Might want to skim through some of documents at the below page:

        http://developer.postgresql.org/osdn.php


On Thu, 2004-08-19 at 15:46, Jeff Amiel wrote:
> neat....I learn new things about the inner workings of postgreSQL every 
> day....
> so...what is the 'executor'?
> 
> Jeff
> 
> 
> Jan Wieck wrote:
> 
> > On 8/19/2004 3:36 PM, Jeremiah Jahn wrote:
> >
> >> If you could, wouldn't that fix the problem? So, would it be worthwhile
> >> to be able to put a trigger on at least the LO table, maybe even other
> >> system tables (for schema replication). I assume that it's a performance
> >> issue that has prevented this before.
> >
> >
> > No. The issue is that system catalog updates most of the time don't go 
> > through the executor, but call heap_insert(), heap_update and 
> > heap_delete() directly. The trigger mechanism is in the executor.
> >
> >
> > Jan
> >
> >>
> >> -jj- 
> >> On Thu, 2004-08-19 at 13:29, Doug McNaught wrote:
> >>
> >>> Jeremiah Jahn <jeremiah at cs.earlham.edu> writes:
> >>>
> >>> > So it's not possible to just trigger off of the pg_large_object 
> >>> table?
> >>>
> >>> No, you can't put triggers on system tables.
> >>>
> >>> -Doug
> >>
> >
> >
> 
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