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: sawada.mshk@gmail.com
Cc: michael@paquier.xyz, zhjwpku@gmail.com, andrew@dunslane.net, nathandbossart@gmail.com, pgsql-hackers@postgresql.org
Date: 2023-12-14T09:44:14Z
Lists: pgsql-hackers 
Hi,

In <CAD21AoCvjGserrtEU=UcA3Mfyfe6ftf9OXPHv9fiJ9DmXMJ2nQ@mail.gmail.com>
  "Re: Make COPY format extendable: Extract COPY TO format implementations" on Mon, 11 Dec 2023 10:57:15 +0900,
  Masahiko Sawada <sawada.mshk@gmail.com> wrote:

> 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.

Oh, sorry. I didn't notice it.

> 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.

It's for using "${copy_format_name}" such as "json" and
"parquet" as a function name, right? If we use the
"${copy_format_name}" approach, we can't use function names
that are already used by tablesample method handler such as
"system" and "bernoulli" for COPY FORMAT name. Because both
of tablesample method handler function and COPY FORMAT
handler function use "(internal)" as arguments.

I think that tablesample method names and COPY FORMAT names
will not be conflicted but the limitation (using the same
namespace for tablesample method and COPY FORMAT) is
unnecessary limitation.

How about using prefix ("copy_to_${copy_format_name}" or
something) or suffix ("${copy_format_name}_copy_to" or
something) for function names? For example,
"copy_to_json"/"copy_from_json" for "json" COPY FORMAT.

("copy_${copy_format_name}" that returns copy_handler
encapsulating either copy_to/from_handler depending on the
argument may be an option.)


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.