| From: | Andreas Karlsson <andreas(at)proxel(dot)se> |
|---|---|
| To: | Tom Lane <tgl(at)sss(dot)pgh(dot)pa(dot)us>, Andres Freund <andres(at)anarazel(dot)de> |
| Cc: | pgsql-hackers(at)lists(dot)postgresql(dot)org, Andrzej Barszcz <abusinf(at)gmail(dot)com>, pgsql-hackers(at)postgresql(dot)org |
| Subject: | Re: function calls optimization |
| Date: | 2019-10-31 15:05:28 |
| Message-ID: | a2bc0407-a41e-7798-0129-d38a7bd5e359@proxel.se |
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| Lists: | pgsql-hackers |
On 10/31/19 3:45 PM, Tom Lane wrote:
> Andres Freund <andres(at)anarazel(dot)de> writes:
>> On October 31, 2019 7:06:13 AM PDT, Andrzej Barszcz <abusinf(at)gmail(dot)com> wrote:
>>> Any pros and cons ?
>
>> Depends on the actual way of implementing this proposal. Think we need more details than what you idea here.
>
> We've typically supposed that the cost of searching for duplicate
> subexpressions would outweigh the benefits of sometimes finding them.
That is an important concern, but given how SQL does not make it
convenient to re-use partial results of calculations I think such
queries are quite common in real world workloads.
So if we can make it cheap enough I think that it is a worthwhile
optimization.
Andreas
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