RexSqlReflectiveConvertletTable.java

/*
 * 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.rex;

import org.apache.calcite.sql.SqlOperator;

import org.checkerframework.checker.nullness.qual.Nullable;

import java.util.HashMap;
import java.util.Map;

/**
 * Implementation of {@link RexSqlConvertletTable}.
 */
public class RexSqlReflectiveConvertletTable implements RexSqlConvertletTable {
  //~ Instance fields --------------------------------------------------------

  private final Map<Object, Object> map = new HashMap<>();

  //~ Constructors -----------------------------------------------------------

  public RexSqlReflectiveConvertletTable() {
  }

  //~ Methods ----------------------------------------------------------------

  @Override public @Nullable RexSqlConvertlet get(RexCall call) {
    RexSqlConvertlet convertlet;
    final SqlOperator op = call.getOperator();

    // Is there a convertlet for this operator
    // (e.g. SqlStdOperatorTable.plusOperator)?
    convertlet = (RexSqlConvertlet) map.get(op);
    if (convertlet != null) {
      return convertlet;
    }

    // Is there a convertlet for this class of operator
    // (e.g. SqlBinaryOperator)?
    @Nullable Class<?> clazz = op.getClass();
    while (clazz != null) {
      convertlet = (RexSqlConvertlet) map.get(clazz);
      if (convertlet != null) {
        return convertlet;
      }
      clazz = clazz.getSuperclass();
    }

    // Is there a convertlet for this class of expression
    // (e.g. SqlCall)?
    clazz = call.getClass();
    while (clazz != null) {
      convertlet = (RexSqlConvertlet) map.get(clazz);
      if (convertlet != null) {
        return convertlet;
      }
      clazz = clazz.getSuperclass();
    }
    return null;
  }

  /**
   * Registers a convertlet for a given operator instance.
   *
   * @param op         Operator instance, say
   * {@link org.apache.calcite.sql.fun.SqlStdOperatorTable#MINUS}
   * @param convertlet Convertlet
   */
  protected void registerOp(SqlOperator op, RexSqlConvertlet convertlet) {
    map.put(op, convertlet);
  }
}