From: Tom Lane <tgl@sss.pgh.pa.us>
To: Wizard Brony <wizardbrony@gmail.com>
cc: pgsql-general@lists.postgresql.org
Subject: Re: Repeatable Read Isolation Level "transaction start time"
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References: <9CEBFAC7-4372-4FF0-8124-FFFE834B03C6@gmail.com>
Comments: In-reply-to Wizard Brony <wizardbrony@gmail.com>
	message dated "Mon, 23 Sep 2024 11:15:20 -0400"
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Date: Tue, 24 Sep 2024 10:28:46 -0400
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Wizard Brony <wizardbrony@gmail.com> writes:
> But in my testing, I find that according to that statement, the transact=
ion start time is actually "the start of the first non-transaction-control=
 statement in the transaction" (as mentioned earlier in the section). Is m=
y conclusion correct, or am I misunderstanding the documentation?

It's even looser than that, really: it's the first statement that
requires an MVCC snapshot.  From memory, LOCK TABLE is an important
exception --- you can acquire table locks before pinning down
a snapshot, and this is important in some scenarios.

			regards, tom lane