/*
* Copyright © 2014 Cask Data, Inc.
*
* Licensed under the Apache License, Version 2.0 (the "License"); you may not
* use this file except in compliance with the License. You may obtain a copy of
* the License at
*
* http://www.apache.org/licenses/LICENSE-2.0
*
* Unless required by applicable law or agreed to in writing, software
* distributed under the License is distributed on an "AS IS" BASIS, WITHOUT
* WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. See the
* License for the specific language governing permissions and limitations under
* the License.
*/
package co.cask.cdap.api.dataset.lib;
import co.cask.cdap.api.common.Bytes;
import co.cask.cdap.api.data.batch.BatchReadable;
import co.cask.cdap.api.data.batch.BatchWritable;
import co.cask.cdap.api.data.batch.RecordScannable;
import co.cask.cdap.api.data.batch.RecordScanner;
import co.cask.cdap.api.data.batch.RecordWritable;
import co.cask.cdap.api.data.batch.Scannables;
import co.cask.cdap.api.data.batch.Split;
import co.cask.cdap.api.data.batch.SplitReader;
import co.cask.cdap.api.dataset.table.Row;
import co.cask.cdap.api.dataset.table.Scanner;
import co.cask.cdap.api.dataset.table.Table;
import com.google.common.base.Preconditions;
import com.google.common.reflect.TypeToken;
import java.io.IOException;
import java.lang.reflect.Type;
import java.util.List;
import javax.annotation.Nullable;
/**
* A key/value map implementation on top of {@link Table} supporting read, write and delete operations.
*/
public class KeyValueTable extends AbstractDataset implements
BatchReadable<byte[], byte[]>, BatchWritable<byte[], byte[]>,
RecordScannable<KeyValue<byte[], byte[]>>, RecordWritable<KeyValue<byte[], byte[]>> {
// the fixed single column to use for the key
static final byte[] KEY_COLUMN = { 'c' };
private final Table table;
public KeyValueTable(String instanceName, Table table) {
super(instanceName, table);
this.table = table;
}
/**
* Read the value for a given key.
*
* @param key the key to read for
* @return the value for that key, or null if no value was found
*/
@Nullable
public byte[] read(String key) {
return read(Bytes.toBytes(key));
}
/**
* Read the value for a given key.
*
* @param key the key to read for
* @return the value for that key, or null if no value was found
*/
@Nullable
public byte[] read(byte[] key) {
return table.get(key, KEY_COLUMN);
}
/**
* Increment the value for a given key and return the resulting value.
*
* @param key the key to increment
* @return the incremented value of that key
*/
public long incrementAndGet(byte[] key, long value) {
return this.table.incrementAndGet(key, KEY_COLUMN, value);
}
/**
* Write a value to a key.
*
* @param key the key
* @param value the new value
*/
public void write(byte[] key, byte[] value) {
this.table.put(key, KEY_COLUMN, value);
}
/**
* Write a value to a key.
*
* @param key the key
* @param value the new value
*/
public void write(String key, String value) {
this.table.put(Bytes.toBytes(key), KEY_COLUMN, Bytes.toBytes(value));
}
/**
* Write a value to a key.
*
* @param key the key
* @param value the new value
*/
public void write(String key, byte[] value) {
this.table.put(Bytes.toBytes(key), KEY_COLUMN, value);
}
/**
* Increment the value of a key by amount; the key must either not exist yet, or the
* current value at the key must be 8 bytes long to be interpretable as a long.
*
* @param key the key
* @param amount the amount to increment by
*/
public void increment(byte[] key, long amount) {
this.table.increment(key, KEY_COLUMN, amount);
}
/**
* Delete a key.
*
* @param key the key to delete
*/
public void delete(byte[] key) {
this.table.delete(key, KEY_COLUMN);
}
/**
* Compares-and-swaps (atomically) the value of the specified row and column
* by looking for the specified expected value and, if found, replacing with
* the specified new value.
