Horton

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

Masahiko Sawada <sawada.mshk@gmail.com>

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From: Masahiko Sawada <sawada.mshk@gmail.com>
To: Sutou Kouhei <kou@clear-code.com>
Cc: michael@paquier.xyz, zhjwpku@gmail.com, andrew@dunslane.net, nathandbossart@gmail.com, pgsql-hackers@postgresql.org
Date: 2023-12-11T01:57:15Z
Lists: pgsql-hackers 
On Sun, Dec 10, 2023 at 5:55 AM Sutou Kouhei <kou@clear-code.com> wrote:
>
> Hi,
>
> In <CAD21AoDkoGL6yJ_HjNOg9cU=aAdW8uQ3rSQOeRS0SX85LPPNwQ@mail.gmail.com>
>   "Re: Make COPY format extendable: Extract COPY TO format implementations" on Fri, 8 Dec 2023 15:42:06 +0900,
>   Masahiko Sawada <sawada.mshk@gmail.com> wrote:
>
> > So a custom COPY extension would not be able to define SQL functions
> > just like arrow(internal) for example. We might need to define a rule
> > like the function returning copy_in/out_handler must be defined as
> > <method name>_to(internal) and <method_name>_from(internal).
>
> We may not need to add "_to"/"_from" suffix by checking both
> of argument type and return type. Because we use different
> return type for copy_in/out_handler.
>
> But the current LookupFuncName() family doesn't check return
> type. If we use this approach, we need to improve the
> current LookupFuncName() family too.

IIUC we cannot create two same name functions with the same arguments
but a different return value type in the first place. It seems to me
to be an overkill to change such a design.

Another idea is to encapsulate copy_to/from_handler by a super class
like copy_handler. The handler function is called with an argument,
say copyto, and returns copy_handler encapsulating either
copy_to/from_handler depending on the argument.

Regards,

-- 
Masahiko Sawada
Amazon Web Services: https://aws.amazon.com

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.