Message-ID: <c435d703af02097ec19680c2f8d4479292a3d176.camel@j-davis.com>
Subject: Re: Expanding HOT updates for expression and partial indexes
From: Jeff Davis <pgsql@j-davis.com>
To: Greg Burd <greg@burd.me>, pgsql-hackers <pgsql-hackers@postgresql.org>
Date: Wed, 25 Feb 2026 13:03:01 -0800
In-Reply-To: <bce13827-5f98-4d79-b779-ac5fff2b7668@app.fastmail.com>
References: <5165C147-B476-4E3D-AAA9-11C0B966FC4D@greg.burd.me>
	 <9394564A-5764-4DCA-8845-8AE102DE61DC@greg.burd.me>
	 <97769442-2ed7-4fe0-a393-7e2b5ff7ff58@app.fastmail.com>
	 <a9c8ee0d-bb60-418b-847f-49c4332a09c4@app.fastmail.com>
	 <3e1b9075c92808a7356e79087ba51910e5db5a30.camel@j-davis.com>
	 <da3400d5-e5e0-4d24-bd49-822c72c9894f@app.fastmail.com>
	 <fc17cbe85c24ff9d3cf43bfb37e6ca0d483fb2b4.camel@j-davis.com>
	 <e1d06b18-2ebb-466e-bc0f-5d426d17a32e@app.fastmail.com>
	 <akciabcu3b2hchj7adxhu4kovfaozp2pcn2z7sdljfthxcyg4o@7e6sfyzipvyy>
	 <b8e07500-587d-4360-8f9e-89b14d1c0edc@app.fastmail.com>
	 <bce13827-5f98-4d79-b779-ac5fff2b7668@app.fastmail.com>
Content-Type: text/plain; charset="UTF-8"
Content-Transfer-Encoding: quoted-printable
User-Agent: Evolution 3.52.3-0ubuntu1.1 
MIME-Version: 1.0
Archived-At: <https://www.postgresql.org/message-id/c435d703af02097ec19680c2f8d4479292a3d176.camel%40j-davis.com>
Precedence: bulk

On Mon, 2026-02-23 at 14:23 -0500, Greg Burd wrote:
> Hello.
>=20
> Attached is a new patch set that fixes a few issues identified in the
> last set.
>=20
> 0001 - creates a new way to identify the set of attributes both
> modified by the update and referenced by one or more indexes on the
> target relation being updated.=C2=A0 This patch keeps the
> HeapDetermineColumnsInfo() path within heap_update() for calls from
> simple_heap_update() when modified_attrs_valid is set to false.=C2=A0 I'm
> not a huge fan of this, but it does serve as a way to illustrate a
> minimal set of changes easing review a bit.
>=20
> 0002 - splits out the top portion of heap_update() into both
> heapam_tuple_update() and simple_heap_update(), adds a few helper
> functions and tries to reduce repeated code.=C2=A0 The goal here was to
> remove some of the mess related to the various bitmaps used to make
> decisions during the update.

IIUC, a minimal version of this patch set might be:

* add 'mix_attrs' bitmap to API for table_tuple_update
* have executor calculate the bitmap, using the old slot to see if
expression results have changed
* have simple_heap_update calculate the bitmap using heap_fetch to get
the old tuple (would be a redundant pin, but not sure if that's a
problem or not)

And leave the rest mostly unchanged.

Did I miss something? If not, it would be nice to see such a minimal
patch and/or understand why we don't follow that approach.

Regards,
	Jeff Davis