4.3. Non-blocking Statement Execution

JDBC query execution can indefinitely block the calling thread when a statement is executed or a resultset is being iterated. In some situations you may wish to have your calling threads held in these blocked states. When using embedded connections, you may optionally use the org.teiid.jdbc.TeiidStatement and org.teiid.jdbc.TeiidPreparedStatement interfaces to execute queries with a callback org.teiid.jdbc.StatementCallback that will be notified of statement events, such as an available row, an exception, or completion. Your calling thread will be free to perform other work. The callback will be executed by an engine processing thread as needed. If your results processing is blocking and you want query processing to run concurrently with results processing, then your callback should implement onRow handling in a multi-threaded manner to allow the engine thread to continue.

PreparedStatement stmt = connection.prepareStatement(sql);
TeiidPreparedStatement tStmt = stmt.unwrap(TeiidPreparedStatement.class);
tStmt.submitExecute(new StatementCallback() {
    @Override
    public void onRow(Statement s, ResultSet rs) {
            //any logic that accesses the current row ...
        System.out.println(rs.getString(1));
    }

    @Override
    public void onException(Statement s, Exception e) throws Exception {
        s.close();
    }

    @Override
    public void onComplete(Statement s) throws Exception {
        s.close();
    }, new RequestOptions()
});

PreparedStatement stmt = connection.prepareStatement(sql);
TeiidPreparedStatement tStmt = stmt.unwrap(TeiidPreparedStatement.class);
tStmt.submitExecute(new StatementCallback() {
    @Override
    public void onRow(Statement s, ResultSet rs) {
            //any logic that accesses the current row ...
        System.out.println(rs.getString(1));
    }

    @Override
    public void onException(Statement s, Exception e) throws Exception {
        s.close();
    }

    @Override
    public void onComplete(Statement s) throws Exception {
        s.close();
    }, new RequestOptions()
});

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Note

The non-blocking logic is limited to statement execution only. Other JDBC operations, such as connection creation or batched executions do not yet have non-blocking options.

If you access forward positions in the onRow method (calling next, isLast, isAfterLast, absolute), they may not yet be valid and a org.teiid.jdbc.AsynchPositioningException will be thrown. That exception is recoverable if caught or can be avoided by calling TeiidResultSet.available() to determine if your desired positioning will be valid.

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4.3. Non-blocking Statement Execution

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