Oleg Bartunov wrote:
Jan,the problem is known and well requested. From your promotion it's not clear what's an idea ?Tom Lane wrote:=?UTF-8?B?SmFuIFVyYmHFhHNraQ==?= <[EMAIL PROTECTED]> writes:2. Implement better selectivity estimates for FTS.
OK, after reading through the some of the code the idea is to write a custom typanalyze function for tsvector columns. It could look inside the tsvectors, compute the most commonly appearing lexemes and store that information in pg_statistics. Then there should be a custom selectivity function for @@ and friends, that would look at the lexemes in pg_statistics, see if the tsquery it got matches some/any of them and return a result based on that.
I have a feeling that in many cases identifying the top 50 to 300 lexemes would be enough to talk about text search selectivity with a degree of confidence. At least we wouldn't give overly low estimates for queries looking for very popular words, which I believe is worse than givng an overly high estimate for a obscure query (am I wrong here?).
Regards, Jan -- Jan Urbanski GPG key ID: E583D7D2 ouden estin
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