Re: Partial index on date column
От | Christopher Kings-Lynne |
---|---|
Тема | Re: Partial index on date column |
Дата | |
Msg-id | 02bf01c2e46a$70c17c70$6500a8c0@fhp.internal обсуждение исходный текст |
Ответ на | Partial index on date column ("Dave Page" <dpage@vale-housing.co.uk>) |
Ответы |
Re: Partial index on date column
Re: Partial index on date column |
Список | pgsql-hackers |
> "Christopher Kings-Lynne" <chriskl@familyhealth.com.au> writes: > > Obviously to you and I, referrer=1 implies that referrer is not null, but > > the planner doesn't know that. > > Actually the planner does make exactly that deduction in some other > contexts --- but I'm hesitant to expend the cycles for partial indexes. > Partial-index condition matching is a horribly difficult problem in > general, and we only attempt a few limited cases right now. I don't > think we want to put a general-purpose theorem prover in there --- > so it comes down to the likelihood of spotting a match in some cases, > versus the wasted cycles of checking for a match in every query that > doesn't fit the pattern. Yeah, it's not really a problem for me, I just put the extra clause in. Is indexing excluding NULLs a common application of partial indexes? It's basically all I use it for, when a column has like 90-95% NULLS and I want to exclude them from the index. Is it worth hard-coding in the IS NOT NULL case? Chris
В списке pgsql-hackers по дате отправления: