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.rel.type.RelDataTypeField;
  import org.apache.calcite.sql.SqlIdentifier;
  import org.apache.calcite.sql.SqlNode;
  import org.apache.calcite.sql.SqlNodeList;
  import org.apache.calcite.sql.SqlSelect;
  
  import org.checkerframework.checker.nullness.qual.Nullable;
  
  import java.util.List;
  
  /**
   * Represents the name-resolution context for expressions in an ORDER BY clause.
   *
   * <p>In some dialects of SQL, the ORDER BY clause can reference column aliases
   * in the SELECT clause. For example, the query
   *
   * <blockquote><code>SELECT empno AS x<br>
   * FROM emp<br>
   * ORDER BY x</code></blockquote>
   *
   * <p>is valid.
   */
  public class OrderByScope extends DelegatingScope {
    //~ Instance fields --------------------------------------------------------
  
    private final SqlNodeList orderList;
    private final SqlSelect select;
  
    //~ Constructors -----------------------------------------------------------
  
    OrderByScope(
        SqlValidatorScope parent,
        SqlNodeList orderList,
        SqlSelect select) {
      super(parent);
      this.orderList = orderList;
      this.select = select;
    }
  
    //~ Methods ----------------------------------------------------------------
  
    @Override public SqlNode getNode() {
      return orderList;
    }
  
    @Override public void findAllColumnNames(List<SqlMoniker> result) {
      final SqlValidatorNamespace ns = validator.getNamespaceOrThrow(select);
      addColumnNames(ns, result);
    }
  
    @Override public SqlQualified fullyQualify(SqlIdentifier identifier) {
      // If it's a simple identifier, look for an alias.
      if (identifier.isSimple()
          && validator.config().conformance().isSortByAlias()) {
        SqlQualified qualified = qualifyUsingAlias(select, identifier);
        if (qualified != null) {
          return qualified;
        }
      }
      return super.fullyQualify(identifier);
    }
  
    @Override public @Nullable RelDataType resolveColumn(String name, SqlNode ctx) {
      final SqlValidatorNamespace selectNs = validator.getNamespaceOrThrow(select);
      final RelDataType rowType = selectNs.getRowType();
      final SqlNameMatcher nameMatcher = validator.catalogReader.nameMatcher();
      final RelDataTypeField field = nameMatcher.field(rowType, name);
      if (field != null) {
        return field.getType();
      }
      final SqlValidatorScope selectScope = validator.getSelectScope(select);
      return selectScope.resolveColumn(name, ctx);
    }
  
    @Override public void validateExpr(SqlNode expr) {
      SqlNode expanded = validator.expandOrderExpr(select, expr);
  
      // expression needs to be valid in parent scope too
      parent.validateExpr(expanded);
    }
  }
  