| From: | "David G(dot) Johnston" <david(dot)g(dot)johnston(at)gmail(dot)com> |
|---|---|
| To: | lebedewwasya(at)gmail(dot)com, pgsql-docs(at)lists(dot)postgresql(dot)org |
| Subject: | Re: 13.2.1. Read Committed Isolation Level |
| Date: | 2024-07-16 15:37:51 |
| Message-ID: | CAKFQuwY2=UTnpcuzEhTFKwOHLafS-jUGtxf72R63mjGs66ROxQ@mail.gmail.com |
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| Lists: | pgsql-docs |
On Tue, Jul 16, 2024 at 7:06 AM PG Doc comments form <noreply(at)postgresql(dot)org>
wrote:
> Or does it mean that contrary to Read
> Committed Isolation Level, uncommitted changes from a parallel transaction
> can affect the execution of an INSERT command?
>
This. Because you are keying off of an unique index that has independent
isolation mechanics. Upon attempting to insert a row that will violate the
unique constraint enforced by the index the system must wait to see whether
the earlier transaction commits. If it doesn't, the insert proceeds. If
it does, the conflict clause is evaluated - updating the now committed row
(or just doing nothing if that option is specified.)
David J.
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