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base repository: postgresql-cfbot/postgresql
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  • 6 commits
  • 28 files changed
  • 4 contributors

Commits on Apr 29, 2025

  1. IOS/TableAM: Support AM-specific fast visibility tests 

    Previously, we assumed VM_ALL_VISIBLE is universal across all AMs. This
is probably not the case, so we introduce a new table method called
"table_index_vischeck_tuples" which allows anyone to ask the AM whether
a tuple is definitely visible to everyone or might be invisible to
someone.

The API is intended to replace direct calls to VM_ALL_VISIBLE and as such
doesn't include "definitely dead to everyone", as the Heap AM's VM doesn't
support *definitely dead* as output for its lookups; and thus it would be
too expensive for the Heap AM to produce such results.

A future commit will use this inside GIST and SP-GIST to fix a race
condition between IOS and VACUUM, which causes a bug with tuple
visibility, and a further patch will add support for this to nbtree.
    @MMeent
    MMeent authored and Commitfest Bot committed Apr 29, 2025
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  2. GIST: Fix visibility issues in IOS 

    Previously, GIST IOS could buffer tuples from pages while VACUUM came
along and cleaned up an ALL_DEAD tuple, marking the tuple's page
ALL_VISIBLE again and making IOS mistakenly believe the tuple is indeed
visible.

With this patch, pins now conflict with GIST vacuum, and we now do
preliminary visibility checks to be used by IOS so that the IOS
infrastructure knows to recheck the heap page even if that page is now
ALL_VISIBLE.

Idea from Heikki Linnakangas
    @MMeent
    MMeent authored and Commitfest Bot committed Apr 29, 2025
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  3. SP-GIST: Fix visibility issues in IOS 

    Previously, SP-GIST IOS could buffer tuples from pages while VACUUM came
along and cleaned up an ALL_DEAD tuple, marking the tuple's page
ALL_VISIBLE again and making IOS mistakenly believe the tuple is indeed
visible.

With this patch, pins now conflict with SP-GIST vacuum, and we now do
preliminary visibility checks to be used by IOS so that the IOS
infrastructure knows to recheck the heap page even if that page is now
ALL_VISIBLE.

Idea from Heikki Linnakangas
    @MMeent
    MMeent authored and Commitfest Bot committed Apr 29, 2025
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  4. NBTree: Reduce Index-Only Scan pin duration 

    Previously, we would keep a pin on every leaf page while we were returning
tuples to the scan.  With this patch, we utilize the newly introduced
table_index_vischeck_tuples API to pre-check visibility of all TIDs, and
thus unpin the page well ahead of when we'd usually be ready with returning
and processing all index tuple results.  This reduces the time VACUUM may
have to wait for a pin, and can increase performance with reduced redundant
VM checks.
    @MMeent
    MMeent authored and Commitfest Bot committed Apr 29, 2025
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  5. Test for IOS/Vacuum race conditions in index AMs 

    Add regression tests that demonstrate wrong results can occur with index-only
scans in GiST and SP-GiST indexes when encountering tuples being removed by a
concurrent VACUUM operation.

With these tests the index AMs are also expected to not block VACUUM even when
they're used inside a cursor.

Co-authored-by: Matthias van de Meent <[email protected]>
Co-authored-by: Peter Geoghegan <[email protected]>
Co-authored-by: Michail Nikolaev <[email protected]>
Discussion: https://www.postgresql.org/message-id/flat/CANtu0oi0rkR%2BFsgyLXnGZ-uW2950-urApAWLhy-%2BV1WJD%3D_ZXA%40mail.gmail.com
    @MMeent @petergeoghegan
    3 people authored and Commitfest Bot committed Apr 29, 2025
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  6. [CF 5542] v12 - Fix buffer pinning logic in [SP-]Gist 

    This branch was automatically generated by a robot using patches from an
email thread registered at:

https://commitfest.postgresql.org/patch/5542

The branch will be overwritten each time a new patch version is posted to
the thread, and also periodically to check for bitrot caused by changes
on the master branch.

Patch(es): https://www.postgresql.org/message-id/CAEze2WgnHJF66BtviDFNCPy26gLrb+tfns-Bi62DBfReH0-UCg@mail.gmail.com
Author(s): Peter Geoghegan, Michail Nikolaev, Matthias van de Meent
    Commitfest Bot committed Apr 29, 2025
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