ZhangYao has posted comments on this change. ( 
http://gerrit.cloudera.org:8080/14107 )

Change subject: KUDU-2921: Exposing the table statistics to spark relation.
......................................................................


Patch Set 5:

> > 1. For java client when using new RPC:
 > > new java client -> old server -> leads to execption
 >
 > OK, because the exception is only seen when invoking the new APIs.
 > It's not visible in any existing APIs, right?
 Right.

 > > 2. For spark client:
 > > new spark client depends on new java client.
 > > new spark client -> old server -> leads to execption
 >
 > This is what concerns me. Under what circumstances is there an
 > exception? When invoking some new API? Or in existing data paths?
 >
 > If the latter, we need to address it. We take great care to ensure
 > Kudu is both forward and backward compatible, whether it be across
 > the wire (i.e. between server and client), or across a library
 > boundary (i.e. between client and application). It wouldn't be OK
 > for someone running with the new Spark integration against an old
 > server to have a degraded experience in _existing_ functionality.
 > If it's brand new functionality (i.e. a new API in the client),
 > that's fine.

I got it. In previous patch because when creating relation it will call 
getStatistic automatically so it will cause exception with old server . I used  
a config to decide whether to use getStatistics or not. That's for new spark 
client with old server user if he doesn't open that conf, it can work well.


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Gerrit-Project: kudu
Gerrit-Branch: master
Gerrit-MessageType: comment
Gerrit-Change-Id: I7742a76708f989b0ccc8ba417f3390013e260175
Gerrit-Change-Number: 14107
Gerrit-PatchSet: 5
Gerrit-Owner: ZhangYao <[email protected]>
Gerrit-Reviewer: Adar Dembo <[email protected]>
Gerrit-Reviewer: Andrew Wong <[email protected]>
Gerrit-Reviewer: Grant Henke <[email protected]>
Gerrit-Reviewer: Hao Hao <[email protected]>
Gerrit-Reviewer: Kudu Jenkins (120)
Gerrit-Reviewer: Tidy Bot (241)
Gerrit-Reviewer: Todd Lipcon <[email protected]>
Gerrit-Reviewer: ZhangYao <[email protected]>
Gerrit-Comment-Date: Fri, 30 Aug 2019 06:26:15 +0000
Gerrit-HasComments: No

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