performance issue MySQL 5.7

Question

I've migrated my MySQL Database from 5.6 to version 5.7. Now I got a performance issue.

Specific statement are executed in both versions and I noticed that 5.7 is significant slower. Especially with large amount of Data.

Even a simple select statement is much slower

5.6: 2,948 sec
5.7: 6,536 sec

In my application i've got more complex statements that take way more time to execute so it get's unusable.

I've also noticed that the field count of my table matters in 5.7 but not in 5.6.

The configuration values in the my.ini didn't change.

To test this issue you can use the following code:

#Create Tables
DROP TABLE IF EXISTS aTest;
DROP TABLE IF EXISTS sTest;
CREATE TABLE `aTest` (
    `T_BETREFF` CHAR(40) NOT NULL DEFAULT '',
    `T_DATUM` DATETIME NOT NULL DEFAULT '0000-00-00 00:00:00',
    `T_ZEIT` CHAR(5) NOT NULL DEFAULT '',
    `T_SACHBEARB` CHAR(2) NOT NULL DEFAULT '',
    `SYS_UID` INT NOT NULL AUTO_INCREMENT,
    `SYS_DATE` TIMESTAMP NOT NULL DEFAULT CURRENT_TIMESTAMP ON UPDATE CURRENT_TIMESTAMP,
    UNIQUE INDEX `TODO01` (`SYS_UID`),
    INDEX `TODO02` (`T_SACHBEARB`)
)
COLLATE='latin1_swedish_ci'
ENGINE=MyISAM;

CREATE TABLE `sTest` (
    `V_NR` CHAR(2) NOT NULL DEFAULT '',
    `V_NAME` CHAR(30) NOT NULL DEFAULT '',
    `SYS_UID` INT NOT NULL AUTO_INCREMENT,
    `SYS_DATE` TIMESTAMP NOT NULL DEFAULT CURRENT_TIMESTAMP ON UPDATE CURRENT_TIMESTAMP,
    UNIQUE INDEX `S_VERK01` (`SYS_UID`),
    UNIQUE INDEX `S_VERK02` (`V_NR`)
)
COLLATE='latin1_swedish_ci'
ENGINE=MyISAM;

#Fill Tables
DROP PROCEDURE IF EXISTS load_foo_atest_data;
DELIMITER //
CREATE PROCEDURE load_foo_atest_data()
BEGIN
    DECLARE v_max int unsigned default 1000000;
    DECLARE v_counter INT UNSIGNED DEFAULT 0;

    WHILE v_counter < v_max DO
        INSERT INTO aTest (T_BETREFF, T_DATUM, T_ZEIT, T_SACHBEARB) VALUES('TEST 1234,', NOW(), '00:00', v_counter DIV 100000 * 10);
        IF (v_counter MOD 100000 = 0) THEN
            INSERT INTO sTest (V_NR, V_NAME) VALUES(v_counter DIV 100000 * 10, CONCAT('TEST', v_counter));
        END IF;
        SET v_counter=v_counter+1;
    END WHILE;
END //
DELIMITER ;

call load_foo_atest_data();

Here my statement:

FLUSH TABLES;
SELECT * FROM atest
LEFT JOIN sTEST ON v_nr = t_sachbearb
GROUP BY atest.sys_uid
ORDER BY t_datum DESC, t_zeit DESC

EDIT

EXPLAIN results:

5.6:

+----+-------------+-------+--------+---------------+----------+---------+-------------------------------------------+---------+---------------------------------+
| id | select_type | table |  type  | possible_keys |   key    | key_len |                    ref                    |  rows   |              Extra              |
+----+-------------+-------+--------+---------------+----------+---------+-------------------------------------------+---------+---------------------------------+
|  1 | SIMPLE      | atest | ALL    | TODO01        | NULL     | NULL    | NULL                                      | 1000000 | Using temporary; Using filesort |
|  1 | SIMPLE      | sTEST | eq_ref | S_VERK02      | S_VERK02 | 2       | obs_mysql_bergau_57test.atest.T_SACHBEARB |       1 | NULL                            |
+----+-------------+-------+--------+---------------+----------+---------+-------------------------------------------+---------+---------------------------------+

