Add SQL-callable pg_get_object_address

This allows access to get_object_address from SQL, which is useful to
obtain OID addressing information from data equivalent to that emitted
by the parser.  This is necessary infrastructure of a project to let
replication systems propagate object dropping events to remote servers,
where the schema might be different than the server originating the
DROP.

This patch also adds support for OBJECT_DEFAULT to get_object_address;
that is, it is now possible to refer to a column's default value.

Catalog version bumped due to the new function.

Reviewed by Stephen Frost, Heikki Linnakangas, Robert Haas, Andres
Freund, Abhijit Menon-Sen, Adam Brightwell.

Author: alvherre

src/backend/catalog/objectaddress.c

@@ -1055,6 +1055,7 @@ EventTriggerSupportsObjectType(ObjectType obtype)
 		case OBJECT_COLUMN:
 		case OBJECT_COLLATION:
 		case OBJECT_CONVERSION:
+		case OBJECT_DEFAULT:
 		case OBJECT_DOMAIN:
 		case OBJECT_DOMCONSTRAINT:
 		case OBJECT_EXTENSION:

src/backend/commands/event_trigger.c

@@ -705,13 +705,11 @@ pts_error_callback(void *arg)
 /*
  * Given a string that is supposed to be a SQL-compatible type declaration,
  * such as "int4" or "integer" or "character varying(32)", parse
- * the string and convert it to a type OID and type modifier.
- * If missing_ok is true, InvalidOid is returned rather than raising an error
- * when the type name is not found.
+ * the string and return the result as a TypeName.
+ * If the string cannot be parsed as a type, an error is raised.
  */
-void
-parseTypeString(const char *str, Oid *typeid_p, int32 *typmod_p,
-				bool missing_ok)
+TypeName *
+typeStringToTypeName(const char *str)
 {
 	StringInfoData buf;
 	List	   *raw_parsetree_list;
@@ -720,7 +718,6 @@ parseTypeString(const char *str, Oid *typeid_p, int32 *typmod_p,
 	TypeCast   *typecast;
 	TypeName   *typeName;
 	ErrorContextCallback ptserrcontext;
-	Type		tup;
 
 	/* make sure we give useful error for empty input */
 	if (strspn(str, " \t\n\r\f") == strlen(str))
@@ -779,13 +776,39 @@ parseTypeString(const char *str, Oid *typeid_p, int32 *typmod_p,
 		typecast->arg == NULL ||
 		!IsA(typecast->arg, A_Const))
 		goto fail;
+
 	typeName = typecast->typeName;
 	if (typeName == NULL ||
 		!IsA(typeName, TypeName))
 		goto fail;
 	if (typeName->setof)
 		goto fail;
 
+	pfree(buf.data);
+
+	return typeName;
+
+fail:
+	ereport(ERROR,
+			(errcode(ERRCODE_SYNTAX_ERROR),
+			 errmsg("invalid type name \"%s\"", str)));
+}
+
+/*
+ * Given a string that is supposed to be a SQL-compatible type declaration,
+ * such as "int4" or "integer" or "character varying(32)", parse
+ * the string and convert it to a type OID and type modifier.
+ * If missing_ok is true, InvalidOid is returned rather than raising an error
+ * when the type name is not found.
+ */
+void
+parseTypeString(const char *str, Oid *typeid_p, int32 *typmod_p, bool missing_ok)
+{
+	TypeName   *typeName;
+	Type		tup;
+
+	typeName = typeStringToTypeName(str);
+
 	tup = LookupTypeName(NULL, typeName, typmod_p, missing_ok);
 	if (tup == NULL)
 	{
@@ -808,13 +831,4 @@ parseTypeString(const char *str, Oid *typeid_p, int32 *typmod_p,
 		*typeid_p = HeapTupleGetOid(tup);
 		ReleaseSysCache(tup);
 	}
-
-	pfree(buf.data);
-
-	return;
-
-fail:
-	ereport(ERROR,
-			(errcode(ERRCODE_SYNTAX_ERROR),
-			 errmsg("invalid type name \"%s\"", str)));
 }

src/backend/parser/parse_type.c

@@ -53,6 +53,6 @@
  */
 
 /*							yyyymmddN */
-#define CATALOG_VERSION_NO	201412232
+#define CATALOG_VERSION_NO	201412233
 
