HIVE-28211: Restore hive-exec-core jar

[simhadri-g]

What changes were proposed in this pull request?

The hive-exec-core jar is used by spark, oozie, hudi and many other pojects. Removal of the hive-exec-core jar has caused the following issues.

Spark : https://lists.apache.org/list?dev@hive.apache.org:lte=1M:joda
Oozie: https://lists.apache.org/thread/yld75ltf9y8d9q3cow3xqlg0fqyj6mkg
Hudi: apache/hudi#8147

Until the we shade & relocate dependencies in hive-exec, we should restore the hive-exec core jar .

Why are the changes needed?

Does this PR introduce any user-facing change?

Is the change a dependency upgrade?

How was this patch tested?

[zabetak]

Hey @simhadri-g, thanks for taking the initiative.

I would prefer before moving forward with this change to reach consensus in the community. Maybe its removal was a mistake but it did have some advantages. Please start or comment on an existing thread in the dev list and we can continue the discussion there.

Moreover, if we decide to restore the core jar it should be done under a separate JIRA ticket. HIVE-26220 is about shading problems so this is not strictly related. The shading problems will have to be resolved anyways.

[simhadri-g]

Sure @zabetak , i will start or continue an existing mail thread shortly.
I have created a new jira for this as well: https://issues.apache.org/jira/browse/HIVE-28211

The intention for this jira was to provide a smoother transition from the hive-exec-core to hive-exec jar for down stream projects .

Thanks!

[sonarcloud]

Quality Gate passed

Issues
1 New issue
0 Accepted issues

Measures
0 Security Hotspots
No data about Coverage
No data about Duplication

See analysis details on SonarCloud

[pan3793]

+1 for restoring hive-exec-core. currently hive-exec shades classes but does not relocate, which can not be consumed by lots of downstream projects, choosing hive-exec-core and handling transitive deps manually is the only choice.

Handling hive transitive deps is always a challenge for downstream projects.

forward my previous comments on google/guava#6666 (comment)

hive-exec-2.3.7.jar is actually a standalone jar, and hive-exec-2.3.7-core.jar is actually the original normal jar. Unfortunately, hive-exec-2.3.7.jar seems to be abused as a normal dependency widely.

and #4888 (comment)

Seems reducing dependencies is not a mission in the Hive project

[simhadri-g]

Thanks @zabetak and @pan3793

I have started a mail thread on this here: https://lists.apache.org/thread/t2vzf1mydnzsckctcvfl93srrod4w76j

Thanks!

[dengzhhu653]

+1 from my side, as relocating the class seems not an easy task, it requires careful tests, which may in turn causing some inconvenience and delay of upgrading to the new major release for downstream project.

[ayushtkn]

LGTM

[ayushtkn]

We have enough agreement on the ML as well, merging.