I add empty TableView with column resize policy set to TableView.UNCONSTRAINED_RESIZE_POLICY to Scene. When all columns are visible, there is no horizontal scroll bar (it's right), but when i resize main window and not all columns are visible, there is no horizontal scroll bar too, i think it shouldn't be so, and horizontal scroll bar should be visible.
If table is not empty there is horizontal scroll bar when not all columns are visible. If i remove all rows, horizontal scroll bar disappears.
Analog bug was in qt qml tableview and it was fixed.

Here is an example:

import java.util.ArrayList;

import javafx.application.Application;
import javafx.beans.property.SimpleBooleanProperty;
import javafx.beans.property.SimpleDoubleProperty;
import javafx.beans.property.SimpleIntegerProperty;
import javafx.beans.property.SimpleStringProperty;
import javafx.collections.FXCollections;
import javafx.collections.ObservableList;
import javafx.event.ActionEvent;
import javafx.event.EventHandler;
import javafx.geometry.Pos;
import javafx.scene.Scene;
import javafx.scene.control.Button;
import javafx.scene.control.SelectionMode;
import javafx.scene.control.TableColumn;
import javafx.scene.control.TableView;
import javafx.scene.control.TableColumn.SortType;
import javafx.scene.control.cell.PropertyValueFactory;
import javafx.scene.layout.ColumnConstraints;
import javafx.scene.layout.GridPane;
import javafx.scene.layout.HBox;
import javafx.scene.layout.Priority;
import javafx.scene.layout.RowConstraints;
import javafx.stage.Stage;
import javafx.util.Callback;

public class MainWindowFX extends Application {

@Override
public void start(Stage primaryStage) throws Exception {
primaryStage.setTitle("Hello World!");

Button b = new Button("Add");
Button b1 = new Button("Del");

final TableView<Test> table = new TableView<>();

table.setEditable(true);
table.setTableMenuButtonVisible(true);

final TableColumn<Test, Number> c1 = new TableColumn<>("ID");
c1.setCellValueFactory(new PropertyValueFactory<Test, Number>("id"));

final TableColumn<Test, String> c2 = new TableColumn<>("Name");
c2.setCellValueFactory(new PropertyValueFactory<Test, String>("name"));

TableColumn<Test, Number> c3 = new TableColumn<>("Price");
c3.setCellValueFactory(new PropertyValueFactory<Test, Number>("price"));

TableColumn<Test, Boolean> c4 = new TableColumn<>("Is");
c4.setCellValueFactory(new PropertyValueFactory<Test, Boolean>("is"));

table.setSortPolicy(new Callback<TableView<Test>, Boolean>() {
@Override
public Boolean call(TableView<Test> param) {
for (TableColumn<Test, ?> tc : param.getSortOrder()) {
if (tc == c2) {
return false;
}
}
return TableView.DEFAULT_SORT_POLICY.call(param);
}
});
table.getColumns().addAll(c1, c2, c3, c4);

final ObservableList<Test> data = FXCollections.observableList(new ArrayList<Test>());
table.setItems(data);

table.getSelectionModel().setSelectionMode(SelectionMode.SINGLE);

c1.setSortType(SortType.ASCENDING);
table.getSortOrder().add(c1);

b.setOnAction(new EventHandler<ActionEvent>() {
@Override
public void handle(ActionEvent event) {
int MAXN = 10;// 2000000;
ArrayList<Test> list = new ArrayList<>(MAXN);
for (int i = 0; i < MAXN; i++) {
Test tmp = new Test(i, Integer.toString(i), i, (i % 2 == 0) ? (false) : (true));
list.add(i, tmp);
}
data.addAll(list);
c1.setPrefWidth(100);

table.sort();
}
});
b1.setOnAction(new EventHandler<ActionEvent>() {
@Override
public void handle(ActionEvent event) {
table.getItems().remove(0);
}
});

GridPane root = new GridPane();
ColumnConstraints column1 = new ColumnConstraints();
column1.setHgrow(Priority.ALWAYS);
root.getColumnConstraints().addAll(column1);
RowConstraints row1 = new RowConstraints();
row1.setVgrow(Priority.ALWAYS);
root.getRowConstraints().addAll(row1);
root.add(table, 0, 0);

HBox h = new HBox();
h.setAlignment(Pos.CENTER_RIGHT);
h.getChildren().add(b);
h.getChildren().add(b1);
root.add(h, 0, 1);

primaryStage.setScene(new Scene(root, 500, 600));
primaryStage.show();
}

public static void main(String[] args) {
Application.launch(args);
}

public static class Test {
private final SimpleIntegerProperty id = new SimpleIntegerProperty(0);
private final SimpleStringProperty name = new SimpleStringProperty("");
private final SimpleDoubleProperty price = new SimpleDoubleProperty(0);
private final SimpleBooleanProperty is = new SimpleBooleanProperty(false);

private Test() {}

private Test(int id, String name, double price, boolean is) {
this.id.set(id);
this.name.set(name);
this.price.set(price);
this.is.set(is);
}

public int getId() {
return id.get();
}

public void setId(int id) {
this.id.set(id);
}

public String getName() {
return name.get();
}

public void setName(String name) {
this.name.set(name);
}

public double getPrice() {
return price.get();
}

public void setPrice(double price) {
this.price.set(price);
}

public boolean isIs() {
return is.get();
}

public void setIs(boolean is) {
this.is.set(is);
}
}
}

Resize window, so that not all columns are visible, there is no horizontal scroll bar, then click "add" button, and scroll bar will be shown.