5.1.7 Container Creation and Deletion

Overview

This chapter describes how to create/delete GridDB containers.

Collection and Timeseries Container

There are 2 container types, a timeseries container and a collection.

• Timeseries container
  • A container that specializes for data whcih is consisted of the pair of time and value, such as sensor data.
  • The TIMESTAMP data can be specified in a row key.
  • It is possible to acquire the data in a specified period of time or to aggregate the data.
  • Value can be linearly interpolated when register or retreive the data.
• Collection
  • Collection is a general purpose container.
  • Collection does not have any functions related to timeseries data, however it can be used with any data type in a key and it can be used in the same way as the other key-value database.

Here are some programming samples to create or delete each type of containers.

How to create a Collection

Collection can be created as follows.

List.1 Creating a Collection(WeatherStationLogic.java)

// Create Collection
Collection<String, WeatherStation> weatherStationCol =
        store.putCollection("weather_station", WeatherStation.class);
return weatherStationCol;

• L.34-35: Use GridStore.putCollection(String, Class) method to create a Collection.
  A container name should be specified to String, and WeatherStation class which can be created in chapter Schema definition should be set to Class.
  A created Collection will obtained as an instance of com.toshiba.mwcloud.gs.Collection class.

List.2 Releasing a Collection(CollectionCreate.java)

} finally {
    // Close Connection
    weatherStationCol.close();
}

• L.183: Use Collection.close() method to release associated resources by closing the created Collection.

How to create a Timeseries Container

Timeseries Container can be created as follows.

List.3 Creating a Timeseries Container(InstrumentLogLogic.java)

for (int i = 0; i < WeatherStationLogic.JP_PREFECTURE; i++) {
    // Create TimeSeries Container
    TimeSeries<InstrumentLog> ts =
            store.putTimeSeries("weather_station_" + (i + 1), InstrumentLog.class);

    (snip)
}

• L.137-138: Use GridStore.putTimeSeries(String, Class) method to create a Timeseries Container.
  A Timeseries container name should be specified to String, and InstrumentLog class which can be created in chapter Schema definition should be set to Class.
  A created Timeseries Container will obtained as an instance of com.toshiba.mwcloud.gs.TimeSeries class.

List.4 Releasing a Timeseries Container(InstrumentLogLogic.java)

// Close TimeSeries Container
ts.close();

• L.56: In the same manner as Collection, use Collection.close() method to release associated resources by closing the created Timeseries Container.

How to delete a Container

List.5 Deleting Collection(WeatherStationLogic.java)

public void dropCollection(GridStore store) throws GSException {
    // Drop Collection
    store.dropCollection("weather_station");
}

• L.47: Use GridStore.dropCollection(String) method to delete a Collection.

List.6 Deleting Timeseries Container(SampleTimeSeries.java)

public void dropTimeSeries(GridStore store, String name) throws GSException {
    // Drop TimeSeries Container
    store.dropTimeSeries(name);
}

• L.69: Use GridStore.dropTimeSeries(String) method to delete a Timeseries Container.

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This chapter provided how to create or delete 2 types of Container, a Collection and a Timeseries Container.
Container can be easily created or deleted by simply preparing a container name and a class that represents the rows.

Here we describe only the static method of preparing a class that represents a row in advance, but there is a way to dynamically create a Container without providing a class.
Please refer to Meta-information for more details.

Complete source code

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

Download: container-create-drop.zip