Feedback-ID: ia2694551:Fastmail
Date: Mon, 6 Apr 2026 12:48:23 +0200
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>
Subject: Re: Adding REPACK [concurrently]
Message-ID: <202604061043.4tvvhamrwnlc@alvherre.pgsql>
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On 2026-Apr-06, Mihail Nikalayeu wrote:

> repack.c:2725
> 
>     if (!VARATT_IS_EXTERNAL(varlen))
>           continue;
> 
> I think it should be VARATT_IS_EXTERNAL_INDIRECT - the same as in pgrepack:244.

Right.

> Also,  after
> 
> natt_ext--;
> 
> I think it worth to add
> 
> Assert(natt_ext >= 0);
> 
> or Assert(natt_ext == 0); but in another place.
> 
> Or exit early with
>      for (int i = 0; i < desc->natts && natt_ext > 0; i++)

Hmm, how about something like this?

            natt_ext--;
            if (natt_ext < 0)
                ereport(ERROR,
                        errcode(ERRCODE_DATA_CORRUPTED),
                        errmsg("insufficient number of attributes stored separately"));

I'd like to give more details, such as the tuple's identity, but that
seems hard ...

> ----------------------------
> repack.c:2587
> 
>     table_tuple_insert(rel, slot, GetCurrentCommandId(true),
>        HEAP_INSERT_NO_LOGICAL, NULL);
> 
> More idiomatic to use TABLE_INSERT_NO_LOGICAL instead.

Ah right.

> ----------------------------
> repack.c:2696
> 
>      ExecForceStoreHeapTuple(tup, slot, false);
> 
> AFAIU there is a memory leak here. Memory allocated above (for tuple)
> is not freed in any way, because shouldFree == false.
> Also, ExecClearTuple (tts_virtual_clear for virtual tuples) requires
> TTS_SHOULDFREE to be set to free anything.

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.

> -------------------------
> grab ShareUpdateExclusiveLock (jsut like VACUUM
> 
> typo in "just"

Right.

> --------------------------
> 
> "If the identity index is not set due to replica identity being, PK"
> 
> Missing "FULL" after "being"?

Ah yeah, I rewrote this.

> -------------------------
> 
> Commit message:
> 
> "intial copy" -> "initial copy"
> "backed performing REPACK" -> "backend performing REPACK"

Thanks!

-- 
Álvaro Herrera         PostgreSQL Developer  —  https://www.EnterpriseDB.com/
"Sallah, I said NO camels! That's FIVE camels; can't you count?"
(Indiana Jones)