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.linq4j.tree.BlockBuilder;
  import org.apache.calcite.linq4j.tree.Expression;
  import org.apache.calcite.linq4j.tree.Expressions;
  import org.apache.calcite.linq4j.tree.ParameterExpression;
  import org.apache.calcite.plan.RelOptCluster;
  import org.apache.calcite.plan.RelTraitSet;
  import org.apache.calcite.rel.RelNode;
  import org.apache.calcite.rel.core.Collect;
  import org.apache.calcite.rel.type.RelDataType;
  import org.apache.calcite.sql.type.SqlTypeName;
  import org.apache.calcite.sql.type.SqlTypeUtil;
  import org.apache.calcite.util.BuiltInMethod;
  
  import static java.util.Objects.requireNonNull;
  
  /** Implementation of {@link org.apache.calcite.rel.core.Collect} in
   * {@link org.apache.calcite.adapter.enumerable.EnumerableConvention enumerable calling convention}. */
  public class EnumerableCollect extends Collect implements EnumerableRel {
    /**
     * Creates an EnumerableCollect.
     *
     * <p>Use {@link #create} unless you know what you're doing.
     *
     * @param cluster   Cluster
     * @param traitSet  Trait set
     * @param input     Input relational expression
     * @param rowType   Row type
     */
    public EnumerableCollect(RelOptCluster cluster, RelTraitSet traitSet,
        RelNode input, RelDataType rowType) {
      super(cluster, traitSet, input, rowType);
      assert getConvention() instanceof EnumerableConvention;
      assert getConvention() == input.getConvention();
    }
  
    @Deprecated // to be removed before 2.0
    public EnumerableCollect(RelOptCluster cluster, RelTraitSet traitSet,
        RelNode input, String fieldName) {
      this(cluster, traitSet, input,
          deriveRowType(cluster.getTypeFactory(), SqlTypeName.MULTISET, fieldName,
              input.getRowType()));
    }
  
    /**
     * Creates an EnumerableCollect.
     *
     * @param input          Input relational expression
     * @param rowType        Row type
     */
    public static Collect create(RelNode input, RelDataType rowType) {
      final RelOptCluster cluster = input.getCluster();
      final RelTraitSet traitSet =
          cluster.traitSet().replace(EnumerableConvention.INSTANCE);
      return new EnumerableCollect(cluster, traitSet, input, rowType);
    }
  
    @Override public EnumerableCollect copy(RelTraitSet traitSet,
        RelNode newInput) {
      return new EnumerableCollect(getCluster(), traitSet, newInput, rowType());
    }
  
    @Override public Result implement(EnumerableRelImplementor implementor, Prefer pref) {
      final BlockBuilder builder = new BlockBuilder();
      final EnumerableRel child = (EnumerableRel) getInput();
      // REVIEW zabetak January 7, 2019: Even if we ask the implementor to provide a result
      // where records are represented as arrays (Prefer.ARRAY) this may not be respected.
      final Result result = implementor.visitChild(this, 0, child, Prefer.ARRAY);
      final PhysType physType =
          PhysTypeImpl.of(
              implementor.getTypeFactory(),
              getRowType(),
              JavaRowFormat.LIST);
  
      final SqlTypeName collectionType = getCollectionType();
  
      // final Enumerable child = <<child adapter>>;
      // final Enumerable<Object[]> converted = child.select(<<conversion code>>);
      // if collectionType is ARRAY or MULTISET: final List<Object[]> list = converted.toList();
      // if collectionType is MAP:               final Map<Object, Object> map = converted.toMap();
      Expression child_ =
          builder.append(
              "child", result.block);
  
      Expression conv_ = child_;
      Expression collectionExpr;
      switch (collectionType) {
      case ARRAY:
      case MULTISET:
        RelDataType collectionComponentType =
            requireNonNull(rowType().getFieldList().get(0).getType().getComponentType());
        RelDataType childRecordType = result.physType.getRowType().getFieldList().get(0).getType();
  
        if (!SqlTypeUtil.sameNamedType(collectionComponentType, childRecordType)) {
          // In the internal representation of multisets , every element must be a record. In case the
          // result above is a scalar type we have to wrap it around a physical type capable of
          // representing records. For this reason the following conversion is necessary.
          // REVIEW zabetak January 7, 2019: If we can ensure that the input to this operator
          // has the correct physical type (e.g., respecting the Prefer.ARRAY above)
          // then this conversion can be removed.
          conv_ =
              builder.append(
                  "converted", result.physType.convertTo(child_, JavaRowFormat.ARRAY));
        }
  
        collectionExpr =
            builder.append("list",
                Expressions.call(conv_,
                    BuiltInMethod.ENUMERABLE_TO_LIST.method));
        break;
      case MAP:
        // Convert input 'Object[]' to MAP data, we don't specify a comparator, just
        // keep the original order of this map. (the inner map is a LinkedHashMap)
        ParameterExpression input = Expressions.parameter(Object.class, "input");
  
        // keySelector lambda: input -> ((Object[])input)[0]
        Expression keySelector =
            Expressions.lambda(
                Expressions.arrayIndex(Expressions.convert_(input, Object[].class),
                    Expressions.constant(0)), input);
  
        // valueSelector lambda: input -> ((Object[])input)[1]
        Expression valueSelector =
            Expressions.lambda(
                Expressions.arrayIndex(Expressions.convert_(input, Object[].class),
                    Expressions.constant(1)), input);
  
        collectionExpr =
            builder.append("map",
                Expressions.call(conv_,
                    BuiltInMethod.ENUMERABLE_TO_MAP.method, keySelector, valueSelector));
        break;
      default:
        throw new IllegalArgumentException("unknown collection type " + collectionType);
      }
  
      builder.add(
          Expressions.return_(null,
              Expressions.call(
                  BuiltInMethod.SINGLETON_ENUMERABLE.method, collectionExpr)));
  
      return implementor.result(physType, builder.toBlock());
    }
  }
  