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.adapter.enumerable;
  
  import org.apache.calcite.plan.RelOptCluster;
  import org.apache.calcite.plan.RelTraitSet;
  import org.apache.calcite.rel.RelCollationTraitDef;
  import org.apache.calcite.rel.RelNode;
  import org.apache.calcite.rel.core.Project;
  import org.apache.calcite.rel.metadata.RelMdCollation;
  import org.apache.calcite.rel.metadata.RelMetadataQuery;
  import org.apache.calcite.rel.type.RelDataType;
  import org.apache.calcite.rex.RexNode;
  import org.apache.calcite.util.Pair;
  import org.apache.calcite.util.Util;
  
  import com.google.common.collect.ImmutableList;
  import com.google.common.collect.ImmutableSet;
  
  import org.checkerframework.checker.nullness.qual.Nullable;
  
  import java.util.List;
  
  /** Implementation of {@link org.apache.calcite.rel.core.Project} in
   * {@link org.apache.calcite.adapter.enumerable.EnumerableConvention enumerable calling convention}. */
  public class EnumerableProject extends Project implements EnumerableRel {
    /**
     * Creates an EnumerableProject.
     *
     * <p>Use {@link #create} unless you know what you're doing.
     *
     * @param cluster  Cluster this relational expression belongs to
     * @param traitSet Traits of this relational expression
     * @param input    Input relational expression
     * @param projects List of expressions for the input columns
     * @param rowType  Output row type
     */
    public EnumerableProject(
        RelOptCluster cluster,
        RelTraitSet traitSet,
        RelNode input,
        List<? extends RexNode> projects,
        RelDataType rowType) {
      super(cluster, traitSet, ImmutableList.of(), input, projects, rowType, ImmutableSet.of());
      assert getConvention() instanceof EnumerableConvention;
    }
  
    @Deprecated // to be removed before 2.0
    public EnumerableProject(RelOptCluster cluster, RelTraitSet traitSet,
        RelNode input, List<? extends RexNode> projects, RelDataType rowType,
        int flags) {
      this(cluster, traitSet, input, projects, rowType);
      Util.discard(flags);
    }
  
    /** Creates an EnumerableProject, specifying row type rather than field
     * names. */
    public static EnumerableProject create(final RelNode input,
        final List<? extends RexNode> projects, RelDataType rowType) {
      final RelOptCluster cluster = input.getCluster();
      final RelMetadataQuery mq = cluster.getMetadataQuery();
      final RelTraitSet traitSet =
          cluster.traitSet().replace(EnumerableConvention.INSTANCE)
              .replaceIfs(RelCollationTraitDef.INSTANCE,
                  () -> RelMdCollation.project(mq, input, projects));
      return new EnumerableProject(cluster, traitSet, input, projects, rowType);
    }
  
    @Override public EnumerableProject copy(RelTraitSet traitSet, RelNode input,
        List<RexNode> projects, RelDataType rowType) {
      return new EnumerableProject(getCluster(), traitSet, input,
          projects, rowType);
    }
  
    @Override public Result implement(EnumerableRelImplementor implementor, Prefer pref) {
      // EnumerableCalcRel is always better
      throw new UnsupportedOperationException();
    }
  
    @Override public @Nullable Pair<RelTraitSet, List<RelTraitSet>> passThroughTraits(
        RelTraitSet required) {
      return EnumerableTraitsUtils.passThroughTraitsForProject(required, exps,
          input.getRowType(), input.getCluster().getTypeFactory(), traitSet);
    }
  
    @Override public @Nullable Pair<RelTraitSet, List<RelTraitSet>> deriveTraits(
        final RelTraitSet childTraits, final int childId) {
      return EnumerableTraitsUtils.deriveTraitsForProject(childTraits, childId, exps,
          input.getRowType(), input.getCluster().getTypeFactory(), traitSet);
    }
  }
  