11/13/2012: Exampe of Storing User and Friends Information in Accumulo
This example shows one way to store user and friend information in one Accumulo table. Each friend category becomes a Column Family and each friend's user id becomes a Column Qualifier. After the inserts a small query is run to loop over old friends.
package com.codebits.accumulo;
import java.io.IOException;
import java.util.Iterator;
import java.util.Map;
import org.apache.accumulo.core.client.AccumuloException;
import org.apache.accumulo.core.client.AccumuloSecurityException;
import org.apache.accumulo.core.client.BatchWriter;
import org.apache.accumulo.core.client.Connector;
import org.apache.accumulo.core.client.Instance;
import org.apache.accumulo.core.client.Scanner;
import org.apache.accumulo.core.client.TableExistsException;
import org.apache.accumulo.core.client.TableNotFoundException;
import org.apache.accumulo.core.client.mock.MockInstance;
import org.apache.accumulo.core.data.Key;
import org.apache.accumulo.core.data.Mutation;
import org.apache.accumulo.core.data.Range;
import org.apache.accumulo.core.data.Value;
import org.apache.accumulo.core.security.Authorizations;
import org.apache.hadoop.io.Text;
public class UserAndFriendsDriver {
public static void main(String[] args) throws IOException, AccumuloException, AccumuloSecurityException, TableExistsException, TableNotFoundException {
Instance mock = new MockInstance("development");
Connector connector = mock.getConnector("root", "password".getBytes());
connector.tableOperations().create("TABLEA");
BatchWriter wr = connector.createBatchWriter("TABLEA", 10000000, 10000, 5);
Mutation m = new Mutation(new Text("john"));
m.put("info:name", "", "john henry");
m.put("info:gender", "", "male");
m.put("friend:old", "mark", "");
wr.addMutation(m);
m = new Mutation(new Text("mary"));
m.put("info:name", "", "mark wiggins");
m.put("info:gender", "", "female");
m.put("friend:new", "mark", "");
m.put("friend:old", "lucas", "");
m.put("friend:old", "aaron", "");
wr.addMutation(m);
wr.close();
Scanner scanner = connector.createScanner("TABLEA", new Authorizations());
scanner.setRange(new Range("a", "z"));
scanner.fetchColumnFamily(new Text("friend:old"));
Iterator<Map.Entry<Key, Value>> iterator = scanner.iterator();
while (iterator.hasNext()) {
Map.Entry<Key, Value> entry = iterator.next();
Key key = entry.getKey();
System.out.println("Old Friends: " + key.getRow() + " -> " + key.getColumnQualifier());
}
}
}
11/12/2012: How Can I Use Reverse Sort On Integer (or Long) Accumulo Keys?
Here is code with debugging (i.e., the original key is retained) so that you can see the reverse sort is working.
package com.codebits.accumulo;
import java.io.ByteArrayOutputStream;
import java.io.IOException;
import java.nio.ByteBuffer;
import java.util.Arrays;
import java.util.Iterator;
import java.util.Map;
import org.apache.accumulo.core.client.AccumuloException;
import org.apache.accumulo.core.client.AccumuloSecurityException;
import org.apache.accumulo.core.client.BatchWriter;
import org.apache.accumulo.core.client.Connector;
import org.apache.accumulo.core.client.Instance;
import org.apache.accumulo.core.client.Scanner;
import org.apache.accumulo.core.client.TableExistsException;
import org.apache.accumulo.core.client.TableNotFoundException;
import org.apache.accumulo.core.client.mock.MockInstance;
import org.apache.accumulo.core.data.Key;
import org.apache.accumulo.core.data.Mutation;
import org.apache.accumulo.core.data.Value;
import org.apache.accumulo.core.security.Authorizations;
import org.apache.hadoop.io.Text;
public class ReversingIntSortOrderWithMockInstanceDriver {
static byte[] convert(int value) {
byte[] key = ByteBuffer.allocate(4).putInt(value).array();
byte[] reverse_key = ByteBuffer.allocate(4).putInt(Integer.MAX_VALUE - value).array();
byte[] rv = new byte[8];
for (int i = 0; i < 4; i++) {
rv[i] = reverse_key[i];
}
for (int i = 0; i < 4; i++) {
rv[i + 4] = key[i];
}
return rv;
}
public static String toHexString(byte[] ba) {
StringBuilder str = new StringBuilder();
for (int i = 0; i < ba.length; i++)
str.append(String.format("%x", ba[i]));
return str.toString();
}
public static void main(String[] args) throws IOException, AccumuloException, AccumuloSecurityException, TableExistsException, TableNotFoundException {
Instance mock = new MockInstance("development");
Connector connector = mock.getConnector("root", "password".getBytes());
connector.tableOperations().create("TABLEA");
BatchWriter wr = connector.createBatchWriter("TABLEA", 10000000, 10000, 5);
for (int i = 5; i > 0; --i) {
byte[] key = convert(i);
Mutation m = new Mutation(new Text(key));
m.put("cf", "cq", "value");
wr.addMutation(m);
}
wr.close();
Scanner scanner = connector.createScanner("TABLEA", new Authorizations());
Iterator<Map.Entry<Key, Value>> iterator = scanner.iterator();
while (iterator.hasNext()) {
Map.Entry entry = iterator.next();
Key key = entry.getKey();
System.out.println(toHexString(key.getRow().getBytes()));
}
}
}
This code produces this output:7ffffffa0005 7ffffffb0004 7ffffffc0003 7ffffffd0002 7ffffffe0001I'll leave it to the reader to remove the debugging code.