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From: Noah Misch <[email protected]>
To: Andres Freund <[email protected]>
Cc: Alvaro Herrera <[email protected]>
Cc: vignesh C <[email protected]>
Cc: Antonin Houska <[email protected]>
Cc: Srinath Reddy Sadipiralla <[email protected]>
Cc: Amit Kapila <[email protected]>
Cc: Mihail Nikalayeu <[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: Mon, 6 Apr 2026 18:10:56 -0700
Message-ID: <[email protected]> (raw)
In-Reply-To: <pbqm52nsviwojptiszg2g6pqntbhnhaotbxshiysnensshnuv5@v6pmney4jror>
References: <CALDaNm3tiKhtegx5Cawi34UjbHmNGEDNAtScGM1RgWRtV-5_0Q@mail.gmail.com>
	<[email protected]>
	<pbqm52nsviwojptiszg2g6pqntbhnhaotbxshiysnensshnuv5@v6pmney4jror>

On Mon, Apr 06, 2026 at 05:11:30PM -0400, Andres Freund wrote:
>   heap_insert()
>   ->CacheInvalidateHeapTuple()
>   ->CacheInvalidateHeapTupleCommon()
>   ->AssertCouldGetRelation()
> not being cheap and running a *lot*.
> 
> Admittedly it's way worse if you build with -O0, which I tend to do to make
> debugging easier.
> 
> In that config, the assert single-handled increases the time for a repack by
> 35% or so.
> 
> 
> Noah, is there any reason we need to do the AssertCouldGetRelation() before
> the !IsCatalogRelation(relation)? Given that the goal is to make
> RelationGetRelid() safe, it doesn't seem there is?

By running AssertCouldGetRelation() during every INSERT statement, this
detects cases that would be unsafe when the target of the INSERT happens to be
a system catalog.  Little of our INSERT/UPDATE coverage targets a system
catalog.  Hence, the current position is better for detection.

I wonder if this got slower in v19.  In v14-v18, the assert's cost is
proportional to the number of held lwlocks, often 0 or 1.  In v19, it's
proportional to PrivateRefCountHash cardinality.

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  Subject: Re: Adding REPACK [concurrently]
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