From: Andy Fan <zhihuifan1213@163.com>
To: PostgreSQL Hackers <pgsql-hackers@lists.postgresql.org>
Subject: Re: raise ERROR between EndPrepare and PostPrepare_Locks causes
 ROLLBACK 2pc PAINC
In-Reply-To: <87341p7dc4.fsf@163.com> (Andy Fan's message of "Tue, 24 Mar 2026
	18:04:43 +0800")
References: <87341p7dc4.fsf@163.com>
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Date: Wed, 25 Mar 2026 08:39:07 +0800
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Andy Fan <zhihuifan1213@163.com> writes:

> Hi,
>
> With the following hack in PrepareTransaction:
>
> @@ -2697,6 +2697,8 @@ PrepareTransaction(void)
>  	 */
>  	EndPrepare(gxact);
>  
> +	elog(ERROR, "some error");
> +
>  	/*
>  	 * Now we clean up backend-internal state and release internal resources.
>  	 */
>
> Then we can do the following test:
> CREATE TABLE t(a int);
> begin;
> insert into t values(1);
> prepare transaction 'foo';
> ERROR: some error.  //  before the lock transfer
> rollback prepared 'foo';
> PANIC:  failed to re-find shared lock object // because lock is released
> when ERROR.

I found a similar but not exactly same case at 2014 [1] which 
might be helpful to recall a boarder understanding on this area. 

[1] https://www.postgresql.org/message-id/534AF601.1030007%40vmware.com

-- 
Best Regards
Andy Fan