bk commit into 5.0 tree (igor:1.2508) BUG#28728

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ChangeSet@stripped, 2007-06-02 11:44:16-07:00, igor@stripped +3 -0
  Fixed bug #28728: a crash when executing EXPLAIN EXTENDED for a query
  using a derived table over a grouping subselect.
  
  This crash happens only when materialization of the derived tables 
  requires creation of auxiliary temporary table, for example when
  a grouping operation is carried out with usage of a temporary table.
  
  The crash happened because EXPLAIN EXTENDED when printing the query
  expression made an attempt to use the objects created in the mem_root
  of the temporary table which has been already freed by the moment
  when printing is called.
  
  This bug appeared after the method Item_field::print() had been 
  introduced.    

  mysql-test/r/subselect.result@stripped, 2007-06-02 11:44:11-07:00, igor@stripped +10 -0
    Added a test case for bug #28728.

  mysql-test/t/subselect.test@stripped, 2007-06-02 11:44:11-07:00, igor@stripped +14 -0
    Added a test case for bug #28728.

  sql/sql_select.cc@stripped, 2007-06-02 11:44:12-07:00, igor@stripped +11 -0
    Fixed bug #28728: a crash when executing EXPLAIN EXTENDED for a query
    using a derived table over a grouping subselect.
    The crash happened because EXPLAIN EXTENDED when printing the query
    expression made an attempt to use the objects created in the mem_root
    of the temporary table which has been already freed by the moment
    when printing is accomplished.
    The fix in JOIN::exec() ensures using existing objects when printing 
    subselects for a derived tables by EXPLAIN EXTENDED.
      

# This is a BitKeeper patch.  What follows are the unified diffs for the
# set of deltas contained in the patch.  The rest of the patch, the part
# that BitKeeper cares about, is below these diffs.
# User:	igor
# Host:	olga.mysql.com
# Root:	/home/igor/dev-opt/mysql-5.0-opt-bug28728

--- 1.528/sql/sql_select.cc	2007-06-02 11:44:22 -07:00
+++ 1.529/sql/sql_select.cc	2007-06-02 11:44:22 -07:00
@@ -2075,6 +2075,17 @@
   thd->examined_row_count+= curr_join->examined_rows;
   DBUG_PRINT("counts", ("thd->examined_row_count: %lu",
                         (ulong) thd->examined_row_count));
+
+  /* 
+    With EXPLAIN EXTENDED we have to restore original ref_array
+    for a derived table which is always materialized.
+    Otherwise we would not be able to print the query  correctly.
+  */ 
+  if (items0 &&
+      (thd->lex->describe & DESCRIBE_EXTENDED) &&
+      select_lex->linkage == DERIVED_TABLE_TYPE)      
+    set_items_ref_array(items0);
+
   DBUG_VOID_RETURN;
 }
 

--- 1.190/mysql-test/r/subselect.result	2007-06-02 11:44:22 -07:00
+++ 1.191/mysql-test/r/subselect.result	2007-06-02 11:44:22 -07:00
@@ -4071,4 +4071,14 @@
 2	GA
 4	FL
 DROP TABLE t1,t2;
+CREATE TABLE t1 (a int);
+INSERT INTO t1 VALUES (1), (2);
+EXPLAIN EXTENDED
+SELECT * FROM (SELECT count(*) FROM t1 GROUP BY a) as res;
+id	select_type	table	type	possible_keys	key	key_len	ref	rows	Extra
+1	PRIMARY	<derived2>	ALL	NULL	NULL	NULL	NULL	2	
+2	DERIVED	t1	ALL	NULL	NULL	NULL	NULL	2	Using temporary; Using filesort
+Warnings:
+Note	1003	select `res`.`count(*)` AS `count(*)` from (select count(0) AS `count(*)` from `test`.`t1` group by `test`.`t1`.`a`) `res`
+DROP TABLE t1;
 End of 5.0 tests.

--- 1.152/mysql-test/t/subselect.test	2007-06-02 11:44:22 -07:00
+++ 1.153/mysql-test/t/subselect.test	2007-06-02 11:44:22 -07:00
@@ -2906,4 +2906,18 @@
 
 DROP TABLE t1,t2;
 
+#
+# Bug #28728: crash with EXPLAIN EXTENDED for a query with a derived table
+#             over a grouping subselect
+# 
+
+CREATE TABLE t1 (a int);
+
+INSERT INTO t1 VALUES (1), (2);
+
+EXPLAIN EXTENDED
+SELECT * FROM (SELECT count(*) FROM t1 GROUP BY a) as res;
+
+DROP TABLE t1;
+
 --echo End of 5.0 tests.