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.sql.validate;
  
  import org.apache.calcite.rel.type.RelDataType;
  import org.apache.calcite.sql.SqlCall;
  import org.apache.calcite.sql.SqlKind;
  import org.apache.calcite.sql.SqlNode;
  import org.apache.calcite.util.Util;
  
  import org.checkerframework.checker.nullness.qual.Nullable;
  
  import static org.apache.calcite.util.Static.RESOURCE;
  
  import static java.util.Objects.requireNonNull;
  
  /**
   * Namespace based upon a set operation (UNION, INTERSECT, EXCEPT).
   */
  public class SetopNamespace extends AbstractNamespace {
    //~ Instance fields --------------------------------------------------------
  
    private final SqlCall call;
  
    //~ Constructors -----------------------------------------------------------
  
    /**
     * Creates a <code>SetopNamespace</code>.
     *
     * @param validator     Validator
     * @param call          Call to set operator
     * @param enclosingNode Enclosing node
     */
    protected SetopNamespace(
        SqlValidatorImpl validator,
        SqlCall call,
        SqlNode enclosingNode) {
      super(validator, enclosingNode);
      this.call = call;
    }
  
    //~ Methods ----------------------------------------------------------------
  
    @Override public @Nullable SqlNode getNode() {
      return call;
    }
  
    @Override public SqlMonotonicity getMonotonicity(String columnName) {
      SqlMonotonicity monotonicity = null;
      int index = getRowType().getFieldNames().indexOf(columnName);
      if (index < 0) {
        return SqlMonotonicity.NOT_MONOTONIC;
      }
      for (SqlNode operand : call.getOperandList()) {
        final SqlValidatorNamespace namespace =
            requireNonNull(validator.getNamespace(operand),
                () -> "namespace for " + operand);
        monotonicity =
            combine(monotonicity,
                namespace.getMonotonicity(
                    namespace.getRowType().getFieldNames().get(index)));
      }
      return Util.first(monotonicity, SqlMonotonicity.NOT_MONOTONIC);
    }
  
    private static SqlMonotonicity combine(@Nullable SqlMonotonicity m0,
        SqlMonotonicity m1) {
      if (m0 == null) {
        return m1;
      }
      if (m1 == null) {
        return m0;
      }
      if (m0 == m1) {
        return m0;
      }
      if (m0.unstrict() == m1) {
        return m1;
      }
      if (m1.unstrict() == m0) {
        return m0;
      }
      return SqlMonotonicity.NOT_MONOTONIC;
    }
  
    @Override public RelDataType validateImpl(RelDataType targetRowType) {
      switch (call.getKind()) {
      case UNION:
      case INTERSECT:
      case EXCEPT:
        final SqlValidatorScope scope =
            requireNonNull(validator.scopes.get(call),
                () -> "scope for " + call);
        for (SqlNode operand : call.getOperandList()) {
          if (!operand.isA(SqlKind.QUERY)) {
            throw validator.newValidationError(operand,
                RESOURCE.needQueryOp(operand.toString()));
          }
          validator.validateQuery(operand, scope, targetRowType);
        }
        return call.getOperator().deriveType(
            validator,
            scope,
            call);
      default:
        throw new AssertionError("Not a query: " + call.getKind());
      }
    }
  }
  