Horton

Re: Make COPY format extendable: Extract COPY TO format implementations

Sutou Kouhei <kou@clear-code.com>

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From: Sutou Kouhei <kou@clear-code.com>
To: zhjwpku@gmail.com
Cc: sawada.mshk@gmail.com, michael@paquier.xyz, andrew@dunslane.net, nathandbossart@gmail.com, pgsql-hackers@postgresql.org
Date: 2023-12-15T04:45:31Z
Lists: pgsql-hackers 
Hi,

In <CAEG8a3JuShA6g19Nt_Ejk15BrNA6PmeCbK7p81izZi71muGq3g@mail.gmail.com>
  "Re: Make COPY format extendable: Extract COPY TO format implementations" on Fri, 15 Dec 2023 11:27:30 +0800,
  Junwang Zhao <zhjwpku@gmail.com> wrote:

>> > Adding a prefix or suffix would be one option but to give extensions
>> > more flexibility, another option would be to support format = 'custom'
>> > and add the "handler" option to specify a copy handler function name
>> > to call. For example, COPY ... FROM ... WITH (FORMAT = 'custom',
>> > HANDLER = 'arrow_copy_handler').
>>
> I like the prefix/suffix idea, easy to implement. *custom* is not a FORMAT,
> and user has to know the name of the specific handler names, not
> intuitive.

Ah! I misunderstood this idea. "custom" is the special
format to use "HANDLER". I thought that we can use it like

   (FORMAT = 'arrow', HANDLER = 'arrow_copy_handler_impl1')

and

   (FORMAT = 'arrow', HANDLER = 'arrow_copy_handler_impl2')

.

>> Interesting. If we use this option, users can choose an COPY
>> FORMAT implementation they like from multiple
>> implementations. For example, a developer may implement a
>> COPY FROM FORMAT = 'json' handler with PostgreSQL's JSON
>> related API and another developer may implement a handler
>> with simdjson[1] which is a fast JSON parser. Users can
>> choose whichever they like.
> Not sure about this, why not move Json copy handler to contrib
> as an example for others, any extensions share the same format
> function name and just install one? No bound would implement
> another CSV or TEXT copy handler IMHO.

I should have used a different format not JSON as an example
for easy to understand. I just wanted to say that extension
developers can implement another implementation without
conflicting another implementation.


Thanks,
-- 
kou

Commits

  1. Refactor Copy{From|To}GetRoutine() to use pass-by-reference argument.

  2. Refactor COPY FROM to use format callback functions.

  3. Refactor COPY TO to use format callback functions.

  4. Another try to fix BF failure introduced in commit ddd5f4f54a.

  5. Revert "Refactor CopyReadAttributes{CSV,Text}() to use a callback in COPY FROM"

  6. Improve COPY TO performance when server and client encodings match

  7. Simplify signature of CopyAttributeOutCSV() in copyto.c

  8. Revert "Refactor CopyAttributeOut{CSV,Text}() to use a callback in COPY TO"

  9. Refactor CopyAttributeOut{CSV,Text}() to use a callback in COPY TO

  10. Refactor CopyReadAttributes{CSV,Text}() to use a callback in COPY FROM

  11. Add progress reporting of skipped tuples during COPY FROM.

  12. pgbench: Add \syncpipeline

  13. meson: Make gzip and tar optional

  14. Export the external file reader used in COPY FROM as APIs.