'C' function (spi?) for datetime UPDATE trigger - HOW?

Hi All

I sent this in a few days ago, but got no reply, so now here it is again:)

Need: Update a datetime field to the current time upon a record being
UPDATE'd. (To keep track of modification times)

This seems pertty basic, has any one already done this?
I am very open to any better approaches/ideas.

How I tryed to do it: (see comments below)
Starting with /usr/src/pgsql/contrib/spi/insert_username.c
I turned it into dtstamp.c as follows:

/*
* dtstamp.c (DateTimeSTAMP.c) was insert_username.c
* $Modified: Thu Oct 16 08:13:42 1997 by brook $
* $Modified: Sun Aug 16 1998 by Terry Mackintosh $
*
* update a datetime colum in response to a trigger
* usage: dtstamp(column_name)
*/

#include "executor/spi.h" /* this is what you need to work with SPI */
#include "commands/trigger.h" /* -"- and triggers */
#include <time.h>
/* #include "miscadmin.h" /* Prob. not needed? for GetPgUserName() */

HeapTuple dtstamp(void);

HeapTuple dtstamp(void)
{
Trigger *trigger; /* to get trigger name */
int nargs; /* # of arguments */
/* Datum newval; /* new value of column */
char **args; /* arguments */
char *relname; /* triggered relation name */
Relation rel; /* triggered relation */
HeapTuple rettuple = NULL;
TupleDesc tupdesc; /* tuple description */
int attnum;

/* New, create a datetime string as m/d/y h:m */

time_t runningtime; /* time in seconds */
struct tm *tptr; /* a time structure */
char datetime[20]; /* will have the finished p. */

time( &runningtime );
tptr = localtime(&runningtime);
sprintf( datetime, "%d/%d/%d %d:%d", tptr->tm_mon, tptr->tm_mday, tptr->tm_year + 1900, tptr->tm_hour, tptr->tm_min );

/* End New for now, more at the bottom */

/* sanity checks from dtstamp.c */
if (!CurrentTriggerData)
elog(ERROR, "dtstamp: triggers are not initialized");

if (TRIGGER_FIRED_FOR_STATEMENT(CurrentTriggerData->tg_event))
elog(ERROR, "dtstamp: can't process STATEMENT events");

if (TRIGGER_FIRED_AFTER(CurrentTriggerData->tg_event))
elog(ERROR, "dtstamp: must be fired before event");

if (TRIGGER_FIRED_BY_INSERT(CurrentTriggerData->tg_event))
rettuple = CurrentTriggerData->tg_trigtuple;
else if (TRIGGER_FIRED_BY_UPDATE(CurrentTriggerData->tg_event))
rettuple = CurrentTriggerData->tg_newtuple;
else
elog(ERROR, "dtstamp: can't process DELETE events");

rel = CurrentTriggerData->tg_relation;
relname = SPI_getrelname(rel);

trigger = CurrentTriggerData->tg_trigger;

nargs = trigger->tgnargs;
if (nargs != 1)
elog(ERROR, "dtstamp (%s): one argument was expected", relname);

args = trigger->tgargs;
tupdesc = rel->rd_att;

CurrentTriggerData = NULL;

attnum = SPI_fnumber(tupdesc, args[0]);

if (attnum < 0)
elog(ERROR, "dtstamp (%s): there is no attribute %s", relname, args[0]);

/* More NEW stuff

if (SPI_gettypeid(tupdesc, attnum) != DATETIMEOID)
The problem here is, what should this -----^^^^^^^^^^^ be for a
datetime field?

elog(ERROR, "dtstamp (%s): attribute %s must be of DATETIME type.", relname, args[0] );
*/
/* construct new tuple */
/* The next problem is, what is the 'Datum' type?? can it some how be passed
a datetime??
*/
rettuple = SPI_modifytuple(rel, rettuple, 1, &attnum, (Datum *) &datetime, NULL);
if (rettuple == NULL)
elog(ERROR, "dtstamp (%s): %d returned by SPI_modifytuple", relname, SPI_result);

pfree(relname);

return (rettuple);
}

Any (better:) ideas?

Thanks, and have a great day
Terry Mackintosh <terry(at)terrym(dot)com> http://www.terrym.com
sysadmin/owner Please! No MIME encoded or HTML mail, unless needed.

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