From: Andy Fan <zhihuifan1213@163.com>
To: Pg Hackers <pgsql-hackers@lists.postgresql.org>
Cc: Andres Freund <andres@anarazel.de>
Subject: FullTransactionIdAdvance question
Date: Fri, 20 Sep 2024 17:38:40 +0800
Message-ID: <87frpu4qcf.fsf@163.com> (raw)
Hi,
static inline void
FullTransactionIdAdvance(FullTransactionId *dest)
{
dest->value++;
/* see FullTransactionIdAdvance() */
if (FullTransactionIdPrecedes(*dest, FirstNormalFullTransactionId))
return;
while (XidFromFullTransactionId(*dest) < FirstNormalTransactionId)
dest->value++;
}
I understand this functiona as: 'dest->value++' increases the epoch when
necessary and we don't want use the TransactionId which is smaller than
FirstNormalTransactionId. But what is the point of the below code:
/* see FullTransactionIdAdvance() */
if (FullTransactionIdPrecedes(*dest, FirstNormalFullTransactionId))
return;
It looks to me it will be never true(I added a 'Assert(false);' above
the return, make check-world pass). and if it is true somehow, retruning
a XID which is smaller than FirstNormalTransactionId looks strange as
well. IIUC, should we remove it to save a prediction on each
GetNewTransactionId call?
--
Best Regards
Andy Fan
Reply instructions:
You may reply publicly to this message via plain-text email
using any one of the following methods:
* Reply to all the recipients using the --to and --cc options:
reply via email
To: pgsql-hackers@postgresql.org
Cc: zhihuifan1213@163.com, pgsql-hackers@lists.postgresql.org, andres@anarazel.de
Subject: Re: FullTransactionIdAdvance question
In-Reply-To: <87frpu4qcf.fsf@163.com>
* Save the following mbox file, import it into your mail client,
and reply-to-all from there: mbox
This inbox is served by DDX for PostgreSQL; see mirroring instructions
for how to clone and mirror all data and code used for this inbox