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From: Nico Heller <[email protected]>
To: Greg Sabino Mullane <[email protected]>
Cc: Tom Lane <[email protected]>
Cc: [email protected]
Subject: Re: Guarantee order of batched pg_advisory_xact_lock
Date: Thu, 12 Feb 2026 18:56:30 +0000
Message-ID: <[email protected]> (raw)
In-Reply-To: <CAKAnmmKfV4K6CfMuQkfQxccP0JRC5orV1tmaq8pB_+EdCZS1yw@mail.gmail.com>
References: <[email protected]>
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	<[email protected]>
	<[email protected]>
	<[email protected]>
	<CAKAnmmKfV4K6CfMuQkfQxccP0JRC5orV1tmaq8pB_+EdCZS1yw@mail.gmail.com>

For my case that is not true as our keys are globally unique URN 
strings. Thus, only the hashes may collide, but thank you for the insight.

On 2/12/26 15:47, Greg Sabino Mullane wrote:
> On Thu, Feb 12, 2026 at 6:18 AM Nico Heller <[email protected]> wrote:
>
>     I just checked for hash collisions with the following query today:
>
>     SELECT COUNT(*), hashtextextended(key, 0) FROM
>     (
>       SELECT key FROM table1
>       UNION
>
> FWIW, you need UNION ALL, not UNION, if you are trying to detect 
> duplicate values (hashed or not) across tables.
>
> Cheers,
> Greg
>

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