laraconeu 2016 - making the most out of mysql
TRANSCRIPT
Making the most out of MySQL
Gabriela D’Ávila
@gabidavila
Aug 2016
Who?
• Data Engineer
• 2nd year at Laracon EU
• @gabidavila
• http://gabriela.io
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• Online DDL Changes
• SQL Modes
• Generated Columns
• JSON Data Type
• `sys` Schema
What to Expect
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Online DDL Changes on InnoDB
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• In Place (ALGORITHM=INPLACE)
• Rename Index
• VARCHAR from 1 to 255
• Add a Virtual Column
• Table-copy (ALGORITHM=COPY)
• VARCHAR from 256 to 65535
• Add a Column
• Type Conversion
Online DDL Changes
5More Info
SQL Modes
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SQL modes (SELECT @@GLOBAL.sql_mode;)
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+-----------------------------------------------------------------------+ | @@GLOBAL.sql_mode | +-----------------------------------------------------------------------+ | ONLY_FULL_GROUP_BY,STRICT_TRANS_TABLES,NO_ZERO_IN_DATE,NO_ZERO_DATE, || ERROR_FOR_DIVISION_BY_ZERO,NO_AUTO_CREATE_USER,NO_ENGINE_SUBSTITUTION | +-----------------------------------------------------------------------+ 1 row in set (0.00 sec)
On MySQL 5.7:
On MySQL 5.6:
+--------------------------------------------+ | @@GLOBAL.sql_mode | +--------------------------------------------+ | STRICT_TRANS_TABLES,NO_ENGINE_SUBSTITUTION | +--------------------------------------------+ 1 row in set (0.00 sec)
SQL modes comparison
On MySQL 5.6:
• STRICT_TRANS_TABLES
• NO_ENGINE_SUBSTITUTION
On MySQL 5.7
• STRICT_TRANS_TABLES
• NO_ENGINE_SUBSTITUTION
• ONLY_FULL_GROUP_BY
• NO_ZERO_IN_DATE*
• NO_ZERO_DATE*
• ERROR_FOR_DIVISION_BY_ZERO*
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Full list of sql_mode
Example
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Users Table
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Field Type Null Key Default Extra
id int(10) unsigned NO PRI auto_increment
first_name varchar(255) NO NULL
last_name varchar(255) NO NULL
email varchar(255) NO NULL
created_at datetime NO CURRENT_TIMESTAMP
updated_at datetime NO CURRENT_TIMESTAMP on update CURRENT_TIMESTAMP
Repeated emails
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+------+------------+-----------+---------------------+---------------------+---------------------+ | USERS | +------+------------+-----------+---------------------+---------------------+---------------------+ | id | first_name | last_name | email | created_at | updated_at | +------+------------+-----------+---------------------+---------------------+---------------------+ | 2291 | Reta | Bogisich | [email protected] | 2016-08-17 19:23:34 | 2016-08-17 19:23:34 | | 2497 | Marina | Trantow | [email protected] | 2016-08-22 21:59:31 | 2016-08-22 21:59:31 | | 1075 | Lempi | Huels | [email protected] | 2016-08-17 19:24:01 | 2016-08-17 19:24:01 | | 1833 | Jacynthe | Pollich | [email protected] | 2016-08-22 21:59:20 | 2016-08-22 21:59:20 | | 1432 | Mylene | Crooks | [email protected] | 2016-08-22 21:59:29 | 2016-08-22 21:59:29 | +------+------------+-----------+---------------------+---------------------+---------------------+
5.6
Repeated emails
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mysql> SELECT * FROM `users` GROUP BY `email` HAVING count(*) > 1; ERROR 1055 (42000): Expression #1 of SELECT list is not in GROUP BY clause and contains nonaggregated column ‘store.users.id’ which is not functionally dependent on columns in GROUP BY clause; this is incompatible with sql_mode=only_full_group_by
5.7
"Reject queries for which the select list, HAVING condition, or ORDER BY list refer to nonaggregated columns that are neither named in the GROUP BY clause nor are functionally dependent on (uniquely determined by) GROUP BY columns."
Why?
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This happens because the query is grouping by email and MySQL is magically trying to “discover” which field should it bring to the result to the other values since there are more than one result per row.
This mode is known as ONLY_FULL_GROUP_BY.
