Re: SET TRANSACTION and SQL Standard

From: Heikki Linnakangas <heikki(dot)linnakangas(at)enterprisedb(dot)com>
To: Simon Riggs <simon(at)2ndQuadrant(dot)com>
Cc: Peter Eisentraut <peter_e(at)gmx(dot)net>, pgsql-hackers <pgsql-hackers(at)postgresql(dot)org>
Subject: Re: SET TRANSACTION and SQL Standard
Date: 2009-01-09 15:11:05
Message-ID: 49676909.8060703@enterprisedb.com
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Simon Riggs wrote:
> On Fri, 2009-01-09 at 16:14 +0200, Peter Eisentraut wrote:
>> Simon Riggs wrote:
>>> I notice that we allow commands such as
>>>
>>> SET TRANSACTION read only read write read only;
>>>
>>> BEGIN TRANSACTION read only read only read only;
>>>
>>> Unsurprisingly, these violate the SQL Standard:
>>> * p.977 section 19.1 syntax (1)
>>> * p.957 section 17.3 syntax (2)
>> Well, we allow a lot of things. Violations of the SQL standard happen
>> when a command that appears in the standard doesn't do what the standard
>> says. Allowing commands that are not in the standard is not a violation.
>
> Except when the standard explicitly forbids it, as with the above.

No, it just means that the statement "SET TRANSACTION read only read
write read only;" doesn't conform to the standard, and it's therefore
implementation-dependent what it does. See the meaning of "shall" in
Syntax Rules, section "6.3.3.2 Terms denoting rule requirements".

I agree with Tom that the 2nd form is harmless, but we should throw an
error for the first.

--
Heikki Linnakangas
EnterpriseDB http://www.enterprisedb.com

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