Re: minimal update

Andrew Dunstan wrote:
> 
> Bruce,
> 
> did you ever look at completing this?

No, it is still in my email box unaddressed.  Feel free to work on it; I
doubt I can do it for 8.4.

---------------------------------------------------------------------------


> 
> cheers
> 
> andrew
> 
> Andrew Dunstan wrote:
> >
> >
> > Bruce Momjian wrote:
> >> Andrew Dunstan wrote:
> >>  
> >>> Right. In fact, I already had that part in fact - see 
> >>> http://people.planetpostgresql.org/andrew/index.php?/archives/22-Minimal-Update-Trigger.html 
> >>>
> >>>
> >>> What I was waiting for was the part where it gets put in the 
> >>> catalog, documented, etc.
> >>>     
> >>
> >> I can probably do that part.  Send over what you have and I will work on
> >> it.  Thanks.
> >>
> >>   
> >
> > It's very similar to what Gurjeet posted (but designed to work with 
> > earlier postgres versions)
> >
> > cheers
> >
> > andrew
> >
> > ---
> >
> > |#include "postgres.h"
> > #include "commands/trigger.h"
> > #include "access/htup.h"
> >
> > #ifdef PG_MODULE_MAGIC
> > PG_MODULE_MAGIC;
> > #endif
> >
> > /* for pre 8.3 */
> > #ifndef HeapTupleHeaderGetNatts
> > #define HeapTupleHeaderGetNatts(th) (    (th)->t_natts )
> > #endif
> >
> > extern Datum min_update_trigger(PG_FUNCTION_ARGS);
> >
> > PG_FUNCTION_INFO_V1(min_update_trigger);
> >
> > Datum
> > min_update_trigger(PG_FUNCTION_ARGS)
> > {
> >    TriggerData *trigdata = (TriggerData *) fcinfo->context;
> >    HeapTuple   newtuple, oldtuple, rettuple;
> >
> >    /* make sure it's called as a trigger at all */
> >    if (!CALLED_AS_TRIGGER(fcinfo))
> >        elog(ERROR, "min_update_trigger: not called by trigger manager");
> >
> >    /* and that it's called on update */
> >    if (! TRIGGER_FIRED_BY_UPDATE(trigdata->tg_event))
> >        elog(ERROR, "min_update_trigger: not called on update");
> >
> >    /* and that it's called before update */
> >    if (! TRIGGER_FIRED_BEFORE(trigdata->tg_event))
> >        elog(ERROR, "min_update_trigger: not called before update");
> >
> >    /* and that it's called for each row */
> >    if (! TRIGGER_FIRED_FOR_ROW(trigdata->tg_event))
> >        elog(ERROR, "min_update_trigger: not called for each row");
> >
> >        /* get tuple dat, set default return */
> >        rettuple  = newtuple = trigdata->tg_newtuple;
> >        oldtuple = trigdata->tg_trigtuple;
> >
> >    if (newtuple->t_len == oldtuple->t_len &&
> >                newtuple->t_data->t_hoff == oldtuple->t_data->t_hoff &&
> >                HeapTupleHeaderGetNatts(newtuple->t_data) == 
> > HeapTupleHeaderGetNatts(oldtuple->t_data) &&
> >                (newtuple->t_data->t_infomask & ~HEAP_XACT_MASK) == 
> >                (oldtuple->t_data->t_infomask & ~HEAP_XACT_MASK) &&
> >                memcmp(((char *)newtuple->t_data) + 
> > offsetof(HeapTupleHeaderData, t_bits),
> >                           ((char *)oldtuple->t_data) + 
> > offsetof(HeapTupleHeaderData, t_bits),
> >                           newtuple->t_len - 
> > offsetof(HeapTupleHeaderData, t_bits)) == 0)
> >                  rettuple = NULL;
> >
> >    return PointerGetDatum(rettuple);
> > }|
> >
> >
> >
> >

--  Bruce Momjian  <bruce@momjian.us>        http://momjian.us EnterpriseDB
http://enterprisedb.com
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