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: tgl@sss.pgh.pa.us, zhjwpku@gmail.com, michael@paquier.xyz, pgsql-hackers@postgresql.org
Date: 2025-03-17T20:50:03Z
Lists: pgsql-hackers 
On Tue, Mar 4, 2025 at 4:06 PM Sutou Kouhei <kou@clear-code.com> wrote:
>
> Hi,
>
> In <CAD21AoAwOP7p6LgmkPGqPuJ5KbJPPQsSZsFzwCDguwzr9F677Q@mail.gmail.com>
>   "Re: Make COPY format extendable: Extract COPY TO format implementations" on Mon, 3 Mar 2025 11:06:39 -0800,
>   Masahiko Sawada <sawada.mshk@gmail.com> wrote:
>
> > I agree with the fix and the patch looks good to me. I've updated the
> > commit message and am going to push, barring any objections.
>
> Thanks!
>
> I've rebased the patch set. Here is a summary again:

Thank you for updating the patches. Here are some review comments on
the 0001 patch:

+   if (strcmp(format, "text") == 0)
+   {
+       /* "csv_mode == false && binary == false" means "text" */
+       return;
+   }
+   else if (strcmp(format, "csv") == 0)
+   {
+       opts_out->csv_mode = true;
+       return;
+   }
+   else if (strcmp(format, "binary") == 0)
+   {
+       opts_out->binary = true;
+       return;
+   }
+
+   /* custom format */
+   if (!is_from)
+   {
+       funcargtypes[0] = INTERNALOID;
+       handlerOid = LookupFuncName(list_make1(makeString(format)), 1,
+                                   funcargtypes, true);
+   }
+   if (!OidIsValid(handlerOid))
+       ereport(ERROR,
+               (errcode(ERRCODE_INVALID_PARAMETER_VALUE),
+                errmsg("COPY format \"%s\" not recognized", format),
+                parser_errposition(pstate, defel->location)));

I think that built-in formats also need to have their handler
functions. This seems to be a conventional way for customizable
features such as tablesample and access methods, and we can simplify
this function.

---
I think we need to update the documentation to describe how users can
define the handler functions and what each callback function is
responsible for.

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.