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.plan.RelOptCluster;
  import org.apache.calcite.plan.RelTraitSet;
  import org.apache.calcite.rel.RelNode;
  import org.apache.calcite.rel.core.Uncollect;
  import org.apache.calcite.rel.type.RelDataType;
  import org.apache.calcite.rel.type.RelDataTypeField;
  import org.apache.calcite.runtime.SqlFunctions.FlatProductInputType;
  import org.apache.calcite.sql.type.MapSqlType;
  import org.apache.calcite.util.BuiltInMethod;
  
  import com.google.common.primitives.Ints;
  
  import java.util.ArrayList;
  import java.util.Collections;
  import java.util.List;
  
  import static org.apache.calcite.sql.type.NonNullableAccessors.getComponentTypeOrThrow;
  
  /** Implementation of {@link org.apache.calcite.rel.core.Uncollect} in
   * {@link org.apache.calcite.adapter.enumerable.EnumerableConvention enumerable calling convention}. */
  public class EnumerableUncollect extends Uncollect implements EnumerableRel {
    @Deprecated // to be removed before 2.0
    public EnumerableUncollect(RelOptCluster cluster, RelTraitSet traitSet,
        RelNode child) {
      this(cluster, traitSet, child, false);
    }
  
    /** Creates an EnumerableUncollect.
     *
     * <p>Use {@link #create} unless you know what you're doing. */
    public EnumerableUncollect(RelOptCluster cluster, RelTraitSet traitSet,
        RelNode child, boolean withOrdinality) {
      super(cluster, traitSet, child, withOrdinality, Collections.emptyList());
      assert getConvention() instanceof EnumerableConvention;
      assert getConvention() == child.getConvention();
    }
  
    /**
     * Creates an EnumerableUncollect.
     *
     * <p>Each field of the input relational expression must be an array or
     * multiset.
     *
     * @param traitSet Trait set
     * @param input    Input relational expression
     * @param withOrdinality Whether output should contain an ORDINALITY column
     */
    public static EnumerableUncollect create(RelTraitSet traitSet, RelNode input,
        boolean withOrdinality) {
      final RelOptCluster cluster = input.getCluster();
      return new EnumerableUncollect(cluster, traitSet, input, withOrdinality);
    }
  
    @Override public EnumerableUncollect copy(RelTraitSet traitSet,
        RelNode newInput) {
      return new EnumerableUncollect(getCluster(), traitSet, newInput,
          withOrdinality);
    }
  
    @Override public Result implement(EnumerableRelImplementor implementor, Prefer pref) {
      final BlockBuilder builder = new BlockBuilder();
      final EnumerableRel child = (EnumerableRel) getInput();
      final Result result = implementor.visitChild(this, 0, child, pref);
      final PhysType physType =
          PhysTypeImpl.of(
              implementor.getTypeFactory(),
              getRowType(),
              JavaRowFormat.LIST);
  
      // final Enumerable<List<Employee>> child = <<child adapter>>;
      // return child.selectMany(FLAT_PRODUCT);
      final Expression child_ =
          builder.append(
              "child", result.block);
  
      final List<Integer> fieldCounts = new ArrayList<>();
      final List<FlatProductInputType> inputTypes = new ArrayList<>();
  
      Expression lambdaForStructWithSingleItem = null;
      for (RelDataTypeField field : child.getRowType().getFieldList()) {
        final RelDataType type = field.getType();
        if (type instanceof MapSqlType) {
          fieldCounts.add(2);
          inputTypes.add(FlatProductInputType.MAP);
        } else {
          final RelDataType elementType = getComponentTypeOrThrow(type);
          if (elementType.isStruct()) {
            if (elementType.getFieldCount() == 1 && child.getRowType().getFieldList().size() == 1
                && !withOrdinality) {
              // Solves CALCITE-4063: if we are processing a single field, which is a struct with a
              // single item inside, and no ordinality; the result must be a scalar, hence use a
              // special lambda that does not return lists, but the (single) items within those lists
              lambdaForStructWithSingleItem = Expressions.call(BuiltInMethod.FLAT_LIST.method);
            } else {
              fieldCounts.add(elementType.getFieldCount());
              inputTypes.add(FlatProductInputType.LIST);
            }
          } else {
            fieldCounts.add(-1);
            inputTypes.add(FlatProductInputType.SCALAR);
          }
        }
      }
  
      final Expression lambda = lambdaForStructWithSingleItem != null
          ? lambdaForStructWithSingleItem
          : Expressions.call(BuiltInMethod.FLAT_PRODUCT.method,
              Expressions.constant(Ints.toArray(fieldCounts)),
              Expressions.constant(withOrdinality),
              Expressions.constant(
                  inputTypes.toArray(new FlatProductInputType[0])));
      builder.add(
          Expressions.return_(null,
              Expressions.call(child_,
                  BuiltInMethod.SELECT_MANY.method,
                  lambda)));
      return implementor.result(physType, builder.toBlock());
    }
  
  }
  