Horton

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

Masahiko Sawada <sawada.mshk@gmail.com>

View thread View on postgr.es
From: Masahiko Sawada <sawada.mshk@gmail.com>
To: Sutou Kouhei <kou@clear-code.com>, andres@anarazel.de
Cc: michael@paquier.xyz, david.g.johnston@gmail.com, tgl@sss.pgh.pa.us, zhjwpku@gmail.com, pgsql-hackers@postgresql.org
Date: 2025-10-29T20:41:39Z
Lists: pgsql-hackers 
On Mon, Oct 13, 2025 at 7:15 PM Sutou Kouhei <kou@clear-code.com> wrote:
>
> Hi,
>
> In <CAD21AoBkA=g=PN17r_iieru+vLyLtGZ8WvohgANa2vzsMfMogQ@mail.gmail.com>
>   "Re: Make COPY format extendable: Extract COPY TO format implementations" on Mon, 13 Oct 2025 14:40:31 -0700,
>   Masahiko Sawada <sawada.mshk@gmail.com> wrote:
>
> > The patch refactors the CopyToStateData so that we can both hide
> > internal-use-only fields from extensions and extension can use its own
> > state data, while not adding extra indirection layers. TBH I'm really
> > not sure we must fully hide internal fields from extensions. Other
> > extendable components seem not to strictly hide internal information
> > from extensions. I'd suggest starting with only the latter point. That
> > is, we merge fields in CopyToStateInternalData to CopyToStateData.
> > What do you think?
>
> OK. Let's follow the existing style. How about the attached
> patch? It merges CopyToStateInternalData to CopyToStateData.
>

The basic idea of this patch makes sense to me.

Andres, I believe that the current idea deals with your concerns about
performance overheads. Particularly, we separate format-specific
fields (c.f. CopyToStateBuiltinData struct in the patch) from the
commonly-used fields (c.f., CopyToStateData struct), but the whole
fields are stored in the contiguous memory. While the patch needs to
be polished much, could you review if the basic idea of this patch
addresses your concern?

Regards,

-- 
Masahiko Sawada
Amazon Web Services: https://aws.amazon.com

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.