/*
* 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.DictionaryBlockEncoding;
import com.facebook.presto.operator.GroupByHash;
import com.facebook.presto.operator.PageBuilder;
import com.facebook.presto.spi.block.Block;
import com.facebook.presto.spi.block.BlockBuilder;
import com.facebook.presto.spi.block.BlockBuilderStatus;
import com.facebook.presto.spi.block.BlockEncoding;
import com.facebook.presto.spi.type.Type;
import com.google.common.collect.ImmutableList;
import static com.facebook.presto.spi.type.BigintType.BIGINT;
import static com.google.common.base.Preconditions.checkNotNull;
import static com.google.common.base.Preconditions.checkState;
public class DictionaryEncoder
implements Encoder
{
private final Type type;
private final Encoder idWriter;
private final GroupByHash dictionaryBuilder;
private boolean finished;
public DictionaryEncoder(Type type, Encoder idWriter)
{
this.type = type;
this.idWriter = checkNotNull(idWriter, "idWriter is null");
this.dictionaryBuilder = new GroupByHash(ImmutableList.of(type), new int[] {0}, 1_000);
}
@Override
public Encoder append(Block block)
{
checkNotNull(block, "block is null");
checkState(!finished, "already finished");
BlockBuilder idBlockBuilder = BIGINT.createBlockBuilder(new BlockBuilderStatus());
for (int position = 0; position < block.getPositionCount(); position++) {
int key = dictionaryBuilder.putIfAbsent(position, block);
BIGINT.writeLong(idBlockBuilder, key);
}
idWriter.append(idBlockBuilder.build());
return this;
}
@Override
public BlockEncoding finish()
{
checkState(!finished, "already finished");
finished = true;
PageBuilder pageBuilder = new PageBuilder(ImmutableList.of(type));
for (int groupId = 0; groupId < dictionaryBuilder.getGroupCount(); groupId++) {
dictionaryBuilder.appendValuesTo(groupId, pageBuilder, 0);
}
return new DictionaryBlockEncoding(pageBuilder.build().getBlock(0), idWriter.finish());
}
}