1 files changed, 111 insertions, 0 deletions
diff --git a/contrib/lo/lo.c b/contrib/lo/lo.c
new file mode 100644
index 0000000..457be26
--- /dev/null
+++ b/contrib/lo/lo.c
@@ -0,0 +1,111 @@
+/*
+ *	PostgreSQL definitions for managed Large Objects.
+ *
+ *	contrib/lo/lo.c
+ *
+ */
+
+#include "postgres.h"
+
+#include "commands/trigger.h"
+#include "executor/spi.h"
+#include "utils/builtins.h"
+#include "utils/rel.h"
+
+PG_MODULE_MAGIC;
+
+
+/*
+ * This is the trigger that protects us from orphaned large objects
+ */
+PG_FUNCTION_INFO_V1(lo_manage);
+
+Datum
+lo_manage(PG_FUNCTION_ARGS)
+{
+	TriggerData *trigdata = (TriggerData *) fcinfo->context;
+	int			attnum;			/* attribute number to monitor	*/
+	char	  **args;			/* Args containing attr name	*/
+	TupleDesc	tupdesc;		/* Tuple Descriptor				*/
+	HeapTuple	rettuple;		/* Tuple to be returned			*/
+	bool		isdelete;		/* are we deleting?				*/
+	HeapTuple	newtuple;		/* The new value for tuple		*/
+	HeapTuple	trigtuple;		/* The original value of tuple	*/
+
+	if (!CALLED_AS_TRIGGER(fcinfo)) /* internal error */
+		elog(ERROR, "lo_manage: not fired by trigger manager");
+
+	if (!TRIGGER_FIRED_FOR_ROW(trigdata->tg_event)) /* internal error */
+		elog(ERROR, "%s: must be fired for row",
+			 trigdata->tg_trigger->tgname);
+
+	/*
+	 * Fetch some values from trigdata
+	 */
+	newtuple = trigdata->tg_newtuple;
+	trigtuple = trigdata->tg_trigtuple;
+	tupdesc = trigdata->tg_relation->rd_att;
+	args = trigdata->tg_trigger->tgargs;
+
+	if (args == NULL)			/* internal error */
+		elog(ERROR, "%s: no column name provided in the trigger definition",
+			 trigdata->tg_trigger->tgname);
+
+	/* tuple to return to Executor */
+	if (TRIGGER_FIRED_BY_UPDATE(trigdata->tg_event))
+		rettuple = newtuple;
+	else
+		rettuple = trigtuple;
+
+	/* Are we deleting the row? */
+	isdelete = TRIGGER_FIRED_BY_DELETE(trigdata->tg_event);
+
+	/* Get the column we're interested in */
+	attnum = SPI_fnumber(tupdesc, args[0]);
+
+	if (attnum <= 0)
+		elog(ERROR, "%s: column \"%s\" does not exist",
+			 trigdata->tg_trigger->tgname, args[0]);
+
+	/*
+	 * Handle updates
+	 *
+	 * Here, if the value of the monitored attribute changes, then the large
+	 * object associated with the original value is unlinked.
+	 */
+	if (newtuple != NULL &&
+		bms_is_member(attnum - FirstLowInvalidHeapAttributeNumber, trigdata->tg_updatedcols))
+	{
+		char	   *orig = SPI_getvalue(trigtuple, tupdesc, attnum);
+		char	   *newv = SPI_getvalue(newtuple, tupdesc, attnum);
+
+		if (orig != NULL && (newv == NULL || strcmp(orig, newv) != 0))
+			DirectFunctionCall1(be_lo_unlink,
+								ObjectIdGetDatum(atooid(orig)));
+
+		if (newv)
+			pfree(newv);
+		if (orig)
+			pfree(orig);
+	}
+
+	/*
+	 * Handle deleting of rows
+	 *
+	 * Here, we unlink the large object associated with the managed attribute
+	 */
+	if (isdelete)
+	{
+		char	   *orig = SPI_getvalue(trigtuple, tupdesc, attnum);
+
+		if (orig != NULL)
+		{
+			DirectFunctionCall1(be_lo_unlink,
+								ObjectIdGetDatum(atooid(orig)));
+
+			pfree(orig);
+		}
+	}
+
+	return PointerGetDatum(rettuple);
+}