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.druid;
  
  import org.apache.calcite.rel.type.RelDataType;
  import org.apache.calcite.rex.RexNode;
  import org.apache.calcite.sql.SqlOperator;
  
  import org.checkerframework.checker.nullness.qual.Nullable;
  
  /**
   * Defines how to convert a {@link RexNode} with a given Calcite SQL operator to
   * a Druid expression.
   */
  public interface DruidSqlOperatorConverter {
  
    /**
     * Returns the calcite SQL operator corresponding to Druid operator.
     *
     * @return operator
     */
    SqlOperator calciteOperator();
  
  
    /**
     * Translate rexNode to valid Druid expression.
     *
     * @param rexNode rexNode to translate to Druid expression
     * @param rowType row type associated with rexNode
     * @param druidQuery druid query used to figure out configs/fields related like timeZone
     *
     * @return valid Druid expression or null if it can not convert the rexNode
     */
    @Nullable String toDruidExpression(RexNode rexNode, RelDataType rowType, DruidQuery druidQuery);
  }
  