| From: | "Nasby, Jim" <nasbyj(at)amazon(dot)com> |
|---|---|
| To: | David Fetter <david(at)fetter(dot)org> |
| Cc: | Corey Huinker <corey(dot)huinker(at)gmail(dot)com>, "surafel3000(at)gmail(dot)com" <surafel3000(at)gmail(dot)com>, "cmt(at)burggraben(dot)net" <cmt(at)burggraben(dot)net>, "pgsql-hackers(at)lists(dot)postgresql(dot)org" <pgsql-hackers(at)lists(dot)postgresql(dot)org> |
| Subject: | Re: COPY FROM WHEN condition |
| Date: | 2018-10-31 23:21:33 |
| Message-ID: | 5E61B32E-61CB-4EBB-BC8E-BE37DC6E79AB@amazon.com |
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| Lists: | pgsql-hackers |
On Oct 11, 2018, at 10:35 AM, David Fetter <david(at)fetter(dot)org> wrote:
>
>> It didn't get far, but you may want to take a look at a rejected patch for
>> copy_srf() (set returning function)
>> https://www.postgresql.org/message-id/CADkLM%3DdoeiWQX4AGtDNG4PsWfSXz3ai7kY%3DPZm3sUhsUeev9Bg%40mail.gmail.com
>> https://commitfest.postgresql.org/12/869/
>>
>> Having a set returning function gives you the full expressiveness of SQL,
>> at the cost of an extra materialization step.
>
> I wonder whether something JIT-like could elide this. A very
> interesting subset of such WHEN clauses could be pretty
> straight-forward to implement in a pretty efficient way.
Are you thinking something like having a COPY command that provides results in such a way that they could be referenced in a FROM clause (perhaps a COPY that defines a cursor…)?
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