Specifying Field Ranges

When performing multi-key operations in the store, you can specify a range of rows to operate upon. You do this using the FieldRange class, which is accepted by any of the methods which perform bulk reads. This class is used to restrict the selected rows to those matching a range of field values.

For example, suppose you defined a table like this:

CREATE TABLE myTable (
    surname STRING,
    familiarName STRING,
    userID STRING,
    phonenumber STRING,
    address STRING,
    email STRING,
    dateOfBirth STRING,
    PRIMARY KEY (SHARD(surname, familiarName), userID)
) 

The surname contains a person's family name, such as Smith. The familiarName contains their common name, such as Bob, Patricia, Robert, and so forth.

Given this, you could perform operations for all the rows related to users with a surname of Smith, but we can limit the result set to just those users with familiar names that fall alphabetically between Bob and Patricia by specifying a field range.

A FieldRange is created using Table.createFieldRange(). This method takes just one argument — the name of the primary key for which you want to set the range.

In this case, we will define the start of the key range using the string "Bob" and the end of the key range to be "Patricia". Both ends of the key range will be inclusive.

In this example, we use TableIterator, but we could just as easily use this range on any multi-row read operation, such as the TableAPI.multiGet() or TableAPI.multiGetKeys() methods. The FieldRange object is passed to these methods using a MultiRowOptions class instance, which we construct using the FieldRange.createMultiRowOptions() convenience method.

package kvstore.basicExample;

...

import oracle.kv.KVStore;
import oracle.kv.table.FieldRange;
import oracle.kv.table.MultiRowOptions;
import oracle.kv.table.PrimaryKey;
import oracle.kv.table.Row;
import oracle.kv.table.Table;
import oracle.kv.table.TableAPI;
import oracle.kv.table.TableIterator;

...

// KVStore handle creation is omitted for brevity

...

TableAPI tableH = kvstore.getTableAPI();

// The name you give to getTable() must be identical
// to the name that you gave the table when you created
// the table using the CREATE TABLE DDL statement.
Table myTable = tableH.getTable("myTable");

// Construct the PrimaryKey. In this case, we are
// using a partial primary key.
PrimaryKey key = myTable.createPrimaryKey();
key.put("surname", "Smith");

// Create the field range.
FieldRange fh = myTable.createFieldRange("familiarName");
fh.setStart("Bob", true);
fh.setEnd("Patricia", true);
MultiRowOptions mro = fh.createMultiRowOptions();

// Exception handling is omitted, but in production code
// ConsistencyException, RequestTimeException, and FaultException
// would have to be handled.
TableIterator<Row> iter = tableH.tableIterator(key, mro, null);
try {
    while (iter.hasNext()) {
        Row row = iter.next();
        // Examine your row's fields here
    }
} finally {
    if (iter != null) {
        iter.close();
    }
}