From ae025a15988f5491903cd3a2075f308c2773f711 Mon Sep 17 00:00:00 2001
From: Heikki Linnakangas <heikki.linnakangas@iki.fi>
Date: Fri, 26 Aug 2016 16:33:57 +0300
Subject: Support OID system column in postgres_fdw.

You can use ALTER FOREIGN TABLE SET WITH OIDS on a foreign table, but the
oid column read out as zeros, because the postgres_fdw didn't know about
it. Teach postgres_fdw how to fetch it.

Etsuro Fujita, with an additional test case by me.

Discussion: <56E90A76.5000503@lab.ntt.co.jp>
---
 contrib/postgres_fdw/postgres_fdw.c | 28 ++++++++++++++++++++++++++--
 1 file changed, 26 insertions(+), 2 deletions(-)

(limited to 'contrib/postgres_fdw/postgres_fdw.c')

diff --git a/contrib/postgres_fdw/postgres_fdw.c b/contrib/postgres_fdw/postgres_fdw.c
index bfd81c46c86..b92f29958f3 100644
--- a/contrib/postgres_fdw/postgres_fdw.c
+++ b/contrib/postgres_fdw/postgres_fdw.c
@@ -4374,6 +4374,7 @@ make_tuple_from_result_row(PGresult *res,
 	Datum	   *values;
 	bool	   *nulls;
 	ItemPointer ctid = NULL;
+	Oid			oid = InvalidOid;
 	ConversionLocation errpos;
 	ErrorContextCallback errcallback;
 	MemoryContext oldcontext;
@@ -4431,7 +4432,11 @@ make_tuple_from_result_row(PGresult *res,
 		else
 			valstr = PQgetvalue(res, row, j);
 
-		/* convert value to internal representation */
+		/*
+		 * convert value to internal representation
+		 *
+		 * Note: we ignore system columns other than ctid and oid in result
+		 */
 		errpos.cur_attno = i;
 		if (i > 0)
 		{
@@ -4446,7 +4451,7 @@ make_tuple_from_result_row(PGresult *res,
 		}
 		else if (i == SelfItemPointerAttributeNumber)
 		{
-			/* ctid --- note we ignore any other system column in result */
+			/* ctid */
 			if (valstr != NULL)
 			{
 				Datum		datum;
@@ -4455,6 +4460,17 @@ make_tuple_from_result_row(PGresult *res,
 				ctid = (ItemPointer) DatumGetPointer(datum);
 			}
 		}
+		else if (i == ObjectIdAttributeNumber)
+		{
+			/* oid */
+			if (valstr != NULL)
+			{
+				Datum		datum;
+
+				datum = DirectFunctionCall1(oidin, CStringGetDatum(valstr));
+				oid = DatumGetObjectId(datum);
+			}
+		}
 		errpos.cur_attno = 0;
 
 		j++;
@@ -4498,6 +4514,12 @@ make_tuple_from_result_row(PGresult *res,
 	HeapTupleHeaderSetXmin(tuple->t_data, InvalidTransactionId);
 	HeapTupleHeaderSetCmin(tuple->t_data, InvalidTransactionId);
 
+	/*
+	 * If we have an OID to return, install it.
+	 */
+	if (OidIsValid(oid))
+		HeapTupleSetOid(tuple, oid);
+
 	/* Clean up */
 	MemoryContextReset(temp_context);
 
@@ -4525,6 +4547,8 @@ conversion_error_callback(void *arg)
 			attname = NameStr(tupdesc->attrs[errpos->cur_attno - 1]->attname);
 		else if (errpos->cur_attno == SelfItemPointerAttributeNumber)
 			attname = "ctid";
+		else if (errpos->cur_attno == ObjectIdAttributeNumber)
+			attname = "oid";
 
 		relname = RelationGetRelationName(errpos->rel);
 	}
-- 
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