A fix and a test case for Bug#36171 "CREATE TEMPORARY TABLE and

MERGE engine".
Backport the patch from 6.0 by Ingo Struewing:
revid:ingo.struewing@sun.com-20091028183659-6kmv1k3gdq6cpg4d
Bug#36171 - CREATE TEMPORARY TABLE and MERGE engine

In former MySQL versions, up to 5.1.23/6.0.4 it was possible to create
temporary MERGE tables with non-temporary MyISAM tables.
        
This has been changed in the mentioned version due to Bug 19627
(temporary merge table locking). MERGE children were locked through
the parent table. If the parent was temporary, it was not locked and
so the children were not locked either. Parallel use of the MyISAM
tables corrupted them.
       
Since 6.0.6 (WL 4144 - Lock MERGE engine children), the children are
locked independently from the parent. Now it is possible to allow
non-temporary children with a temporary parent. Even though the
temporary MERGE table itself is not locked, each non-temporary
MyISAM table is locked anyway.
        
NOTE: Behavior change: In 5.1.23/6.0.4 we prohibited non-temporary
children with a temporary MERGE table. Now we re-allow it.
An important side-effect is that temporary tables, which overlay
non-temporary MERGE children, overlay the children in the MERGE table.

1 files changed, 11 insertions, 12 deletions

diff --git a/storage/myisammrg/ha_myisammrg.cc b/storage/myisammrg/ha_myisammrg.cc
index 1681f062117..08aa9dfd0e4 100644
--- a/storage/myisammrg/ha_myisammrg.cc
+++ b/storage/myisammrg/ha_myisammrg.cc
@@ -476,10 +476,7 @@ int ha_myisammrg::add_children_list(void)
     child_l->parent_l= parent_l;
     /* Copy select_lex. Used in unique_table() at least. */
     child_l->select_lex= parent_l->select_lex;
-    /*
-      Set the expected table version, to not cause spurious re-prepare.
-      @todo: revise after the fix for Bug#36171
-    */
+    /* Set the expected table version, to not cause spurious re-prepare. */
     child_l->set_table_ref_id(mrg_child_def->get_child_table_ref_type(),
                               mrg_child_def->get_child_def_version());
     /* Link TABLE_LIST object into the children list. */
@@ -618,15 +615,17 @@ extern "C" MI_INFO *myisammrg_attach_children_callback(void *callback_param)
     param->need_compat_check= TRUE;
 
   /*
-    If parent is temporary, children must be temporary too and vice
-    versa. This check must be done for every child on every open because
-    the table def version can overlap between temporary and
-    non-temporary tables. We need to detect the case where a
-    non-temporary table has been replaced with a temporary table of the
-    same version. Or vice versa. A very unlikely case, but it could
-    happen.
+    If child is temporary, parent must be temporary as well. Other
+    parent/child combinations are allowed. This check must be done for
+    every child on every open because the table def version can overlap
+    between temporary and non-temporary tables. We need to detect the
+    case where a non-temporary table has been replaced with a temporary
+    table of the same version. Or vice versa. A very unlikely case, but
+    it could happen. (Note that the condition was different from
+    5.1.23/6.0.4(Bug#19627) to 5.5.6 (Bug#36171): child->s->tmp_table !=
+    parent->s->tmp_table. Tables were required to have the same status.)
   */
-  if (child->s->tmp_table != parent->s->tmp_table)
+  if (child->s->tmp_table && !parent->s->tmp_table)
   {
     DBUG_PRINT("error", ("temporary table mismatch parent: %d  child: %d",
                          parent->s->tmp_table, child->s->tmp_table));