Re: Way to get at parsed trigger 'WHEN' clause expression?

[Melvin Davidson <melvin6925@xxxxxxxxx>]

On Thu, Mar 24, 2016 at 6:58 PM, Melvin Davidson <melvin6925@xxxxxxxxx> wrote:

On Thu, Mar 24, 2016 at 4:05 PM, James Robinson <jlrobins@xxxxxxxxxxxxxxx> wrote:

Folks,

        I see that psql's \d displays trigger information of a table by making a call to pg_catalog.pg_get_triggerdef(), which abstracts away most all need to parse the contents of system catalog pg_trigger. However, we'd like to be able to get at a human readable representation of just the WHEN clause of the trigger _expression_. Function pg_get_expr() looked likely, but fails when fed a pgqual value from pg_trigger ala:

        ERROR: bogus varno: 2

        I suspect that it is falling over dead trying to parse the representation of NEW and / or OLD. Anything built in, or should we just make call to pg_catalog.pg_get_triggerdef() and parse out the WHEN clause text?

Thanks!
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James Robinson
Socialserve.com by Emphasys Software
 

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Your problem description is a bit cloudy. Could you please give just a little more specific and provide

1. Your PostgreSQL version?

2. Your O./S ?

3. The exact trigger definition?

4. Your exact SQL query for pg_get_triggerdef() ?

Little things like that make it so much easier to provide solutions.

--

Melvin Davidson
I reserve the right to fantasize.  Whether or not you
wish to share my fantasy is entirely up to you.

Did you mean something like

SELECT substring(pg_get_triggerdef(tg.oid, TRUE) FROM position('WHEN' in pg_get_triggerdef(tg.oid, TRUE))) AS when_cond
  FROM pg_trigger tg WHERE tg.tgname = 'your_trigger_name';

--

Melvin Davidson
I reserve the right to fantasize.  Whether or not you
wish to share my fantasy is entirely up to you.