Github user cloud-fan commented on a diff in the pull request:
https://github.com/apache/spark/pull/15047#discussion_r78331887
--- 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] {
+ def this(arguments: Seq[Expression]) = this(arguments, 42)
+
+ override def dataType: DataType = IntegerType
+
+ override def prettyName: String = "hive-hash"
+
+ override protected def hasherClassName: String =
classOf[HiveHash].getName
+
+ override protected def computeHash(value: Any, dataType: DataType, seed:
Int): Int = {
+ HiveHashFunction.hash(value, dataType, seed).toInt
+ }
+}
+
+object HiveHashFunction extends InterpretedHashFunction {
+ override protected def hashInt(i: Int, seed: Long): Long = {
+ HiveHasher.hashInt(i, seed.toInt)
+ }
+
+ override protected def hashLong(l: Long, seed: Long): Long = {
+ HiveHasher.hashLong(l, seed.toInt)
+ }
+
+ override protected def hashUnsafeBytes(base: AnyRef, offset: Long, len:
Int, seed: Long): Long = {
+ HiveHasher.hashUnsafeBytes(base, offset, len, seed.toInt)
+ }
+
+ override def hash(value: Any, dataType: DataType, seed: Long): Long = {
+ value match {
+ case s: UTF8String =>
+ val bytes = s.getBytes
+ var result: Int = 0
+ var i = 0
+ while (i < bytes.length) {
+ result = (result * 31) + bytes(i).toInt
+ i += 1
+ }
+ result
+
+
+ case array: ArrayData =>
+ val elementType = dataType match {
+ case udt: UserDefinedType[_] =>
udt.sqlType.asInstanceOf[ArrayType].elementType
--- End diff --
the caller of `hash` guarantees the value matches the data type. So in this
branch, if the value is `ArrayData`, the data type must be `ArrayType` or UDT
of `ArrayType`
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