/*
* 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.operator.scalar;
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.function.Description;
import com.facebook.presto.spi.function.ScalarFunction;
import com.facebook.presto.spi.function.SqlType;
import com.facebook.presto.spi.function.TypeParameter;
import com.facebook.presto.spi.type.Type;
@ScalarFunction("map_keys")
@Description("Returns the keys of the given map(K,V) as an array")
public final class MapKeys
{
private MapKeys() {}
@TypeParameter("K")
@TypeParameter("V")
@SqlType("array(K)")
public static Block getKeys(
@TypeParameter("K") Type keyType,
@SqlType("map(K,V)") Block block)
{
BlockBuilder blockBuilder = keyType.createBlockBuilder(new BlockBuilderStatus(), block.getPositionCount() / 2);
for (int i = 0; i < block.getPositionCount(); i += 2) {
keyType.appendTo(block, i, blockBuilder);
}
return blockBuilder.build();
}
}