Translation
14More Info
Solving using Eloquent
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How we are used to do
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How we should do
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SQL execution
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+-----------+------------------------+-------+ | users_id | email | total | +-----------+------------------------+-------+ | 5056,2291 | [email protected] | 2 | | 7616,2497 | [email protected] | 2 | | 6680,1267 | [email protected] | 2 | | 7426,774 | [email protected] | 2 | | 4940,3964 | [email protected] | 2 | +-----------+------------------------+-------+
Generated Columns
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• No disk space
• INPLACE creation
• Value generated on demand and
• BEFORE triggers
Virtual Columns
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• Uses disk space
• Value updated on INSERT and UPDATE
• Uses table COPY on creation and removal
Stored Columns
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• Can be indexed
• Allows expressions to be used such as:
• Operators
• Built-in functions
• Literals
• Subqueries ARE NOT allowed
Virtual and Stored Columns
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Laravel supports it!
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$ php artisan make:migration add_full_name_virtual
$ php artisan make:migration add_full_name_stored
• price * quantity
• SUBSTRING_INDEX(email, '@', -1)
• FROM_UNIXTIME(created_at)
• JSON_UNQUOTE(JSON_EXTRACT(response,'$.location'))
Other expressions
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JSON
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• Stored as a Binary not TEXT
• TEXT fields can be converted*
• Accessible by $key->value (JSON_EXTRACT alias)
JSON
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• It is costly, it is a table COPY operation
• All rows must be valid, else an error occur
• Index is possible through Generated Columns
Converting TEXT to JSON
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`twitter_users` structure
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Field Type Null Key Default Extra
id int(11) NO PRI auto_increment
id_str varchar(255) NO UNI
screen_name varchar(255) NO INDEX
response json YES
created_at datetime NO CURRENT_TIMESTAMP
updated_at datetime NO CURRENT_TIMESTAMP on update CURRENT_TIMESTAMP
Creating a generated columns in JSON fields
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DESCRIBE `users`;
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Field Type Null Key Default Extra
id int(11) NO PRI auto_increment
id_str varchar(255) NO UNI
screen_name varchar(255) NO INDEX
location varchar(255) YES INDEX STORED GENERATED
profile_image_url varchar(255) YES VIRTUAL GENERATED
response json YES
created_at datetime NO CURRENT_TIMESTAMP
updated_at datetime NO CURRENT_TIMESTAMP on update CURRENT_TIMESTAMP
Users table
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+------------+-----------------+----------------------------+------------------------------------------+--------------------------------+ | id_str | screen_name | location | profile_image_url | response | +------------+-----------------+----------------------------+------------------------------------------+--------------------------------+ | 100838242 | AmbassadorAwsum | San Francisco, CA | http://pbs.twimg.com/profile_images/7631 | {"id": 100838242, "url": "http | | 20039476 | frankdejonge | Amsterdam, North Holland | http://pbs.twimg.com/profile_images/7268 | {"id": 20039476, "url": "https | | 111644778 | ieatkillerbees | New York, NY | http://pbs.twimg.com/profile_images/7108 | {"id": 111644778, "url": "http | | 1359073920 | laraconeu | Amsterdam, Netherlands | http://pbs.twimg.com/profile_images/6847 | {"id": 1359073920, "url": "htt | | 120064855 | n0x13 | Amsterdam, The Netherlands | http://pbs.twimg.com/profile_images/4292 | {"id": 120064855, "url": null, | +------------+-----------------+----------------------------+------------------------------------------+--------------------------------+
MySQL `sys` schema
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• Needs to be installed on 5.6
• Installed by default on 5.7
• MySQL Workbench 6.3 ships with a client for it
• In production should be used in critical query analysis case
MySQL `sys` schema
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What I can do with it?
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*High Cost SQL statements select * from sys.`x$statement_analysis`
Top 5% slower queries select * from sys.`x$statements_with_runtimes_in_95th_percentile`
Use temporary tables select * from sys.`statements_with_temp_tables`
Unused Indexes select * from sys.`schema_unused_indexes`
Full table scans select * from sys.`schema_tables_with_full_table_scans`
*x$ is actually a view duplicated from a table with a more user friendly format
Other changes
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• Passwords can now have expiration date
• NO_ZERO_DATE, NO_ZERO_IN_DATE, ERROR_FOR_DIVISION_BY_ZERO are deprecated and being default in STRICT mode in future versions
• Triggers now supports more than one event per table
• YEAR(2) was deprecated on 5.6, removed on 5.7
Other Changes
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• Twitter: @gabidavila
• Blog: http://gabriela.io
• Freenode: gabidavila
• Feedback: https://joind.in/talk/03f16
• References: MySQL documentation
Thank you!
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