5.7

+----+-------------+-------+------------+--------+---------------+----------+---------+-------------------------------------------+---------+----------+---------------------------------+
| id | select_type | table | partitions |  type  | possible_keys |   key    | key_len |                    ref                    |  rows   | filtered |              Extra              |
+----+-------------+-------+------------+--------+---------------+----------+---------+-------------------------------------------+---------+----------+---------------------------------+
|  1 | SIMPLE      | atest | NULL       | ALL    | TODO01        | NULL     | NULL    | NULL                                      | 1000000 | 100.00   | Using temporary; Using filesort |
|  1 | SIMPLE      | sTEST | NULL       | eq_ref | S_VERK02      | S_VERK02 | 2       | obs_mysql_bergau_57test.atest.T_SACHBEARB |       1 | 100.00   | NULL                            |
+----+-------------+-------+------------+--------+---------------+----------+---------+-------------------------------------------+---------+----------+---------------------------------+

My.ini:

# Other default tuning values
# MySQL Server Instance Configuration File
# ----------------------------------------------------------------------
# Generated by the MySQL Server Instance Configuration Wizard
#
#
# Installation Instructions
# ----------------------------------------------------------------------
#
# On Linux you can copy this file to /etc/my.cnf to set global options,
# mysql-data-dir/my.cnf to set server-specific options
# (@localstatedir@ for this installation) or to
# ~/.my.cnf to set user-specific options.
#
# On Windows you should keep this file in the installation directory 
# of your server (e.g. C:\Program Files\MySQL\MySQL Server X.Y). To
# make sure the server reads the config file use the startup option 
# "--defaults-file". 
#
# To run run the server from the command line, execute this in a 
# command line shell, e.g.
# mysqld --defaults-file="C:\Program Files\MySQL\MySQL Server X.Y\my.ini"
#
# To install the server as a Windows service manually, execute this in a 
# command line shell, e.g.
# mysqld --install MySQLXY --defaults-file="C:\Program Files\MySQL\MySQL Server X.Y\my.ini"
#
# And then execute this in a command line shell to start the server, e.g.
# net start MySQLXY
#
#
# Guildlines for editing this file
# ----------------------------------------------------------------------
#
# In this file, you can use all long options that the program supports.
# If you want to know the options a program supports, start the program
# with the "--help" option.
#
# More detailed information about the individual options can also be
# found in the manual.
#
# For advice on how to change settings please see
# http://dev.mysql.com/doc/refman/5.7/en/server-configuration-defaults.html
#
#
# CLIENT SECTION
# ----------------------------------------------------------------------
#
# The following options will be read by MySQL client applications.
# Note that only client applications shipped by MySQL are guaranteed
# to read this section. If you want your own MySQL client program to
# honor these values, you need to specify it as an option during the
# MySQL client library initialization.
# [client] no-beep

# pipe
# socket=0.0 port=3306

[mysql]

default-character-set=utf8


# SERVER SECTION
# ----------------------------------------------------------------------
#
# The following options will be read by the MySQL Server. Make sure that
# you have installed the server correctly (see above) so it reads this 
# file.
#
# server_type=1 [mysqld]

# The next three options are mutually exclusive to SERVER_PORT below.
# skip-networking

# enable-named-pipe

# shared-memory

# shared-memory-base-name=MYSQL

# The Pipe the MySQL Server will use
# socket=MYSQL

# The TCP/IP Port the MySQL Server will listen on port=3306

# Path to installation directory. All paths are usually resolved relative to this.
# basedir="C:/Program Files/MySQL/MySQL Server 5.7/"

# Path to the database root datadir=C:/ProgramData/MySQL/MySQL Server 5.7\Data

# The default character set that will be used when a new schema or table is
# created and no character set is defined character-set-server = latin1

# The default storage engine that will be used when create new tables when default-storage-engine = MYISAM

# Set the SQL mode to strict sql-mode="STRICT_TRANS_TABLES,NO_AUTO_CREATE_USER,NO_ENGINE_SUBSTITUTION"

# Enable Windows Authentication
# plugin-load=authentication_windows.dll

# General and Slow logging. log-output=FILE general-log=1 general_log_file="PC-THIEL.log" slow-query-log=1 slow_query_log_file="PC-THIEL-slow.log" long_query_time=10

# Binary Logging.
# log-bin

# Error Logging. log-error="PC-THIEL.err"

# Server Id. server-id=1

# Secure File Priv. secure-file-priv="C:/ProgramData/MySQL/MySQL Server 5.7/Uploads"

# The maximum amount of concurrent sessions the MySQL server will
# allow. One of these connections will be reserved for a user with
# SUPER privileges to allow the administrator to login even if the
# connection limit has been reached. max_connections=1000

