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:

## Enter into table creation mode
table create -name myTable
## Now add the fields
add-field -type STRING -name surname
add-field -type STRING -name familiarName
add-field -type STRING -name userID
add-field -type STRING -name phonenumber
add-field -type STRING -name address
add-field -type STRING -name email
add-field -type STRING -name dateOfBirth
primary-key -field surname -field familiarName -field userID 
shard-key -field surname -field familiarName
## Exit table creation mode
exit

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 named Bob Smith and Patricia Smith by specifying a field range.

A FieldRange class instance 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. Once you have the FieldRange object, you can set the start and end values for the range. You also indicate whether the range values are inclusive.

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 TableAPI.multiGet() or TableAPI.multiGetKeys(). 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 CLI's 'table create' command.
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(); 
    }
}