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Date: Tue, 24 Mar 2026 17:01:12 -0400
From: "Greg Burd" <greg@burd.me>
To: "Nathan Bossart" <nathandbossart@gmail.com>
Cc: "Jeff Davis" <pgsql@j-davis.com>,
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Subject: Re: Expanding HOT updates for expression and partial indexes
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On Tue, Mar 24, 2026, at 3:44 PM, Nathan Bossart wrote:
> On Tue, Mar 24, 2026 at 02:02:07PM -0400, Greg Burd wrote:
>> On Mon, Mar 23, 2026, at 2:39 PM, Nathan Bossart wrote:
>>> On Tue, Mar 17, 2026 at 02:04:11PM -0400, Greg Burd wrote:
>>>> - *	INDEX_ATTR_BITMAP_SUMMARIZED	Columns included in summarizing indexes
>>>> + *	INDEX_ATTR_BITMAP_INDEXED		Columns referenced by indexes
>>>> + *	INDEX_ATTR_BITMAP_SUMMARIZED	Columns only included in summarizing indexes
>>>
>>>> -	Bitmapset  *summarizedattrs;	/* columns with summarizing indexes */
>>>> +	Bitmapset  *indexedattrs;	/* columns referenced by indexes */
>>>> +	Bitmapset  *summarizedattrs;	/* columns only in summarizing indexes */
>>>
>>> As before, the comment changes for the summarized-attr-related stuff seem
>>> unnecessary.
>> 
>> I disagree, the "only" is required to highlight the logic change here.
>> Before this patch summarized attrs could overlap with indexed attrs, now
>> it should not.  This makes the logic a bit easier later in
>> HeapUpdateHotAllowable().
>
> My bad, you are right.

Hey Nathan,

No worries, that's why we talk about it. :)

>> So, we go from 3 calls to RelationGetIndexAttrBitmap() to 1, or at most 2
>> when there's a summarizing index (which is frequently the case).

I meant to say that the common case (no summarizing indexes) we don't need more than the 1 bitmap, only in the less common case do we even need to get the *only* summarized attrs from relcache.

>> This feels more logical, cleaner, and has less overhead but supports the
>> same HOT logic.
>
> Nice.

I'm happy that you agree!

> -- 
> nathan

best.

-greg