5.1.11 Collection Modification

Overview

This section describes modifying the schema and the index of a GridDB collection.

Schema Modification

You can modify the schema by adding or deleting columns in a container after the container has been created.
This example demonstrates how to modify a newly created class with a new column in addition to WeatherStation class.
In addition, there is a way to modify the schema without creating a new class. Please refer to Meta-information for more details.

List.1 Modified Class (AnotherWeatherStation.java)

package sample.row;

import com.toshiba.mwcloud.gs.RowKey;

public class AnotherWeatherStation {
    / **
    * 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;

    / **
    * Added field to WeatherStation
    * /
    public String description;
}

L.35: The newly added column.

In the case creating a new collection, the GridStore.putCollection(String, Class) method is used, and the case modifying schema of column, the method with parameters of modification options GridStore.putCollection(String, Class, boolean) is used.

List.2 putCollection Method

< K, R > Collection < K, R > putCollection (java.lang.String name,
                                    java.lang.Class < R > rowType,
                                    boolean modifiable)
                                    throws GSException

You can modify a schema of an existing collection with setting the modifiable parameter to true.
However there are several conditions in order to modify. Please refer to GridDB API Reference for more information.

List.3 Modifying the collection to be added a new column (CollectionModify.java)

// Modify ano ther schema Collection
Collection  ano therWeatherStationCol =
        store.putCollection("weather_station", AnotherWeatherStation.class, true );

L.29-30: Set the modifiable paramater to true.

Add an Index

You can set an Index to column in GridDB identically with general RDB.

List.4 Adding an Index (CollectionIndex.java)

// Create Index
weatherStationCol.createIndex("id");
weatherStationCol.createIndex("name", IndexType.TREE);

L.34: Add an index with specifying a column name id of the measuring instrument ID with Container.createIndex(String) method.
L.35: Add ab index specifying a column name of the measuring instrument name with Container.createIndex(String, IndexType) method and set IndexType.TREE to the index type.

Types of indexes are as follows:

Table.1 Index types

Index type	Description
HASH	High speed retrieval, but not suitable for the operation of reading Row sequentially and impossible to set in the TimeSeries container.
TREE	It is suitable for a retrival specifying that whether the value is larger or smaller than a retrieval vulue to a retrieval range.

There are index types which can not be specified owing to the container type or the column type. Please refer to GridDB API Reference and GridDB Technical Reference for more information.

Delete an Index

Index set in the column can be deleted.

List.5 Delete an Index (CollectionIndex.java)

// Drop Index
weatherStationCol.dropIndex("id");
weatherStationCol.dropIndex("name");

L.38-39: Delete an Index with the Container.dropIndex (String) method specifying column name set to the index.

Complete source code

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

Download: collection_modify.zip