cancel() is supported, but it does not support cancelling an in-progress
single-row insert.
cancel() supports stopping a long-running SELECT, UPDATE or DELETE, but only
between individual rows.
timbo wrote:
> I have a test case (below) where a long running db operation is
> launched in a thread, and a separate thread invokes cancel() on the
> executing Statement. The cancel() does not seem to have any effect,
> and does not throw an exception in the calling thread or the statement
> thread. The statement is in fact successfully committed to the db.
>
> Is Statement.cancel() really supported by h2?
>
> +++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++
> +++++++
> package persistence.perf;
>
> import java.sql.Connection;
> import java.sql.DriverManager;
> import java.sql.PreparedStatement;
> import java.sql.ResultSet;
> import java.sql.SQLException;
> import java.sql.Statement;
>
> public class CancelCreateTest extends Thread {
>
> protected PreparedStatement ps;
> protected boolean createDone = false;
>
> public void run() {
> longCreate();
> }
>
> private void longCreate() {
> System.out.println("" + System.currentTimeMillis() + " begin
> create");
> Connection conn = null;
> try {
> conn = getConnection();
> conn.setAutoCommit(false);
> ps = conn.prepareStatement("INSERT INTO RESOURCE (DATA)
> VALUES(?)");
> ps.setBytes(1, new byte[20000000]);
> ps.executeUpdate();
> conn.commit();
> System.out.println("" + System.currentTimeMillis()
> + " committed create");
> } catch (SQLException sqe) {
> sqe.printStackTrace();
> try {
> conn.rollback();
> System.out.println("" + System.currentTimeMillis()
> + " rolled back create");
> } catch (SQLException sqe1) {
> sqe1.printStackTrace();
> }
> } finally {
> try {
> if (conn != null) {
> conn.close();
> }
> } catch (SQLException sqe) {
> sqe.printStackTrace();
> }
> createDone = true;
> }
> }
>
> private int getNumRows() throws SQLException {
> int count = -1;
> Connection conn = getConnection();
> Statement stmt = conn.createStatement();
> ResultSet rs = stmt.executeQuery("SELECT COUNT(*) FROM RESOURCE");
> if (rs.next()) {
> count = rs.getInt(1);
> }
> conn.close();
> return count;
> }
>
> private void setup() throws Exception {
> Class.forName("org.h2.Driver");
> Connection conn = getConnection();
> Statement stmt = conn.createStatement();
> stmt.executeUpdate("CREATE TABLE RESOURCE(DATA BLOB)");
> stmt.close();
> conn.close();
> }
>
> private void cleanup() throws SQLException {
> Connection conn = getConnection();
> Statement stmt = conn.createStatement();
> stmt.executeUpdate("DROP TABLE RESOURCE");
> stmt.close();
> conn.close();
> }
>
> private Connection getConnection() throws SQLException {
> return DriverManager.getConnection("jdbc:h2:db/test", "sa", "");
> }
>
> public static void main(String[] args) {
> CancelCreateTest test = new CancelCreateTest();
> try {
> test.setup();
> } catch (Exception e) {
> e.printStackTrace();
> }
> test.start();
> try {
> Thread.sleep(300);
> } catch (InterruptedException e) {
> }
> try {
> test.ps.cancel();
> System.out.println("" + System.currentTimeMillis()
> + " cancel complete");
> } catch (SQLException sqe) {
> sqe.printStackTrace();
> }
> while (!test.createDone) {
> try {
> Thread.sleep(500);
> } catch (InterruptedException e) {
> }
> }
> int numRows = -1;
> try {
> numRows = test.getNumRows();
> } catch (SQLException sqe) {
> sqe.printStackTrace();
> }
> System.out.println("" + System.currentTimeMillis() + " " + numRows
> + " rows found");
> try {
> test.cleanup();
> } catch (SQLException e) {
> e.printStackTrace();
> }
> }
> }
> +++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++
> +++++++
> output:
> 1320285691079 begin create
> 1320285691379 cancel complete
> 1320285691603 committed create
> 1320285692801 1 rows found
>
>
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