Enforce simple protocol on ReplicationConn

replication.go

@@ -163,6 +163,7 @@ func ReplicationConnect(config ConnConfig) (r *ReplicationConn, err error) {
 		config.RuntimeParams = make(map[string]string)
 	}
 	config.RuntimeParams["replication"] = "database"
+	config.PreferSimpleProtocol = true
 
 	c, err := Connect(config)
 	if err != nil {

replication_test.go

@@ -343,3 +343,28 @@ func TestStandbyStatusParsing(t *testing.T) {
 		t.Errorf("Unexpected write position %d", status.WalWritePosition)
 	}
 }
+
+func TestSimpleProtocolEnforcement(t *testing.T) {
+	if replicationConnConfig == nil {
+		t.Skip("Skipping due to undefined replicationConnConfig")
+	}
+
+	replicationConn := mustReplicationConnect(t, *replicationConnConfig)
+	defer closeReplicationConn(t, replicationConn)
+
+	query := "select count(*) from pg_replication_slots"
+
+	// Check that the simple query protocol is used by default
+	rows, err := replicationConn.Query(query)
+	if err != nil {
+		t.Fatalf("Query failed: %v", err)
+	}
+	rows.Close()
+
+	// Check that using the extended query protocol will fail
+	rows, err = replicationConn.QueryEx(context.Background(), query, &pgx.QueryExOptions{SimpleProtocol: false})
+	if err == nil {
+		t.Fatal("Query expected to fail.")
+	}
+	rows.Close()
+}