Re: Compatibility GUC for serializable

From: Pavel Stehule <pavel(dot)stehule(at)gmail(dot)com>
To: Robert Haas <robertmhaas(at)gmail(dot)com>
Cc: Josh Berkus <josh(at)agliodbs(dot)com>, pgsql-hackers(at)postgresql(dot)org
Subject: Re: Compatibility GUC for serializable
Date: 2011-01-11 05:02:40
Message-ID: AANLkTi=L0LisyzKjUoWcdM=vLmXkdevVooN5TWjicnkp@mail.gmail.com
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2011/1/11 Robert Haas <robertmhaas(at)gmail(dot)com>:
> On Mon, Jan 10, 2011 at 1:17 PM, Josh Berkus <josh(at)agliodbs(dot)com> wrote:
>> I'm going to disagree here. For a large, sprawling, legacy application
>> changing SERIALIZABLE to REPEATABLE READ in every place in the code
>> which might call it can be prohibitively difficult.
>
> What makes you think that would be necessary?  That'd require someone
> (a) using serializable, and (b) wanting it to be broken?  I think the
> most common reaction would be "thank goodness, this thing actually
> works now".

it works, but not works perfect. Some "important" toolkit like
performance benchmarks doesn't work with PostgreSQL without failures.
It's one reason why PostgreSQL has less score in some enterprise
rating than MySQL. It working for current user, but it not works well
for users who should do decision for migration to PostgreSQL. I don't
see a problem in GUC, but it isn't a problem - more significant
problem is current PostgreSQL's serializable implementation in general
(that should work on more SQL servers) applications. It's a break for
one class of customers.

Regards

Pavel Stehule

>
>> Further, many such
>> applications would be written with workarounds for broken serializable
>> behavior, workarounds which would behave unpredictably after an upgrade.
>
> Uh...  you want to support that with an example?  Because my first
> reaction is "that's FUD".
>
> --
> Robert Haas
> EnterpriseDB: http://www.enterprisedb.com
> The Enterprise PostgreSQL Company
>
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