Extend object-access hook machinery to support post-alter events.

This also slightly widens the scope of what we support in terms of
post-create events.

KaiGai Kohei, with a few changes, mostly to the comments, by me

src/include/catalog/heap.h

@@ -96,9 +96,11 @@ extern List *AddRelationNewConstraints(Relation rel,
 						  List *newColDefaults,
 						  List *newConstraints,
 						  bool allow_merge,
-						  bool is_local);
+						  bool is_local,
+						  bool is_internal);
 
-extern void StoreAttrDefault(Relation rel, AttrNumber attnum, Node *expr);
+extern void StoreAttrDefault(Relation rel, AttrNumber attnum,
+							 Node *expr, bool is_internal);
 
 extern Node *cookDefault(ParseState *pstate,
 			Node *raw_default,

src/include/catalog/index.h

@@ -72,7 +72,8 @@ extern void index_constraint_create(Relation heapRelation,
 						bool mark_as_primary,
 						bool update_pgindex,
 						bool remove_old_dependencies,
-						bool allow_system_table_mods);
+						bool allow_system_table_mods,
+						bool is_internal);
 
 extern void index_drop(Oid indexId, bool concurrent);
 

src/include/catalog/objectaccess.h

@@ -22,6 +22,11 @@
  * OAT_DROP should be invoked just before deletion of objects; typically
  * deleteOneObject(). Its arguments are packed within ObjectAccessDrop.
  *
+ * OAT_POST_ALTER should be invoked just after the object is altered,
+ * but before the command counter is incremented.  An extension using the
+ * hook can use SnapshotNow and SnapshotSelf to get the old and new
+ * versions of the tuple.
+ *
  * Other types may be added in the future.
  */
 typedef enum ObjectAccessType
@@ -57,20 +62,51 @@ typedef struct
 } ObjectAccessDrop;
 
 /*
- * Hook, and a macro to invoke it.
+ * Arguments of OAT_POST_ALTER event
  */
+typedef struct
+{
+	/*
+	 * This identifier is used when system catalog takes two IDs
+	 * to identify a particular tuple of the catalog.
+	 * It is only used when the caller want to identify an entry
+	 * of pg_inherits, pg_db_role_setting or pg_user_mapping.
+	 * Elsewhere, InvalidOid should be set.
+	 */
+	Oid			auxiliary_id;
+
+	/*
+	 * If this flag is set, the user hasn't requested that the object be
+	 * altered, but we're doing it anyway for some internal reason.
+	 * Permissions-checking hooks may want to skip checks if, say, we're
+	 * alter the constraints of a temporary heap during CLUSTER.
+	 */
+	bool		is_internal;
+} ObjectAccessPostAlter;
+
+/* Plugin provides a hook function matching this signature. */
 typedef void (*object_access_hook_type) (ObjectAccessType access,
 													 Oid classId,
 													 Oid objectId,
 													 int subId,
 													 void *arg);
 
+/* Plugin sets this variable to a suitable hook function. */
 extern PGDLLIMPORT object_access_hook_type object_access_hook;
 
+/* Core code uses these functions to call the hook (see macros below). */
 extern void RunObjectPostCreateHook(Oid classId, Oid objectId, int subId,
 									bool is_internal);
 extern void RunObjectDropHook(Oid classId, Oid objectId, int subId,
 							  int dropflags);
+extern void RunObjectPostAlterHook(Oid classId, Oid objectId, int subId,
+								   Oid auxiliaryId, bool is_internal);
+
+/*
+ * The following macros are wrappers around the functions above; these should
+ * normally be used to invoke the hook in lieu of calling the above functions
+ * directly.
+ */
 
 #define InvokeObjectPostCreateHook(classId,objectId,subId)			\
 	InvokeObjectPostCreateHookArg((classId),(objectId),(subId),false)
@@ -90,4 +126,15 @@ extern void RunObjectDropHook(Oid classId, Oid objectId, int subId,
 							  (dropflags));							\
 	} while(0)
 
+#define InvokeObjectPostAlterHook(classId,objectId,subId)			\
+	InvokeObjectPostAlterHookArg((classId),(objectId),(subId),		\
+								 InvalidOid,false)
+#define InvokeObjectPostAlterHookArg(classId,objectId,subId,		\
+									 auxiliaryId,is_internal)		\
+	do {															\
+		if (object_access_hook)										\
+			RunObjectPostAlterHook((classId),(objectId),(subId),	\
+								   (auxiliaryId),(is_internal));	\
+	} while(0)
+
 #endif   /* OBJECTACCESS_H */

src/include/catalog/pg_constraint.h

@@ -232,7 +232,8 @@ extern Oid CreateConstraintEntry(const char *constraintName,
 					  const char *conSrc,
 					  bool conIsLocal,
 					  int conInhCount,
-					  bool conNoInherit);
+					  bool conNoInherit,
+					  bool is_internal);
 
 extern void RemoveConstraintById(Oid conId);
 extern void RenameConstraintById(Oid conId, const char *newname);

src/include/commands/cluster.h

@@ -23,13 +23,14 @@ extern void cluster_rel(Oid tableOid, Oid indexOid, bool recheck,
 			bool verbose, int freeze_min_age, int freeze_table_age);
 extern void check_index_is_clusterable(Relation OldHeap, Oid indexOid,
 						   bool recheck, LOCKMODE lockmode);
-extern void mark_index_clustered(Relation rel, Oid indexOid);
+extern void mark_index_clustered(Relation rel, Oid indexOid, bool is_internal);
 
 extern Oid	make_new_heap(Oid OIDOldHeap, Oid NewTableSpace);
 extern void finish_heap_swap(Oid OIDOldHeap, Oid OIDNewHeap,
 				 bool is_system_catalog,
 				 bool swap_toast_by_content,
 				 bool check_constraints,
+				 bool is_internal,
 				 TransactionId frozenXid,
 				 MultiXactId frozenMulti);
 

src/include/commands/tablecmds.h

@@ -58,7 +58,7 @@ extern Oid RenameConstraint(RenameStmt *stmt);
 extern Oid RenameRelation(RenameStmt *stmt);
 
 extern void RenameRelationInternal(Oid myrelid,
-					   const char *newrelname);
+					   const char *newrelname, bool is_internal);
 
 extern void find_composite_type_dependencies(Oid typeOid,
 								 Relation origRelation,