grouping_with_window_funcs()
   }
 }
 
+
+/*
+  @brief
+    Perform a partial cleanup for the JOIN_TAB structure
+
+  @note
+    this is used to cleanup resources for the re-execution of correlated
+    subqueries.
+*/
+void JOIN_TAB::partial_cleanup()
+{
+  if (!table)
+    return;
+
+  if (table->is_created())
+  {
+    table->file->ha_index_or_rnd_end();
+    DBUG_PRINT("info", ("close index: %s.%s  alias: %s",
+               table->s->db.str,
+               table->s->table_name.str,
+               table->alias.c_ptr()));
+    if (aggr)
+    {
+      int tmp= 0;
+      if ((tmp= table->file->extra(HA_EXTRA_NO_CACHE)))
+        table->file->print_error(tmp, MYF(0));
+    }
+  }
+  delete filesort_result;
+  filesort_result= NULL;
+  free_cache(&read_record);
+}
+
+
 /**
   @} (end of group Query_Optimizer)
 */
-- 
cgit v1.2.1