# Query cache is used to cache SELECT results and later return them
# without actual executing the same query once again. Having the query
# cache enabled may result in significant speed improvements, if your
# have a lot of identical queries and rarely changing tables. See the
# "Qcache_lowmem_prunes" status variable to check if the current value
# is high enough for your load.
# Note: In case your tables change very often or if your queries are
# textually different every time, the query cache may result in a
# slowdown instead of a performance improvement. query_cache_size = 2G

# The number of open tables for all threads. Increasing this value
# increases the number of file descriptors that mysqld requires.
# Therefore you have to make sure to set the amount of open files
# allowed to at least 4096 in the variable "open-files-limit" in
# section [mysqld_safe] table_open_cache=2000

# Maximum size for internal (in-memory) temporary tables. If a table
# grows larger than this value, it is automatically converted to disk
# based table This limitation is for a single table. There can be many
# of them. tmp_table_size=3G

# How many threads we should keep in a cache for reuse. When a client
# disconnects, the client's threads are put in the cache if there aren't
# more than thread_cache_size threads from before.  This greatly reduces
# the amount of thread creations needed if you have a lot of new
# connections. (Normally this doesn't give a notable performance
# improvement if you have a good thread implementation.) thread_cache_size=10

#*** MyISAM Specific options
# The maximum size of the temporary file MySQL is allowed to use while
# recreating the index (during REPAIR, ALTER TABLE or LOAD DATA INFILE.
# If the file-size would be bigger than this, the index will be created
# through the key cache (which is slower). myisam_max_sort_file_size=100G

# If the temporary file used for fast index creation would be bigger
# than using the key cache by the amount specified here, then prefer the
# key cache method.  This is mainly used to force long character keys in
# large tables to use the slower key cache method to create the index. myisam_sort_buffer_size=6G

# Size of the Key Buffer, used to cache index blocks for MyISAM tables.
# Do not set it larger than 30% of your available memory, as some memory
# is also required by the OS to cache rows. Even if you're not using
# MyISAM tables, you should still set it to 8-64M as it will also be
# used for internal temporary disk tables. key_buffer_size = 8G

# Size of the buffer used for doing full table scans of MyISAM tables.
# Allocated per thread, if a full scan is needed. read_buffer_size=64K read_rnd_buffer_size=256K

#*** INNODB Specific options ***
# innodb_data_home_dir=0.0

# Use this option if you have a MySQL server with InnoDB support enabled
# but you do not plan to use it. This will save memory and disk space
# and speed up some things.
# skip-innodb

# If set to 1, InnoDB will flush (fsync) the transaction logs to the
# disk at each commit, which offers full ACID behavior. If you are
# willing to compromise this safety, and you are running small
# transactions, you may set this to 0 or 2 to reduce disk I/O to the
# logs. Value 0 means that the log is only written to the log file and
# the log file flushed to disk approximately once per second. Value 2
# means the log is written to the log file at each commit, but the log
# file is only flushed to disk approximately once per second. innodb_flush_log_at_trx_commit=1

# The size of the buffer InnoDB uses for buffering log data. As soon as
# it is full, InnoDB will have to flush it to disk. As it is flushed
# once per second anyway, it does not make sense to have it very large
# (even with long transactions). innodb_log_buffer_size=1M

# InnoDB, unlike MyISAM, uses a buffer pool to cache both indexes and
# row data. The bigger you set this the less disk I/O is needed to
# access data in tables. On a dedicated database server you may set this
# parameter up to 80% of the machine physical memory size. Do not set it
# too large, though, because competition of the physical memory may
# cause paging in the operating system.  Note that on 32bit systems you
# might be limited to 2-3.5G of user level memory per process, so do not
# set it too high. innodb_buffer_pool_size=8M

# Size of each log file in a log group. You should set the combined size
# of log files to about 25%-100% of your buffer pool size to avoid
# unneeded buffer pool flush activity on log file overwrite. However,
# note that a larger logfile size will increase the time needed for the
# recovery process. innodb_log_file_size=48M

# Number of threads allowed inside the InnoDB kernel. The optimal value
# depends highly on the application, hardware as well as the OS
# scheduler properties. A too high value may lead to thread thrashing. innodb_thread_concurrency=17

# The increment size (in MB) for extending the size of an auto-extend InnoDB system tablespace file when it becomes full. innodb_autoextend_increment=64

# The number of regions that the InnoDB buffer pool is divided into.
# For systems with buffer pools in the multi-gigabyte range, dividing the buffer pool into separate instances can improve concurrency,
# by reducing contention as different threads read and write to cached pages. innodb_buffer_pool_instances=8

