Add test for combocid handling

test_runner/regress/test_combocid.py

@@ -0,0 +1,37 @@
+from fixtures.neon_fixtures import NeonEnvBuilder
+
+
+def test_combocid(neon_env_builder: NeonEnvBuilder):
+    env = neon_env_builder.init_start()
+    endpoint = env.endpoints.create_start("main")
+
+    conn = endpoint.connect()
+    cur = conn.cursor()
+    n_records = 100000
+
+    cur.execute("create table t(id integer, val integer)")
+    cur.execute(f"insert into t values (generate_series(1,{n_records}), 0)")
+
+    cur.execute("begin")
+
+    cur.execute("update t set val=val+1")
+    assert cur.rowcount == n_records
+    cur.execute("update t set val=val+1")
+    assert cur.rowcount == n_records
+    cur.execute("update t set val=val+1")
+    assert cur.rowcount == n_records
+
+    cur.execute("delete from t")
+    assert cur.rowcount == n_records
+    cur.execute("delete from t")
+    assert cur.rowcount == 0
+
+    cur.execute(f"insert into t values (generate_series(1,{n_records}), 0)")
+    cur.execute("update t set val=val+1")
+    assert cur.rowcount == n_records
+    cur.execute("update t set val=val+1")
+    assert cur.rowcount == n_records
+    cur.execute("update t set val=val+1")
+    assert cur.rowcount == n_records
+
+    cur.execute("rollback")