1 files changed, 127 insertions, 0 deletions
diff --git a/contrib/spi/autoinc.c b/contrib/spi/autoinc.c
new file mode 100644
index 0000000..8bf7422
--- /dev/null
+++ b/contrib/spi/autoinc.c
@@ -0,0 +1,127 @@
+/*
+ * contrib/spi/autoinc.c
+ */
+#include "postgres.h"
+
+#include "access/htup_details.h"
+#include "catalog/pg_type.h"
+#include "commands/sequence.h"
+#include "commands/trigger.h"
+#include "executor/spi.h"
+#include "utils/builtins.h"
+#include "utils/rel.h"
+
+PG_MODULE_MAGIC;
+
+PG_FUNCTION_INFO_V1(autoinc);
+
+Datum
+autoinc(PG_FUNCTION_ARGS)
+{
+	TriggerData *trigdata = (TriggerData *) fcinfo->context;
+	Trigger    *trigger;		/* to get trigger name */
+	int			nargs;			/* # of arguments */
+	int		   *chattrs;		/* attnums of attributes to change */
+	int			chnattrs = 0;	/* # of above */
+	Datum	   *newvals;		/* vals of above */
+	bool	   *newnulls;		/* null flags for above */
+	char	  **args;			/* arguments */
+	char	   *relname;		/* triggered relation name */
+	Relation	rel;			/* triggered relation */
+	HeapTuple	rettuple = NULL;
+	TupleDesc	tupdesc;		/* tuple description */
+	bool		isnull;
+	int			i;
+
+	if (!CALLED_AS_TRIGGER(fcinfo))
+		/* internal error */
+		elog(ERROR, "not fired by trigger manager");
+	if (!TRIGGER_FIRED_FOR_ROW(trigdata->tg_event))
+		/* internal error */
+		elog(ERROR, "must be fired for row");
+	if (!TRIGGER_FIRED_BEFORE(trigdata->tg_event))
+		/* internal error */
+		elog(ERROR, "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, "cannot process DELETE events");
+
+	rel = trigdata->tg_relation;
+	relname = SPI_getrelname(rel);
+
+	trigger = trigdata->tg_trigger;
+
+	nargs = trigger->tgnargs;
+	if (nargs <= 0 || nargs % 2 != 0)
+		/* internal error */
+		elog(ERROR, "autoinc (%s): even number gt 0 of arguments was expected", relname);
+
+	args = trigger->tgargs;
+	tupdesc = rel->rd_att;
+
+	chattrs = (int *) palloc(nargs / 2 * sizeof(int));
+	newvals = (Datum *) palloc(nargs / 2 * sizeof(Datum));
+	newnulls = (bool *) palloc(nargs / 2 * sizeof(bool));
+
+	for (i = 0; i < nargs;)
+	{
+		int			attnum = SPI_fnumber(tupdesc, args[i]);
+		int32		val;
+		Datum		seqname;
+
+		if (attnum <= 0)
+			ereport(ERROR,
+					(errcode(ERRCODE_TRIGGERED_ACTION_EXCEPTION),
+					 errmsg("\"%s\" has no attribute \"%s\"",
+							relname, args[i])));
+
+		if (SPI_gettypeid(tupdesc, attnum) != INT4OID)
+			ereport(ERROR,
+					(errcode(ERRCODE_TRIGGERED_ACTION_EXCEPTION),
+					 errmsg("attribute \"%s\" of \"%s\" must be type INT4",
+							args[i], relname)));
+
+		val = DatumGetInt32(SPI_getbinval(rettuple, tupdesc, attnum, &isnull));
+
+		if (!isnull && val != 0)
+		{
+			i += 2;
+			continue;
+		}
+
+		i++;
+		chattrs[chnattrs] = attnum;
+		seqname = CStringGetTextDatum(args[i]);
+		newvals[chnattrs] = DirectFunctionCall1(nextval, seqname);
+		/* nextval now returns int64; coerce down to int32 */
+		newvals[chnattrs] = Int32GetDatum((int32) DatumGetInt64(newvals[chnattrs]));
+		if (DatumGetInt32(newvals[chnattrs]) == 0)
+		{
+			newvals[chnattrs] = DirectFunctionCall1(nextval, seqname);
+			newvals[chnattrs] = Int32GetDatum((int32) DatumGetInt64(newvals[chnattrs]));
+		}
+		newnulls[chnattrs] = false;
+		pfree(DatumGetTextPP(seqname));
+		chnattrs++;
+		i++;
+	}
+
+	if (chnattrs > 0)
+	{
+		rettuple = heap_modify_tuple_by_cols(rettuple, tupdesc,
+											 chnattrs, chattrs,
+											 newvals, newnulls);
+	}
+
+	pfree(relname);
+	pfree(chattrs);
+	pfree(newvals);
+	pfree(newnulls);
+
+	return PointerGetDatum(rettuple);
+}