[SPARK-12130] Replace shuffleManagerClass with shortShuffleMgrNames in ExternalShuffleBlockResolver

[lianhuiwang]

Replace shuffleManagerClassName with shortShuffleMgrName is to reduce time of string's comparison. and put sort's comparison on the front. cc @JoshRosen @andrewor14

[andrewor14]

looks OK, but why not add a field in ShuffleManager itself that sets this? So you can just do shuffleManager.name or something here

[lianhuiwang]

@andrewor14 Now I add shortShuffleMgrName to ShuffleManager for getting its short Name. How do you think? Thanks.

[SparkQA]

Test build #47197 has finished for PR 10131 at commit c67cdca.

• This patch passes all tests.
• This patch merges cleanly.
• This patch adds no public classes.

[andrewor14]

I would make these vals since we don't ever expect them to change within a shuffle manager

[andrewor14]

Minor comment but this looks good otherwise.

[lianhuiwang]

@andrewor14 thanks. I think now it's ok.

[SparkQA]

Test build #47710 has finished for PR 10131 at commit 2259fba.

• This patch passes all tests.
• This patch merges cleanly.
• This patch adds no public classes.

[SparkQA]

Test build #47711 has finished for PR 10131 at commit 8bb4bce.

• This patch passes all tests.
• This patch merges cleanly.
• This patch adds no public classes.

[SparkQA]

Test build #47716 has finished for PR 10131 at commit 22e0e91.

• This patch passes all tests.
• This patch merges cleanly.
• This patch adds no public classes.

[andrewor14]

just call this shortName

[andrewor14]

LGTM, merging into master. I'll fix the comment on merge.

[lianhuiwang]

@andrewor14 OK, Thanks.