Function moddatetime

contrib/spi/moddatetime.c:29–130

PG_FUNCTION_INFO_V1(moddatetime);

Datum
moddatetime(PG_FUNCTION_ARGS)
{
	TriggerData *trigdata = (TriggerData *) fcinfo->context;
	Trigger    *trigger;		/* to get trigger name */
	int			nargs;			/* # of arguments */
	int			attnum;			/* positional number of field to change */
	Oid			atttypid;		/* type OID of field to change */
	Datum		newdt;			/* The current datetime. */
	bool		newdtnull;		/* null flag for it */
	char	  **args;			/* arguments */
	char	   *relname;		/* triggered relation name */
	Relation	rel;			/* triggered relation */
	HeapTuple	rettuple = NULL;
	TupleDesc	tupdesc;		/* tuple description */

	if (!CALLED_AS_TRIGGER(fcinfo))
		/* internal error */
		elog(ERROR, "moddatetime: not fired by trigger manager");

	if (!TRIGGER_FIRED_FOR_ROW(trigdata->tg_event))
		/* internal error */
		elog(ERROR, "moddatetime: must be fired for row");

	if (!TRIGGER_FIRED_BEFORE(trigdata->tg_event))
		/* internal error */
		elog(ERROR, "moddatetime: must be fired before event");

	if (TRIGGER_FIRED_BY_INSERT(trigdata->tg_event))
		/* internal error */
		elog(ERROR, "moddatetime: cannot process INSERT events");
	else if (TRIGGER_FIRED_BY_UPDATE(trigdata->tg_event))
		rettuple = trigdata->tg_newtuple;
	else
		/* internal error */
		elog(ERROR, "moddatetime: cannot process DELETE events");

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

	trigger = trigdata->tg_trigger;

	nargs = trigger->tgnargs;

	if (nargs != 1)
		/* internal error */
		elog(ERROR, "moddatetime (%s): A single argument was expected", relname);

	args = trigger->tgargs;
	/* must be the field layout? */
	tupdesc = rel->rd_att;

	/*
	 * This gets the position in the tuple of the field we want. args[0] being
	 * the name of the field to update, as passed in from the trigger.
	 */
	attnum = SPI_fnumber(tupdesc, args[0]);