CODEWITHSUNDEEP
mysqlcachingmemcachedbufferinnodb
Neel
Neel

Reputation: 9880

Isint Memcached doing the same job as Buffer pool in Innodb?

This is what I understand it as:

Buffer Pool in Innodb: This stores the index and data from Sql table and caches it for future queries so it doesn't need to bother Mysql all the time.

Memcached: this is used to store the data received from Innodb and caches it so it doesn't need to keep asking Innodb each time.

Aren't they both doing the same thing I.e caching the response in Ram so it is faster and reduces I/o and sql parsing? Then why add another layer of memcached on top of Innodb Buffer pool?

Upvotes: 1

Views: 365

Answers (1)

Andreas Wederbrand
Andreas Wederbrand

Reputation: 39981

The Buffer pool is managed by InnoDB. Everything needed to do queries must be in the buffer pool so data already in there gets evicted if needed when new data is read from disk to be used in the current query.

Joins between tables is still done and can be costly, even if the tables are in the buffer pool.

Memcached on the other hand is a key-value store. No relational operations can be performed on data stored there, just inserts and retrievals. It is also distributed making it possible to build huge clusters.

Typically the results of long running or heavy queries are stored in memcached for a period of time, taking load of the database.

Upvotes: 2

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