5.1.6 Schema definition

Overview

This chapter describes the schema definition and data types.

Schema definition

Data of the measuring instruments and instrument log that will be handled in this sample application are defined in the container as follows.

Table.1 Container Information

Data	Container type	Quantity	Container name	Row key
Measuring instrument	Collection	1	weather_station	Instrument ID
Instrument log	TimeSeries Container	1 per instrument	weather_station_ (Example:weather_station_1)	Logging date and time

One collection will be created with rows corresponding to different measuring instruments..
One TimeSeries container will be created as the instrument log for each measuring instrument.
The instrument ID to will be included in the instrument log's container name.

There are two ways to use Container in your programs.
One is to pre-define the class statically which represents a row of the container.
The other is to create a Container dynamically without preparing the pre-defined class.
Here we describe only the static method, so please refer to Meta-information for more details about dynamic method.

List.1 Measuring instrument class(WeatherStation.java)

package sample.row;

import com.toshiba.mwcloud.gs.RowKey;

/**
* Class that represents the definition of the schema.
*/
public class WeatherStation {
    /**
    * ID of WeatherStation
    */
    @RowKey
    public String id;

    /**
    * Name of WeatherStation
    */
    public String name;

    /**
    * Installation Latitude
    */
    public double latitude;

    /**
    * Installation Longitude
    */
    public double longitude;

    /**
    * Camera exists or not
    */
    public boolean hasCamera;
}

L.12: The @RowKey annotates the field to be used as a row key.

List.2 Instrument log class(InstrumentLog.java)

package sample.row;

import java.sql.Blob;
import java.util.Date;

import com.toshiba.mwcloud.gs.RowKey;

/**
* Class that represents the definition of the Row of Instrument log.
*/
public class InstrumentLog {
    /**
    * Timestamp of log
    */
    @RowKey
    public Date timestamp;

    /**
    * ID of Weather Station
    */
    public String weatherStationId;

    /**
    * Temperature of the measurement result
    */
    public float temperture;

    /**
    * Image data obtained by photographing the sky
    */
    public Blob liveImage;
}

L.15: The @RowKey annotates the field to be used as a row key.

Column Data Types

The following types of data can be used in a GridDB column.

Table.2 Available column type

Column Type	Type in Program	Description
BOOL	boolean or Boolean	TRUE or FALSE.
STRING	String	Zero or more Unicode characters excluding the NULL character (U+0000).
BYTE	Byte or byte	Integer value in the following range.(-2⁷ to 2⁷-1)
SHORT	Short or short	Integer value in the following range.(-2¹⁵ to 2¹⁵-1)
INTEGER	Integer or int	Integer value in the following range.(-2³¹ to 2³¹-1)
LONG	Long or long	Integer value in the following range.(-2⁶³ to 2⁶³-1)
FLOAT	Float or float	Single-precision floating point number.
DOUBLE	Double or double	Double-precision floating point number.
TIMESTAMP	java.util.Date	Combination of a date and time consisting of year, month, day, hour, minute and second.
BLOB	java.sql.Blob	Binary data.

All types except BLOB can be stored as an array.

This chapter demonstrated how to define a schema and use it in your GridDB applications.
Please refer to the GridDB Programming Tutorial for more details on schema definitions.

Complete source code

The complete source code used in this sample can be downloaded from the following:

Download: container-schema.zip