add test_oldestXid to check value after node restart

test_runner/batch_others/test_oldestXid.py

@@ -0,0 +1,51 @@
+import pytest
+import getpass
+import psycopg2
+import time
+import os
+
+pytest_plugins = ("fixtures.zenith_fixtures")
+
+#
+# Test pg_control values after recreating a postgres instance
+#
+def test_oldestxid(zenith_cli, pageserver, postgres, pg_bin, repo_dir):
+    zenith_cli.run(["branch", "test_oldestxid", "empty"]);
+
+    pg = postgres.create_start('test_oldestxid')
+    print("postgres is running on 'test_oldestxid' branch")
+
+    pg_conn = psycopg2.connect(pg.connstr());
+    pg_conn.set_isolation_level(psycopg2.extensions.ISOLATION_LEVEL_AUTOCOMMIT)
+    cur = pg_conn.cursor()
+
+    # Create table, and insert a row
+    cur.execute('CREATE TABLE foo (t text)');
+    cur.execute("INSERT INTO foo VALUES ('bar')");
+
+    cur.execute('checkpoint')
+    cur.execute('SELECT oldest_xid FROM pg_control_checkpoint();')
+    oldest_xid = cur.fetchone()[0]
+
+    # Stop, and destroy the Postgres instance. Then recreate and restart it.
+    pg_conn.close();
+    pg.stop();
+
+    # capture old pg_controldata output for debugging purposes
+    pgdatadir = os.path.join(repo_dir, 'pgdatadirs/test_oldestxid')
+    pg_bin.run_capture(['pg_controldata', pgdatadir])
+
+    pg.destroy();
+    pg.create_start('test_oldestxid');
+    pg_conn = psycopg2.connect(pg.connstr());
+    pg_conn.set_isolation_level(psycopg2.extensions.ISOLATION_LEVEL_AUTOCOMMIT)
+    cur = pg_conn.cursor()
+
+    cur.execute('SELECT oldest_xid FROM pg_control_checkpoint();')
+    oldest_xid_new = cur.fetchone()[0]
+
+    assert(oldest_xid_new == oldest_xid)
+
+    # capture new pg_controldata output for debugging purposes
+    pgdatadir = os.path.join(repo_dir, 'pgdatadirs/test_oldestxid')
+    pg_bin.run_capture(['pg_controldata', pgdatadir])