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: jian.universality@gmail.com
Cc: sawada.mshk@gmail.com, david.g.johnston@gmail.com, tgl@sss.pgh.pa.us, zhjwpku@gmail.com, michael@paquier.xyz, pgsql-hackers@postgresql.org
Date: 2025-04-07T06:34:18Z
Lists: pgsql-hackers 
Hi,

In <CACJufxG=njY32g=YAF4T6rvXySN56VFbYt4ffjLTRBYQTKPAFg@mail.gmail.com>
  "Re: Make COPY format extendable: Extract COPY TO format implementations" on Sun, 6 Apr 2025 19:29:46 +0800,
  jian he <jian.universality@gmail.com> wrote:

> I did a brief review of v39-0001 and v39-0002.
> 
> text:
> COPY_FILE
> COPY_FRONTEND
> still appear on comments in copyfrom_internal.h and copyto.c,
> Should it be removed?

Good catch!
I found them in copy{from,to}_internal.h but couldn't find
them in copyto.c. It's a typo, right?

We should update them instead of removing them. I'll update
them in the next patch set.


> +#include "commands/copyto_internal.h"
> #include "commands/progress.h"
> #include "executor/execdesc.h"
> #include "executor/executor.h"
> #include "executor/tuptable.h"
> 
> "copyto_internal.h" already include:
> 
> #include "executor/execdesc.h"
> #include "executor/tuptable.h"
> so you should removed
> "
> #include "executor/execdesc.h"
> #include "executor/tuptable.h"
> "
> in copyto.c.

You're right. I'll update this too in the next patch set.

> CREATE FUNCTION test_copy_format(internal)
>     RETURNS copy_handler
>     AS 'MODULE_PATHNAME', 'test_copy_format'
>     LANGUAGE C;
> src/backend/commands/copy.c: ProcessCopyOptions
>             if (strcmp(fmt, "text") == 0)
>                  /* default format */ ;
>             else if (strcmp(fmt, "csv") == 0)
>                 opts_out->csv_mode = true;
>             else if (strcmp(fmt, "binary") == 0)
>                 opts_out->binary = true;
>             else
>             {
>                 List       *qualified_format;
>                 ....
>             }
> what if our customized format name is one of "csv", "binary", "text",
> then that ELSE branch will never be reached.
> then our customized format is being shadowed?

Right. We should not use customized format handlers to keep
backward compatibility.

> https://www.postgresql.org/docs/current/error-message-reporting.html
> "The extra parentheses were required before PostgreSQL version 12, but
> are now optional."
> 
> means that
>     ereport(NOTICE, (errmsg("CopyFromInFunc: attribute: %s",
> format_type_be(atttypid))));
> can change to
>     ereport(NOTICE, errmsg("CopyFromInFunc: attribute: %s",
> format_type_be(atttypid)));
> 
> all
> ereport(ERROR, (errcode(ERRCODE_INVALID_PARAMETER_VALUE), ....
> 
> can also be simplified to
> 
> ereport(ERROR, errcode(ERRCODE_INVALID_PARAMETER_VALUE), ....

Oh, I didn't notice it. Can we do it as a separated patch
because we have many codes that use this style in
copy*.c. The separated patch should update this style at
once.


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.