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From: Jeff Davis <[email protected]>
To: Greg Burd <[email protected]>
To: Burd, Greg <[email protected]>
Cc: [email protected] <[email protected]>
Subject: Re: Expanding HOT updates for expression and partial indexes
Date: Thu, 09 Oct 2025 12:27:15 -0700
Message-ID: <[email protected]> (raw)
In-Reply-To: <[email protected]>
References: <[email protected]>
	<[email protected]>

On Tue, 2025-10-07 at 17:36 -0400, Greg Burd wrote:
> After reviewing how updates work in the executor, I discovered that
> during execution the new tuple slot is populated with the information
> from ExecBuildUpdateProjection() and the old tuple, but that most
> importantly for this use case that function created a bitmap of the
> modified columns (the columns specified in the update).  This bitmap
> isn't the same as the one produced by HeapDetermineColumnsInfo() as
> the
> latter excludes attributes that are not changed after testing
> equality
> with the helper function heap_attr_equals() where as the former will
> include attributes that appear in the update but are the same value
> as
> before.  This, happily, is immaterial for the purposes of my function
> ExecExprIndexesRequireUpdates() which simply needs to check to see if
> index tuples generated are unchanged.  So I had all I needed to run
> the
> checks ahead of acquiring the lock on the buffer.

You're still calling ExecExprIndexesRequireUpdates() from within
heap_update(). Can't you do that inside of ExecUpdatePrologue() or
thereabouts?

Regards,
	Jeff Davis

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