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I know that SQL query will use query cache to receive data instead of reprocess all of the data. Here the question I would like to ask,
I working with a server of database and I'm one of the developer that working on it and I need to do performance testing on queries that i handling
If I clear the query cache
example using FLUSH QUERY CACHE; or RESET QUERY CACHE;,
will it affect others developer or it only clears away my local query cache?
If it will affect others, is there any way to clear locally or allow my query won't use the query cache for testing
919
Every query requires a query plan before it is actually executed. This query plan is stored in SQL Server query plan cache. This way when that query is run again, SQL Server doesn't need to create another query plan; rather it uses the cached query plan which improved database performance.
The SQL statement cache is a feature that lets you store in a buffer identical SQL statements that are executed repeatedly so the statements can be reused among different user sessions without the need for per-session memory allocation.
To clear SQL Server's cache, run DBCC DROPCLEANBUFFERS , which clears all data from the cache. Then run DBCC FREEPROCCACHE , which clears the stored procedure cache.
Query cache is a prominent MySQL feature that speeds up data retrieval from a database. It achieves this by storing MySQL SELECT statements together with the retrieved record set in memory, then if a client requests identical queries it can serve the data faster without executing commands again from the database.
Two clarifications to begin with:
MySQL query cache is a server-side feature, there's no such thing as "local cache". You're probably confused by the LOCAL keyword in FLUSH command. As docs explain it's just an alias for NO_WRITE_TO_BINLOG (thus it's related to replication and "local" means "this server").
MySQL will only return cached data if you've enabled the feature and either made it default or opted-in with the SQL_CACHE hint. In my experience, most servers do not have it by default.
Let's now answer your question. At The MySQL Query Cache we can read:
The query cache is shared among sessions, so a result set generated by one client can be sent in response to the same query issued by another client.
Which makes sense: a cache that cannot reuse stored data is not as useful.
I don't know what you want to test exactly. Your data should always be fresh:
The query cache does not return stale data. When tables are modified, any relevant entries in the query cache are flushed.
However you might want to get an idea of how long the query takes to run. You can always opt out with the SQL_NO_CACHE keyword:
The server does not use the query cache. It neither checks the query cache to see whether the result is already cached, nor does it cache the query result.
Just take into account that a query that runs for the second time might run faster even without cache because part of the data segments might be already loaded into RAM.
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Try using the SQL_NO_CACHE option in your query.This will stop MySQL caching the results
SELECT SQL_NO_CACHE * FROM TABLE
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