automerge

mysql-test/include/index_merge1.inc

@@ -527,4 +527,30 @@ where exists (select 1 from t2, t3
 
 drop table t0, t1, t2, t3;
 
+--echo #
+--echo # BUG#44810: index merge and order by with low sort_buffer_size 
+--echo # crashes server!
+--echo #
+CREATE TABLE t1(a VARCHAR(128),b VARCHAR(128),KEY(A),KEY(B));
+INSERT INTO t1 VALUES (REPEAT('a',128),REPEAT('b',128));
+INSERT INTO t1 SELECT * FROM t1;
+INSERT INTO t1 SELECT * FROM t1;
+INSERT INTO t1 SELECT * FROM t1;
+INSERT INTO t1 SELECT * FROM t1;
+INSERT INTO t1 SELECT * FROM t1;
+INSERT INTO t1 SELECT * FROM t1;
+SET SESSION sort_buffer_size=1;
+EXPLAIN 
+SELECT * FROM t1 FORCE INDEX(a,b) WHERE a LIKE 'a%' OR b LIKE 'b%' 
+  ORDER BY a,b;
+# we don't actually care about the result : we're checking if it crashes
+--disable_result_log
+SELECT * FROM t1 FORCE INDEX(a,b) WHERE a LIKE 'a%' OR b LIKE 'b%' 
+  ORDER BY a,b;
+--enable_result_log
+
+SET SESSION sort_buffer_size=DEFAULT;
+DROP TABLE t1;
+
+
 --echo End of 5.0 tests

mysql-test/r/index_merge_myisam.result

@@ -557,6 +557,30 @@ a
 1
 2
 drop table t0, t1, t2, t3;
+#
+# BUG#44810: index merge and order by with low sort_buffer_size 
+# crashes server!
+#
+CREATE TABLE t1(a VARCHAR(128),b VARCHAR(128),KEY(A),KEY(B));
+INSERT INTO t1 VALUES (REPEAT('a',128),REPEAT('b',128));
+INSERT INTO t1 SELECT * FROM t1;
+INSERT INTO t1 SELECT * FROM t1;
+INSERT INTO t1 SELECT * FROM t1;
+INSERT INTO t1 SELECT * FROM t1;
+INSERT INTO t1 SELECT * FROM t1;
+INSERT INTO t1 SELECT * FROM t1;
+SET SESSION sort_buffer_size=1;
+Warnings:
+Warning	1292	Truncated incorrect sort_buffer_size value: '1'
+EXPLAIN 
+SELECT * FROM t1 FORCE INDEX(a,b) WHERE a LIKE 'a%' OR b LIKE 'b%' 
+ORDER BY a,b;
+id	select_type	table	type	possible_keys	key	key_len	ref	rows	Extra
+1	SIMPLE	t1	index_merge	a,b	a,b	131,131	NULL	64	Using sort_union(a,b); Using where; Using filesort
+SELECT * FROM t1 FORCE INDEX(a,b) WHERE a LIKE 'a%' OR b LIKE 'b%' 
+ORDER BY a,b;
+SET SESSION sort_buffer_size=DEFAULT;
+DROP TABLE t1;
 End of 5.0 tests
 #---------------- ROR-index_merge tests -----------------------
 SET SESSION STORAGE_ENGINE = MyISAM;

sql/sql_select.cc

@@ -13490,9 +13490,24 @@ create_sort_index(THD *thd, JOIN *join, ORDER *order,
   tab->records= table->sort.found_records;	// For SQL_CALC_ROWS
   if (select)
   {
+    /*
+      We need to preserve tablesort's output resultset here, because
+      QUICK_INDEX_MERGE_SELECT::~QUICK_INDEX_MERGE_SELECT (called by
+      SQL_SELECT::cleanup()) may free it assuming it's the result of the quick
+      select operation that we no longer need. Note that all the other parts of
+      this data structure are cleaned up when
+      QUICK_INDEX_MERGE_SELECT::get_next encounters end of data, so the next
+      SQL_SELECT::cleanup() call changes sort.io_cache alone.
+    */
+    IO_CACHE *tablesort_result_cache;
+
+    tablesort_result_cache= table->sort.io_cache;
+    table->sort.io_cache= NULL;
+
     select->cleanup();				// filesort did select
     tab->select= 0;
     table->quick_keys.clear_all();  // as far as we cleanup select->quick
+    table->sort.io_cache= tablesort_result_cache;
   }
   tab->select_cond=0;
   tab->last_inner= 0;