New moddatetime contrib from Terry Mackintosh.

contrib/spi/Makefile

@@ -12,7 +12,7 @@ CFLAGS+= -DREFINT_VERBOSE
 endif
 
 TARGETS= refint$(DLSUFFIX) refint.sql timetravel$(DLSUFFIX) timetravel.sql \
-		autoinc$(DLSUFFIX) autoinc.sql \
+		autoinc$(DLSUFFIX) autoinc.sql moddatetime$(DLSUFFIX) moddatetime.sql \
 		insert_username$(DLSUFFIX) insert_username.sql
 
 CLEANFILES+= $(TARGETS)

contrib/spi/moddatetime.c

+/*
+moddatetime.c
+
+What is this?
+It is a function to be called from a trigger for the perpose of updating
+a modification datetime stamp in a record when that record is UPDATEd.
+
+Credits
+This is 95%+ based on autoinc.c, which I used as a starting point as I do
+not really know what I am doing.  I also had help from 
+Jan Wieck <jwieck@debis.com> who told me about the datetime_in("now") function.
+OH, me, I'm Terry Mackintosh <terry@terrym.com>
+*/
+
+#include "executor/spi.h"		/* this is what you need to work with SPI */
+#include "commands/trigger.h"	/* -"- and triggers */
+
+HeapTuple	moddatetime(void);
+
+HeapTuple moddatetime()
+{
+	Trigger		*trigger;		/* to get trigger name */
+	int			nargs;			/* # of arguments */
+	int			attnum;			/* positional number of field to change */
+	Datum			newdt;			/* The current datetime. */
+	char			**args;			/* arguments */
+	char			*relname;		/* triggered relation name */
+	Relation		rel;				/* triggered relation */
+	HeapTuple	rettuple = NULL;
+	TupleDesc	tupdesc;			/* tuple description */
+
+	if (!CurrentTriggerData)
+		elog(ERROR, "moddatetime: triggers are not initialized.");
+
+	if (TRIGGER_FIRED_FOR_STATEMENT(CurrentTriggerData->tg_event))
+		elog(ERROR, "moddatetime: can't process STATEMENT events.");
+
+	if (TRIGGER_FIRED_AFTER(CurrentTriggerData->tg_event))
+		elog(ERROR, "moddatetime: must be fired before event.");
+
+	if (TRIGGER_FIRED_BY_INSERT(CurrentTriggerData->tg_event))
+		elog(ERROR, "moddatetime: must be fired before event.");
+	else if (TRIGGER_FIRED_BY_UPDATE(CurrentTriggerData->tg_event))
+		rettuple = CurrentTriggerData->tg_newtuple;
+	else
+		elog(ERROR, "moddatetime: 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, "moddatetime (%s): A single argument was expected.", relname);
+
+	args = trigger->tgargs;
+	/* must be the field layout? */
+	tupdesc = rel->rd_att;
+
+	/* Why do this? */
+	CurrentTriggerData = NULL;
+
+	/* Get the current datetime. */
+	newdt = datetime_in("now");
+
+	/* This gets the position in the turple 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]);
+
+	/* This is were we check to see if the feild we are suppost to update even
+		exits.  The above function must return -1 if name not found?
+	*/
+	if (attnum < 0)
+		elog(ERROR, "moddatetime (%s): there is no attribute %s", relname,
+			args[0]);
+			
+	/* OK, this is where we make sure the datetime field that we are 
+		modifying is really a datetime field.
+		Hay, error checking, what a novel idea !-)
+	*/
+	if (SPI_gettypeid(tupdesc, attnum) != DATETIMEOID )
+		elog(ERROR, "moddatetime (%s): attribute %s must be of DATETIME type",
+			 relname, args[0]);
+
+/* 1 is the number of items in the arrays attnum and newdt. 
+	attnum is the positional number of the field to be updated.
+	newdt is the new datetime stamp.
+	NOTE that attnum and newdt are not arrays, but then a 1 ellement array
+	is not an array any more then they are.  Thus, they can be considered a
+	one element array.
+*/
+	rettuple = SPI_modifytuple(rel, rettuple, 1, &attnum, &newdt, NULL);
+
+	if (rettuple == NULL)
+		elog(ERROR, "moddatetime (%s): %d returned by SPI_modifytuple",
+			 relname, SPI_result);
+
+/* Clean up */
+	pfree(relname);
+
+	return (rettuple);
+}

contrib/spi/moddatetime.example

+DROP TABLE mdt;
+
+CREATE TABLE mdt (
+	id		int4,
+	idesc		text,
+	moddate datetime DEFAULT datetime(CURRENT_TIMESTAMP) NOT NULL
+);
+
+CREATE TRIGGER mdt_moddatetime
+	BEFORE UPDATE ON mdt
+	FOR EACH ROW 
+	EXECUTE PROCEDURE moddatetime (moddate);
+
+INSERT INTO mdt VALUES (1, 'first');
+INSERT INTO mdt VALUES (2, 'second');
+INSERT INTO mdt VALUES (3, 'third');
+
+SELECT * FROM mdt;
+
+UPDATE mdt SET id = 4
+	WHERE id = 1;
+UPDATE mdt SET id = 5
+	WHERE id = 2;
+UPDATE mdt SET id = 6
+	WHERE id = 3;
+
+SELECT * FROM mdt;

contrib/spi/moddatetime.source

+DROP FUNCTION moddatetime();
+
+CREATE FUNCTION moddatetime() 
+	RETURNS opaque 
+	AS '_OBJWD_/moddatetime_DLSUFFIX_'
+	LANGUAGE 'c';