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* [Pljava-dev] Triggerdata questions
@ 2005-07-05 18:03
2005-07-05 19:41 ` [Pljava-dev] Triggerdata questions
0 siblings, 1 reply; 2+ messages in thread
From: @ 2005-07-05 18:03 UTC (permalink / raw)
Hi everyone,
I have a number of tables in a db, let's call it Main, which are a
replication of tables that are in other databases (more than one). All
the tables in db Main are empty, they are just used for front end
access and defining the relations that may exist between the tables
from the different databases.
When an insert (for ex.) is issued to db Main a trigger is fired
that calls a java function that supposedly would re-issue the insert
to the real db. But i don't know how this can be done. Using the
triggerdata passed to my function i tried the following:
(being td the Triggerdata received by the function)
Statement stat = (td.getNew()).getStatement();
The function always throws a nullPointerException. From what i've
read, the resultSet returned by .getNew() is always null on inserts
and deletes, so this must be where the exception comes from, but even
on an update the resultSet seems to be returning a null value.
And what i want to ask you is if you think this can be done this
way? If so, what am i doing wrong? If not, do you see another
solution?
Thanks in advance.
^ permalink raw reply [nested|flat] 2+ messages in thread
* [Pljava-dev] Triggerdata questions
2005-07-05 18:03 [Pljava-dev] Triggerdata questions
@ 2005-07-05 19:41 `
0 siblings, 0 replies; 2+ messages in thread
From: @ 2005-07-05 19:41 UTC (permalink / raw)
Joao,
There's a couple of misconseptions:
First, the ResultSet returned by getNew() and getOld() on a TriggerData
are special purpose single row ResultSet used as an access mechanism to
the NEW and OLD tuples of the trigger. There will never be a statement
associated with those sets. The getStatement() method will always return
null.
Second, the td.getNew() is never null on an BEFORE/AFTER INSERT ON EACH
ROW trigger. An ON EACH ROW trigger will only return null on getNew() if
the trigger is a BEFORE/AFTER DELETE. All STATEMENT triggers will return
null on both getNew() and getOld() since there's no tuple associated
with the statement as a whole.
Third, triggers are not an ideal way of achiving replication. What do
you do when a transaction is rolled back? You would probably be better
off looking at stuff like http://gborg.postgresql.org/project/slony1 or
perhaps the recent ON COMMIT triggers found here
http://gorda.di.uminho.pt/community.
Regards,
Thomas Hallgren
Joao Afonso wrote:
> Hi everyone,
>
> I have a number of tables in a db, let's call it Main, which are a
>replication of tables that are in other databases (more than one). All
>the tables in db Main are empty, they are just used for front end
>access and defining the relations that may exist between the tables
>from the different databases.
>
> When an insert (for ex.) is issued to db Main a trigger is fired
>that calls a java function that supposedly would re-issue the insert
>to the real db. But i don't know how this can be done. Using the
>triggerdata passed to my function i tried the following:
>
> (being td the Triggerdata received by the function)
>
> Statement stat = (td.getNew()).getStatement();
>
> The function always throws a nullPointerException. From what i've
>read, the resultSet returned by .getNew() is always null on inserts
>and deletes, so this must be where the exception comes from, but even
>on an update the resultSet seems to be returning a null value.
>
> And what i want to ask you is if you think this can be done this
>way? If so, what am i doing wrong? If not, do you see another
>solution?
>
> Thanks in advance.
>_______________________________________________
>Pljava-dev mailing list
>Pljava-dev at gborg.postgresql.org
>http://gborg.postgresql.org/mailman/listinfo/pljava-dev
>
>
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