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.sql.SqlFunction;
  import org.apache.calcite.sql.SqlFunctionCategory;
  import org.apache.calcite.sql.SqlKind;
  import org.apache.calcite.sql.SqlOperatorBinding;
  import org.apache.calcite.sql.SqlSyntax;
  import org.apache.calcite.sql.type.OperandTypes;
  import org.apache.calcite.sql.type.SqlReturnTypeInference;
  import org.apache.calcite.sql.validate.SqlMonotonicity;
  
  /**
   * Base class for functions such as "USER", "CURRENT_ROLE", and "CURRENT_PATH".
   */
  public class SqlBaseContextVariable extends SqlFunction {
    //~ Constructors -----------------------------------------------------------
  
    /** Creates a SqlBaseContextVariable. */
    protected SqlBaseContextVariable(String name,
        SqlReturnTypeInference returnType, SqlFunctionCategory category) {
      super(name, SqlKind.OTHER_FUNCTION, returnType, null, OperandTypes.NILADIC,
          category);
    }
  
    //~ Methods ----------------------------------------------------------------
  
    @Override public SqlSyntax getSyntax() {
      return SqlSyntax.FUNCTION_ID;
    }
  
    // All of the string constants are monotonic.
    @Override public SqlMonotonicity getMonotonicity(SqlOperatorBinding call) {
      return SqlMonotonicity.CONSTANT;
    }
  
    // Plans referencing context variables should never be cached
    @Override public boolean isDynamicFunction() {
      return true;
    }
  }
  