Horton
Menu

Re: Adding REPACK [concurrently]

Alvaro Herrera <alvherre@alvh.no-ip.org>

View thread
From: Alvaro Herrera <alvherre@alvh.no-ip.org>
To: Mihail Nikalayeu <mihailnikalayeu@gmail.com>
Cc: Antonin Houska <ah@cybertec.at>, Srinath Reddy Sadipiralla <srinath2133@gmail.com>, Amit Kapila <amit.kapila16@gmail.com>, Matthias van de Meent <boekewurm+postgres@gmail.com>, Pg Hackers <pgsql-hackers@lists.postgresql.org>, Robert Treat <rob@xzilla.net>
Date: 2026-04-06T22:22:32Z
Lists: pgsql-hackers

Attachments

Hello,

On 2026-Apr-06, Mihail Nikalayeu wrote:

> > Yeah but I don't want the virtual tuple to be materialized (which would
> > happen in tts_virtual_materialize if I set shouldFree=true).  The memory
> > should be freed in
> >                 ResetPerTupleExprContext(chgcxt->cc_estate);
> > anyway, right?  Maybe deserves a comment.
> 
> Not sure, ResetPerTupleExprContext resets just "ExecutorState".
> But slots are created in another memory context.
> 
> Also, we can't reset slot->tts_mcxt itself - it will free the slot also.

So what I ended up doing, is to just not change to the slot's context in
restore_tuple.  That was just dumb (mea culpa).  So all the memory we
allocate for the slot lives in the executor context, and goes away on
the ResetPerTupleExprContext call at the bottom of the loop.  BTW I
don't understand why you say that function only resets ExecutorState --
as far as I can tell, it does this

#define ResetPerTupleExprContext(estate) \
	do { \
		if ((estate)->es_per_tuple_exprcontext) \
			ResetExprContext((estate)->es_per_tuple_exprcontext); \
	} while (0)

which in turn does

#define ResetExprContext(econtext) \
	MemoryContextReset((econtext)->ecxt_per_tuple_memory)

which AFAICT is exactly what we want.

Anyway, here's the three missing parts.  I have not yet edited the
deadlock-checker one to protect autovacuum from processing tables under
repack.

-- 
Álvaro Herrera        Breisgau, Deutschland  —  https://www.EnterpriseDB.com/

Commits

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

  1. Allow old WAL recycling during REPACK CONCURRENTLY

  2. Advance restart_lsn more eagerly in LogicalConfirmReceivedLocation

  3. Remove unnecessary signal handler change

  4. Improve REPACK (CONCURRENTLY) error messages some more

  5. Revert "Allow logical replication snapshots to be database-specific"

  6. Move REPACK (CONCURRENTLY) test out of stock regression tests

  7. REPACK: do not require REPLICATION or LOGIN

  8. Add missing initialization

  9. Simplify declaration of memcpy target

  10. Reserve replication slots specifically for REPACK

  11. doc: Add an example of REPACK (CONCURRENTLY)

  12. Allow logical replication snapshots to be database-specific

  13. Avoid different-size pointer-to-integer cast

  14. Fix valgrind failure

  15. Add CONCURRENTLY option to REPACK

  16. Rename cluster.c to repack.c (and corresponding .h)

  17. Allow index_create to suppress index_build progress reporting

  18. Make index_concurrently_create_copy more general

  19. Document the 'command' column of pg_stat_progress_repack

  20. Introduce the REPACK command

  21. Toggle logical decoding dynamically based on logical slot presence.

  22. Split vacuumdb to create vacuuming.c/h

  23. Remove ReorderBufferTupleBuf structure.

  24. Revert changes to CONCURRENTLY that "sped up" Xmin advance

  25. VACUUM: ignore indexing operations with CONCURRENTLY