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.adapter.java.JavaTypeFactory;
  import org.apache.calcite.linq4j.tree.BlockBuilder;
  import org.apache.calcite.linq4j.tree.Expression;
  import org.apache.calcite.linq4j.tree.Expressions;
  import org.apache.calcite.linq4j.tree.Primitive;
  import org.apache.calcite.plan.DeriveMode;
  import org.apache.calcite.plan.RelOptCluster;
  import org.apache.calcite.plan.RelTraitSet;
  import org.apache.calcite.rel.RelCollation;
  import org.apache.calcite.rel.RelCollationTraitDef;
  import org.apache.calcite.rel.RelDistributionTraitDef;
  import org.apache.calcite.rel.RelFieldCollation;
  import org.apache.calcite.rel.RelNode;
  import org.apache.calcite.rel.core.Values;
  import org.apache.calcite.rel.metadata.RelMdCollation;
  import org.apache.calcite.rel.metadata.RelMdDistribution;
  import org.apache.calcite.rel.metadata.RelMetadataQuery;
  import org.apache.calcite.rel.type.RelDataType;
  import org.apache.calcite.rel.type.RelDataTypeField;
  import org.apache.calcite.rex.RexLiteral;
  import org.apache.calcite.util.BuiltInMethod;
  import org.apache.calcite.util.Pair;
  
  import com.google.common.collect.ImmutableList;
  import com.google.common.collect.Ordering;
  
  import org.checkerframework.checker.nullness.qual.Nullable;
  
  import java.lang.reflect.Type;
  import java.util.ArrayList;
  import java.util.List;
  
  import static java.util.Objects.requireNonNull;
  
  /** Implementation of {@link org.apache.calcite.rel.core.Values} in
   * {@link org.apache.calcite.adapter.enumerable.EnumerableConvention enumerable calling convention}. */
  public class EnumerableValues extends Values implements EnumerableRel {
    /** Creates an EnumerableValues. */
    private EnumerableValues(RelOptCluster cluster, RelDataType rowType,
        ImmutableList<ImmutableList<RexLiteral>> tuples, RelTraitSet traitSet) {
      super(cluster, rowType, tuples, traitSet);
    }
  
    /** Creates an EnumerableValues. */
    public static EnumerableValues create(RelOptCluster cluster,
        final RelDataType rowType,
        final ImmutableList<ImmutableList<RexLiteral>> tuples) {
      final RelMetadataQuery mq = cluster.getMetadataQuery();
      final RelTraitSet traitSet =
          cluster.traitSetOf(EnumerableConvention.INSTANCE)
              .replaceIfs(RelCollationTraitDef.INSTANCE,
                  () -> RelMdCollation.values(mq, rowType, tuples))
              .replaceIf(RelDistributionTraitDef.INSTANCE,
                  () -> RelMdDistribution.values(rowType, tuples));
      return new EnumerableValues(cluster, rowType, tuples, traitSet);
    }
  
    @Override public RelNode copy(RelTraitSet traitSet, List<RelNode> inputs) {
      assert inputs.isEmpty();
      return new EnumerableValues(getCluster(), getRowType(), tuples, traitSet);
    }
  
    @Override public @Nullable RelNode passThrough(final RelTraitSet required) {
      RelCollation collation = required.getCollation();
      if (collation == null || collation.isDefault()) {
        return null;
      }
  
      // A Values with 0 or 1 rows can be ordered by any collation.
      if (tuples.size() > 1) {
        Ordering<List<RexLiteral>> ordering = null;
        // Generate ordering comparator according to the required collations.
        for (RelFieldCollation fc : collation.getFieldCollations()) {
          Ordering<List<RexLiteral>> comparator = RelMdCollation.comparator(fc);
          if (ordering == null) {
            ordering = comparator;
          } else {
            ordering = ordering.compound(comparator);
          }
        }
        // Check whether the tuples are sorted by required collations.
        if (!requireNonNull(ordering, "ordering").isOrdered(tuples)) {
          return null;
        }
      }
  
      // The tuples order satisfies the collation, we just create a new
      // relnode with required collation info.
      return copy(traitSet.replace(collation), ImmutableList.of());
    }
  
    @Override public DeriveMode getDeriveMode() {
      return DeriveMode.PROHIBITED;
    }
  
    @Override public Result implement(EnumerableRelImplementor implementor, Prefer pref) {
  /*
            return Linq4j.asEnumerable(
                new Object[][] {
                    new Object[] {1, 2},
                    new Object[] {3, 4}
                });
  */
      final JavaTypeFactory typeFactory =
          (JavaTypeFactory) getCluster().getTypeFactory();
      final BlockBuilder builder = new BlockBuilder();
      final PhysType physType =
          PhysTypeImpl.of(
              implementor.getTypeFactory(),
              getRowType(),
              pref.preferCustom());
      final Type rowClass = physType.getJavaRowType();
  
      final List<Expression> expressions = new ArrayList<>();
      final List<RelDataTypeField> fields = getRowType().getFieldList();
      for (List<RexLiteral> tuple : tuples) {
        final List<Expression> literals = new ArrayList<>();
        for (Pair<RelDataTypeField, RexLiteral> pair
            : Pair.zip(fields, tuple)) {
          literals.add(
              RexToLixTranslator.translateLiteral(
                  pair.right,
                  pair.left.getType(),
                  typeFactory,
                  RexImpTable.NullAs.NULL));
        }
        expressions.add(physType.record(literals));
      }
      builder.add(
          Expressions.return_(
              null,
              Expressions.call(
                  BuiltInMethod.AS_ENUMERABLE.method,
                  Expressions.newArrayInit(
                      Primitive.box(rowClass), expressions))));
      return implementor.result(physType, builder.toBlock());
    }
  }
  