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Re: [HACKERS] type cache for concat functions - Mailing list pgsql-hackers

From Dmitry Dolgov
Subject Re: [HACKERS] type cache for concat functions
Date
Msg-id CA+q6zcX9=zD1-edrAni_4HXPL-PbjYDeYFdxD2-CEojdr0Pq9Q@mail.gmail.com
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In response to [HACKERS] type cache for concat functions  (Pavel Stehule <pavel.stehule@gmail.com>)
Responses Re: [HACKERS] type cache for concat functions  (Pavel Stehule <pavel.stehule@gmail.com>)
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> On 20 May 2017 at 10:03, Pavel Stehule <pavel.stehule@gmail.com> wrote:
>
> Now concat is 2x times slower than || operator. With cached FmgrInfo for
> output function it will be only 5%.

Looks nice and does what's expected (what else one may need from a Saturday
evening). I just can mention that from what I see the previous version of
`concat` is slower the more arguments are getting involved, so looks like it
can be more than 2x.

Also, it was a little bit confusing to see that the function `concat` behaves
differently from operator `||` in terms of performance. When you're looking at
the code it's becoming obvious, but I couldn't find any mention about that in
the documentation.

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