Re: Functions and transactions - Mailing list pgsql-admin

I guess first we should understand why the insert B waits at all,the
insert A did not commit ,right ,then how did it found any pkey_id =
NEW.pkey_id? That means you have already had those while starting your
experiment.
So ,insert B wait for those "old" rows not for your insert (i mean an
INSERT) to commit.Once the A function commits the old rows are released
but the INSERT is not yet done!it will take place only now when the
trigger of A is done.
This means that you have transaction in a wrong place  - place it around
the insert not inside the trigger and commit AFTER the insert .
All this is an assumption only ,not realy sure if i am right.
Evgeny
Kris Kiger wrote:
> transaction_isolation
> -----------------------
> read committed
>
> Running Postgres 7.4  btw
>
> Kris
>
> Tsirkin Evgeny wrote:
>
>>
>> What transaction level are you using?
>> Evgeny.
>> Kris Kiger wrote:
>>
>>> Here is my problem.  I have a function that is triggered on insert.
>>> For simplicity's sake, lets say the function looks like this:
>>>
>>> CREATE OR REPLACE FUNCTION dostuff_on_insert() RETURNS TRIGGER AS '
>>> DECLARE lockrows RECORD;
>>> BEGIN
>>>    select into lockrows * from table1 where pkey_id = NEW.pkey_id for
>>> update on table1;
>>>    update table1 set active = false where NEW.pkey_id = pkey_id and
>>> active;
>>>    NEW.active := true;
>>> END;
>>> 'language 'plpgsql';
>>>
>>> I have two inserts, lets say insert A and insert B.  A new explicit
>>> transaction block is started with the intent of executing insert A.
>>>
>>> begin;
>>> insert into table1 (stuff) VALUES (morestuff);
>>>
>>>
>>> At this time another terminal is opened up and insert B is executed
>>> in the same fasion:
>>>
>>> begin;
>>> insert into table1 (stuff) VALUES (different_more_stuff);
>>>
>>> In my two open terminals insert A has completed and insert B is
>>> waiting for insert A's transaction to be committed, before it can
>>> move on.  I commit insert A and check to see how many active row's I
>>> have for that ID (there should be 1, the new row).
>>>
>>> commit;
>>> select * from table1;
>>>
>>> I find that there is one active row.  Everything is fine at this
>>> point.  Now, I commit insert B, that has just finished, because
>>> insert A has been committed.  I expect to see 1 active row, because
>>> the update contained in the function has not been executed, and has
>>> therefore not grabbed a snapshot of the table yet.  I expect that the
>>> new row from insert A will be updated as well.
>>>
>>> commit;
>>> select * from table1;
>>>
>>> To my surprise, I see 2 active rows.  What i'm assuming is happening
>>> with the transaction must be flawed.  Does the function handle a
>>> transaction outside of the one the insert is using?  Just trying to
>>> figure out what exactly is going on and why.
>>> Thanks in advance for the insight.  If it would be easier to
>>> understand by having me paste what is happening directly from the
>>> terminals, let me know.
>>>
>>> Kris
>>>
>>> ---------------------------(end of broadcast)---------------------------
>>> TIP 4: Don't 'kill -9' the postmaster
>>
>>
>>
>
>
> ---------------------------(end of broadcast)---------------------------
> TIP 5: Have you checked our extensive FAQ?
>
>               http://www.postgresql.org/docs/faq