Add an interface to lookup a type by its corresponding relation id.

This will be used by FDW and probably should have existed prior.

Author: James William Pye

src/tupledesc.c

@@ -628,6 +628,10 @@ tupd_item(PyObj self, Py_ssize_t i)
 		pg_att_nulls[Anum_pg_attribute_attacl-1] = true;
 #endif
 
+#ifdef Anum_pg_attribute_attoptions
+		pg_att_nulls[Anum_pg_attribute_attoptions-1] = true;
+#endif
+
 		/*
 		 * XXX: Need a better way to construct a pg_attribute Datum.
 		 */

src/type/type.c

@@ -42,6 +42,7 @@
 #include "pypg/python.h"
 #include "pypg/postgres.h"
 #include "pypg/extension.h"
+#include "pypg/pl.h"
 #include "pypg/error.h"
 #include "pypg/tupledesc.h"
 #include "pypg/type/type.h"
@@ -1874,7 +1875,27 @@ type_check_constraints(PyObj self, PyObj ob)
 	return(Py_None);
 }
 
+static PyObj
+type_from_relation_id(PyObj subtype, PyObj oid_ob)
+{
+	Oid oid;
+
+	if (Oid_FromPyObject(oid_ob, &oid))
+		return(NULL);
+
+	return(PyPgType_FromTableOid(oid));
+}
+
 static PyMethodDef PyPgType_Methods[] = {
+	{"from_relation_id", (PyCFunction) type_from_relation_id, METH_O|METH_CLASS,
+		PyDoc_STR(
+"Postgres.Type.from_relation_id(oid)\n\n"
+":param oid: The Oid of the relation to lookup.\n"
+":type oid: An object suitable for use as an :py:class:`Postgres.types.oid`.\n"
+":returns: The corresponding Postgres.Type instance.\n"
+":rtype: :py:class:`Postgres.Type`\n\n"
+"Construct a type instance from the given table Oid."
+)},
 	{"typinput", (PyCFunction) PyPgType_typinput_method, METH_VARARGS,
 	PyDoc_STR("create an instance of the type using the given string data")},
 	{"typoutput", (PyCFunction) PyPgType_typoutput, METH_O,

test/expected/pg_9_1/type.out

@@ -152,3 +152,20 @@ Traceback (most recent call last):
  Postgres.Exception
 
 [public.check_typisdefined(oid)]
+-- Lookup the Type using the table's oid
+DROP TABLE IF EXISTS explicit_lookup;
+NOTICE:  table "explicit_lookup" does not exist, skipping
+CREATE TABLE explicit_lookup (i int, t text);
+CREATE OR REPLACE FUNCTION lookup_tables_type(oid) RETURNS TEXT LANGUAGE python AS
+$$
+import Postgres
+
+def main(oid):
+	return str(list(Postgres.Type.from_relation_id(oid).descriptor))
+$$;
+SELECT lookup_tables_type('explicit_lookup'::regclass);
+                                                          lookup_tables_type                                                          
+--------------------------------------------------------------------------------------------------------------------------------------
+ [pg_attribute('(44800,i,23,-1,4,1,0,0,-1,t,p,i,f,f,f,t,0,0,,)'), pg_attribute('(44800,t,25,-1,-1,2,0,-1,-1,f,x,i,f,f,f,t,0,100,,)')]
+(1 row)
+

test/sql/type.sql

@@ -119,3 +119,16 @@ def main(oid):
 $python$;
 
 SELECT check_typisdefined((SELECT oid FROM pg_type WHERE typname = 'shell_check' LIMIT 1));
+
+-- Lookup the Type using the table's oid
+DROP TABLE IF EXISTS explicit_lookup;
+CREATE TABLE explicit_lookup (i int, t text);
+CREATE OR REPLACE FUNCTION lookup_tables_type(oid) RETURNS TEXT LANGUAGE python AS
+$$
+import Postgres
+
+def main(oid):
+	return str(list(Postgres.Type.from_relation_id(oid).descriptor))
+$$;
+
+SELECT lookup_tables_type('explicit_lookup'::regclass);