commit b31d587d71f75115b02dd1bf6230a56722c67832
Author: Ian Barwick <ian@2ndquadrant.com>
Date:   Wed Sep 9 14:37:40 2020 +0900

    test for standby row visibility

diff --git a/src/test/recovery/Makefile b/src/test/recovery/Makefile
index fa8e031526..2d9a9701fc 100644
--- a/src/test/recovery/Makefile
+++ b/src/test/recovery/Makefile
@@ -9,7 +9,7 @@
 #
 #-------------------------------------------------------------------------

-EXTRA_INSTALL=contrib/test_decoding
+EXTRA_INSTALL=contrib/test_decoding contrib/dblink

 subdir = src/test/recovery
 top_builddir = ../../..
diff --git a/src/test/recovery/t/021_row_visibility.pl b/src/test/recovery/t/021_row_visibility.pl
new file mode 100644
index 0000000000..5f591d131e
--- /dev/null
+++ b/src/test/recovery/t/021_row_visibility.pl
@@ -0,0 +1,84 @@
+# Checks that a standby session can see all expected rows
+use strict;
+use warnings;
+
+use PostgresNode;
+use TestLib;
+use Test::More tests => 1;
+
+# Initialize primary node
+my $node_primary = get_new_node('primary');
+$node_primary->init(allows_streaming => 1);
+$node_primary->start;
+
+$node_primary->safe_psql('postgres',
+	'CREATE EXTENSION dblink');
+
+
+# Add an arbitrary table
+$node_primary->safe_psql('postgres',
+	'CREATE TABLE public.foo (id INT)');
+
+# Take backup
+my $backup_name = 'my_backup';
+$node_primary->backup($backup_name);
+
+# Create streaming standby from backup
+my $node_standby = get_new_node('standby');
+$node_standby->init_from_backup($node_primary, $backup_name,
+	has_streaming => 1);
+$node_standby->start;
+
+sleep(5);
+# Check row visibility in an existing standby session
+
+my ($res, $stdout, $stderr) = $node_standby->psql(
+    'postgres',
+    sprintf(
+        <<'EO_SQL',
+DO $$
+  DECLARE
+    primary_lsn pg_lsn;
+    insert_xmin xid;
+    standby_rec RECORD;
+  BEGIN
+    SELECT INTO primary_lsn, insert_xmin
+           t1.primary_lsn, t1.xmin
+           FROM dblink(
+              'host=%s port=%i dbname=postgres',
+              'INSERT INTO public.foo VALUES (1) RETURNING pg_catalog.pg_current_wal_lsn(), xmin'
+           ) AS t1(primary_lsn pg_lsn, xmin xid);
+
+    LOOP
+      EXIT WHEN pg_catalog.pg_last_wal_replay_lsn() > primary_lsn;
+    END LOOP;
+
+    SELECT INTO standby_rec
+           id
+      FROM public.foo
+     WHERE id = 1 AND xmin = insert_xmin;
+
+    IF FOUND
+      THEN
+        RAISE NOTICE 'row found';
+      ELSE
+        RAISE NOTICE 'row not found';
+    END IF;
+
+  END;
+$$;
+EO_SQL
+        $node_primary->host,
+        $node_primary->port,
+    ),
+);
+
+
+like (
+    $stderr,
+    qr/row found/,
+    'check that inserted row is visible on the standby',
+);
+
+$node_primary->stop;
+$node_standby->stop;