DEV-10595 MariaDB daemon leaks memory with specific query

The issue was that in some extreme cases when doing GROUP BY,
buffers for temporary blobs where not properly cleared.

mysql-test/r/group_min_max_innodb.result

@@ -286,3 +286,19 @@ F	28	28
 F	29	29
 F	30	30
 DROP TABLE t0,t1,t2;
+#
+# MDEV-MariaDB daemon leaks memory with specific query
+#
+CREATE TABLE t1 (`voter_id` int(11) unsigned NOT NULL,
+`language_id` int(11) unsigned NOT NULL DEFAULT '1'
+) ENGINE=InnoDB DEFAULT CHARSET=utf8;
+CREATE TABLE t2 (`voter_id` int(10) unsigned NOT NULL DEFAULT '0',
+`serialized_c` mediumblob) ENGINE=InnoDB DEFAULT CHARSET=utf8;
+insert into t2 values (1,repeat("a",1000)),(2,repeat("a",1000)),(3,repeat("b",1000)),(4,repeat("c",1000)),(4,repeat("b",1000));
+SELECT GROUP_CONCAT(t1.language_id SEPARATOR ',') AS `translation_resources`, `d`.`serialized_c` FROM t2 AS `d` LEFT JOIN t1 ON `d`.`voter_id` = t1.`voter_id` GROUP BY `d`.`voter_id` ORDER BY 10-d.voter_id+RAND()*0;
+translation_resources	serialized_c
+NULL	cccccccccccccccccccccccccccccccccccccccccccccccccccccccccccccccccccccccccccccccccccccccccccccccccccccccccccccccccccccccccccccccccccccccccccccccccccccccccccccccccccccccccccccccccccccccccccccccccccccccccccccccccccccccccccccccccccccccccccccccccccccccccccccccccccccccccccccccccccccccccccccccccccccccccccccccccccccccccccccccccccccccccccccccccccccccccccccccccccccccccccccccccccccccccccccccccccccccccccccccccccccccccccccccccccccccccccccccccccccccccccccccccccccccccccccccccccccccccccccccccccccccccccccccccccccccccccccccccccccccccccccccccccccccccccccccccccccccccccccccccccccccccccccccccccccccccccccccccccccccccccccccccccccccccccccccccccccccccccccccccccccccccccccccccccccccccccccccccccccccccccccccccccccccccccccccccccccccccccccccccccccccccccccccccccccccccccccccccccccccccccccccccccccccccccccccccccccccccccccccccccccccccccccccccccccccccccccccccccccccccccccccccccccccccccccccccccccccccccccccccccccccccccccccccccccccccccccccccccccccccccccccccccccccccccccccccccccccccccccccccccccccccccccccccccccccccccccccccccccccc
+NULL	bbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbb
+NULL	aaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaa
+NULL	aaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaa
+drop table t1,t2;

mysql-test/t/group_min_max_innodb.test

@@ -230,3 +230,16 @@ eval EXPLAIN $query;
 eval $query;
 
 DROP TABLE t0,t1,t2;
+
+--echo #
+--echo # MDEV-MariaDB daemon leaks memory with specific query
+--echo #
+
+CREATE TABLE t1 (`voter_id` int(11) unsigned NOT NULL,
+  `language_id` int(11) unsigned NOT NULL DEFAULT '1'
+) ENGINE=InnoDB DEFAULT CHARSET=utf8;
+CREATE TABLE t2 (`voter_id` int(10) unsigned NOT NULL DEFAULT '0',
+  `serialized_c` mediumblob) ENGINE=InnoDB DEFAULT CHARSET=utf8;
+insert into t2 values (1,repeat("a",1000)),(2,repeat("a",1000)),(3,repeat("b",1000)),(4,repeat("c",1000)),(4,repeat("b",1000));
+SELECT GROUP_CONCAT(t1.language_id SEPARATOR ',') AS `translation_resources`, `d`.`serialized_c` FROM t2 AS `d` LEFT JOIN t1 ON `d`.`voter_id` = t1.`voter_id` GROUP BY `d`.`voter_id` ORDER BY 10-d.voter_id+RAND()*0;
+drop table t1,t2;

sql/sql_class.h

@@ -3607,6 +3607,11 @@ public:
       save_copy_field_end= copy_field_end= NULL;
     }
   }
+  void free_copy_field_data()
+  {
+    for (Copy_field *ptr= copy_field ; ptr != copy_field_end ; ptr++)
+      ptr->tmp.free();
+  }
 };
 
 class select_union :public select_result_interceptor

sql/sql_select.cc

@@ -8277,7 +8277,24 @@ JOIN::make_simple_join(JOIN *parent, TABLE *temp_table)
   */
   if (!tmp_join || tmp_join != this)
     tmp_table_param.cleanup();
+  else
+  {
+    /*
+      Free data buffered in copy_fields, but keep data pointed by copy_field
+      around for next iteration (possibly stored in save_copy_fields).
+
+      It would be logically simpler to not clear copy_field
+      below, but as we have loops that runs over copy_field to
+      copy_field_end that should not be done anymore, it's simpler to
+      just clear the pointers.
+
+      Another option would be to just clear copy_field_end and not run
+      the loops if this is not set or to have tmp_table_param.cleanup()
+      to run cleanup on save_copy_field if copy_field is not set.
+    */
+    tmp_table_param.free_copy_field_data();
     tmp_table_param.copy_field= tmp_table_param.copy_field_end=0;
+  }
   first_record= sort_and_group=0;
   send_records= (ha_rows) 0;
 
@@ -10866,7 +10883,7 @@ void JOIN::join_free()
 /**
   Free resources of given join.
 
-  @param fill   true if we should free all resources, call with full==1
+  @param full   true if we should free all resources, call with full==1
                 should be last, before it this function can be called with
                 full==0
 
@@ -10982,7 +10999,7 @@ void JOIN::cleanup(bool full)
     /*
       If we have tmp_join and 'this' JOIN is not tmp_join and
       tmp_table_param.copy_field's  of them are equal then we have to remove
-      pointer to  tmp_table_param.copy_field from tmp_join, because it qill
+      pointer to  tmp_table_param.copy_field from tmp_join, because it will
       be removed in tmp_table_param.cleanup().
     */
     if (tmp_join &&