[SPARK-18271][SQL]hash udf in HiveSessionCatalog.hiveFunctions is redundant

[windpiger]

What changes were proposed in this pull request?

when lookupfunction in HiveSessionCatalog, first look up in spark's build-in functionRegistry, if it not existed, then look up the Hive'S build-in functions which are listed in Seq(hiveFunctions).

But the [hash] function is already in spark's build-in functionRegistry list, so it will never to go to look up in Hive's hiveFunctions list, so the [hash] function which is in Hive's hiveFunctions is redundant, we can remove it.

[cloud-fan]

ok to test

[cloud-fan]

LGTM

[SparkQA]

Test build #68138 has finished for PR 15766 at commit c3a0389.

• This patch fails Spark unit tests.
• This patch merges cleanly.
• This patch adds no public classes.

[andrewor14]

retest this please

[SparkQA]

Test build #68152 has finished for PR 15766 at commit c3a0389.

• This patch fails Spark unit tests.
• This patch merges cleanly.
• This patch adds no public classes.

[rxin]

Don't we actually unregister the Spark built-in one when testing Hive?

[cloud-fan]

@rxin good catch! We do unregister the spark builtin hash in test: https://github.com/apache/spark/blob/master/sql/hive/compatibility/src/test/scala/org/apache/spark/sql/hive/execution/HiveCompatibilitySuite.scala#L60-L61

So we have a little more work to do here, we should register the hive hash function in that test suite.

[gatorsmile]

I am working on the related issue in #14498

[windpiger]

@rxin @cloud-fan you are rigth,hash should be unregistered and replace with Hive's hash, or we could put the failed hash testcase into blacklist as @gatorsmile 's work #14498 . I will close the PR

[windpiger]

@cloud-fan I will appreciate that you can help to close this PR~

[cloud-fan]

Only the owner(yourself) can close this PR.