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| | MyISAM: Key Cache || https://dev.mysql.com/doc/refman/5.7/en/myisam-key-cache.html | | | MyISAM: Key Cache || https://dev.mysql.com/doc/refman/5.7/en/myisam-key-cache.html |
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| | InnoDB: Buffer Pool || https://dev.mysql.com/doc/refman/5.7/en/innodb-buffer-pool.html
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| | InnoDB: MemcacheD Plugin || https://dev.mysql.com/doc/refman/5.7/en/innodb-memcached.html
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| |} | | |} |
| </blockquote><!-- Documentation --> | | </blockquote><!-- Documentation --> |
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| |} | | |} |
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| == Query Cache (<8.0) ==
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| <blockquote>
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| {{ NOTE |
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| It is disabled by default starting in MySQL-5.6<br>
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| https://dev.mysql.com/blog-archive/mysql-8-0-retiring-support-for-the-query-cache/
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| }}
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| The query cache is a key-value store of cacheable-queries, and their result.<br>
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| This interferes with benchmarking, since repeat queries may be much faster to lookup.
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| To avoid the query cache:
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| <syntaxhighlight lang="mysql">
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| # 1. Add a calculated-function to your selected rows - since they are not cacheable
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| # TODO: validate
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| SELECT ..., NOW() FROM ...
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| # 2. Use 'SQL_NO_CACHE' in your query
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| # (This often has not worked for me)
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| SELECT SQL_NO_CACHE ... FROM ...
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| </syntaxhighlight>
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| It is implemented as an LRU key-value store for exact (byte-for-byte) query matches.<br>
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| Each cache entry knows which tables it references for permissions, and cache-invalidation.<br>
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| Whenever any row is changed in a table, all cache entries using that table are purged.
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| <syntaxhighlight lang="mysql">
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| SHOW VARIABLES LIKE 'query_cache_type'; # cache is 'ON/OFF/DEMAND'
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| SHOW VARIABLES LIKE 'query_cache_size'; # max capacity of cache
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| </syntaxhighlight>
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| </blockquote><!-- The Query Cache -->
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| == The OS Cache ==
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| <blockquote>
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| {{ TODO |
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| research. Apparently most prominent in MyISAM tables? }}
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| </blockquote><!-- The OS Cache -->
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| == Table Cache ==
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| <blockquote>
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| Used differently by different storage engines.
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| </blockquote><!-- Table Cache -->
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| </blockquote><!-- General --> | | </blockquote><!-- General --> |
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