Re: How to mark a transaction as SERIALIZABLE?

Thanks for the link. I've done some more reading, and now it appears
impossible to set the isolation level of a transaction from within a
function.

CREATE OR REPLACE FUNCTION test(character varying)
RETURNS integer AS
$BODY$
BEGIN
SET TRANSACTION ISOLATION LEVEL SERIALIZABLE;
RETURN 1;
END;
$BODY$
LANGUAGE plpgsql VOLATILE

Creates successfully, but when executed reports : "ERROR: SET TRANSACTION
ISOLATION LEVEL must be called before any query". I believe this is
happening because I'm exercising the function with :

select * from test('test');

so that select is executed prior to the SET TRANSACTION. If I remove the SET
TRANSACTION command from the function, and then call it by :

SET TRANSACTION ISOLATION LEVEL SERIALIZABLE;
select * from test('test');

that works. So, is that the correct way to set the isolation level for a
function? Thanks again for your help.

On Tue, Nov 2, 2010 at 5:13 AM, Thom Brown <thom(at)linux(dot)com> wrote:

> On 2 November 2010 01:51, Joe Carr <joe(dot)carr(at)gmail(dot)com> wrote:
>
>> In version 9.0, I've been reading
>> http://www.postgresql.org/docs/9.0/interactive/sql-begin.html. I've been
>> using the following :
>>
>> CREATE OR REPLACE FUNCTION test(character varying)
>> RETURNS SETOF integer AS
>> $BODY$
>>
>> BEGIN TRANSACTION ISOLATION LEVEL SERIALIZABLE;
>> --SET TRANSACTION ISOLATION LEVEL SERIALIZABLE;
>> RETURN 1;
>> END;
>> $BODY$
>> LANGUAGE plpgsql VOLATILE
>>
>> which returns with the error :
>> ERROR: syntax error at or near "TRANSACTION"
>> LINE 1: TRANSACTION ISOLATION LEVEL SERIALIZABLE
>>
>> if the BEGIN line is empty with no semi-colon, the function will work :
>> CREATE OR REPLACE FUNCTION test(character varying)
>> RETURNS integer AS
>> $BODY$
>>
>> BEGIN
>> --TRANSACTION ISOLATION LEVEL SERIALIZABLE;
>> --SET TRANSACTION ISOLATION LEVEL SERIALIZABLE;
>>
>> RETURN 1;
>> END;
>> $BODY$
>> LANGUAGE plpgsql VOLATILE
>>
>> but if I place a semi-colon after BEGIN (e.g. BEGIN;), I get the error :
>> ERROR: syntax error at or near ";"
>> LINE 5: BEGIN;
>>
>> So any help you may be able to provide in the BEGIN syntax (or whatever
>> I'm doing wrong) is greatly appreciated. Thanks!
>>
>> -Joe
>>
>>
> BEGIN in your function isn't the same as BEGIN in an SQL statement block.
> It merely marks where the function begins, not the transaction. Note that
> you also shouldn't use a semi-colon after the BEGIN in a function. See this
> page for more info:
> http://www.postgresql.org/docs/9.0/interactive/plpgsql-structure.html
>
> --
> Thom Brown
> Twitter: @darkixion
> IRC (freenode): dark_ixion
> Registered Linux user: #516935
>