Re: postgresql_fdw issues with triggers on the foreign tables

From: Albe Laurenz <laurenz(dot)albe(at)wien(dot)gv(dot)at>
To: "Eelke Klein *EXTERN*" <eelke(at)bolt(dot)nl>, "pgsql-general(at)postgresql(dot)org" <pgsql-general(at)postgresql(dot)org>
Subject: Re: postgresql_fdw issues with triggers on the foreign tables
Date: 2014-07-23 15:28:24
Message-ID: A737B7A37273E048B164557ADEF4A58B17D1F5F2@ntex2010i.host.magwien.gv.at
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Eelke Klein wrote:
> I'm experimenting with using foreign data wrappers to get data from one database to another. Most
> things work perfectly but I am encountering two issues with triggers on the foreign tables.
>
> The first one is when a query triggers a trigger on the foreign table the trigger doesn't have any
> search_path. Not even a select on a table in public will work from the trigger unless I specify the
> schema name.

Wouldn't a trigger that depends on the current search_path setting be
pretty dangerous anyway? Anybody can change the setting.
I'd suggest that you make the trigger more robust.

> The second problem has to do with DEFAULT values. One of the tables i'm inserting data on has a column
> called id of type bigserial. This column is not filled by the INSERT statement I'm using so should use
> it's default which is nextval('...'::regclass); However in the BEFORE INSERT trigger the value of
> NEW.id IS NULL while normally it would already be assigned a value from the sequence.

That is actually working as intended, see this thread:
http://www.postgresql.org/message-id/24107.1363027848@sss.pgh.pa.us
Nobody could come up with a better solution.

> The issues with the triggers do not occur when they are triggered by statements executed directly on
> the database. Only when the statements come from the FDW I have these issues.

Can you reproduce the trigger problem without postgres_fdw by setting "search_path=pg_catalog" ?

Yours,
Laurenz Albe

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