Horton

Re: Table AM Interface Enhancements

Andres Freund <andres@anarazel.de>

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From: Andres Freund <andres@anarazel.de>
To: Robert Haas <robertmhaas@gmail.com>
Cc: Alexander Korotkov <aekorotkov@gmail.com>, Pavel Borisov <pashkin.elfe@gmail.com>, Melanie Plageman <melanieplageman@gmail.com>, Japin Li <japinli@hotmail.com>, Mark Dilger <mark.dilger@enterprisedb.com>, PostgreSQL Hackers <pgsql-hackers@lists.postgresql.org>, Michael Paquier <michael@paquier.xyz>, Heikki Linnakangas <hlinnaka@iki.fi>, Thomas Munro <thomas.munro@gmail.com>, Nazir Bilal Yavuz <byavuz81@gmail.com>
Date: 2024-04-16T15:59:56Z
Lists: pgsql-hackers 
Hi,

On 2024-04-16 08:31:24 -0400, Robert Haas wrote:
> On Tue, Apr 16, 2024 at 6:52 AM Alexander Korotkov <aekorotkov@gmail.com> wrote:
> > Taking a closer look at acquire_sample_rows(), I think it would be
> > good if table AM implementation would care about block-level (or
> > whatever-level) sampling.  So that acquire_sample_rows() just fetches
> > tuples one-by-one from table AM implementation without any care about
> > blocks.  Possible table_beginscan_analyze() could take an argument of
> > target number of tuples, then those tuples are just fetches with
> > table_scan_analyze_next_tuple().  What do you think?
> 
> Andres is the expert here, but FWIW, that plan seems reasonable to me.
> One downside is that every block-based tableam is going to end up with
> a very similar implementation, which is kind of something I don't like
> about the tableam API in general: if you want to make something that
> is basically heap plus a little bit of special sauce, you have to copy
> a mountain of code. Right now we don't really care about that problem,
> because we don't have any other tableams in core, but if we ever do, I
> think we're going to find ourselves very unhappy with that aspect of
> things. But maybe now is not the time to start worrying. That problem
> isn't unique to analyze, and giving out-of-core tableams the
> flexibility to do what they want is better than not.

I think that can partially be addressed by having more "block oriented AM"
helpers in core, like we have for table_block_parallelscan*. Doesn't work for
everything, but should for something like analyze.

Greetings,

Andres Freund

Commits

  1. Remove extra comment at TableAmRoutine.scan_analyze_next_block

  2. revert: Generalize relation analyze in table AM interface

  3. Revert: Allow table AM to store complex data structures in rd_amcache

  4. Revert: Allow table AM tuple_insert() method to return the different slot

  5. Revert: Allow locking updated tuples in tuple_update() and tuple_delete()

  6. Revert: Let table AM insertion methods control index insertion

  7. Revert: Custom reloptions for table AM

  8. Provide a way block-level table AMs could re-use acquire_sample_rows()

  9. Custom reloptions for table AM

  10. Use streaming I/O in ANALYZE.

  11. Revert "Custom reloptions for table AM"

  12. Let table AM insertion methods control index insertion

  13. Generalize relation analyze in table AM interface

  14. Improve error message for tts_(virtual|minimal)_is_current_xact_tuple

  15. Add comments on some MinimalTupleSlots methods usage

  16. Add TupleTableSlotOps.is_current_xact_tuple() method

  17. Allow table AM tuple_insert() method to return the different slot

  18. Allow table AM to store complex data structures in rd_amcache