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: Masahiko Sawada <sawada.mshk@gmail.com>
Cc: Sutou Kouhei <kou@clear-code.com>, "tgl@sss.pgh.pa.us" <tgl@sss.pgh.pa.us>, "zhjwpku@gmail.com" <zhjwpku@gmail.com>, "michael@paquier.xyz" <michael@paquier.xyz>, "pgsql-hackers@postgresql.org" <pgsql-hackers@postgresql.org>
Date: 2025-03-29T05:57:56Z
Lists: pgsql-hackers 
On Friday, March 28, 2025, Masahiko Sawada <sawada.mshk@gmail.com> wrote:
>
>
> One problem in the following chunk I can see is:
>
> +           qualified_format = stringToQualifiedNameList(format, NULL);
> +           DeconstructQualifiedName(qualified_format, &schema, &fmt);
> +           if (!schema || strcmp(schema, "pg_catalog") == 0)
> +           {
> +               if (strcmp(fmt, "csv") == 0)
> +                   opts_out->csv_mode = true;
> +               else if (strcmp(fmt, "binary") == 0)
> +                   opts_out->binary = true;
> +           }
>
> Non-qualified names depend on the search_path value so it's not
> necessarily a built-in format. If the user specifies 'csv' with
> seach_patch = 'myschema, pg_catalog', the COPY command unnecessarily
> sets csv_mode true. I think we can instead check if the retrieved
> handler function's OID matches the built-in formats' ones. Also, it's
> weired to me that cstate has csv_mode and binary fields even though
> the format should have already been known by the callback functions.
>

I considered it a feature that a schema-less reference to text, csv, or
binary always resolves to the core built-in handlers.  As does an
unspecified format default of text.

To use an extension that chooses to override that format name would require
schema qualification.

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.