file_fdw: Fix for generated columns

Since file_fdw uses COPY internally, but COPY doesn't allow listing
generated columns in its column list, we need to make sure that we
don't add generated columns to the column lists internally generated
by file_fdw.
Reported-by: Erik Rijkers <er@xs4all.nl>

contrib/file_fdw/file_fdw.c

@@ -922,6 +922,10 @@ check_selective_binary_conversion(RelOptInfo *baserel,
 			/* Skip dropped attributes (probably shouldn't see any here). */
 			if (attr->attisdropped)
 				continue;
+			/* Skip generated columns (COPY won't accept them in the column
+			 * list) */
+			if (attr->attgenerated)
+				continue;
 			*columns = lappend(*columns, makeString(pstrdup(attname)));
 		}
 	}

contrib/file_fdw/input/file_fdw.source

@@ -189,6 +189,12 @@ SELECT tableoid::regclass, * FROM p1;
 SELECT tableoid::regclass, * FROM p2;
 DROP TABLE pt;
 
+-- generated column tests
+CREATE FOREIGN TABLE gft1 (a int, b text, c text GENERATED ALWAYS AS ('foo') STORED) SERVER file_server
+OPTIONS (format 'csv', filename '@abs_srcdir@/data/list1.csv', delimiter ',');
+SELECT a, c FROM gft1;
+DROP FOREIGN TABLE gft1;
+
 -- privilege tests
 SET ROLE regress_file_fdw_superuser;
 SELECT * FROM agg_text ORDER BY a;

contrib/file_fdw/output/file_fdw.source

@@ -375,6 +375,17 @@ SELECT tableoid::regclass, * FROM p2;
 (3 rows)
 
 DROP TABLE pt;
+-- generated column tests
+CREATE FOREIGN TABLE gft1 (a int, b text, c text GENERATED ALWAYS AS ('foo') STORED) SERVER file_server
+OPTIONS (format 'csv', filename '@abs_srcdir@/data/list1.csv', delimiter ',');
+SELECT a, c FROM gft1;
+ a |   c    
+---+--------
+ 1 | _null_
+ 1 | _null_
+(2 rows)
+
+DROP FOREIGN TABLE gft1;
 -- privilege tests
 SET ROLE regress_file_fdw_superuser;
 SELECT * FROM agg_text ORDER BY a;