Github user hvanhovell commented on a diff in the pull request:
https://github.com/apache/spark/pull/20817#discussion_r174416499
--- Diff:
sql/catalyst/src/main/scala/org/apache/spark/sql/catalyst/util/RandomUUIDGenerator.scala
---
@@ -0,0 +1,38 @@
+/*
+ * 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.catalyst.util
+
+import java.util.UUID
+
+import scala.util.Random
+
+/**
+ * This class is used to generate a UUID from Pseudo-Random Numbers
produced by
+ * Scala Random.
+ *
+ * For the algorithm, see RFC 4122: A Universally Unique IDentifier (UUID)
URN Namespace,
+ * section 4.4 "Algorithms for Creating a UUID from Truly Random or
Pseudo-Random Numbers".
+ */
+case class RandomUUIDGenerator(random: Random) {
+ def getNextUUID(): UUID = {
+ val mostSigBits = (random.nextLong() & 0xFFFFFFFFFFFF0FFFL) |
0x0000000000004000L
+ val leastSigBits = (random.nextLong() | 0x8000000000000000L) &
0xBFFFFFFFFFFFFFFFL
+
+ new UUID(mostSigBits, leastSigBits)
--- End diff --
I think we need to use a different RNG. `java.util.Random` only has 48 bits
of state, which is less than the 122 bits we need for random number generation.
Something like [PCG](http://pcg-random.org/) or a Mersenne twister would work.
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