Github user hvanhovell commented on a diff in the pull request:
https://github.com/apache/spark/pull/15047#discussion_r78299559
--- Diff: sql/hive/src/main/scala/org/apache/spark/sql/hive/HiveHash.scala
---
@@ -0,0 +1,145 @@
+/*
+ * 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.hive
+
+import org.apache.spark.sql.catalyst.InternalRow
+import org.apache.spark.sql.catalyst.expressions._
+import org.apache.spark.sql.catalyst.util.{ArrayData, MapData}
+import org.apache.spark.sql.types._
+import org.apache.spark.unsafe.Platform
+import org.apache.spark.unsafe.types.UTF8String
+
+/**
+ * Simulates Hive's hashing function at
+ *
org.apache.hadoop.hive.serde2.objectinspector.ObjectInspectorUtils#hashcode()
in Hive
+ *
+ * We should use this hash function for both shuffle and bucket of Hive
tables, so that
+ * we can guarantee shuffle and bucketing have same data distribution
+ *
+ * TODO: Support Decimal and date related types
+ */
+@ExpressionDescription(
+ usage = "_FUNC_(a1, a2, ...) - Returns a hash value of the arguments.")
+case class HiveHash(children: Seq[Expression], seed: Int) extends
HashExpression[Int] {
--- End diff --
It might be the easiest to isolate element hashing for
`Maps`/`Arrays`/`Rows` in the super class. Code generation is basically string
concatenation with some fancy tricks (look in `CodegenContext`). Ping me if you
need a hand.
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