how do I use java concurrency while running select querys

Question

I have three queries to run all are like "select * from table" they are taking so much time. I want to run all query in parallel using java concurrency, how I achieve this.

Create 3 task classes which implement Callable and have query execution as call() method body, executor with 3 threads, submit these tasks (you'll get back Futures) and get results. — Andrew Logvinov
– Andrew Logvinov, Commented Jun 11, 2014 at 13:21

Fradenger · Accepted Answer · 2014-06-11 13:34:58Z

2

You can wrap your db calls in a Callable like this:

public class SqlTask implements Callable<ResultSet> {

    private String sql;

    public SqlTask(final String sql) {
        this.sql = sql;
    }

    @Override
    public ResultSet call() throws Exception {
        Connection connection = ...; // get connection
        Statement stmt = connection.createStatement();
        return stmt.executeQuery(this.sql);
    }
}

and then execute them in parralel using an ExecutorService, for example:

    final ExecutorService executor = Executors.newCachedThreadPool();
    final Future<ResultSet> futureResult1 = executor.submit (new SqlTask("SELECT * FROM table1"));
    final Future<ResultSet> futureResult2 = executor.submit(new SqlTask("SELECT * FROM table2"));
    final Future<ResultSet> futureResult3 = executor.submit(new SqlTask("SELECT * FROM table3"));
    final ResultSet result1 = futureResult1.get();
    final ResultSet result2 = futureResult2.get();
    final ResultSet result3 = futureResult3.get();

edited Jun 11, 2014 at 13:34

answered Jun 11, 2014 at 13:21

Fradenger

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2 Comments

user3543851 Over a year ago

thank you..and how I get three resultset back? I mean how I refer that three resultset?

Fradenger Over a year ago

Ok, I have added that. Future is a container for some asynchronous results. Then you call get() on it to get the real result (this call might block until the query returns)

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