[SPARK-24846][SQL] Made hashCode ExprId independent of jvmId

[gvr]

What changes were proposed in this pull request?

Made ExprId hashCode independent of jvmId to make canonicalization independent of JVM, by overriding hashCode (and necessarily also equality) to depend on id only

How was this patch tested?

Created a unit test ExprIdSuite
Ran all unit tests of sql/catalyst

[hvanhovell]

ok to test

[hvanhovell]

@gvr can you clean-up the description somewhat? It currently also has part of the template in it.

[hvanhovell]

otherwise, LGTM pending jenkins

[gvr]

Updated description, thanks @hvanhovell

[SparkQA]

Test build #93240 has finished for PR 21806 at commit 68d6f19.

• This patch passes all tests.
• This patch merges cleanly.
• This patch adds the following public classes (experimental):
• case class ExprId(id: Long, jvmId: UUID)

[viirya]

The change looks fine. However I'm wondering that have we had chance to compare hash code between expr ids from different jvms?

[hvanhovell]

@viirya this current change is only useful when you compare canonicalized plans created on different JVMs. This has come up when we tried to detect changes in plans over spark versions (plan stability) and when people are writing to caches used by multiple clusters.

[viirya]

@hvanhovell Got it. Thanks for your explanation. LGTM.

[HyukjinKwon]

LGTM too

[hvanhovell]

Merging to master. Thanks!