Re: minimal update

Bruce,

did you ever look at completing this?

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);
> }|
>
>
>
>