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One Billion Tables in MySQL 8.0 with ZFS
source link: https://www.tuicool.com/articles/hit/FbUrie2
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The short version
I created > one billion InnoDB tables in MySQL 8.0 (tables, not rows) just for fun. Here is the proof:
$ mysql -A Welcome to the MySQL monitor. Commands end with ; or \g. Your MySQL connection id is 1425329 Server version: 8.0.12 MySQL Community Server - GPL Copyright (c) 2000, 2018, Oracle and/or its affiliates. All rights reserved. Oracle is a registered trademark of Oracle Corporation and/or its affiliates. Other names may be trademarks of their respective owners. Type 'help;' or '\h' for help. Type '\c' to clear the current input statement. mysql> select count(*) from information_schema.tables; +------------+ | count(*) | +------------+ | 1011570298 | +------------+ 1 row in set (6 hours 57 min 6.31 sec)
Yes, it took 6 hours and 57 minutes to count them all!
Why does anyone need one billion tables?
In my previous blog post, I created and tested MySQL 8.0 with 40 million tables (that was a real case study). The One Billion Tables project is not a real world scenario, however. I was challenged by Billion Tables Project (BTP) in PostgreSQL, and decided to repeat it with MySQL, creating 1 billion InnoDB tables.
As an aside: I think MySQL 8.0 is the first MySQL version where creating 1 billion InnoDB tables is even practically possible.
Challenges with one billion InnoDB tables
Disk space
The first and one of the most important challenges is disk space. InnoDB allocates data pages on disk when creating .ibd files. Without disk level compression we need > 25Tb of disk. The good news: we have ZFS which provides transparent disk compression. Here’s how the disk utilization looks:
Actual data (apparent-size):
# du -sh --apparent-size /mysqldata/ 26T /mysqldata/
Compressed data:
# du -sh /mysqldata/ 2.4T /mysqldata/
Compression ratio:
# zfs get compression,compressratio ... mysqldata/mysql/data compressratio 7.14x - mysqldata/mysql/data compression gzip inherited from mysqldata/mysql
(Looks like the compression ratio reported is not 100% correct, we expect ~10x compression ratio.)
Too many tiny files
This is usually the big issue with databases that create a file per table. With MySQL 8.0 we can create a shared tablespace and “assign” a table to it. I created a tablespace per database, and created 1000 tables in each database.
The result:
mysql> select count(*) from information_schema.schemata; +----------+ | count(*) | +----------+ | 1011575 | +----------+ 1 row in set (1.31 sec)
Creating tables
Another big challenge is how to create tables fast enough so it will not take months. I have used three approaches:
- Disabled all possible consistency checks in MySQL, and decreased the innodb page size to 4K (these config options are NOT for production use)
- Created tables in parallel: as the mutex contention bug in MySQL 8.0 has been fixed, creating tables in parallel works fine.
- Use local NVMe cards on top of an AWS ec2 i3.8xlarge instance
my.cnf config file ( I repeat: do not use this in production ):
[mysqld] default-authentication-plugin = mysql_native_password performance_schema=0 datadir=/mysqldata/mysql/data socket=/mysqldata/mysql/data/mysql.sock log-error = /mysqldata/mysql/log/error.log skip-log-bin=1 innodb_log_group_home_dir = /mysqldata/mysql/log/ innodb_doublewrite = 0 innodb_checksum_algorithm=none innodb_log_checksums=0 innodb_flush_log_at_trx_commit=0 innodb_log_file_size=2G innodb_buffer_pool_size=100G innodb_page_size=4k innodb_flush_method=nosync innodb_io_capacity_max=20000 innodb_io_capacity=5000 innodb_buffer_pool_instances=32 innodb_stats_persistent = 0 tablespace_definition_cache = 524288 schema_definition_cache = 524288 table_definition_cache = 524288 table_open_cache=524288 table_open_cache_instances=32 open-files-limit=1000000
ZFS pool:
# zpool status pool: mysqldata state: ONLINE scan: scrub repaired 0B in 1h49m with 0 errors on Sun Oct 14 02:13:17 2018 config: NAME STATE READ WRITE CKSUM mysqldata ONLINE 0 0 0 nvme0n1 ONLINE 0 0 0 nvme1n1 ONLINE 0 0 0 nvme2n1 ONLINE 0 0 0 nvme3n1 ONLINE 0 0 0 errors: No known data errors
A simple “deploy” script to create tables in parallel (includes the sysbench table structure):
#/bin/bash
function do_db {
db_exist=$(mysql -A -s -Nbe "select 1 from information_schema.schemata where schema_name = '$db'")
if [ "$db_exist" == "1" ]; then echo "Already exists: $db"; return 0; fi;
tbspace="create database $db; use $db; CREATE TABLESPACE $db ADD DATAFILE '$db.ibd' engine=InnoDB";
#echo "Tablespace $db.ibd created!"
