Horton

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

Masahiko Sawada <sawada.mshk@gmail.com>

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From: Masahiko Sawada <sawada.mshk@gmail.com>
To: Vladlen Popolitov <v.popolitov@postgrespro.ru>
Cc: Sutou Kouhei <kou@clear-code.com>, zhjwpku@gmail.com, michael@paquier.xyz, pgsql-hackers@postgresql.org
Date: 2025-02-05T06:10:35Z
Lists: pgsql-hackers 
On Tue, Feb 4, 2025 at 6:19 PM Vladlen Popolitov
<v.popolitov@postgrespro.ru> wrote:
>
> Masahiko Sawada писал(а) 2025-02-05 08:32:
> > On Tue, Feb 4, 2025 at 2:46 AM Vladlen Popolitov
>
> >> >>  Standard PostgreSQL realisation for new methods to use USING
> >> >>  keyword. Every
> >> >> new method could have own options (FORMAT is option of internal 'copy
> >> >> from/to'
> >> >> methods),
> >> >
> >> > Ah, I didn't think about USING.
> >> >
> >> > You suggest "COPY ... USING json" not "COPY ... FORMAT json"
> >> > like "CREATE INDEX ... USING custom_index", right? It will
> >> > work. If we use this interface, we should reject "COPY
> >> > ... FORMAT ... USING" (both of FORMAT/USING are specified).
> >> >
> >> >
> >> I cannot recommend about rejecting, I do not know details
> >> of realisation of this part of code. Just idea - FORMAT value
> >> could be additional option to copy handler or NULL
> >> if it is omitted.
> >>   If you add extensibility, than every handler will be the
> >> extension, that can handle one or more formats.
> >
> > Hmm, if we use the USING clause to specify the format type, we end up
> > having two ways to specify the format type (e.g., 'COPY ... USING
> > text' and 'COPY .. WITH (format = text)'), which seems to confuse
> > users.
> WITH clause has list of options defined by copy method define in USING.
> The clause WITH (format=text) has options defined for default copy
> method,
> but other methods will define own options. Probably they do not need
> the word 'format' in options. The same as in index access methods.
>   For example, copy method parquete:
> COPY ... USING parquete WITH (row_group_size=1000000)
>   copy method parquete need and will define the word 'row_group_size'
> in options, the word 'format' will be wrong for it.

I think it's orthological between the syntax and options passed to the
custom format extension. For example, even if we specify the options
like "COPY ... WITH (format 'parquet', row_group_size '1000000',
on_error 'ignore)", we can pass only non-built-in options (i.e. only
row_group_size) to the extension.

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.