 #endif

src/include/catalog/catversion.h

@@ -55,6 +55,7 @@ extern HeapTuple get_catalog_object_by_oid(Relation catalog,
 extern char *getObjectDescription(const ObjectAddress *object);
 extern char *getObjectDescriptionOids(Oid classid, Oid objid);
 
+extern int read_objtype_from_string(const char *objtype);
 extern char *getObjectTypeDescription(const ObjectAddress *object);
 extern char *getObjectIdentity(const ObjectAddress *address);
 

src/include/catalog/objectaddress.h

@@ -3036,6 +3036,9 @@ DESCR("get identification of SQL object");
 DATA(insert OID = 3839 (  pg_identify_object		PGNSP PGUID 12 1 0 0 0 f f f f t f s 3 0 2249 "26 26 23" "{26,26,23,25,25,25,25}" "{i,i,i,o,o,o,o}" "{classid,objid,subobjid,type,schema,name,identity}" _null_ pg_identify_object _null_ _null_ _null_ ));
 DESCR("get machine-parseable identification of SQL object");
 
+DATA(insert OID = 3954 (  pg_get_object_address    PGNSP PGUID 12 1 0 0 0 f f f f t f s 3 0 2249 "25 1009 1009" "{25,1009,1009,26,26,23}" "{i,i,i,o,o,o}" "{type,name,args,classid,objid,subobjid}" _null_ pg_get_object_address _null_ _null_ _null_ ));
+DESCR("get OID-based object address from name/args arrays");
+
 DATA(insert OID = 2079 (  pg_table_is_visible		PGNSP PGUID 12 10 0 0 0 f f f f t f s 1 0 16 "26" _null_ _null_ _null_ _null_ pg_table_is_visible _null_ _null_ _null_ ));
 DESCR("is table visible in search path?");
 DATA(insert OID = 2080 (  pg_type_is_visible		PGNSP PGUID 12 10 0 0 0 f f f f t f s 1 0 16 "26" _null_ _null_ _null_ _null_ pg_type_is_visible _null_ _null_ _null_ ));

src/include/catalog/pg_proc.h

@@ -1185,6 +1185,7 @@ typedef enum ObjectType
 	OBJECT_COLLATION,
 	OBJECT_CONVERSION,
 	OBJECT_DATABASE,
+	OBJECT_DEFAULT,
 	OBJECT_DOMAIN,
 	OBJECT_DOMCONSTRAINT,
 	OBJECT_EVENT_TRIGGER,

src/include/nodes/parsenodes.h

@@ -47,6 +47,7 @@ extern Datum stringTypeDatum(Type tp, char *string, int32 atttypmod);
 
 extern Oid	typeidTypeRelid(Oid type_id);
 
+extern TypeName *typeStringToTypeName(const char *str);
 extern void parseTypeString(const char *str, Oid *typeid_p, int32 *typmod_p, bool missing_ok);
 
 #define ISCOMPLEX(typeid) (typeidTypeRelid(typeid) != InvalidOid)

src/include/parser/parse_type.h

@@ -1201,6 +1201,9 @@ extern Datum pg_last_committed_xact(PG_FUNCTION_ARGS);
 extern Datum pg_describe_object(PG_FUNCTION_ARGS);
 extern Datum pg_identify_object(PG_FUNCTION_ARGS);
 
+/* catalog/objectaddress.c */
+extern Datum pg_get_object_address(PG_FUNCTION_ARGS);
+
 /* commands/constraint.c */
 extern Datum unique_key_recheck(PG_FUNCTION_ARGS);