2 files changed, 135 insertions, 0 deletions
diff --git a/contrib/spi/moddatetime.c b/contrib/spi/moddatetime.c
new file mode 100644
index 0000000..3eb7004
--- /dev/null
+++ b/contrib/spi/moddatetime.c
@@ -0,0 +1,130 @@
+/*
+moddatetime.c
+
+contrib/spi/moddatetime.c
+
+What is this?
+It is a function to be called from a trigger for the purpose 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 timestamp_in("now") function.
+OH, me, I'm Terry Mackintosh <terry@terrym.com>
+*/
+#include "postgres.h"
+
+#include "access/htup_details.h"
+#include "catalog/pg_type.h"
+#include "commands/trigger.h"
+#include "executor/spi.h"
+#include "utils/builtins.h"
+#include "utils/rel.h"
+
+PG_MODULE_MAGIC;
+
+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]);
+
+	/*
+	 * This is where we check to see if the field we are supposed to update
+	 * even exists.
+	 */
+	if (attnum <= 0)
+		ereport(ERROR,
+				(errcode(ERRCODE_TRIGGERED_ACTION_EXCEPTION),
+				 errmsg("\"%s\" has no attribute \"%s\"",
+						relname, args[0])));
+
+	/*
+	 * Check the target field has an allowed type, and get the current
+	 * datetime as a value of that type.
+	 */
+	atttypid = SPI_gettypeid(tupdesc, attnum);
+	if (atttypid == TIMESTAMPOID)
+		newdt = DirectFunctionCall3(timestamp_in,
+									CStringGetDatum("now"),
+									ObjectIdGetDatum(InvalidOid),
+									Int32GetDatum(-1));
+	else if (atttypid == TIMESTAMPTZOID)
+		newdt = DirectFunctionCall3(timestamptz_in,
+									CStringGetDatum("now"),
+									ObjectIdGetDatum(InvalidOid),
+									Int32GetDatum(-1));
+	else
+	{
+		ereport(ERROR,
+				(errcode(ERRCODE_TRIGGERED_ACTION_EXCEPTION),
+				 errmsg("attribute \"%s\" of \"%s\" must be type TIMESTAMP or TIMESTAMPTZ",
+						args[0], relname)));
+		newdt = (Datum) 0;		/* keep compiler quiet */
+	}
+	newdtnull = false;
+
+	/* Replace the attnum'th column with newdt */
+	rettuple = heap_modify_tuple_by_cols(rettuple, tupdesc,
+										 1, &attnum, &newdt, &newdtnull);
+
+	/* Clean up */
+	pfree(relname);
+
+	return PointerGetDatum(rettuple);
+}
diff --git a/contrib/spi/moddatetime.control b/contrib/spi/moddatetime.control
new file mode 100644
index 0000000..93dfac5
--- /dev/null
+++ b/contrib/spi/moddatetime.control
@@ -0,0 +1,5 @@
+# moddatetime extension
+comment = 'functions for tracking last modification time'
+default_version = '1.0'
+module_pathname = '$libdir/moddatetime'
+relocatable = true