Github user JoshRosen commented on a diff in the pull request:
https://github.com/apache/spark/pull/6444#discussion_r34095513
--- Diff:
core/src/main/java/org/apache/spark/util/collection/unsafe/sort/PrefixComparators.java
---
@@ -0,0 +1,123 @@
+/*
+ * 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.util.collection.unsafe.sort;
+
+import com.google.common.base.Charsets;
+import com.google.common.primitives.Longs;
+import org.apache.spark.annotation.Private;
+import org.apache.spark.unsafe.types.UTF8String;
+
+@Private
+public class PrefixComparators {
+ private PrefixComparators() {}
+
+ public static final StringPrefixComparator STRING = new
StringPrefixComparator();
+ public static final IntPrefixComparator INTEGER = new
IntPrefixComparator();
+ public static final LongPrefixComparator LONG = new
LongPrefixComparator();
+ public static final FloatPrefixComparator FLOAT = new
FloatPrefixComparator();
+ public static final DoublePrefixComparator DOUBLE = new
DoublePrefixComparator();
+
+ public static final class StringPrefixComparator extends
PrefixComparator {
+ @Override
+ public int compare(long aPrefix, long bPrefix) {
+ // TODO: this can certainly be done more efficiently
+ byte[] a = Longs.toByteArray(aPrefix);
+ byte[] b = Longs.toByteArray(bPrefix);
+ for (int i = 0; i < 8; i++) {
+ if (a[i] == b[i]) continue;
+ if (a[i] > b[i]) return -1;
+ else if (a[i] < b[i]) return 1;
+ }
+ return 0;
+ }
+
+ public long computePrefix(UTF8String value) {
+ // TODO: this can certainly be done more efficiently
+ return value == null ? 0L : computePrefix(value.toString());
+ }
+
+ public long computePrefix(String value) {
+ // TODO: this can certainly be done more efficiently
+ if (value == null || value.length() == 0) {
+ return 0L;
+ } else {
+ String first4Chars = value.substring(0, Math.min(3, value.length()
- 1));
+ byte[] utf16Bytes = first4Chars.getBytes(Charsets.UTF_16);
+ byte[] padded = new byte[8];
+ if (utf16Bytes.length < 8) {
+ System.arraycopy(utf16Bytes, 0, padded, 0, utf16Bytes.length);
+ }
+ return Longs.fromByteArray(padded);
+ }
+ }
+ }
+
+ public static final class IntPrefixComparator extends PrefixComparator {
+ @Override
+ public int compare(long aPrefix, long bPrefix) {
+ int a = (int) aPrefix;
+ int b = (int) bPrefix;
+ return (a < b) ? -1 : (a > b) ? 1 : 0;
+ }
+
+ public final long NULL_PREFIX = computePrefix(Integer.MIN_VALUE);
--- End diff --
I think it's technically fine for `null` and `Integer.MIN_VALUE` to have
the same prefix; in that case, we'll fall back to comparing the actual values
to distinguish between these two cases.
---
If your project is set up for it, you can reply to this email and have your
reply appear on GitHub as well. If your project does not have this feature
enabled and wishes so, or if the feature is enabled but not working, please
contact infrastructure at [email protected] or file a JIRA ticket
with INFRA.
---
---------------------------------------------------------------------
To unsubscribe, e-mail: [email protected]
For additional commands, e-mail: [email protected]
