On Tue, Sep 24, 2024 at 8:29 AM David G. Johnston <david.g.johnston@xxxxxxxxx> wrote:
On Monday, September 23, 2024, Wizard Brony <wizardbrony@xxxxxxxxx> wrote:https://www.postgresql.org/docs/16/transaction-iso.html#XACT-REPEATABLE-READ
The PostgreSQL documentation for the Repeatable Read Isolation Level states the following:
“UPDATE, DELETE, MERGE, SELECT FOR UPDATE, and SELECT FOR SHARE commands behave the same as SELECT in terms of searching for target rows: they will only find target rows that were committed as of the transaction start time.”
What is defined as the "transaction start time?" When I first read the statement, 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 start time is actually "the start of the first non-transaction-control statement in the transaction" (as mentioned earlier in the section). Is my conclusion correct, or am I misunderstanding the documentation?
Probably, since indeed the transaction cannot start at begin because once it does start it cannot be modified.
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