StatsCalculator.java

/*
 * 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.cost;

import com.facebook.presto.Session;
import com.facebook.presto.spi.plan.PlanNode;
import com.facebook.presto.sql.planner.TypeProvider;
import com.facebook.presto.sql.planner.iterative.IterativeOptimizer;
import com.facebook.presto.sql.planner.iterative.Lookup;

public interface StatsCalculator
{
    /**
     * Calculate stats for the {@code node}.
     *
     * @param node The node to compute stats for.
     * @param sourceStats The stats provider for any child nodes' stats, if needed to compute stats for the {@code node}
     * @param lookup Lookup to be used when resolving source nodes, allowing stats calculation to work within {@link IterativeOptimizer}
     * @param types
     */
    PlanNodeStatsEstimate calculateStats(
            PlanNode node,
            StatsProvider sourceStats,
            Lookup lookup,
            Session session,
            TypeProvider types);

    /**
     * Presto Optimizer will call this once for a query that needs StatsCalculator interface. It is called
     * with the root PlanNode, so StatsCalculator can prepare for future `calculateStats` calls.
     *
     * @param root Root of plan tree for query
     * @return true if registration succeeds, otherwise return false
     */
    default boolean registerPlan(
            PlanNode root,
            Session session,
            long startTimeInNano,
            long timeoutInMilliseconds)
    {
        // no-op
        return false;
    }
}