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From: Wizard Brony <wizardbrony@gmail.com>
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Subject: Repeatable Read Isolation Level "transaction start time"
Message-Id: <9CEBFAC7-4372-4FF0-8124-FFFE834B03C6@gmail.com>
Date: Mon, 23 Sep 2024 11:15:20 -0400
To: pgsql-general@lists.postgresql.org
Archived-At: <https://www.postgresql.org/message-id/9CEBFAC7-4372-4FF0-8124-FFFE834B03C6%40gmail.com>
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https://www.postgresql.org/docs/16/transaction-iso.html#XACT-REPEATABLE-READ=


The PostgreSQL documentation for the Repeatable Read Isolation Level states t=
he following:

=E2=80=9CUPDATE, DELETE, MERGE, SELECT FOR UPDATE, and SELECT FOR SHARE comm=
ands behave the same as SELECT in terms of searching for target rows: they w=
ill only find target rows that were committed as of the transaction start ti=
me.=E2=80=9D

What is defined as the "transaction start time?" When I first read the state=
ment, I interpreted it as the start of the transaction:

BEGIN;
SET TRANSACTION ISOLATION LEVEL REPEATABLE READ;

But in my testing, I find that according to that statement, the transaction s=
tart time is actually "the start of the first non-transaction-control statem=
ent in the transaction" (as mentioned earlier in the section). Is my conclus=
ion correct, or am I misunderstanding the documentation?=