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Bug #18592390 QUERY TO I_S.TABLES AND I_S.COLUMNS LEADS TO HUGE MEMORY USAGE

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Description: On an example MySQL instance with 28k empty
InnoDB tables, a specific query to information_schema.tables
and information_schema.columns leads to memory consumption
over 38GB RSS.

Analysis: In get_all_tables() call, we fill the I_S tables
from frm files and storage engine. As part of that process
we call make_table_name_list() and allocate memory for all
the 28k frm file names in the THD mem_root through
make_lex_string_root(). Since it has been called around
28k * 28k times there is a huge memory getting hogged in
THD mem_root. This causes the RSS to grow to 38GB.

Fix: As part of fix we are creating a temporary mem_root
in get_all_tables and passing it to fill_fiels(). There we
replace the THD mem_root with the temporary mem_root and
allocates the file names in temporary mem_root and frees
it once we fill the I_S tables in get_all_tables and
re-assign the original mem_root back to THD mem_root.

Note: Checked the massif out put with the fix now the memory growth is just around 580MB at peak.
This commit is contained in:
V S Murthy Sidagam
2015-04-27 23:50:13 +05:30
parent 7797ef4dec
commit c3870e089a
2 changed files with 58 additions and 14 deletions
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5
sql/sql_show.h
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@ -1,4 +1,4 @@
/* Copyright (c) 2005, 2010, Oracle and/or its affiliates. All rights reserved.
/* Copyright (c) 2005, 2015, Oracle and/or its affiliates. All rights reserved.
This program is free software; you can redistribute it and/or modify
it under the terms of the GNU General Public License as published by
@ -82,7 +82,8 @@ enum find_files_result {
#define IS_FILES_EXTRA 37
find_files_result find_files(THD *thd, List<LEX_STRING> *files, const char *db,
const char *path, const char *wild, bool dir);
const char *path, const char *wild, bool dir,
MEM_ROOT *tmp_mem_root);
int store_create_info(THD *thd, TABLE_LIST *table_list, String *packet,
HA_CREATE_INFO *create_info_arg, bool show_database);