Transactions and functions

On 09/23/2016 08:44 AM, Арсен Арутюнян wrote:

Hello all

i have the table

create table testpr(id serial,priority integer,unique(priority)
DEFERRABLE, primary key(id));

and procedure:

CREATE OR REPLACE FUNCTION JobPriorityChange(JobId bigint,NewPrior
integer) RETURNS void AS $$
DECLARE
PrevPrior integer;
BEGIN
PrevPrior := (select priority from testpr where id=JobId);
if PrevPrior > NewPrior then
WITH u as(update testpr set priority=NewPrior where id=JobId) update
testpr set priority=priority+1 where priority>=NewPrior and
priority<PrevPrior and id<>JobId;
ELSIF PrevPrior < NewPrior then
WITH u as(update testpr set priority=NewPrior where id=JobId) update
testpr set priority=priority-1 where priority<=NewPrior and
priority>PrevPrior and id<>JobId;
END IF;
END;
$$ LANGUAGE plpgsql;

according to:
https://www.postgresql.org/docs/9.5/static/plpgsql-structure.html

"Functions and trigger procedures are always executed within a
transaction established by an outer query — they cannot start or commit
that transaction, since there would be no context for them to execute
in. However, a block containing an EXCEPTION clause effectively forms a
subtransaction that can be rolled back without affecting the outer
transaction. For more about that see Section 40.6.6."

would you like to help me with several questions:
1)are all functions atomic?
2)are they execute in a single query?

So yes.

--
Arsen Arutyunyan

--
Adrian Klaver
adrian.klaver@aklaver.com

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On Fri, Sep 23, 2016 at 9:14 PM, Арсен Арутюнян <arutar@bk.ru> wrote:

would you like to help me with several questions:
1)are all functions atomic?

Yes, of course.

2)are they execute in a single query?

Same as executing n-number of SQL statements between BEGIN-COMMIT block.

Regards,
Amul

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