Horton

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

David G. Johnston <david.g.johnston@gmail.com>

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From: "David G. Johnston" <david.g.johnston@gmail.com>
To: jian he <jian.universality@gmail.com>
Cc: Sutou Kouhei <kou@clear-code.com>, sawada.mshk@gmail.com, tgl@sss.pgh.pa.us, zhjwpku@gmail.com, michael@paquier.xyz, pgsql-hackers@postgresql.org
Date: 2025-04-06T16:20:56Z
Lists: pgsql-hackers 
On Sun, Apr 6, 2025 at 4:30 AM jian he <jian.universality@gmail.com> wrote:

>
> 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?
>
>
Yes.  The user of your extension can specify a schema name to get access to
your conflicting format name choice but all the existing code out there
that relied on text/csv/binary being the built-in options continue to
behave the same no matter the search_path.

David J.

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.