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From "Ning Li (JIRA)" <>
Subject [jira] Commented: (LUCENE-1035) Optional Buffer Pool to Improve Search Performance
Date Fri, 26 Oct 2007 14:52:50 GMT


Ning Li commented on LUCENE-1035:

> Were the tests run using the same set of queries they were warmed for?

Yes, the same set of queries were used. The warm-up and the real run are two separate runs,
which means the file system cache is warmed, but not the buffer pool.

Yes, it'd much better if a real query log could be obtained. I'll take a look at the AOL query
log. I used to have an intranet query log which has a lot of term locality. That's why I think
this could provide a good improvement.

> There are better ways to optimize for that, e.g., by caching hit lists, no?

That's useful and that's for exact query match. If there are a lot of shared query term but
not exact query match, caching hit list won't help. This is sort of caching posting list but

> Optional Buffer Pool to Improve Search Performance
> --------------------------------------------------
>                 Key: LUCENE-1035
>                 URL:
>             Project: Lucene - Java
>          Issue Type: Improvement
>          Components: Store
>            Reporter: Ning Li
>         Attachments: LUCENE-1035.patch
> Index in RAMDirectory provides better performance over that in FSDirectory.
> But many indexes cannot fit in memory or applications cannot afford to
> spend that much memory on index. On the other hand, because of locality,
> a reasonably sized buffer pool may provide good improvement over FSDirectory.
> This issue aims at providing such an optional buffer pool layer. In cases
> where it fits, i.e. a reasonable hit ratio can be achieved, it should provide
> a good improvement over FSDirectory.

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