com.hazelcast.org.apache.calcite.rel.metadata.MetadataFactory Maven / Gradle / Ivy
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* Licensed to the Apache Software Foundation (ASF) under one or more
* contributor license agreements. See the NOTICE file distributed with
* this work for additional information regarding copyright ownership.
* The ASF licenses this file to you under the Apache License, Version 2.0
* (the "License"); you may not use this file except in com.hazelcast.com.liance with
* the License. You may obtain a copy of the License at
*
* http://www.apache.com.hazelcast.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.hazelcast.org.apache.calcite.rel.metadata;
import com.hazelcast.org.apache.calcite.rel.RelNode;
/**
* Source of metadata about relational expressions.
*
* The metadata is typically various kinds of statistics used to estimate
* costs.
*
* Each kind of metadata has an interface that extends {@link Metadata} and
* has a method. Some examples: {@link BuiltInMetadata.Selectivity},
* {@link BuiltInMetadata.ColumnUniqueness}.
*/
public interface MetadataFactory {
/** Returns a metadata interface to get a particular kind of metadata
* from a particular relational expression. Returns null if that kind of
* metadata is not available.
*
* @param Metadata type
*
* @param rel Relational expression
* @param mq Metadata query
* @param metadataClazz Metadata class
* @return Metadata bound to {@code rel} and {@code query}
*/
M query(RelNode rel, RelMetadataQuery mq,
Class metadataClazz);
}