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: 2023-12-15T00:53:05Z
Lists: pgsql-hackers 
Hi,

In <CAD21AoCZv3cVU+NxR2s9J_dWvjrS350GFFr2vMgCH8wWxQ5hTQ@mail.gmail.com>
  "Re: Make COPY format extendable: Extract COPY TO format implementations" on Fri, 15 Dec 2023 05:19:43 +0900,
  Masahiko Sawada <sawada.mshk@gmail.com> wrote:

> To avoid collisions, extensions can be created in a
> different schema than public.

Thanks. I didn't notice it.

> And note that built-in format copy handler doesn't need to
> declare its handler function.

Right. I know it.

> Adding a prefix or suffix would be one option but to give extensions
> more flexibility, another option would be to support format = 'custom'
> and add the "handler" option to specify a copy handler function name
> to call. For example, COPY ... FROM ... WITH (FORMAT = 'custom',
> HANDLER = 'arrow_copy_handler').

Interesting. If we use this option, users can choose an COPY
FORMAT implementation they like from multiple
implementations. For example, a developer may implement a
COPY FROM FORMAT = 'json' handler with PostgreSQL's JSON
related API and another developer may implement a handler
with simdjson[1] which is a fast JSON parser. Users can
choose whichever they like.

But specifying HANDLER = '...' explicitly is a bit
inconvenient. Because only one handler will be installed in
most use cases. In the case, users don't need to choose one
handler.

If we choose this option, it may be better that we also
provide a mechanism that can work without HANDLER. Searching
a function by name like tablesample method does is an option.


[1]: https://github.com/simdjson/simdjson


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.