From: Jaime Casanova <systemguards@gmail.com>
To: ogjunk-pgjedan@yahoo.com <ogjunk-pgjedan@yahoo.com>
Cc: pgsql-sql@postgresql.org
Subject: Re: READ COMMITTE without START TRANSACTION?
Date: Fri, 10 Mar 2006 22:44:26 -0500
Message-ID: <c2d9e70e0603101944g2b0238b6o9d3781f280b5ef85@mail.gmail.com> (raw)
In-Reply-To: <20060311010855.4341.qmail@web50314.mail.yahoo.com>
References: <20060311010855.4341.qmail@web50314.mail.yahoo.com>
On 3/10/06, ogjunk-pgjedan@yahoo.com <ogjunk-pgjedan@yahoo.com> wrote:
> Hello,
>
> I need to run some SELECT queries that take a while (10+ minutes) to complete, and I'm wondering about the isolation about the results I get. More precisely, while my SELECT is running, the DB is being updated by another application, and I am wondering which, if any, data changes my SELECT will see.
>
> Example:
> If I start my SELECT at 10:00, and it finishes at 10:10, will my results include data that was inserted between 10:00 and 10:10?
> Similarly, will my result include data that was updated between 10:00 and 10:10?
> The same question for data that was deleted during that period.
>
no
> If it matters, my SELECT runs from psql client, while concurrent inserts, updates, and deletes are executed from a separate application (webapp).
>
doesn't really matters
> For my purposes in this case I need the SELECT to get the results that represent data right at the beginning of the query - a snapshot. I read this: http://www.postgresql.org/docs/8.1/static/transaction-iso.html and it looks like this is the default PG behaviour (READ COMMITTED)
>
yes, it is
> Question:
> If I do not explicitly START TRANSACTION before the SELECT, will this READ COMMITTED XA behaviour still be in effect?
>
yes. all statements not executed inside a transaction block are in an
implicit transaction
> Thanks,
> Otis
>
>
--
regards,
Jaime Casanova
"What they (MySQL) lose in usability, they gain back in benchmarks, and that's
all that matters: getting the wrong answer really fast."
Randal L. Schwartz
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To: pgsql-sql@postgresql.org
Cc: systemguards@gmail.com, ogjunk-pgjedan@yahoo.com
Subject: Re: READ COMMITTE without START TRANSACTION?
In-Reply-To: <c2d9e70e0603101944g2b0238b6o9d3781f280b5ef85@mail.gmail.com>
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