# Determines the number of threads that can enter InnoDB concurrently. innodb_concurrency_tickets=5000

# Specifies how long in milliseconds (ms) a block inserted into the old sublist must stay there after its first access before
# it can be moved to the new sublist. innodb_old_blocks_time=1000

# It specifies the maximum number of .ibd files that MySQL can keep open at one time. The minimum value is 10. innodb_open_files=300

# When this variable is enabled, InnoDB updates statistics during metadata statements. innodb_stats_on_metadata=0

# When innodb_file_per_table is enabled (the default in 5.6.6 and higher), InnoDB stores the data and indexes for each newly created table
# in a separate .ibd file, rather than in the system tablespace. innodb_file_per_table=1

# Use the following list of values: 0 for crc32, 1 for strict_crc32, 2 for innodb, 3 for strict_innodb, 4 for none, 5 for strict_none. innodb_checksum_algorithm=0

# The number of outstanding connection requests MySQL can have.
# This option is useful when the main MySQL thread gets many connection requests in a very short time.
# It then takes some time (although very little) for the main thread to check the connection and start a new thread.
# The back_log value indicates how many requests can be stacked during this short time before MySQL momentarily
# stops answering new requests.
# You need to increase this only if you expect a large number of connections in a short period of time. back_log=80

# If this is set to a nonzero value, all tables are closed every flush_time seconds to free up resources and
# synchronize unflushed data to disk.
# This option is best used only on systems with minimal resources. flush_time=0

# The minimum size of the buffer that is used for plain index scans, range index scans, and joins that do not use
# indexes and thus perform full table scans. join_buffer_size=256K

# The maximum size of one packet or any generated or intermediate string, or any parameter sent by the
# mysql_stmt_send_long_data() C API function. max_allowed_packet=4M

# If more than this many successive connection requests from a host are interrupted without a successful connection,
# the server blocks that host from performing further connections. max_connect_errors=1000

# Changes the number of file descriptors available to mysqld.
# You should try increasing the value of this option if mysqld gives you the error "Too many open files". open_files_limit=4161

# Set the query cache type. 0 for OFF, 1 for ON and 2 for DEMAND. query_cache_type = 1

# If you see many sort_merge_passes per second in SHOW GLOBAL STATUS output, you can consider increasing the
# sort_buffer_size value to speed up ORDER BY or GROUP BY operations that cannot be improved with query optimization
# or improved indexing. sort_buffer_size=256K

# The number of table definitions (from .frm files) that can be stored in the definition cache.
# If you use a large number of tables, you can create a large table definition cache to speed up opening of tables.
# The table definition cache takes less space and does not use file descriptors, unlike the normal table cache.
# The minimum and default values are both 400. table_definition_cache=1400

# Specify the maximum size of a row-based binary log event, in bytes.
# Rows are grouped into events smaller than this size if possible. The value should be a multiple of 256. binlog_row_event_max_size=8K

# If the value of this variable is greater than 0, a replication slave synchronizes its master.info file to disk.
# (using fdatasync()) after every sync_master_info events. sync_master_info=10000

# If the value of this variable is greater than 0, the MySQL server synchronizes its relay log to disk.
# (using fdatasync()) after every sync_relay_log writes to the relay log. sync_relay_log=10000

# If the value of this variable is greater than 0, a replication slave synchronizes its relay-log.info file to disk.
# (using fdatasync()) after every sync_relay_log_info transactions. sync_relay_log_info=10000

query_cache_limit = 30M collation-server = latin1_swedish_ci default_tmp_storage_engine = MYISAM


myisam_use_mmap concurrent_insert = AUTO

Answer 1

Without a SQLFiddle, I cannot be sure, but I think your problem is caused by a change to the performance tuning of "group by" in 5.7.

I'm not totally sure, but I think this means that query optimizer decisions that used to make sense no longer work so well. In your sample query, for instance, the EXPLAIN shows the query is using an index on the smaller table.

In the code you've posted, I don't think the "group by" clause does much - you're still retrieving every row because sysdate should be unique.

In this specific case, you may get better results by creating an index on table atest with columns t_sachbearb, atest.sys_uid, t_datum DESC, t_zeit DESC. This should cause the query optimizer to pick the index on the larger column, and use that for the filtering and sorting.

I'd consider rewriting without group by to support "distinct" requirements where possible.

Where not, you may need to look at the individual "EXPLAIN" output and optimize the indexes.