On 02/16/2011 12:50 AM, Iker Arizmendi wrote:
> Hello all,
>
> I'm running into what seems like an abnormally large
> performance drop on on some FTS queries that use
> matchinfo when compared to those that don't.
>
> I created an FTS table using the following:
>
> CREATE VIRTUAL TABLE test
> USING FTS4(rowid, content);
>
> and then filled it with ~2 million docs of ~10 tokens
> each which resulted in a file of around 275 MB. After
> running "optimize" on the table I issued a query with
> 3 terms like so:
>
> SELECT length(content) FROM test
> WHERE MATCH "w1 OR w2 OR w3"
>
> which returned ~164,000 rows in 1.1 seconds. However,
> if I throw in a call to matchinfo:
>
> SELECT length(matchinfo(test, 'x')) FROM test
> WHERE MATCH "w1 OR w2 OR w3"
>
> the query takes 7.5 minutes. It seems FTS is getting
> stuck calculating the 2nd and 3rd part of the "x"
> matchinfo data ("hits all rows" and "docs with hits")
> but it's not clear why this should take so long.
> Any ideas on what might be causing the slowdown?
Can you make the database available for download? And
supply the exact query you are using too? I'd like to
know why this is. Thanks.
Dan.
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