Trigger function for inserting user names.

Install compiled functions into $(LIBDIR)/contrib.
(Thanks to Brook Milligan <brook@trillium.NMSU.Edu>)

contrib/spi/Makefile

@@ -3,6 +3,8 @@ SRCDIR= ../../src
 
 include $(SRCDIR)/Makefile.global
 
+CONTRIBDIR=$(LIBDIR)/contrib
+
 CFLAGS+= $(CFLAGS_SL) -I$(SRCDIR)/include
 
 ifdef REFINT_VERBOSE
@@ -10,16 +12,24 @@ CFLAGS+= -DREFINT_VERBOSE
 endif
 
 TARGETS= refint$(DLSUFFIX) refint.sql timetravel$(DLSUFFIX) timetravel.sql \
-		autoinc$(DLSUFFIX) autoinc.sql
+		autoinc$(DLSUFFIX) autoinc.sql \
+		insert_username$(DLSUFFIX) insert_username.sql
 
 CLEANFILES+= $(TARGETS)
 
 all:: $(TARGETS)
 
+install:: all $(CONTRIBDIR)
+	$(INSTALL) -c README $(CONTRIBDIR)/README.spi
+	for f in *.example *.sql *$(DLSUFFIX); do $(INSTALL) -c $$f $(CONTRIBDIR)/$$f; done
+
+$(CONTRIBDIR):
+	mkdir -p $(CONTRIBDIR)
+
 %.sql: %.source
 	rm -f $@; \
 	C=`pwd`; \
-	sed -e "s:_OBJWD_:$$C:g" \
+	sed -e "s:_OBJWD_:$(CONTRIBDIR):g" \
 	    -e "s:_DLSUFFIX_:$(DLSUFFIX):g" < $< > $@
 
 clean: 

contrib/spi/README

@@ -122,3 +122,16 @@ as many column/sequence pairs as you need).
 autoinc.source).
 
 
+4. insert_username.c - function for inserting user names.
+
+   You have to create BEFORE INSERT OR UPDATE trigger using the function
+insert_username(). You have to specify as a function argument: the column
+name (of text type) in which user names will be inserted.  Note that user
+names will be inserted irregardless of the initial value of the field, so
+that users cannot bypass this functionality by simply defining the field to
+be NOT NULL.
+
+   There is an example in insert_username.example.
+
+   To CREATE FUNCTION use insert_username.sql (will be made by gmake from
+insert_username.source).

contrib/spi/insert_username.c

+/*
+ * insert_username.c
+ * $Modified: Thu Oct 16 08:13:42 1997 by brook $
+ *
+ * insert user name in response to a trigger
+ * usage:  insert_username (column_name)
+ */
+
+#include "executor/spi.h"		/* this is what you need to work with SPI */
+#include "commands/trigger.h"		/* -"- and triggers */
+#include "miscadmin.h"			/* for GetPgUserName() */
+
+HeapTuple	insert_username (void);
+
+HeapTuple
+insert_username ()
+{
+	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;
+
+				/* sanity checks from autoinc.c */		
+	if (!CurrentTriggerData)
+		elog(WARN, "insert_username: triggers are not initialized");
+	if (TRIGGER_FIRED_FOR_STATEMENT(CurrentTriggerData->tg_event))
+		elog(WARN, "insert_username: can't process STATEMENT events");
+	if (TRIGGER_FIRED_AFTER(CurrentTriggerData->tg_event))
+		elog(WARN, "insert_username: 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(WARN, "insert_username: can't process DELETE events");
+	
+	rel = CurrentTriggerData->tg_relation;
+	relname = SPI_getrelname(rel);
+	
+	trigger = CurrentTriggerData->tg_trigger;
+
+	nargs = trigger->tgnargs;
+	if (nargs != 1)
+		elog(WARN, "insert_username (%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(WARN, "insert_username (%s): there is no attribute %s", relname, args[0]);
+	if (SPI_gettypeid (tupdesc, attnum) != TEXTOID)
+		elog(WARN, "insert_username (%s): attribute %s must be of TEXT type", 
+				relname, args[0]);
+
+				/* create fields containing name */
+	newval = PointerGetDatum (textin (GetPgUserName ()));
+
+				/* construct new tuple */
+	rettuple = SPI_modifytuple (rel, rettuple, 1, &attnum, &newval, NULL);
+	if ( rettuple == NULL )
+		elog (WARN, "insert_username (%s): %d returned by SPI_modifytuple",
+			relname, SPI_result);
+	
+	pfree (relname);
+
+	return (rettuple);
+}

contrib/spi/insert_username.example

+DROP TABLE username_test;
+
+CREATE TABLE username_test (
+	name		text,
+	username	text not null
+);
+
+CREATE TRIGGER insert_usernames
+	BEFORE INSERT OR UPDATE ON username_test
+	FOR EACH ROW 
+	EXECUTE PROCEDURE insert_username (username);
+
+INSERT INTO username_test VALUES ('nothing');
+INSERT INTO username_test VALUES ('null', null);
+INSERT INTO username_test VALUES ('empty string', '');
+INSERT INTO username_test VALUES ('space', ' ');
+INSERT INTO username_test VALUES ('tab', '	');
+INSERT INTO username_test VALUES ('name', 'name');
+
+SELECT * FROM username_test;
+

contrib/spi/insert_username.source

+DROP FUNCTION insert_username();
+
+CREATE FUNCTION insert_username() 
+	RETURNS opaque 
+	AS '_OBJWD_/insert_username_DLSUFFIX_'
+	LANGUAGE 'c';