
io.prestosql.operator.scalar.EmptyMapConstructor Maven / Gradle / Ivy
/*
* 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 io.prestosql.operator.scalar;
import io.prestosql.spi.block.Block;
import io.prestosql.spi.block.BlockBuilder;
import io.prestosql.spi.function.Description;
import io.prestosql.spi.function.ScalarFunction;
import io.prestosql.spi.function.SqlType;
import io.prestosql.spi.function.TypeParameter;
import io.prestosql.spi.type.MapType;
import io.prestosql.spi.type.Type;
@Description("Creates an empty map")
@ScalarFunction("map")
public final class EmptyMapConstructor
{
private final Block emptyMap;
public EmptyMapConstructor(@TypeParameter("map(unknown,unknown)") Type mapType)
{
BlockBuilder mapBlockBuilder = mapType.createBlockBuilder(null, 1);
mapBlockBuilder.beginBlockEntry();
mapBlockBuilder.closeEntry();
emptyMap = ((MapType) mapType).getObject(mapBlockBuilder.build(), 0);
}
@SqlType("map(unknown,unknown)")
public Block map()
{
return emptyMap;
}
}
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