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Re: New IndexAM API controlling index vacuum strategies

Peter Geoghegan <pg@bowt.ie>

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From: Peter Geoghegan <pg@bowt.ie>
To: Masahiko Sawada <sawada.mshk@gmail.com>
Cc: PostgreSQL-development <pgsql-hackers@postgresql.org>
Date: 2021-03-02T05:34:40Z
Lists: pgsql-hackers 
On Mon, Mar 1, 2021 at 7:00 PM Peter Geoghegan <pg@bowt.ie> wrote:
> I think that you're right. However, in practice it isn't harmful
> because has_dead_tuples is only used when "all_visible = true", and
> only to detect corruption (which should never happen). I think that it
> should be fixed as part of this work, though.

Currently the first callsite that calls the new
lazy_vacuum_table_and_indexes() function in the patch
("skip_index_vacuum.patch") skips index vacuuming in exactly the same
way as the second and final lazy_vacuum_table_and_indexes() call site.
Don't we need to account for maintenance_work_mem in some way?

lazy_vacuum_table_and_indexes() should probably not skip index
vacuuming when we're close to exceeding the space allocated for the
LVDeadTuples array. Maybe we should not skip when
vacrelstats->dead_tuples->num_tuples is greater than 50% of
dead_tuples->max_tuples? Of course, this would only need to be
considered when lazy_vacuum_table_and_indexes() is only called once
for the entire VACUUM operation (otherwise we have far too little
maintenance_work_mem/dead_tuples->max_tuples anyway).

-- 
Peter Geoghegan

Commits

Same data as JSON: GET /api/v1/messages/:b64id/commits the thread's linked commits as JSON, with link sources. API reference →

  1. Don't truncate heap when VACUUM's failsafe is in effect.

  2. Teach VACUUM to bypass unnecessary index vacuuming.

  3. Add wraparound failsafe to VACUUM.

  4. Truncate line pointer array during VACUUM.

  5. Remove tupgone special case from vacuumlazy.c.

  6. Refactor lazy_scan_heap() loop.

  7. Propagate parallel VACUUM's buffer access strategy.

  8. Simplify state managed by VACUUM.

  9. Notice that heap page has dead items during VACUUM.

  10. Adjust lazy_scan_heap() accounting comments.

  11. Use full 64-bit XID for checking if a deleted GiST page is old enough.

  12. Fix some problems with VACUUM (INDEX_CLEANUP FALSE).