5.1.20 Multi-Query

What is Multi-Query

Note: The concept of Multi-Query is described in our GridDB_TechnicalReference (Section 4.7.2)

Create query

List.1 Create query(MultiQuery.java)

private static List<Query<?>> createQueries(TimeSeries<InstrumentLog> logTs)
		throws ParseException, GSException {
// Set TimeSeries conditions
Date start = TimestampUtils.getFormat().parse("2016-07-01T06:00:00Z");
Date end = TimestampUtils.getFormat().parse("2016-07-01T18:00:00Z");

List<Query<?>> queries = new ArrayList<>();

// Get Max Temperture
String maxTempertureTql = String.format(
		"SELECT MAX(temperture) WHERE"
				+ " TIMESTAMP('%s') < timestamp AND timestamp < TIMESTAMP('%s')",
		TimestampUtils.format(start), TimestampUtils.format(end));
Query<AggregationResult> maxTempertureQuery =
		logTs.query(maxTempertureTql, AggregationResult.class);
queries.add(maxTempertureQuery);

// Get Min Temperture
String minTempertureTql = String.format(
		"SELECT MIN(temperture) WHERE"
				+ " TIMESTAMP('%s') < timestamp AND timestamp < TIMESTAMP('%s')",
		TimestampUtils.format(start), TimestampUtils.format(end));
Query<AggregationResult> minTempertureQuery =
		logTs.query(minTempertureTql, AggregationResult.class);
queries.add(minTempertureQuery);

// Get Average
String avgTempertureTql = String.format(
		"SELECT AVG(temperture) WHERE"
				+ " TIMESTAMP('%s') < timestamp AND timestamp < TIMESTAMP('%s')",
		TimestampUtils.format(start), TimestampUtils.format(end));
Query<AggregationResult> avgTempertureQuery =
		logTs.query(avgTempertureTql, AggregationResult.class);
queries.add(avgTempertureQuery);

// Retrieve by time range
Query<InstrumentLog> timeRangeQuery = logTs.query(start, end);
queries.add(timeRangeQuery);

return queries;
}

Multi-Query execution

List.2 Multi-Query execution(MultiQuery.java)

// Create Connection
store = gridLogic.createGridStore();

// Get InstrumentLog
TimeSeries<InstrumentLog> logTs =
		store.getTimeSeries("weather_station_1", InstrumentLog.class);

// Create query list
List<Query<?>> queries = createQueries(logTs);

// Execute Multi Query
store.fetchAll(queries);

Result of Multi-Query execution

List.3 Obtain of Multi-Query results(MultiQuery.java)

// Retrieve reulsts
for (Query<?> query : queries) {
RowSet<?> rowSet = query.getRowSet();
while (rowSet.hasNext()) {
		Object rowObj = rowSet.next();
		if (rowObj instanceof AggregationResult) {
		// When retrieve AggregationResult
		AggregationResult aggregation = (AggregationResult) rowObj;
		System.out.println("AggregationResult:" + aggregation.getDouble());

		} else if (rowObj instanceof InstrumentLog) {
		// When retrieve InstrumentLog
		InstrumentLog log = (InstrumentLog) rowObj;
		System.out.println(String.format("%s\t%-20s\t%-10s", log.timestamp,
				log.weatherStationId, log.temperture));

		} else {
		// Do not reach in this sample
		System.out.println(rowObj);
		}
}
}

List.4 Result of Multi-Get execution

AggregationResult:70.0
AggregationResult:50.0
AggregationResult:60.0
Fri Jul 01 15:00:00 EDT 2016    weather_station_1       75.0
Fri Jul 01 18:00:00 EDT 2016    weather_station_1       70.0
Fri Jul 01 21:00:00 EDT 2016    weather_station_1       60.0
Sat Jul 02 00:00:00 EDT 2016    weather_station_1       50.0
Sat Jul 02 03:00:00 EDT 2016    weather_station_1       60.0
AggregationResult:70.0
AggregationResult:50.0
AggregationResult:60.0
Fri Jul 01 15:00:00 EDT 2016    weather_station_2       75.0
Fri Jul 01 18:00:00 EDT 2016    weather_station_2       70.0
Fri Jul 01 21:00:00 EDT 2016    weather_station_2       60.0
Sat Jul 02 00:00:00 EDT 2016    weather_station_2       50.0
Sat Jul 02 03:00:00 EDT 2016    weather_station_2       60.0

Source Code

Complete source code used in this sample can be downloaded from the following.

Download:multi-query.zip