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∟Storage Engines in MySQL Server

∟MySQL System Variables for InnoDB Engine

This section describes some important MySQL system variables that control the behavior of the InnoDB storage engine.

As of MySQL 8.0, there are 144 system variables to control the behavior of the InnoDB storage engine. Here are some important ones you should pay attention:

• innodb_buffer_pool_size (Default: 134217728) - The size in bytes of the buffer pool, the memory area where InnoDB caches table and index data.
• innodb_change_buffering (Default: all) - Whether InnoDB performs change buffering, an optimization that delays write operations to secondary indexes so that the I/O operations can be performed sequentially.
• innodb_commit_concurrency (Default: 0 (any number)) - The number of threads that can commit at the same time.
• innodb_compression_level (Default: 6) - Specifies the level of zlib compression to use for InnoDB compressed tables and indexes. A higher value lets you fit more data onto a storage device, at the expense of more CPU overhead during compression.
• innodb_ddl_buffer_size (Default: 1048576) - Maximum buffer size in bytes for DDL operations.
• innodb_ddl_threads (Default: 4) - Maximum number of parallel threads for the sort and build phases of index creation. Applies to online DDL operations that create or rebuild secondary indexes.
• innodb_deadlock_detect (Default: ON) - Used to disable deadlock detection. On high concurrency systems, deadlock detection can cause a slowdown when numerous threads wait for the same lock.
• innodb_dedicated_server (Default: OFF) - Only consider enabling innodb_dedicated_server if the MySQL instance resides on a dedicated server where it can use all available system resources.
• innodb_default_row_format (Default: DYNAMIC) - Defines the default row format for InnoDB tables and user-created temporary tables.
• innodb_directories (Default: NULL) - Directories to scan at startup for tablespace files.
• innodb_extend_and_initialize (Default: ON) - Controls how space is allocated to file-per-table and general tablespaces on Linux systems.
• innodb_file_per_table (Default: ON) - When innodb_file_per_table is enabled, tables are created in file-per-table tablespaces by default.
• innodb_ft_cache_size (Default: 8000000) - The memory allocated, in bytes, for the InnoDB FULLTEXT search index cache, which holds a parsed document in memory while creating an InnoDB FULLTEXT index.
• innodb_ft_num_word_optimize (Default: 2000) - Number of words to process during each OPTIMIZE TABLE operation on an InnoDB FULLTEXT index.
• innodb_ft_total_cache_size (Default: 640000000) - The total memory allocated, in bytes, for the InnoDB full-text search index cache for all tables.
• innodb_io_capacity (Default: 200) - The number of I/O operations per second (IOPS) available to InnoDB background tasks, such as flushing pages from the buffer pool and merging data from the change buffer.
• innodb_lock_wait_timeout (Default: 50) - The length of time in seconds an InnoDB transaction waits for a row lock before giving up.
• innodb_log_buffer_size (Default: 16777216) - The size in bytes of the buffer that InnoDB uses to write to the log files on disk.
• innodb_log_file_size (Default: 50331648) - The size in bytes of each log file in a log group.
• innodb_max_dirty_pages_pct (Default: 90) - InnoDB tries to flush data from the buffer pool so that the percentage of dirty pages does not exceed this value.
• innodb_monitor_enable (Default: NULL) - Enables InnoDB metrics counters. Counter data may be queried using the INFORMATION_SCHEMA.INNODB_METRICS table.
• innodb_page_cleaners (Default: 4) - The number of page cleaner threads that flush dirty pages from buffer pool instances.
• innodb_page_size (Default: 16384) - Specifies the page size for InnoDB tablespaces.
• innodb_parallel_read_threads (Default: 4) - The number of threads that can be used for parallel clustered index reads.
• innodb_print_all_deadlocks (Default: OFF) - When this option is enabled, information about all deadlocks in InnoDB user transactions is recorded in the mysqld error log.
• innodb_purge_threads (Default: 4) - The number of background threads devoted to the InnoDB purge operation.
• innodb_random_read_ahead (Default: OFF) - Enables the random read-ahead technique for optimizing InnoDB I/O.
• innodb_read_io_threads (Default: 4) - The number of I/O threads for read operations in InnoDB.
• innodb_read_only (Default: OFF) - Starts InnoDB in read-only mode.
• innodb_rollback_on_timeout (Default: OFF) - InnoDB rolls back only the last statement on a transaction timeout by default.
• innodb_stats_auto_recalc (Default: ON) - Causes InnoDB to automatically recalculate persistent statistics after the data in a table is changed substantially.
• innodb_status_output (Default: OFF) - Enables or disables periodic output for the standard InnoDB Monitor.
• innodb_strict_mode (Default: ON) - When enabled, InnoDB returns errors rather than warnings for certain conditions.
• innodb_sync_array_size (Default: 1) - Defines the size of the mutex/lock wait array.
• innodb_table_locks (Default: ON) - If autocommit = 0, InnoDB honors LOCK TABLES.
• innodb_thread_concurrency (Default: 0 (any)) - Maximum number of threads permitted inside of InnoDB.
• innodb_write_io_threads (Default: 4) - The number of I/O threads for write operations in InnoDB.

You can see the all InnoDB related system variables and their current values using the "SHOW VARIABLES ..." statement:

mysql> show variables like '%innodb%';
...

Table of Contents

 About This Book

 Introduction of SQL

 MySQL Introduction and Installation

 Introduction of MySQL Programs

 PHP Programs and MySQL Server

 Perl Programs and MySQL Servers

 Java Programs and MySQL Servers

 Datatypes and Data Literals

 Operations and Expressions

 Character Strings and Bit Strings

 Commonly Used Functions

 Table Column Types for Different Types of Values

 Using DDL to Create Tables and Indexes

 Using DML to Insert, Update and Delete Records

 Using SELECT to Query Database

 Window Functions for Statistical Analysis

 Use Index for Better Performance

 Transaction Management and Isolation Levels

 Locks Used in MySQL

 Defining and Calling Stored Procedures

 Variables, Loops and Cursors Used in Stored Procedures

 System, User-Defined and Stored Procedure Variables

 MySQL Server Administration

►Storage Engines in MySQL Server

 What Are Storage Engines

 What Is InnoDB Storage Engine

 Convert Table to InnoDB Storage Engine

 Clustered Index Used by InnoDB Engine

 Statistic Information on InnoDB Tables

 MySQL Status Variables for InnoDB Engine

►MySQL System Variables for InnoDB Engine

 InnoDB Storage Engine - Primary and Secondary Indexes

 Performance Tuning and Optimization

 Bulk Changes on Large Tables

 MySQL Server on macOS

 Installing MySQL Server on Linux

 Connection, Performance and Second Instance on Linux

 Archived Tutorials

 References

 Full Version in PDF/EPUB

MySQL System Variables for InnoDB Engine - Updated in 2023, by Herong Yang