/*
* 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 com.facebook.presto.serde;
import com.facebook.presto.block.dictionary.Dictionary.DictionaryBuilder;
import com.facebook.presto.tuple.Tuple;
import com.facebook.presto.tuple.TupleInfo;
import com.google.common.base.Function;
import com.google.common.collect.Iterables;
import static com.facebook.presto.tuple.Tuples.createTuple;
import static com.google.common.base.Preconditions.checkNotNull;
import static com.google.common.base.Preconditions.checkState;
public class DictionaryEncoder
implements Encoder
{
private final Encoder idWriter;
private TupleInfo tupleInfo;
private DictionaryBuilder dictionaryBuilder;
private boolean finished;
public DictionaryEncoder(Encoder idWriter)
{
this.idWriter = checkNotNull(idWriter, "idWriter is null");
}
@Override
public Encoder append(Iterable<Tuple> tuples)
{
checkNotNull(tuples, "tuples is null");
checkState(!finished, "already finished");
Iterable<Tuple> idTuples = Iterables.transform(tuples, new Function<Tuple, Tuple>()
{
@Override
public Tuple apply(Tuple tuple)
{
if (tupleInfo == null) {
tupleInfo = tuple.getTupleInfo();
dictionaryBuilder = new DictionaryBuilder(tupleInfo);
}
long id = dictionaryBuilder.getId(tuple);
return createTuple(id);
}
});
idWriter.append(idTuples);
return this;
}
@Override
public BlockEncoding finish()
{
checkState(tupleInfo != null, "nothing appended");
checkState(!finished, "already finished");
finished = true;
return new DictionaryBlockEncoding(dictionaryBuilder.build(), idWriter.finish());
}
}