1 files changed, 92 insertions, 0 deletions
diff --git a/contrib/spi/insert_username.c b/contrib/spi/insert_username.c
new file mode 100644
index 0000000..a2e1747
--- /dev/null
+++ b/contrib/spi/insert_username.c
@@ -0,0 +1,92 @@
+/*
+ * contrib/spi/insert_username.c
+ *
+ * insert user name in response to a trigger
+ * usage:  insert_username (column_name)
+ */
+#include "postgres.h"
+
+#include "access/htup_details.h"
+#include "catalog/pg_type.h"
+#include "commands/trigger.h"
+#include "executor/spi.h"
+#include "miscadmin.h"
+#include "utils/builtins.h"
+#include "utils/rel.h"
+
+PG_MODULE_MAGIC;
+
+PG_FUNCTION_INFO_V1(insert_username);
+
+Datum
+insert_username(PG_FUNCTION_ARGS)
+{
+	TriggerData *trigdata = (TriggerData *) fcinfo->context;
+	Trigger    *trigger;		/* to get trigger name */
+	int			nargs;			/* # of arguments */
+	Datum		newval;			/* new value of column */
+	bool		newnull;		/* null flag */
+	char	  **args;			/* arguments */
+	char	   *relname;		/* triggered relation name */
+	Relation	rel;			/* triggered relation */
+	HeapTuple	rettuple = NULL;
+	TupleDesc	tupdesc;		/* tuple description */
+	int			attnum;
+
+	/* sanity checks from autoinc.c */
+	if (!CALLED_AS_TRIGGER(fcinfo))
+		/* internal error */
+		elog(ERROR, "insert_username: not fired by trigger manager");
+	if (!TRIGGER_FIRED_FOR_ROW(trigdata->tg_event))
+		/* internal error */
+		elog(ERROR, "insert_username: must be fired for row");
+	if (!TRIGGER_FIRED_BEFORE(trigdata->tg_event))
+		/* internal error */
+		elog(ERROR, "insert_username: must be fired before event");
+
+	if (TRIGGER_FIRED_BY_INSERT(trigdata->tg_event))
+		rettuple = trigdata->tg_trigtuple;
+	else if (TRIGGER_FIRED_BY_UPDATE(trigdata->tg_event))
+		rettuple = trigdata->tg_newtuple;
+	else
+		/* internal error */
+		elog(ERROR, "insert_username: 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, "insert_username (%s): one argument was expected", relname);
+
+	args = trigger->tgargs;
+	tupdesc = rel->rd_att;
+
+	attnum = SPI_fnumber(tupdesc, args[0]);
+
+	if (attnum <= 0)
+		ereport(ERROR,
+				(errcode(ERRCODE_TRIGGERED_ACTION_EXCEPTION),
+				 errmsg("\"%s\" has no attribute \"%s\"", relname, args[0])));
+
+	if (SPI_gettypeid(tupdesc, attnum) != TEXTOID)
+		ereport(ERROR,
+				(errcode(ERRCODE_TRIGGERED_ACTION_EXCEPTION),
+				 errmsg("attribute \"%s\" of \"%s\" must be type TEXT",
+						args[0], relname)));
+
+	/* create fields containing name */
+	newval = CStringGetTextDatum(GetUserNameFromId(GetUserId(), false));
+	newnull = false;
+
+	/* construct new tuple */
+	rettuple = heap_modify_tuple_by_cols(rettuple, tupdesc,
+										 1, &attnum, &newval, &newnull);
+
+	pfree(relname);
+
+	return PointerGetDatum(rettuple);
+}