Bug #26492721 MYSQL/INNODB CRASHES DURING ALTER TABLE

PROBLEM

While doing an alter table that does multiple change columns , the heap
assigned for the particular table increases and corresponding increase
to dict_sys->size isn't done because of which the dict_sys->size keeps
decreasing with every iteration of set of alter tables provided in the
bug page hitting the assertion dict_sys->size > 0 .

FIX

Fix is to add a check for any table heap size increase during change
column and add the increased value of heap size to dict_sys->size to
avoid it getting diminished on subsequent runs of alter tables.

Reviewed by: Jimmy Yang<[email protected]>
RB: 17817

Author: Aakanksha Verma

storage/innobase/dict/dict0mem.cc

@@ -1,6 +1,6 @@
 /*****************************************************************************
 
-Copyright (c) 1996, 2016, Oracle and/or its affiliates. All Rights Reserved.
+Copyright (c) 1996, 2017, Oracle and/or its affiliates. All Rights Reserved.
 Copyright (c) 2012, Facebook Inc.
 
 This program is free software; you can redistribute it and/or modify it under
@@ -300,11 +300,20 @@ dict_mem_table_col_rename_low(
 		char*	col_names;
 
 		if (to_len > from_len) {
+			ulint table_size_before_rename_col
+                                = mem_heap_get_size(table->heap);
 			col_names = static_cast<char*>(
 				mem_heap_alloc(
 					table->heap,
 					full_len + to_len - from_len));
-
+			ulint table_size_after_rename_col
+                                = mem_heap_get_size(table->heap);
+			if (table_size_before_rename_col
+                                != table_size_after_rename_col) {
+                                dict_sys->size +=
+                                        table_size_after_rename_col
+                                                - table_size_before_rename_col;
+                        }
 			memcpy(col_names, table->col_names, prefix_len);
 		} else {
 			col_names = const_cast<char*>(table->col_names);