com.hazelcast.org.apache.calcite.rel.hint.Hintable Maven / Gradle / Ivy
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* 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 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.
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package com.hazelcast.org.apache.calcite.rel.hint;
import com.hazelcast.org.apache.calcite.linq4j.function.Experimental;
import com.hazelcast.org.apache.calcite.rel.RelNode;
import com.hazelcast.com.google.common.collect.ImmutableList;
import java.util.ArrayList;
import java.util.LinkedHashSet;
import java.util.List;
import java.util.Objects;
import java.util.Set;
/**
* {@link Hintable} is a kind of {@link RelNode} that can attach {@link RelHint}s.
*
* This interface is experimental, {@link RelNode}s that implement it
* have a constructor parameter named "hints" used to construct relational expression
* with given hints.
*
*
Current design is not that elegant and mature, because we have to
* copy the hints whenever these relational expressions are copied or used to
* derive new relational expressions.
* Even though we have implemented the mechanism to propagate the hints, for large queries,
* there would be many cases where the hints are not copied to the right RelNode,
* and the effort/memory is wasted if we are copying the hint to a RelNode
* but the hint is not used.
*/
@Experimental
public interface Hintable {
/**
* Attaches list of hints to this relational expression.
*
*
This method is only for internal use during sql-to-rel conversion.
*
*
Sub-class should return a new copy of the relational expression.
*
*
The default implementation merges the given hints with existing ones,
* put them in one list and eliminate the duplicates; then
* returns a new copy of this relational expression with the merged hints.
*
* @param hintList The hints to attach to this relational expression
* @return Relational expression with the hints {@code hintList} attached
*/
default RelNode attachHints(List hintList) {
Objects.requireNonNull(hintList, "hintList");
final Set hints = new LinkedHashSet<>(getHints());
hints.addAll(hintList);
return withHints(new ArrayList<>(hints));
}
/**
* Returns a new relational expression with the specified hints {@code hintList}.
*
* This method should be overridden by every logical node that supports hint.
* It is only for internal use during decorrelation.
*
*
Sub-class should return a new copy of the relational expression.
*
*
The default implementation returns the relational expression directly
* only because not every kind of relational expression supports hints.
*
* @return Relational expression with set up hints
*/
default RelNode withHints(List hintList) {
return (RelNode) this;
}
/**
* Returns the hints of this relational expressions as an immutable list.
*/
ImmutableList getHints();
}