Fixed bug #604503.

If the expression for a virtual column of table contained datetime
comparison then the execution of the second query that used this
virtual column caused a crash. It happened because the execution
of the first query that used this virtual column inserted a cached
item into the expression tree. The cached tree was allocated in
the statement memory while the expression tree was allocated in
the table memory.
Now the cached items that are inserted into expressions for virtual
columns with datetime comparisons are always allocated in the same
mem_root as the expressions for virtual columns. So now the inserted
cached items are valid for any queries that use these virtual columns. 

1 files changed, 22 insertions, 12 deletions

diff --git a/sql/table.cc b/sql/table.cc
index 451515c1262..334596e28b2 100644
--- a/sql/table.cc
+++ b/sql/table.cc
@@ -1928,10 +1928,8 @@ end:
     parses it, building an item object for it. The pointer to this item is
     placed into in field->vcol_info.expr_item. After this the function performs
     semantic analysis of the item by calling the the function fix_vcol_expr.
-    Since the defining expression is part of the table definition the item
-    for it is created in table->memroot within a separate Query_arena.
-    The free_list of this arena is saved in field->vcol_info.item_free_list
-    to be freed when the table defition is removed from the TABLE_SHARE cache.
+    Since the defining expression is part of the table definition the item for
+    it is created in table->memroot within the special arena TABLE::expr_arena.
 
   @note
     Before passing 'vcol_expr" to the parser the function embraces it in 
@@ -1988,9 +1986,18 @@ bool unpack_vcol_info_from_frm(THD *thd,
   */
   Query_arena *backup_stmt_arena_ptr= thd->stmt_arena;
   Query_arena backup_arena;
-  Query_arena vcol_arena(&table->mem_root, Query_arena::INITIALIZED);
-  thd->set_n_backup_active_arena(&vcol_arena, &backup_arena);
-  thd->stmt_arena= &vcol_arena;
+  Query_arena *vcol_arena= table->expr_arena;
+  if (!vcol_arena)
+  {
+    Query_arena expr_arena(&table->mem_root, Query_arena::INITIALIZED);
+    if (!(vcol_arena= (Query_arena *) alloc_root(&table->mem_root,
+                                                 sizeof(Query_arena))))
+      goto err;
+    *vcol_arena= expr_arena;
+    table->expr_arena= vcol_arena;
+  }
+  thd->set_n_backup_active_arena(vcol_arena, &backup_arena);
+  thd->stmt_arena= vcol_arena;
 
   thd->lex->parse_vcol_expr= TRUE;
   old_character_set_client= thd->variables.character_set_client;
@@ -2012,7 +2019,6 @@ bool unpack_vcol_info_from_frm(THD *thd,
     field->vcol_info= 0;
     goto err;
   }
-  field->vcol_info->item_free_list= thd->free_list;
   goto end;
 
 err:
@@ -2021,7 +2027,8 @@ err:
   thd->free_items();
 end:
   thd->stmt_arena= backup_stmt_arena_ptr;
-  thd->restore_active_arena(&vcol_arena, &backup_arena);
+  if (vcol_arena)
+    thd->restore_active_arena(vcol_arena, &backup_arena);
   thd->variables.character_set_client= old_character_set_client;
 
   DBUG_RETURN(rc);
@@ -2444,12 +2451,12 @@ int closefrm(register TABLE *table, bool free_share)
   }
   my_free((char*) table->alias, MYF(MY_ALLOW_ZERO_PTR));
   table->alias= 0;
+  if (table->expr_arena)
+    table->expr_arena->free_items();
   if (table->field)
   {
     for (Field **ptr=table->field ; *ptr ; ptr++)
     {
-      if ((*ptr)->vcol_info)
-        free_items((*ptr)->vcol_info->item_free_list);
       delete *ptr;
     }
     table->field= 0;
@@ -5416,6 +5423,7 @@ size_t max_row_length(TABLE *table, const uchar *data)
 /*
   @brief Compute values for virtual columns used in query
 
+  @param  thd              Thread handle
   @param  table            The TABLE object
   @param  for_write        Requests to compute only fields needed for write   
   
@@ -5432,7 +5440,7 @@ size_t max_row_length(TABLE *table, const uchar *data)
     >0   Error occurred when storing a virtual field value
 */
 
-int update_virtual_fields(TABLE *table, bool for_write)
+int update_virtual_fields(THD *thd, TABLE *table, bool for_write)
 {
   DBUG_ENTER("update_virtual_fields");
   Field **vfield_ptr, *vfield;
@@ -5440,6 +5448,7 @@ int update_virtual_fields(TABLE *table, bool for_write)
   if (!table || !table->vfield)
     DBUG_RETURN(0);
 
+  thd->reset_arena_for_cached_items(table->expr_arena);
   /* Iterate over virtual fields in the table */
   for (vfield_ptr= table->vfield; *vfield_ptr; vfield_ptr++)
   {
@@ -5458,6 +5467,7 @@ int update_virtual_fields(TABLE *table, bool for_write)
       DBUG_PRINT("info", ("field '%s' - skipped", vfield->field_name));
     }
   }
+  thd->reset_arena_for_cached_items(0);
   DBUG_RETURN(0);
 }