content: /*
   * 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 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 org.apache.calcite.rel.rules;
  
  import org.apache.calcite.plan.RelOptMaterialization;
  import org.apache.calcite.plan.RelOptMaterializations;
  import org.apache.calcite.plan.RelOptPlanner;
  import org.apache.calcite.plan.RelOptRuleCall;
  import org.apache.calcite.plan.RelOptUtil;
  import org.apache.calcite.plan.RelRule;
  import org.apache.calcite.plan.SubstitutionVisitor;
  import org.apache.calcite.plan.hep.HepPlanner;
  import org.apache.calcite.plan.hep.HepProgram;
  import org.apache.calcite.plan.hep.HepProgramBuilder;
  import org.apache.calcite.rel.RelNode;
  import org.apache.calcite.rel.core.Filter;
  import org.apache.calcite.rel.core.TableScan;
  import org.apache.calcite.tools.RelBuilderFactory;
  
  import com.google.common.base.Suppliers;
  
  import org.immutables.value.Value;
  
  import java.util.Collections;
  import java.util.List;
  import java.util.function.Supplier;
  
  /**
   * Planner rule that converts
   * a {@link org.apache.calcite.rel.core.Filter}
   * on a {@link org.apache.calcite.rel.core.TableScan}
   * to a {@link org.apache.calcite.rel.core.Filter} on a Materialized View.
   *
   * @see org.apache.calcite.rel.rules.materialize.MaterializedViewRules#FILTER_SCAN
   */
  @Value.Enclosing
  public class MaterializedViewFilterScanRule
      extends RelRule<MaterializedViewFilterScanRule.Config>
      implements TransformationRule {
  
    private static final Supplier<HepProgram> PROGRAM = Suppliers.memoize(() ->
        new HepProgramBuilder()
            .addRuleInstance(CoreRules.FILTER_PROJECT_TRANSPOSE)
            .addRuleInstance(CoreRules.PROJECT_MERGE)
            .build());
  
    //~ Constructors -----------------------------------------------------------
  
    /** Creates a MaterializedViewFilterScanRule. */
    protected MaterializedViewFilterScanRule(Config config) {
      super(config);
    }
  
    @Deprecated // to be removed before 2.0
    public MaterializedViewFilterScanRule(RelBuilderFactory relBuilderFactory) {
      this(Config.DEFAULT.withRelBuilderFactory(relBuilderFactory)
          .as(Config.class));
    }
  
    //~ Methods ----------------------------------------------------------------
  
    @Override public void onMatch(RelOptRuleCall call) {
      final Filter filter = call.rel(0);
      final TableScan scan = call.rel(1);
      apply(call, filter, scan);
    }
  
    protected void apply(RelOptRuleCall call, Filter filter, TableScan scan) {
      final RelOptPlanner planner = call.getPlanner();
      final List<RelOptMaterialization> materializations =
          planner.getMaterializations();
      if (!materializations.isEmpty()) {
        RelNode root =
            filter.copy(filter.getTraitSet(), Collections.singletonList(scan));
        List<RelOptMaterialization> applicableMaterializations =
            RelOptMaterializations.getApplicableMaterializations(root, materializations);
        for (RelOptMaterialization materialization : applicableMaterializations) {
          if (RelOptUtil.areRowTypesEqual(scan.getRowType(),
              materialization.queryRel.getRowType(), false)) {
            RelNode target = materialization.queryRel;
            final HepPlanner hepPlanner =
                new HepPlanner(PROGRAM.get(), planner.getContext());
            hepPlanner.setRoot(target);
            target = hepPlanner.findBestExp();
            List<RelNode> subs = new SubstitutionVisitor(target, root)
                .go(materialization.tableRel);
            for (RelNode s : subs) {
              call.transformTo(s);
            }
          }
        }
      }
    }
  
    /** Rule configuration. */
    @Value.Immutable
    public interface Config extends RelRule.Config {
      Config DEFAULT = ImmutableMaterializedViewFilterScanRule.Config.of()
          .withOperandFor(Filter.class, TableScan.class);
  
      @Override default MaterializedViewFilterScanRule toRule() {
        return new MaterializedViewFilterScanRule(this);
      }
  
      /** Defines an operand tree for the given classes. */
      default Config withOperandFor(Class<? extends Filter> filterClass,
          Class<? extends TableScan> scanClass) {
        return withOperandSupplier(b0 ->
            b0.operand(filterClass).oneInput(b1 ->
                b1.operand(scanClass).noInputs()))
            .as(Config.class);
      }
    }
  }
  