Horton

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

Andres Freund <andres@anarazel.de>

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From: Andres Freund <andres@anarazel.de>
To: Masahiko Sawada <sawada.mshk@gmail.com>
Cc: Sutou Kouhei <kou@clear-code.com>, michael@paquier.xyz, david.g.johnston@gmail.com, tgl@sss.pgh.pa.us, zhjwpku@gmail.com, pgsql-hackers@postgresql.org
Date: 2025-07-15T12:36:58Z
Lists: pgsql-hackers 
Hi,

On 2025-07-14 03:28:16 +0900, Masahiko Sawada wrote:
> I've reviewed the 0001 and 0002 patches. The API implemented in the
> 0002 patch looks good to me, but I'm concerned about the capsulation
> of copy state data. With the v42 patches, we pass the whole
> CopyToStateData to the extension codes, but most of the fields in
> CopyToStateData are internal working state data that shouldn't be
> exposed to extensions. I think we need to sort out which fields are
> exposed or not. That way, it would be safer and we would be able to
> avoid exposing copyto_internal.h and extensions would not need to
> include copyfrom_internal.h.
> 
> I've implemented a draft patch for that idea. In the 0001 patch, I
> moved fields that are related to internal working state from
> CopyToStateData to CopyToExectuionData. COPY routine APIs pass a
> pointer of CopyToStateData but extensions can access only fields
> except for CopyToExectuionData. In the 0002 patch, I've implemented
> the registration API and some related APIs based on your v42 patch.
> I've made similar changes to COPY FROM codes too.

I've not followed the development of this patch - but I continue to be
concerned about the performance impact it has as-is and the amount of COPY
performance improvements it forecloses.

This seems to add yet another layer of indirection to a lot of hot functions
like CopyGetData() etc.

Greetings,

Andres Freund

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.