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.fun;
  
  import org.apache.calcite.linq4j.Ord;
  import org.apache.calcite.sql.SqlCall;
  import org.apache.calcite.sql.SqlInternalOperator;
  import org.apache.calcite.sql.SqlKind;
  import org.apache.calcite.sql.SqlNode;
  import org.apache.calcite.sql.SqlNodeList;
  import org.apache.calcite.sql.SqlOperator;
  import org.apache.calcite.sql.SqlWriter;
  
  /** {@code EXTEND} operator.
   *
   * <p>Adds columns to a table's schema, as in
   * {@code SELECT ... FROM emp EXTEND (horoscope VARCHAR(100))}.
   *
   * <p>Not standard SQL. Added to Calcite to support Phoenix, but can be used to
   * achieve schema-on-query against other adapters.
   */
  class SqlExtendOperator extends SqlInternalOperator {
    SqlExtendOperator() {
      super("EXTEND", SqlKind.EXTEND, MDX_PRECEDENCE);
    }
  
    @Override public void unparse(SqlWriter writer, SqlCall call, int leftPrec,
        int rightPrec) {
      final SqlOperator operator = call.getOperator();
      assert call.operandCount() == 2;
      final SqlWriter.Frame frame =
          writer.startList(SqlWriter.FrameTypeEnum.SIMPLE);
      call.operand(0).unparse(writer, leftPrec, operator.getLeftPrec());
      writer.setNeedWhitespace(true);
      writer.sep(operator.getName());
      final SqlNodeList list = call.operand(1);
      final SqlWriter.Frame frame2 = writer.startList("(", ")");
      for (Ord<SqlNode> node2 : Ord.zip(list)) {
        if (node2.i > 0 && node2.i % 2 == 0) {
          writer.sep(",");
        }
        node2.e.unparse(writer, 2, 3);
      }
      writer.endList(frame2);
      writer.endList(frame);
    }
  }
  