Re: pgsql: Refactor COPY FROM to use format callback functions.

On 2025-02-28 Fr 2:55 PM, Masahiko Sawada wrote:
> On Fri, Feb 28, 2025 at 11:47 AM Andrew Dunstan <andrew(at)dunslane(dot)net> wrote:
>>
>> On 2025-02-28 Fr 1:31 PM, Masahiko Sawada wrote:
>>
>> Refactor COPY FROM to use format callback functions.
>>
>> This commit introduces a new CopyFromRoutine struct, which is a set of
>> callback routines to read tuples in a specific format. It also makes
>> COPY FROM with the existing formats (text, CSV, and binary) utilize
>> these format callbacks.
>>
>> This change is a preliminary step towards making the COPY FROM command
>> extensible in terms of input formats.
>>
>> Similar to 2e4127b6d2d, this refactoring contributes to a performance
>> improvement by reducing the number of "if" branches that need to be
>> checked on a per-row basis when sending field representations in text
>> or CSV mode. The performance benchmark results showed ~5% performance
>> gain in text or CSV mode.
>>
>> Author: Sutou Kouhei <kou(at)clear-code(dot)com>
>> Reviewed-by: Masahiko Sawada <sawada(dot)mshk(at)gmail(dot)com>
>> Reviewed-by: Michael Paquier <michael(at)paquier(dot)xyz>
>> Reviewed-by: Andres Freund <andres(at)anarazel(dot)de>
>> Reviewed-by: Tomas Vondra <tomas(dot)vondra(at)enterprisedb(dot)com>
>> Reviewed-by: Junwang Zhao <zhjwpku(at)gmail(dot)com>
>> Discussion: https://postgr.es/m/20231204.153548.2126325458835528809.kou@clear-code.com
>>
>>
>>
>> This patch has completely broken the file_textarray fdw, which uses NextCopyFromRawFields(). Removing that from API is not a good thing.
>>
> Thank you for pointing it out.
>
> I've just posted my analysis[1] and am planning to revive that API
> (Sutou-san already proposed an idea). Could you please check if the
> idea would work for file_text_array_fdw?
>

Looks OK, I think. You could even use the Internal function further down
in the file and avoid a function call.

cheers

andrew

--
Andrew Dunstan
EDB: https://www.enterprisedb.com