Creating JSON Tables

This topic describes how to create HPE Ezmeral Data Fabric Database JSON tables using either programmatic APIs or dbshell.

NOTE Before creating a table, you typically create a directory and MapR volume. This is not required; however, it is a good practice. For example, assuming both the directory and volume names are sample, the command would be:

// Create directories with hadoop
hadoop fs -mkdir /sample

// Create a MapR volume using maprcli create volume
maprcli volume create -name sample -path /sample -type rw

The following Java code examples show you how to create a table in the following ways:

By using the default values for the table attributes,
By setting specific values for the table attributes.

See the Admin and TableDescriptor APIs for more information.

The following example shows how to create a table by calling an Admin object's createTable() method and passing, as an argument, the path that you want to use for the new table:

public void createJSONTable(String tablePath) throws DBException {
    try (Admin admin = MapRDB.newAdmin()) {
        if (!admin.tableExists(tablePath)) {
            admin.createTable(tablePath);
         }
    }
}

Tables created with this version of the createTable() method use the default values for their attributes.

Alternatively, the following example how to create a table by passing a TableDescriptor object as an argument to the createTable() method:

/* Create a TableDescriptor for the table to create,
 * passing in the path of the table. 
 */
TableDescriptor tableDescriptor = MapRDB.newTableDescriptor(tablePath);
   
/* Pass the TableDescriptor object and the path to the table
 * to the Admin.createTable() method. 
 */
public void createJSONTable(String tablePath, TableDescriptor tableDescriptor) throws DBException {
    try (Admin admin = MapRDB.newAdmin()) {
        if (!admin.tableExists(tablePath)) {
            admin.createTable(tableDescriptor);
        }
    }
}

This alternative allows you to set values for some of the table's attributes.

To create a table in the Node.js OJAI client, call the Connection.createStore() method:

connection.createStore(table_path)
    .then((store) => {
        // Process result
        ...
    });

The method returns a DocumentStore object.

To create a table in the Python OJAI client, call the Connection.create_store() method:

store = connection.create_store(store_path=table_path)

The method returns a DocumentStore object.

The following dbshell command shows code syntax for creating a table:

# mapr dbshell
maprdb root:> create /<tablePath>/<tableName>

To create a table in the C# OJAI client, call the connection.CreateStore(string storePath) method:

var store = connection.CreateStore(string storePath);

The method returns a DocumentStore object.

To create a table in the Go OJAI client, call the connection.CreateStore() function:

store, error := connection.CreateStore("/store_path")

The function returns a new DocumentStore and an error.