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From: Alvaro Herrera <[email protected]>
To: Mihail Nikalayeu <[email protected]>
Cc: Antonin Houska <[email protected]>
Cc: Srinath Reddy Sadipiralla <[email protected]>
Cc: Amit Kapila <[email protected]>
Cc: Matthias van de Meent <[email protected]>
Cc: Pg Hackers <[email protected]>
Cc: Robert Treat <[email protected]>
Subject: Re: Adding REPACK [concurrently]
Date: Tue, 7 Apr 2026 00:22:32 +0200
Message-ID: <[email protected]> (raw)
In-Reply-To: <CADzfLwWFr9h_+cbSQvPpdxgLbVL5wwxFRx21ezNvLYgJM=FVCQ@mail.gmail.com>

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/

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