[BEAM-1512] Optimize leaf transforms materialization

[aviemzur]

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[aviemzur]

R: @amitsela
Cc: @staslev

[coveralls]

Coverage remained the same at 69.187% when pulling 62644dc on aviemzur:optimize-leaf-materialization into 4063019 on apache:master.

[asfbot]

Refer to this link for build results (access rights to CI server needed):
https://builds.apache.org/job/beam_PreCommit_Java_MavenInstall/7590/
--none--

[coveralls]

Coverage increased (+0.003%) to 69.19% when pulling 62644dc on aviemzur:optimize-leaf-materialization into 4063019 on apache:master.

[asfbot]

Refer to this link for build results (access rights to CI server needed):
https://builds.apache.org/job/beam_PreCommit_Java_MavenInstall/7591/
--none--

[staslev]

That's quite elegant.

I guess the proof that it really works lies in the fact the tests have managed to pass but just out of curiosity, did you have a chance to give it a try in cluster mode?

[aviemzur]

@staslev Yeah, ran it on cluster as well. Looks good!

[amitsela]

LGTM, merging.