com.facebook.presto.jdbc.internal.spi.plan.LogicalProperties 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.plan;
import com.facebook.presto.jdbc.internal.spi.relation.VariableReferenceExpression;
import java.util.Set;
/**
* Logical properties represent constraints that hold for a final or intermediate result produced by a PlanNode.
* They are used by the optimizer to enable query transformations that lead to better performing plans.
* For example, unique constraints can be used to eliminate redundant distinct operations.
* This is the interface used by optimizer rules to perform optimizations based upon logical properties.
*
* In this initial phase logical properties computed are based solely upon key constraints. In the future
* support for referential constraints, functional dependencies, and others will be added and
* hence this interface will become more robust over time.
*/
public interface LogicalProperties
{
/**
* Determines if the set of variables form a unique constraint for a final or
* intermediate result produced by a PlanNode.
*
* @param keyVars
* @return True if the set of variables form a unique constraint or false otherwise.
*/
boolean isDistinct(Set keyVars);
/**
* Determines if there is provably at most one tuple in a final or
* intermediate result set produced by a PlanNode.
*
* @return True if there is provably at most one tuple or false otherwise.
*/
boolean isAtMostSingleRow();
/**
* Determines if there is provably at most n tuples in a final or
* intermediate result set produced by a PlanNode.
*
* @return True if there is provably at most one tuple or false otherwise.
*/
boolean isAtMost(long n);
/**
* Determines whether one set of expressions (expressions) can be realized/rewritten
* in terms of the other (targetVariables) using EquivalenceClasses
*
* @param expressions
* @param targetVariables
* @return True if all expressions can be realized in terms of targetVariables
*/
boolean canBeHomogenized(Set expressions, Set targetVariables);
}