Tips & Tricks – How to implement Optimizer Index Caching in InnoDB?

Optimizer Index Caching is a feature in InnoDB that allows the caching of index statistics in the buffer pool to improve query performance. It helps the MySQL query optimizer make better decisions by utilizing the cached index statistics instead of reading them from disk repeatedly. Implementing Optimizer Index Caching in InnoDB involves the following steps:

Configure the innodb_stats_persistent Parameter:

Enable the innodb_stats_persistent parameter in your MySQL configuration file (my.cnf) or set it dynamically using the SET GLOBAL command. This parameter determines whether InnoDB should persistently cache index statistics in the buffer pool.

[mysqld]
innodb_stats_persistent = 1

Setting innodb_stats_persistent to 1 enables index statistics caching, while setting it to 0 disables caching.

Monitor and Adjust innodb_stats_persistent_sample_pages:

The innodb_stats_persistent_sample_pages parameter controls the number of index pages sampled during the index statistics gathering process. By default, it is set to 20, which means InnoDB samples 20 index pages per table. You can adjust this value based on the size of your tables and the desired level of accuracy in the index statistics.

[mysqld]
innodb_stats_persistent_sample_pages = 100

Increasing the value of innodb_stats_persistent_sample_pages allows for a more accurate representation of index statistics, but it also requires more memory.

Monitor and Adjust innodb_stats_transient_sample_pages:

The innodb_stats_transient_sample_pages parameter controls the number of index pages sampled during the transient index statistics gathering process. Transient index statistics are used for queries executed before the persistent index statistics are collected. By default, it is set to 8, which means InnoDB samples 8 index pages per table. You can adjust this value based on your workload and query patterns.

[mysqld]
innodb_stats_transient_sample_pages = 20

Increasing the value of innodb_stats_transient_sample_pages improves the accuracy of transient index statistics, but it consumes additional memory.

Collect Persistent Index Statistics:

After enabling Optimizer Index Caching, you need to collect and persist the index statistics in the buffer pool. This can be done by running the ANALYZE TABLE statement for the desired tables.

ANALYZE TABLE your_table_name;

The ANALYZE TABLE statement triggers the collection of index statistics and updates the persistent cache in the buffer pool.

Monitor and Adjust Performance:

Once Optimizer Index Caching is implemented, monitor the query performance and analyze the impact. Keep an eye on the query execution plans, query response times, and overall system resource usage. Adjust the cache-related parameters as necessary to optimize performance and memory utilization.

SHOW STATUS LIKE 'innodb_buffer_pool%';

Use the SHOW STATUS command to monitor the buffer pool statistics and observe the memory consumption.

By implementing Optimizer Index Caching in InnoDB and adjusting the relevant parameters, you can improve query performance by leveraging cached index statistics. However, it’s important to consider the trade-offs, such as memory consumption and the need for regular index statistics updates, to ensure optimal performance in your specific workload.

About Shiv Iyer 444 Articles
Open Source Database Systems Engineer with a deep understanding of Optimizer Internals, Performance Engineering, Scalability and Data SRE. Shiv currently is the Founder, Investor, Board Member and CEO of multiple Database Systems Infrastructure Operations companies in the Transaction Processing Computing and ColumnStores ecosystem. He is also a frequent speaker in open source software conferences globally.