[GitHub] spark pull request #22079: [SPARK-23207][SPARK-22905][SQL][BACKPORT-2.2] Shu...

[squito <gi...@git.apache.org>]

Github user squito commented on a diff in the pull request:

    https://github.com/apache/spark/pull/22079#discussion_r209815627
  
    --- Diff: sql/catalyst/src/main/java/org/apache/spark/sql/execution/RecordBinaryComparator.java ---
    @@ -0,0 +1,70 @@
    +/*
    + * 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.spark.sql.execution;
    +
    +import org.apache.spark.unsafe.Platform;
    +import org.apache.spark.util.collection.unsafe.sort.RecordComparator;
    +
    +public final class RecordBinaryComparator extends RecordComparator {
    +
    +  // TODO(jiangxb) Add test suite for this.
    +  @Override
    +  public int compare(
    +      Object leftObj, long leftOff, int leftLen, Object rightObj, long rightOff, int rightLen) {
    +    int i = 0;
    +    int res = 0;
    +
    +    // If the arrays have different length, the longer one is larger.
    +    if (leftLen != rightLen) {
    +      return leftLen - rightLen;
    +    }
    +
    +    // The following logic uses `leftLen` as the length for both `leftObj` and `rightObj`, since
    +    // we have guaranteed `leftLen` == `rightLen`.
    +
    +    // check if stars align and we can get both offsets to be aligned
    +    if ((leftOff % 8) == (rightOff % 8)) {
    +      while ((leftOff + i) % 8 != 0 && i < leftLen) {
    +        res = (Platform.getByte(leftObj, leftOff + i) & 0xff) -
    +                (Platform.getByte(rightObj, rightOff + i) & 0xff);
    +        if (res != 0) return res;
    +        i += 1;
    +      }
    +    }
    +    // for architectures that support unaligned accesses, chew it up 8 bytes at a time
    +    if (Platform.unaligned() || (((leftOff + i) % 8 == 0) && ((rightOff + i) % 8 == 0))) {
    +      while (i <= leftLen - 8) {
    +        res = (int) ((Platform.getLong(leftObj, leftOff + i) -
    +                Platform.getLong(rightObj, rightOff + i)) % Integer.MAX_VALUE);
    +        if (res != 0) return res;
    --- End diff --
    
    good question, @jiangxb1987 any thoughts on this?  (it was this way in the original)


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