Re: procost for to_tsvector

Hi,

On 2015-03-11 14:40:16 +0000, Andrew Gierth wrote:
> An issue that comes up regularly on IRC is that text search queries,
> especially on relatively modest size tables or for relatively
> non-selective words, often misplan as a seqscan based on the fact that
> to_tsvector has procost=1.

I've also seen this regularly outside IRC.

> Clearly this cost number is ludicrous.

Yea.

> Getting the right cost estimate would obviously mean taking the cost of
> detoasting into account

Well, that's not done in other cases where you could either, so there's
precedence for being inaccurate ;)

> ,but even without doing that, there's a strong
> argument that it should be increased to at least the order of 100.
> (With the default cpu_operator_cost that would make each to_tsvector
> call cost 0.25.)

100 sounds good to me. IIRC that's what has been proposed before.

Greetings,

Andres Freund

-- Andres Freund                       http://www.2ndQuadrant.com/PostgreSQL Development, 24x7 Support, Training &
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