bzr commit into mysql-5.1-bugteam branch (anurag.shekhar:2768) Bug#30590

[Anurag Shekhar]

#At file:///home/anurag/mysqlsrc/mysql-5.1-bugteam/ based on revid:patrick.crews@stripped

 2768 Anurag Shekhar	2009-02-04
      Bug#30590 delete from memory table with composite btree primary key
      
      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 I have introduced a new variable in HP_INFO structure (deleted) 
      which remembers the number of deleted (initialized while opening the file) 
      nodes since last_pos is updated. If this value differs from the value of 
      deleted nodes in shared structure last_pos is invalidated (set to zero).
modified:
  include/heap.h
  mysql-test/r/heap_btree.result
  mysql-test/t/heap_btree.test
  storage/heap/hp_open.c
  storage/heap/hp_rnext.c

per-file messages:
  include/heap.h
    Added new field in HP_INFO to remember number of deleted nodes since last_pos was last updated.
  mysql-test/r/heap_btree.result
    Updated result for newly introduced test.
  mysql-test/t/heap_btree.test
    Added new case to test self join with delete.
  storage/heap/hp_open.c
    Initializes HP_INFO's deleted field to shared->deleted (value while opening the file)
  storage/heap/hp_rnext.c
    Introduced new test to check if any more node has been deleted since last_pos was updated. If it has then invalidate last_pos (by setting it to zero).
=== modified file 'include/heap.h'
--- a/include/heap.h	2007-07-24 22:58:12 +0000
+++ b/include/heap.h	2009-02-04 08:28:11 +0000
@@ -179,6 +179,9 @@ typedef struct st_heap_info
   THR_LOCK_DATA lock;
 #endif
   LIST open_list;
+  int deleted;                    /* Record number of deleted keys in tree
+                                     If this value isn't same as s->deleted 
+                                     last_pos should be reinitialized */
 } HP_INFO;
 
 

=== modified file 'mysql-test/r/heap_btree.result'
--- a/mysql-test/r/heap_btree.result	2007-10-19 20:12:14 +0000
+++ b/mysql-test/r/heap_btree.result	2009-02-04 08:28:11 +0000
@@ -337,3 +337,7 @@ NULL	NULL
 NULL	1
 drop table t1;
 End of 5.0 tests
+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;

=== modified file 'mysql-test/t/heap_btree.test'
--- a/mysql-test/t/heap_btree.test	2007-10-19 20:12:14 +0000
+++ b/mysql-test/t/heap_btree.test	2009-02-04 08:28:11 +0000
@@ -255,3 +255,11 @@ drop table t1;
 
 --echo End of 5.0 tests
 
+#
+# 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;

=== modified file 'storage/heap/hp_open.c'
--- a/storage/heap/hp_open.c	2007-07-24 22:58:12 +0000
+++ b/storage/heap/hp_open.c	2009-02-04 08:28:11 +0000
@@ -106,6 +106,10 @@ HP_INFO *heap_open(const char *name, int
     info->open_list.data= (void*) info;
     heap_open_list= list_add(heap_open_list,&info->open_list);
   }
+  /*
+    Remember the number of deleted records while opening the file.
+  */
+  info->deleted= share->deleted;
   pthread_mutex_unlock(&THR_LOCK_heap);
   DBUG_RETURN(info);
 }

=== modified file 'storage/heap/hp_rnext.c'
--- a/storage/heap/hp_rnext.c	2007-09-13 12:12:46 +0000
+++ b/storage/heap/hp_rnext.c	2009-02-04 08:28:11 +0000
@@ -32,6 +32,17 @@ int heap_rnext(HP_INFO *info, uchar *rec
   {
     heap_rb_param custom_arg;
 
+    /*
+      Check if any key is deleted in tree since last_pos was
+      updated. If it has then last_pos might be holding a invalid
+      address. Invalidate last_pos and remember the current count
+      of deleted keys.
+     */
+    if (info->deleted != share->deleted) 
+    {
+        info->last_pos= 0;
+        info->deleted= share->deleted;
+    }
     if (info->last_pos)
     {
       /*