Support automatically-updatable views.

This patch makes "simple" views automatically updatable, without the need
to create either INSTEAD OF triggers or INSTEAD rules.  "Simple" views
are those classified as updatable according to SQL-92 rules.  The rewriter
transforms INSERT/UPDATE/DELETE commands on such views directly into an
equivalent command on the underlying table, which will generally have
noticeably better performance than is possible with either triggers or
user-written rules.  A view that has INSTEAD OF triggers or INSTEAD rules
continues to operate the same as before.

For the moment, security_barrier views are not considered simple.
Also, we do not support WITH CHECK OPTION.  These features may be
added in future.

Dean Rasheed, reviewed by Amit Kapila

1 files changed, 31 insertions, 0 deletions

diff --git a/src/backend/utils/adt/misc.c b/src/backend/utils/adt/misc.c
index cd20b838416..407946715e2 100644
--- a/src/backend/utils/adt/misc.c
+++ b/src/backend/utils/adt/misc.c
@@ -28,6 +28,7 @@
 #include "miscadmin.h"
 #include "parser/keywords.h"
 #include "postmaster/syslogger.h"
+#include "rewrite/rewriteHandler.h"
 #include "storage/fd.h"
 #include "storage/pmsignal.h"
 #include "storage/proc.h"
@@ -523,3 +524,33 @@ pg_collation_for(PG_FUNCTION_ARGS)
 		PG_RETURN_NULL();
 	PG_RETURN_TEXT_P(cstring_to_text(generate_collation_name(collid)));
 }
+
+
+/*
+ * information_schema support functions
+ *
+ * Test whether a view (identified by pg_class OID) is insertable-into or
+ * updatable.  The latter requires delete capability too.  This is an
+ * artifact of the way the SQL standard defines the information_schema views:
+ * if we defined separate functions for update and delete, we'd double the
+ * work required to compute the view columns.
+ *
+ * These rely on relation_is_updatable(), which is in rewriteHandler.c.
+ */
+Datum
+pg_view_is_insertable(PG_FUNCTION_ARGS)
+{
+	Oid			viewoid = PG_GETARG_OID(0);
+	int			req_events = (1 << CMD_INSERT);
+
+	PG_RETURN_BOOL(relation_is_updatable(viewoid, req_events));
+}
+
+Datum
+pg_view_is_updatable(PG_FUNCTION_ARGS)
+{
+	Oid			viewoid = PG_GETARG_OID(0);
+	int			req_events = (1 << CMD_UPDATE) | (1 << CMD_DELETE);
+
+	PG_RETURN_BOOL(relation_is_updatable(viewoid, req_events));
+}