Re: Avoiding duplication of code via views -- slower? How do people typically do this?

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От Tom Lane
Тема Re: Avoiding duplication of code via views -- slower? How do people typically do this?
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Msg-id 16227.1360960296@sss.pgh.pa.us
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Ответ на Re: Avoiding duplication of code via views -- slower? How do people typically do this?  (Joe Van Dyk <joe@tanga.com>)
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Joe Van Dyk <joe@tanga.com> writes:
> On Fri, Feb 15, 2013 at 7:43 AM, Tom Lane <tgl@sss.pgh.pa.us> wrote:
>> Try without the useless "is true" bits.

> Huh, that did do the trick. Why does "is true" affect the plan?

Because "(x = y) IS TRUE" isn't the same as "x = y".  (The behavior for
nulls is different.)  And the planner only knows about using the latter
type of condition for indexscans.  Since you need it to convert the
end_at condition into an indexscan to get a fast plan, you lose.

It's conceivable that we could teach the planner about this case, but
I haven't seen enough people doing that to make me think it's worth the
code space and planner cycles.

            regards, tom lane

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