tables=""
for i in {1..1000}
do
table="CREATE TABLE sbtest$i ( id int(10) unsigned NOT NULL AUTO_INCREMENT, k int(10) unsigned NOT NULL DEFAULT '0', c varchar(120) NOT NULL DEFAULT '', pad varchar(60) NOT NULL DEFAULT '', PRIMARY KEY (id), KEY k_1 (k) ) ENGINE=InnoDB DEFAULT CHARSET=latin1 tablespace $db;"
tables="$tables; $table;"
done
echo "$tbspace;$tables" | mysql
}
c=0
echo "starting..."
c=$(mysql -A -s -Nbe "select max(cast(SUBSTRING_INDEX(schema_name, '_', -1) as unsigned)) from information_schema.schemata where schema_name like 'sbtest_%'")
for m in {1..100000}
do
echo "m=$m"
for i in {1..30}
do
let c=$c+1
echo $c
db="sbtest_$c"
do_db &
done
wait
done
How fast did we create tables? Here are some stats:
# mysqladmin -i 10 -r ex|grep Com_create_table ... | Com_create_table | 6497 | | Com_create_table | 6449
So we created ~650 tables per second. The average, above, is per 10 seconds.
Counting the tables
It took > 6 hours to do “count(*) from information_schema.tables”! Here is why:
- MySQL 8.0 uses a new data dictionary (this is great as it avoids creating 1 billion frm files). Everything is stored in this file:
# ls -lah /mysqldata/mysql/data/mysql.ibd -rw-r----- 1 mysql mysql 6.1T Oct 18 15:02 /mysqldata/mysql/data/mysql.ibd
- The information_schema.tables is actually a view:
mysql> show create table information_schema.tables\G *************************** 1. row *************************** View: TABLES Create View: CREATE ALGORITHM=UNDEFINED DEFINER=`mysql.infoschema`@`localhost` SQL SECURITY DEFINER VIEW `information_schema`.`TABLES` AS select `cat`.`name` AS `TABLE_CATALOG`,`sch`.`name` AS `TABLE_SCHEMA`,`tbl`.`name` AS `TABLE_NAME`,`tbl`.`type` AS `TABLE_TYPE`,if((`tbl`.`type` = 'BASE TABLE'),`tbl`.`engine`,NULL) AS `ENGINE`,if((`tbl`.`type` = 'VIEW'),NULL,10) AS `VERSION`,`tbl`.`row_format` AS `ROW_FORMAT`,internal_table_rows(`sch`.`name`,`tbl`.`name`,if(isnull(`tbl`.`partition_type`),`tbl`.`engine`,''),`tbl`.`se_private_id`,(`tbl`.`hidden` <> 'Visible'),`ts`.`se_private_data`,coalesce(`stat`.`table_rows`,0),coalesce(cast(`stat`.`cached_time` as unsigned),0)) AS `TABLE_ROWS`,internal_avg_row_length(`sch`.`name`,`tbl`.`name`,if(isnull(`tbl`.`partition_type`),`tbl`.`engine`,''),`tbl`.`se_private_id`,(`tbl`.`hidden` <> 'Visible'),`ts`.`se_private_data`,coalesce(`stat`.`avg_row_length`,0),coalesce(cast(`stat`.`cached_time` as unsigned),0)) AS `AVG_ROW_LENGTH`,internal_data_length(`sch`.`name`,`tbl`.`name`,if(isnull(`tbl`.`partition_type`),`tbl`.`engine`,''),`tbl`.`se_private_id`,(`tbl`.`hidden` <> 'Visible'),`ts`.`se_private_data`,coalesce(`stat`.`data_length`,0),coalesce(cast(`stat`.`cached_time` as unsigned),0)) AS `DATA_LENGTH`,internal_max_data_length(`sch`.`name`,`tbl`.`name`,if(isnull(`tbl`.`partition_type`),`tbl`.`engine`,''),`tbl`.`se_private_id`,(`tbl`.`hidden` <> 'Visible'),`ts`.`se_private_data`,coalesce(`stat`.`max_data_length`,0),coalesce(cast(`stat`.`cached_time` as unsigned),0)) AS `MAX_DATA_LENGTH`,internal_index_length(`sch`.`name`,`tbl`.`name`,if(isnull(`tbl`.`partition_type`),`tbl`.`engine`,''),`tbl`.`se_private_id`,(`tbl`.`hidden` <> 'Visible'),`ts`.`se_private_data`,coalesce(`stat`.`index_length`,0),coalesce(cast(`stat`.`cached_time` as unsigned),0)) AS `INDEX_LENGTH`,internal_data_free(`sch`.`name`,`tbl`.`name`,if(isnull(`tbl`.`partition_type`),`tbl`.`engine`,''),`tbl`.`se_private_id`,(`tbl`.`hidden` <> 'Visible'),`ts`.`se_private_data`,coalesce(`stat`.`data_free`,0),coalesce(cast(`stat`.`cached_time` as unsigned),0)) AS `DATA_FREE`,internal_auto_increment(`sch`.`name`,`tbl`.`name`,if(isnull(`tbl`.`partition_type`),`tbl`.`engine`,''),`tbl`.`se_private_id`,(`tbl`.`hidden` <> 'Visible'),`ts`.`se_private_data`,coalesce(`stat`.`auto_increment`,0),coalesce(cast(`stat`.`cached_time` as unsigned),0),`tbl`.`se_private_data`) AS `AUTO_INCREMENT`,`tbl`.`created` AS `CREATE_TIME`,internal_update_time(`sch`.`name`,`tbl`.`name`,if(isnull(`tbl`.`partition_type`),`tbl`.`engine`,''),`tbl`.`se_private_id`,(`tbl`.`hidden` <> 'Visible'),`ts`.`se_private_data`,coalesce(cast(`stat`.`update_time` as unsigned),0),coalesce(cast(`stat`.`cached_time` as unsigned),0)) AS `UPDATE_TIME`,internal_check_time(`sch`.`name`,`tbl`.`name`,if(isnull(`tbl`.`partition_type`),`tbl`.`engine`,''),`tbl`.`se_private_id`,(`tbl`.`hidden` <> 'Visible'),`ts`.`se_private_data`,coalesce(cast(`stat`.`check_time` as unsigned),0),coalesce(cast(`stat`.`cached_time` as unsigned),0)) AS `CHECK_TIME`,`col`.`name` AS `TABLE_COLLATION`,internal_checksum(`sch`.`name`,`tbl`.`name`,if(isnull(`tbl`.`partition_type`),`tbl`.`engine`,''),`tbl`.`se_private_id`,(`tbl`.`hidden` <> 'Visible'),`ts`.`se_private_data`,coalesce(`stat`.`checksum`,0),coalesce(cast(`stat`.`cached_time` as unsigned),0)) AS `CHECKSUM`,if((`tbl`.`type` = 'VIEW'),NULL,get_dd_create_options(`tbl`.`options`,if((ifnull(`tbl`.`partition_expression`,'NOT_PART_TBL') = 'NOT_PART_TBL'),0,1))) AS `CREATE_OPTIONS`,internal_get_comment_or_error(`sch`.`name`,`tbl`.`name`,`tbl`.`type`,`tbl`.`options`,`tbl`.`comment`) AS `TABLE_COMMENT` from (((((`mysql`.`tables` `tbl` join `mysql`.`schemata` `sch` on((`tbl`.`schema_id` = `sch`.`id`))) join `mysql`.`catalogs` `cat` on((`cat`.`id` = `sch`.`catalog_id`))) left join `mysql`.`collations` `col` on((`tbl`.`collation_id` = `col`.`id`))) left join `mysql`.`tablespaces` `ts` on((`tbl`.`tablespace_id` = `ts`.`id`))) left join `mysql`.`table_stats` `stat` on(((`tbl`.`name` = `stat`.`table_name`) and (`sch`.`name` = `stat`.`schema_name`)))) where (can_access_table(`sch`.`name`,`tbl`.`name`) and is_visible_dd_object(`tbl`.`hidden`)) character_set_client: utf8 collation_connection: utf8_general_ci
and the explain plan looks like this:
mysql> explain select count(*) from information_schema.tables \G *************************** 1. row *************************** id: 1 select_type: SIMPLE table: cat partitions: NULL type: index possible_keys: PRIMARY key: name key_len: 194 ref: NULL rows: 1 filtered: 100.00 Extra: Using index *************************** 2. row *************************** id: 1 select_type: SIMPLE table: tbl partitions: NULL type: ALL possible_keys: schema_id key: NULL key_len: NULL ref: NULL rows: 1023387060 filtered: 100.00 Extra: Using where; Using join buffer (Block Nested Loop) *************************** 3. row *************************** id: 1 select_type: SIMPLE table: sch partitions: NULL type: eq_ref possible_keys: PRIMARY,catalog_id key: PRIMARY key_len: 8 ref: mysql.tbl.schema_id rows: 1 filtered: 11.11 Extra: Using where *************************** 4. row *************************** id: 1 select_type: SIMPLE table: stat partitions: NULL type: eq_ref possible_keys: PRIMARY key: PRIMARY key_len: 388 ref: mysql.sch.name,mysql.tbl.name rows: 1 filtered: 100.00 Extra: Using index *************************** 5. row *************************** id: 1 select_type: SIMPLE table: ts partitions: NULL type: eq_ref possible_keys: PRIMARY key: PRIMARY key_len: 8 ref: mysql.tbl.tablespace_id rows: 1 filtered: 100.00 Extra: Using index *************************** 6. row *************************** id: 1 select_type: SIMPLE table: col partitions: NULL type: eq_ref possible_keys: PRIMARY key: PRIMARY key_len: 8 ref: mysql.tbl.collation_id rows: 1 filtered: 100.00 Extra: Using index
Conclusions
- I have created more than 1 billion real InnoDB tables with indexes in MySQL 8.0, just for fun, and it worked. It took ~2 weeks to create.
- Probably MySQL 8.0 is the first version where it is even practically possible to create billion InnoDB tables
- ZFS compression together with NVMe cards makes it reasonably cheap to do, for example, by using i3.4xlarge or i3.8xlarge instances on AWS.
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