Github user tejasapatil commented on a diff in the pull request:
https://github.com/apache/spark/pull/17049#discussion_r102882772
--- Diff:
sql/catalyst/src/main/scala/org/apache/spark/sql/catalyst/expressions/hash.scala
---
@@ -781,12 +780,12 @@ object HiveHashFunction extends
InterpretedHashFunction {
var i = 0
val length = struct.numFields
while (i < length) {
- result = (31 * result) + hash(struct.get(i, types(i)), types(i),
seed + 1).toInt
+ result = (31 * result) + hash(struct.get(i, types(i)), types(i),
0).toInt
--- End diff --
The `seed` is something used in murmur3 hash and hive hash does not need
it. See original impl in Hive codebase :
https://github.com/apache/hive/blob/4ba713ccd85c3706d195aeef9476e6e6363f1c21/serde/src/java/org/apache/hadoop/hive/serde2/objectinspector/ObjectInspectorUtils.java#L638
Since the methods related to hashing in Spark already had `seed`, I had to
add it in hive-hash. When I compute the hash, I always need to set `seed` to 0
which is what is done here.
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