Message-ID: <d3b11749-7d0d-40c6-b2be-0e45958881da@dunslane.net>
Date: Fri, 28 Feb 2025 15:14:07 -0500
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Subject: Re: pgsql: Refactor COPY FROM to use format callback functions.
To: Masahiko Sawada <sawada.mshk@gmail.com>
Cc: Masahiko Sawada <msawada@postgresql.org>,
 pgsql-committers@lists.postgresql.org
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From: Andrew Dunstan <andrew@dunslane.net>
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On 2025-02-28 Fr 2:55 PM, Masahiko Sawada wrote:
> On Fri, Feb 28, 2025 at 11:47 AM Andrew Dunstan <andrew@dunslane.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@clear-code.com>
>> Reviewed-by: Masahiko Sawada <sawada.mshk@gmail.com>
>> Reviewed-by: Michael Paquier <michael@paquier.xyz>
>> Reviewed-by: Andres Freund <andres@anarazel.de>
>> Reviewed-by: Tomas Vondra <tomas.vondra@enterprisedb.com>
>> Reviewed-by: Junwang Zhao <zhjwpku@gmail.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