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Old 07-22-2008, 11:31 PM   #1
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Does Mysql InnoDB tales use Key Buffer?

I have a Mysql 5.0.51a server running a reasonable amount (approx 100 tables accross 9 databases) of InnoDB tables. No other storage engines are used.

In Mysql Administrator, under Health, the Key buffer usage is only 27,648. I have allocated 300mb of key buffer. This shows up in Administrator.

As a result, the hitrate is almost always on zero, with a running server. I would like to see eome key caching, as some statements are probalbly costing more than needed.

My tables all have keys, foreign keys and indexes configured. Many of the tables have over 100,000 records in them.

I have been anaylising the Slow query log and making key/ index adjustments as needed. But I still cant get my key buffer to work.

If I added up all of the indexes, it is several GB.

Using a simple exlain select statement with a where, I can see I am using an index. However continually executing the instruction does not make the hitrate go up.

Is it possible that InnoDB does not use this buffer?

The only tables that are not innodb is the Mysql database. I use international timezones and the key usage looks like Mysql is caching the keys only for the mysql database.
Old 07-23-2008, 10:44 AM   #2
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Registered: Jan 2001
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The more advanced engines like InnoDB allocate their own global memory areas that are completely separate from MySQL’s key buffer, table cache, etc.

InnoDB buffer setting will look something like this:

set-variable = innodb_buffer_pool_size=256M
Because the buffer caches both record and index data, it’s likely that you’ll need to choose a buffer pool setting which is larger than the key buffer that you might have used for MyISAM or have used for that matter.


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