From: | Tom Lane <tgl(at)sss(dot)pgh(dot)pa(dot)us> |
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To: | "David G(dot) Johnston" <david(dot)g(dot)johnston(at)gmail(dot)com> |
Cc: | Avery Fischer <biggerfisch(at)gmail(dot)com>, "pgsql-generallists(dot)postgresql(dot)org" <pgsql-general(at)lists(dot)postgresql(dot)org> |
Subject: | Re: Cannot create canonicalization function for user-defined range type |
Date: | 2021-01-20 15:51:31 |
Message-ID: | 596023.1611157891@sss.pgh.pa.us |
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Lists: | pgsql-general |
"David G. Johnston" <david(dot)g(dot)johnston(at)gmail(dot)com> writes:
> On Wed, Jan 20, 2021 at 5:00 AM Avery Fischer <biggerfisch(at)gmail(dot)com> wrote:
>> ERROR: PL/pgSQL functions cannot return type myrange
>> Am I misunderstanding the docs, or are they out-of-date, or is something
>> else going on? How can I create a canonicalization function for my range
>> type?
> Thus one needs to write a C language function if one wishes to implement a
> custom range.
Yeah, that's the only way at the moment. We've not seen much use-case
for writing canonicalization functions in PLs, because of (a) performance
and (b) circularity concerns --- the latter meaning that the PL's own
infrastructure is likely to expect that it can manipulate scalar values
without incurring recursion. These are pretty much the same reasons
why a datatype's I/O functions can't be written in a PL.
regards, tom lane
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