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Large DB - Issues
Posted by: abc def
Date: October 06, 2008 06:29AM

Hello,

We are currently testing MySQL fulltext search for an application that already employs a MySQL backend.

Some specs on the table that we require full-text search (BOOLEAN queries, that is) for:

* 3 fields (id,title,body). Title is a fixed-length string (128chars), body is really plain "fulltext", with an average of 30000 characters.

* we accordingly created a fulltext index for (title,body)

* we require match words with a minimum length of 3 words (ft_min_word_len set accordingly)

* (Development Test) Table Size: 200 MB, Index Size: 30.4 MB (for ~7000 rows) -> we would like the table to grow by at least a factor of 10 though.

The issues are:

1) fulltext search with separate words, i.e. something like '+abc +def' is fast (~0.01s query time), BUT fulltext search with compound expressions, i.e. something like '"abc def"' is SLOW, by orders of magnitude (~ 4-10s query time)!

2) dynamically adding content appears to slow down fulltext search dramatically. Is the index not automatically updated? Only issuing a "REPAIR TABLE bla QUICK;" fixes this. But obviously we can't continuously schedule this command continuously, as it can take a while for completion.

Any ideas or input on how to explain the causes, or on how to go about dealing with said problems?

Thanks!

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