Java Code Examples for com.datastax.driver.core.SimpleStatement#setFetchSize()

/**
 * Execute a range query
 * @param destTable
 * @param range
 */
public void executeRangeQuery(final String destTable, final String format, final Hyperrectangle range) {
	System.out.println("# Execute range query in range " + range);

	final Stopwatch stopwatch = Stopwatch.createStarted();
	final TupleBuilder tupleBuilder = TupleBuilderFactory.getBuilderForFormat(format);

	long readRecords = 0;
	long resultRecords = 0;

	final SimpleStatement statement = new SimpleStatement("SELECT * FROM " + destTable);
	statement.setFetchSize(2000); // Use 2000 tuples per page

	final ResultSet rs = session.execute(statement);

	for (final Row row : rs) {

		// Request next page
	    if (rs.getAvailableWithoutFetching() == 100 && !rs.isFullyFetched()) {
	        rs.fetchMoreResults(); // this is asynchronous
	    }

	    readRecords++;

	    final long id = row.getLong(0);
	    final String text = row.getString(1);

	    final Tuple tuple = tupleBuilder.buildTuple(text, Long.toString(id));

	    if(tuple.getBoundingBox().intersects(range)) {
	    	resultRecords++;
	    }
	}

	System.out.println("# Read records " + readRecords + " result records " + resultRecords);
	System.out.println("# Execution time in sec " + stopwatch.elapsed(TimeUnit.SECONDS));
}
 

/**
 * This executes the query to retrieve result from database.
 * It then converts each row into tuple and emit that into output port.
 */
@Override
public void emitTuples()
{
  String query = queryToRetrieveData();
  logger.debug("select statement: {}", query);

  SimpleStatement stmt = new SimpleStatement(query);
  stmt.setFetchSize(fetchSize);
  try {
    if (nextPageState != null) {
      stmt.setPagingState(nextPageState);
    }
    ResultSet result = store.getSession().execute(stmt);
    nextPageState = result.getExecutionInfo().getPagingState();

    if (!result.isExhausted()) {
      for (Row row : result) {
        T tuple = getTuple(row);
        emit(tuple);
      }
    } else {
      // No rows available wait for some time before retrying so as to not continuously slam the database
      Thread.sleep(waitForDataTimeout);
    }
  } catch (Exception ex) {
    store.disconnect();
    DTThrowable.rethrow(ex);
  }
}
 

/**
 * Execute a join (nested loop join)
 * @param table1
 * @param table2
 * @param range
 */
public void executeJoin(final String table1, final String table2, final String format1,
		final String format2, final Hyperrectangle range, final double padding) {

	System.out.println("# Execute join query in range " + range);

	final Stopwatch stopwatch = Stopwatch.createStarted();

	final TupleBuilder tupleBuilder1 = TupleBuilderFactory.getBuilderForFormat(format1);
    final TupleBuilder tupleBuilder2 = TupleBuilderFactory.getBuilderForFormat(format2);

	long readRecords = 0;
	long resultRecords = 0;

	final SimpleStatement statementTable1 = new SimpleStatement("SELECT * FROM " + table1);
	statementTable1.setFetchSize(2000); // Use 2000 tuples per page

	final ResultSet rs1 = session.execute(statementTable1);

	for (final Row row1 : rs1) {

		// Request next page
	    if (rs1.getAvailableWithoutFetching() == 100 && !rs1.isFullyFetched()) {
	        rs1.fetchMoreResults(); // this is asynchronous
	    }

	    readRecords++;

	    final long id1 = row1.getLong(0);
	    final String text1 = row1.getString(1);

	    final Tuple tuple1 = tupleBuilder1.buildTuple(text1, Long.toString(id1));

	    // Tuple is outside of our query range
	    if(! tuple1.getBoundingBox().intersects(range)) {
	    	continue;
	    }

		// Perform the nested loop join
	    final SimpleStatement statementTable2 = new SimpleStatement("SELECT * FROM " + table2);
		statementTable2.setFetchSize(2000); // Use 2000 tuples per page

		final ResultSet rs2 = session.execute(statementTable2);

		for (final Row row2 : rs2) {
			// Request next page
		    if (rs1.getAvailableWithoutFetching() == 100 && !rs1.isFullyFetched()) {
		        rs1.fetchMoreResults(); // this is asynchronous
		    }

		    readRecords++;

		    final long id2 = row2.getLong(0);
		    final String text2 = row2.getString(1);

		    final Tuple tuple2 = tupleBuilder2.buildTuple(text2, Long.toString(id2));

		    if(tuple1.getBoundingBox().intersects(tuple2.getBoundingBox().enlargeByAmount(padding))) {
		    	resultRecords++;
		    }
		}
	}

	System.out.println("# Read records " + readRecords + " result records " + resultRecords);
	System.out.println("# Execution time in sec " + stopwatch.elapsed(TimeUnit.SECONDS));
}