*
* @param key key to modify
* @param oldValue expected value before change
* @param newValue value to set
* @return true if compare and swap succeeded, false otherwise (stored value is different from expected)
*/
public boolean compareAndSwap(byte[] key, byte[] oldValue, byte[] newValue) throws Exception {
return this.table.compareAndSwap(key, KEY_COLUMN, oldValue, newValue);
}
@Override
public Type getRecordType() {
return new TypeToken<KeyValue<byte[], byte[]>>() { }.getType();
}
@Override
public List<Split> getSplits() {
return table.getSplits();
}
@Override
public RecordScanner<KeyValue<byte[], byte[]>> createSplitRecordScanner(Split split) {
return Scannables.splitRecordScanner(createSplitReader(split), new KeyValueRecordMaker());
}
/**
* Returns splits for a range of keys in the table.
*
* @param numSplits Desired number of splits. If greater than zero, at most this many splits will be returned.
* If less than or equal to zero, any number of splits can be returned.
* @param start if non-null, the returned splits will only cover keys that are greater or equal
* @param stop if non-null, the returned splits will only cover keys that are less
* @return list of {@link Split}
*/
public List<Split> getSplits(int numSplits, byte[] start, byte[] stop) {
return table.getSplits(numSplits, start, stop);
}
@Override
public SplitReader<byte[], byte[]> createSplitReader(Split split) {
return new KeyValueScanner(table.createSplitReader(split));
}
@Override
public void write(KeyValue<byte[], byte[]> keyValue) throws IOException {
write(keyValue.getKey(), keyValue.getValue());
}
/**
* Scans table.
* @param startRow start row inclusive. {@code null} means start from first row of the table
* @param stopRow stop row exclusive. {@code null} means scan all rows to the end of the table
* @return {@link co.cask.cdap.api.dataset.lib.CloseableIterator} of
* {@link co.cask.cdap.api.dataset.lib.KeyValue<byte[],byte[]>}
*/
public CloseableIterator<KeyValue<byte[], byte[]>> scan(byte[] startRow, byte[] stopRow) {
final Scanner scanner = table.scan(startRow, stopRow);
return new AbstractCloseableIterator<KeyValue<byte[], byte[]>>() {
private boolean closed = false;
@Override
protected KeyValue<byte[], byte[]> computeNext() {
Preconditions.checkState(!closed);
Row next = scanner.next();
if (next != null) {
return new KeyValue<byte[], byte[]>(next.getRow(), next.get(KEY_COLUMN));
}
close();
return null;
}
@Override
public void close() {
scanner.close();
endOfData();
closed = true;
}
};
}
/**
* {@link co.cask.cdap.api.data.batch.Scannables.RecordMaker} for {@link #createSplitReader(Split)}.
*/
public class KeyValueRecordMaker implements Scannables.RecordMaker<byte[], byte[], KeyValue<byte[], byte[]>> {
@Override
public KeyValue<byte[], byte[]> makeRecord(byte[] key, byte[] value) {
return new KeyValue<byte[], byte[]>(key, value);
}
}
/**
* The split reader for KeyValueTable.
*/
public class KeyValueScanner extends SplitReader<byte[], byte[]> {
// the underlying KeyValueTable's split reader
private SplitReader<byte[], Row> reader;
public KeyValueScanner(SplitReader<byte[], Row> reader) {
this.reader = reader;
}
@Override
public void initialize(Split split) throws InterruptedException {
this.reader.initialize(split);
}
@Override
public boolean nextKeyValue() throws InterruptedException {
return this.reader.nextKeyValue();
}
@Override
public byte[] getCurrentKey() throws InterruptedException {
return this.reader.getCurrentKey();
}
@Override
public byte[] getCurrentValue() throws InterruptedException {
return this.reader.getCurrentValue().get(KEY_COLUMN);
}
@Override
public void close() {
this.reader.close();
}
}
}