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innodb ft index exact phrase search slow
Posted by: Erik Rooijmans
Date: April 15, 2013 02:13AM

Hi All,

I have a problem regarding exact phrase searching in an innodb full text index.
For the initial test I have added 400.000 text rows (each row consisting of approx. 70 words).

While doing a match against a single word the speed is perfect, however when doing an exact search like match against (' "word1 word2" ') it takes more about 70 seconds

So I started investigating,
- The query is using the index.
- The amount of time taken to run the exact same query for a 2nd time doesn't reduce the overall query time. (So it is not using the cache?) I don't know why this is.

So I started paying with the innodb_ft_cache_size parameter.
By default, if not specified it is set to 8 MB.
By increasing the value to 32 MB and restarting mysql i can indeed see that the cache size has increased.

When running the same query now, it only takes about 39 seconds.

So I dediced to increase the value of innodb_ft_cache_size to 1024 MB.
After restarting mysql and showing its variables, it shows me that the innodb_ft_cache_size is set to 80 MB?

Is this a bug? Or is 80 MB just a limitation?

When I reduce the amount of rows to 100.000 the exact same query runs in and run optimize table the query runs in 2 seconds.

Can somebody help me here?

Regards,

Erik

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