Github user mridulm commented on a diff in the pull request:
https://github.com/apache/spark/pull/22079#discussion_r209705612
--- 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 --
It is possible for two objects to be unequal and yet we consider them as
equal with this code, if the long values are separated by Int.MaxValue.
Any particular reason why this code is written like this with the
inaccuracy and not simply the idiomatic comparator comparison ?
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