Horton

Re: BUG #17255: Server crashes in index_delete_sort_cmp() due to race condition with vacuum

Peter Geoghegan <pg@bowt.ie>

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From: Peter Geoghegan <pg@bowt.ie>
To: Andres Freund <andres@anarazel.de>
Cc: Dmitry Dolgov <9erthalion6@gmail.com>, Alexander Lakhin <exclusion@gmail.com>, Matthias van de Meent <boekewurm+postgres@gmail.com>, PostgreSQL mailing lists <pgsql-bugs@lists.postgresql.org>
Date: 2022-03-11T03:52:24Z
Lists: pgsql-bugs 
On Thu, Mar 10, 2022 at 7:46 PM Andres Freund <andres@anarazel.de> wrote:
> I'm not talking about just moving the vistest acquisition, but also
> vacuum_set_xid_limits(). Which obviously *does* benefit from delaying as long
> as possible.

That sounds hard, or at least a lot of work given the benefits.

As the patch points out, we are required to establish rel_pages after
we have established OldestXmin. We *also* use rel_pages to determine
the size of the dead_items array -- we don't want to allocate space
that couldn't possibly be used (i.e. a dead_items array with room for
more than `MaxHeapTuplesPerPage * rel_pages` dead items in total).

In short, it will be necessary to break that dependency, somehow.
Which is possibly, certainly, but still quite messy.

-- 
Peter Geoghegan

Commits

  1. vacuumlazy.c: Standardize rel_pages terminology.

  2. vacuumlazy.c: document vistest and OldestXmin.

  3. heap pruning: Only call BufferGetBlockNumber() once.

  4. Fix possible HOT corruption when RECENTLY_DEAD changes to DEAD while pruning.

  5. Assert redirect pointers are sensible after heap_page_prune().

  6. Remove tupgone special case from vacuumlazy.c.

  7. Recycle nbtree pages deleted during same VACUUM.

  8. snapshot scalability: Don't compute global horizons while building snapshots.

  9. Refactor heap_page_prune so that instead of changing item states on-the-fly,