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Commit c3870e08 authored by V S Murthy Sidagam's avatar V S Murthy Sidagam
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Bug #18592390 QUERY TO I_S.TABLES AND I_S.COLUMNS LEADS TO HUGE MEMORY USAGE 

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.
parent 7797ef4d
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Inline Side-by-side
Showing with 58 additions and 14 deletions
sql/sql_show.cc
View file @ c3870e08
......@@ -404,13 +404,14 @@ bool mysqld_show_privileges(THD *thd)
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)
{
uint i;
char *ext;
MY_DIR *dirp;
FILEINFO *file;
LEX_STRING *file_name= 0;
MEM_ROOT **root_ptr= NULL, *old_root= NULL;
uint file_name_len;
#ifndef NO_EMBEDDED_ACCESS_CHECKS
uint col_access=thd->col_access;
......@@ -440,6 +441,13 @@ find_files(THD *thd, List<LEX_STRING> *files, const char *db,
DBUG_RETURN(FIND_FILES_DIR);
}
if (tmp_mem_root)
{
root_ptr= my_pthread_getspecific_ptr(MEM_ROOT**, THR_MALLOC);
old_root= *root_ptr;
*root_ptr= tmp_mem_root;
}
for (i=0 ; i < (uint) dirp->number_off_files ; i++)
{
char uname[NAME_LEN + 1]; /* Unencoded name */
......@@ -519,8 +527,11 @@ find_files(THD *thd, List<LEX_STRING> *files, const char *db,
continue;
}
#endif
if (!(file_name=
thd->make_lex_string(file_name, uname, file_name_len, TRUE)) ||
if (!(file_name= tmp_mem_root ?
make_lex_string_root(tmp_mem_root, file_name, uname,
file_name_len, TRUE) :
thd->make_lex_string(file_name, uname,
file_name_len, TRUE)) ||
files->push_back(file_name))
{
my_dirend(dirp);
......@@ -532,6 +543,9 @@ find_files(THD *thd, List<LEX_STRING> *files, const char *db,
(void) ha_find_files(thd, db, path, wild, dir, files);
if (tmp_mem_root)
*root_ptr= old_root;
DBUG_RETURN(FIND_FILES_OK);
}
......@@ -2882,7 +2896,7 @@ enum enum_schema_tables get_schema_table_idx(ST_SCHEMA_TABLE *schema_table)
int make_db_list(THD *thd, List<LEX_STRING> *files,
LOOKUP_FIELD_VALUES *lookup_field_vals,
bool *with_i_schema)
bool *with_i_schema, MEM_ROOT *tmp_mem_root)
{
LEX_STRING *i_s_name_copy= 0;
i_s_name_copy= thd->make_lex_string(i_s_name_copy,
......@@ -2906,7 +2920,8 @@ int make_db_list(THD *thd, List<LEX_STRING> *files,
return 1;
}
return (find_files(thd, files, NullS, mysql_data_home,
lookup_field_vals->db_value.str, 1) != FIND_FILES_OK);
lookup_field_vals->db_value.str, 1, tmp_mem_root) !=
FIND_FILES_OK);
}
......@@ -2948,7 +2963,7 @@ int make_db_list(THD *thd, List<LEX_STRING> *files,
return 1;
*with_i_schema= 1;
return (find_files(thd, files, NullS,
mysql_data_home, NullS, 1) != FIND_FILES_OK);
mysql_data_home, NullS, 1, tmp_mem_root) != FIND_FILES_OK);
}
......@@ -3056,7 +3071,8 @@ int schema_tables_add(THD *thd, List<LEX_STRING> *files, const char *wild)
static int
make_table_name_list(THD *thd, List<LEX_STRING> *table_names, LEX *lex,
LOOKUP_FIELD_VALUES *lookup_field_vals,
bool with_i_schema, LEX_STRING *db_name)
bool with_i_schema, LEX_STRING *db_name,
MEM_ROOT *tmp_mem_root)
{
char path[FN_REFLEN + 1];
build_table_filename(path, sizeof(path) - 1, db_name->str, "", "", 0);
......@@ -3110,7 +3126,8 @@ make_table_name_list(THD *thd, List<LEX_STRING> *table_names, LEX *lex,
lookup_field_vals->table_value.str));
find_files_result res= find_files(thd, table_names, db_name->str, path,
lookup_field_vals->table_value.str, 0);
lookup_field_vals->table_value.str, 0,
tmp_mem_root);
if (res != FIND_FILES_OK)
{
/*
......@@ -3776,6 +3793,9 @@ int get_all_tables(THD *thd, TABLE_LIST *tables, COND *cond)
bool can_deadlock;
DBUG_ENTER("get_all_tables");
MEM_ROOT tmp_mem_root;
init_sql_alloc(&tmp_mem_root, TABLE_ALLOC_BLOCK_SIZE, 0);
/*
In cases when SELECT from I_S table being filled by this call is
part of statement which also uses other tables or is being executed
......@@ -3867,7 +3887,7 @@ int get_all_tables(THD *thd, TABLE_LIST *tables, COND *cond)
goto err;
}
if (make_db_list(thd, &db_names, &lookup_field_vals, &with_i_schema))
if (make_db_list(thd, &db_names, &lookup_field_vals, &with_i_schema, &tmp_mem_root))
goto err;
it.rewind(); /* To get access to new elements in basis list */
while ((db_name= it++))
......@@ -3885,7 +3905,7 @@ int get_all_tables(THD *thd, TABLE_LIST *tables, COND *cond)
List<LEX_STRING> table_names;
int res= make_table_name_list(thd, &table_names, lex,
&lookup_field_vals,
with_i_schema, db_name);
with_i_schema, db_name, &tmp_mem_root);
if (res == 2) /* Not fatal error, continue */
continue;
if (res)
......@@ -3972,9 +3992,10 @@ int get_all_tables(THD *thd, TABLE_LIST *tables, COND *cond)
with_i_schema= 0;
}
}
error= 0;
err:
free_root(&tmp_mem_root, MYF(0));
thd->restore_backup_open_tables_state(&open_tables_state_backup);
DBUG_RETURN(error);
......@@ -4000,6 +4021,27 @@ int fill_schema_schemata(THD *thd, TABLE_LIST *tables, COND *cond)
Returning error status in this case leads to client hangup.
*/
/*
* A temporary class is created to free tmp_mem_root when we return from
* this function, since we have 'return' from this function from many
* places. This is just to avoid goto.
*/
class free_tmp_mem_root
{
public:
free_tmp_mem_root()
{
init_sql_alloc(&tmp_mem_root, TABLE_ALLOC_BLOCK_SIZE, 0);
}
~free_tmp_mem_root()
{
free_root(&tmp_mem_root, MYF(0));
}
MEM_ROOT tmp_mem_root;
};
free_tmp_mem_root dummy_member;
LOOKUP_FIELD_VALUES lookup_field_vals;
List<LEX_STRING> db_names;
LEX_STRING *db_name;
......@@ -4013,11 +4055,12 @@ int fill_schema_schemata(THD *thd, TABLE_LIST *tables, COND *cond)
if (get_lookup_field_values(thd, cond, tables, &lookup_field_vals))
DBUG_RETURN(0);
DBUG_PRINT("INDEX VALUES",("db_name='%s', table_name='%s'",
lookup_field_vals.db_value.str,
lookup_field_vals.table_value.str));
if (make_db_list(thd, &db_names, &lookup_field_vals,
&with_i_schema))
&with_i_schema, &dummy_member.tmp_mem_root))
DBUG_RETURN(1);
/*
......
sql/sql_show.h
View file @ c3870e08
/* 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);
......
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