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From version 4.0.1, MySQL server
features a Query Cache
.
When in use, the query cache stores the text of a SELECT
query
together with the corresponding result that was sent to the client.
If an identical query is later received, the server will retrieve
the results from the query cache rather than parsing and executing the
same query again.
NOTE: The query cache does not return stale data. When data is modified, any relevant entries in the query cache are flushed.
The query cache is extremely useful in an environment where (some) tables don't change very often and you have a lot of identical queries. This is a typical situation for many web servers that use a lot of dynamic content.
Below is some performance data for the query cache. (These results were generated by running the MySQL benchmark suite on a Linux Alpha 2 x 500 MHz with 2 GB RAM and a 64 MB query cache):
query_cache_size=0
.
By disabling the query cache code there is no noticeable overhead.
(query cache can be excluded from code with help of configure option
--without-query-cache
)
13.8.1 How the Query Cache Operates | ||
13.8.2 Query Cache Configuration | ||
13.8.3 Query Cache Options in SELECT | ||
13.8.4 Query Cache Status and Maintenance |
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