bzr commit into mysql-5.0-bugteam branch (anurag.shekhar:2725) Bug#39918

[Anurag Shekhar]

#At file:///home/anurag/mysqlsrc/mysql-5.0-bugteam-39918/ based on revid:sergey.glukhov@stripped

 2725 Anurag Shekhar	2009-04-15
      Bug #39918 memory (heap) engine crashing with b-tree index and DELETE with seg fault
      
      While evaluating self join with delete server uses two instance of handler 
      (with both holding reference to same file). During query evaluation last_pos 
      is cached in handler to improve search performance. But in the mean while 
      second handler is used to delete the node last_pos is holding. This makes 
      the last_pos an invalid and when accessed results in segmentation fault.
      
      To fix this problem disabled delete while scanning if the table appears in
      join list.
     @ mysql-test/r/heap_btree.result
        Updated test result after adding new test for this bug.
     @ mysql-test/t/heap_btree.test
        Added a new test based on the bug.
     @ sql/sql_delete.cc
        Updated to check if the files in delete list appears in join list and disable 
        delete while scanning, if it appears.

    modified:
      mysql-test/r/heap_btree.result
      mysql-test/t/heap_btree.test
      sql/sql_delete.cc
=== modified file 'mysql-test/r/heap_btree.result'
--- a/mysql-test/r/heap_btree.result	2007-10-19 20:04:30 +0000
+++ b/mysql-test/r/heap_btree.result	2009-04-15 11:00:45 +0000
@@ -336,4 +336,8 @@ a	b
 NULL	NULL
 NULL	1
 drop table t1;
+CREATE TABLE t1(a INT, KEY USING BTREE (a)) ENGINE=MEMORY;
+INSERT INTO t1 VALUES(1),(1);
+DELETE a1 FROM t1 AS a1, t1 AS a2 WHERE a1.a=a2.a;
+DROP TABLE t1;
 End of 5.0 tests

=== modified file 'mysql-test/t/heap_btree.test'
--- a/mysql-test/t/heap_btree.test	2007-10-19 20:04:30 +0000
+++ b/mysql-test/t/heap_btree.test	2009-04-15 11:00:45 +0000
@@ -253,5 +253,13 @@ insert into t1 values (1, 1), (3, 3), (2
 select * from t1 where a is null;
 drop table t1;
 
+#
+# bug#39918 - memory (heap) engine crashing while executing self join with delete
+#
+
+CREATE TABLE t1(a INT, KEY USING BTREE (a)) ENGINE=MEMORY;
+INSERT INTO t1 VALUES(1),(1);
+DELETE a1 FROM t1 AS a1, t1 AS a2 WHERE a1.a=a2.a;
+DROP TABLE t1;
 --echo End of 5.0 tests
 

=== modified file 'sql/sql_delete.cc'
--- a/sql/sql_delete.cc	2009-03-27 05:19:50 +0000
+++ b/sql/sql_delete.cc	2009-04-15 11:00:45 +0000
@@ -503,6 +503,11 @@ int mysql_multi_delete_prepare(THD *thd)
       }
     }
   }
+  /*
+    Reset the exclude flag to false so it doesn't interfare
+    with further calls to unique_table
+  */
+  lex->select_lex.exclude_from_table_unique_test= FALSE;
   DBUG_RETURN(FALSE);
 }
 
@@ -538,11 +543,23 @@ multi_delete::initialize_tables(JOIN *jo
     DBUG_RETURN(1);
 
   table_map tables_to_delete_from=0;
+  delete_while_scanning= 1;
   for (walk= delete_tables; walk; walk= walk->next_local)
+  {
     tables_to_delete_from|= walk->table->map;
+    if (unique_table (thd, walk, join->tables_list, false)) 
+    {
+      /*
+       If the table we are going to delete from appears
+       in join, we need to defer delete. So the delete
+       doesn't interfers with the scaning of results.
+      */
+      delete_while_scanning= 0;
+    }
+  }
+
 
   walk= delete_tables;
-  delete_while_scanning= 1;
   for (JOIN_TAB *tab=join->join_tab, *end=join->join_tab+join->tables;
        tab < end;
        tab++)


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