com.facebook.presto.jdbc.internal.spi.ColumnHandle 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 com.facebook.presto.jdbc.internal.spi;
import com.facebook.presto.jdbc.internal.spi.api.Experimental;
import java.util.List;
public interface ColumnHandle
{
/**
* Applies to columns of complex types: arrays, maps and structs. When a query
* uses only some of the subfields, the engine provides the complete list of
* required subfields and the connector is free to prune the rest.
*
* Examples:
* - SELECT a[1], b['x'], x.y.z FROM t
* - SELECT a FROM t WHERE b['y'] > 10
*
* Pruning must preserve the type of the values and support unmodified access.
*
* - Pruning a struct means populating some of the members with null values.
* - Pruning a map means dropping keys not listed in the required subfields.
* - Pruning arrays means dropping values with indices larger than maximum
* required index and filling in remaining non-required indices with nulls.
*/
@Experimental
default ColumnHandle withRequiredSubfields(List subfields)
{
return this;
}
}