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.arrow.vector;
  
  /**
   * Configuration class to determine if null checking should be enabled or disabled for the "get"
   * methods. For example, the get method of class org.apache.arrow.vector.Float8Vector first checks
   * if the value at the given index is null, before retrieving the value. This configuration will
   * turn on and off such checks.
   *
   * <p>Null checking is on by default. You can disable it by setting either the system property or
   * the environmental variable to "false". The system property is named
   * "arrow.enable_null_check_for_get" and the environmental variable is named
   * "ARROW_ENABLE_NULL_CHECK_FOR_GET". When both the system property and the environmental variable
   * are set, the system property takes precedence.
   *
   * <p>Disabling null-checking in the "get" methods may lead to performance improvements. For
   * example, suppose we have the following micro-benchmark:
   *
   * <p>
   *
   * <pre>{@code
   * Float8Vector vector = ...
   *
   * public void test() {
   *   sum = 0;
   *   for (int i = 0; i < 1024; i++) {
   *     vector.set(i, i + 10.0);
   *     safeSum += vector.get(i);
   *   }
   * }
   *
   * }</pre>
   *
   * <p>Performance evaluations of the micro-benchmark with the JMH framework reveal that, disabling
   * null checking has the following effects: 1. The amounts of byte code and assembly code generated
   * by JIT are both smaller. 2. The performance improves by about 30% (2.819 ± 0.005 us/op vs. 4.069
   * ± 0.004 us/op).
   *
   * <p>Therefore, for scenarios where the user can be sure that the null-checking is unnecessary, it
   * is beneficial to disable it with this configuration.
   */
  public class NullCheckingForGet {
  
    /** The flag to indicate if null checking is enabled for "get" methods. */
    public static final boolean NULL_CHECKING_ENABLED;
  
    static {
      String envProperty = System.getenv("ARROW_ENABLE_NULL_CHECK_FOR_GET");
      String sysProperty = System.getProperty("arrow.enable_null_check_for_get");
  
      // The system property has a higher priority than the environmental variable.
      String flagValue = sysProperty;
      if (flagValue == null) {
        flagValue = envProperty;
      }
  
      // The flag is set to false only if the system property/environmental
      // variable is explicitly set to "false".
      NULL_CHECKING_ENABLED = !"false".equals(flagValue);
    }
  
    private NullCheckingForGet() {}
  }
  