Re: tsearch2/GIST performance factors?

Oleg wrote:
> Did you consider *decreasing* SIGLENINT ? Size of index will diminish
> and performance could be increased. I use in current project SIGLENINT=15

The default value for SIGLENINT actually didn't work at all. It was only by increasing it that I got any performance at all. An examination of the GIST indexes showed that most of the first level and many of the second level bitmaps were saturated.

> tsearch2's index is a lossy index, read
> http://www.sai.msu.su/~megera/oddmuse/index.cgi/Tsearch_V2_internals
> so search results should be rechecked !

Yes, thanks. We do indeed recheck the actual results. The tests I'm running are just on the raw index performance - how long does it take to "select ... where dockeys @@ to_tsquery(...)".

> We have our TODO http://www.sai.msu.su/~megera/oddmuse/index.cgi/todo
> and hope to find sponsorhips for fts project for 8.2 release.
> Unfortunately, I didn't find spare time to package tsearchd for you,
> it should certainly help you.

At this point we may not have time to try tsearchd, and unfortunately we're not in a position to sponsor anything yet.

My original question is still bothering me. Is it normal for a keyword that occurs in more than about 2% of the documents to cause such inconsistent performance? Is there any single thing I might look at that would help improve performance (like, do I need more memory? More shared memory? Different config parameters?)

Thanks,
Craig