Alexey Serbin has posted comments on this change. ( 
http://gerrit.cloudera.org:8080/17547 )

Change subject: KUDU-3291: properly disambiguate between deltas of a row with 
the same timestamp
......................................................................


Patch Set 3: Code-Review+1

(8 comments)

LGTM overall, just a couple of questions (just to make sure my understanding is 
correct) and nits.

http://gerrit.cloudera.org:8080/#/c/17547/3//COMMIT_MSG
Commit Message:

http://gerrit.cloudera.org:8080/#/c/17547/3//COMMIT_MSG@36
PS3, Line 36: this counter is
            : propagated to the sub-iterators
Just to make sure I understand this correctly: is there any guarantee that 
those counters would be different for sub-iterators?  Is that because every 
selected delta increases the count?


http://gerrit.cloudera.org:8080/#/c/17547/3/src/kudu/tablet/delta_store.h
File src/kudu/tablet/delta_store.h:

http://gerrit.cloudera.org:8080/#/c/17547/3/src/kudu/tablet/delta_store.h@144
PS3, Line 144: a.disambiguator != b.disambiguator
nit: wrap into PREDICT_TRUE()?


http://gerrit.cloudera.org:8080/#/c/17547/3/src/kudu/tablet/delta_store.h@147
PS3, Line 147: "Could not differentiate between two deltas";
Not a part of this changelist, but does it make sense to drump information on 
deltas into the fatal error message?


http://gerrit.cloudera.org:8080/#/c/17547/3/src/kudu/tablet/delta_store.h@473
PS3, Line 473: DCHECK_GE
Can we put DCHECK_GT() here?  Or it can be that no deltas are selected in a 
sub-iterator?


http://gerrit.cloudera.org:8080/#/c/17547/3/src/kudu/tablet/diff_scan-test.cc
File src/kudu/tablet/diff_scan-test.cc:

http://gerrit.cloudera.org:8080/#/c/17547/3/src/kudu/tablet/diff_scan-test.cc@228
PS3, Line 228: &
nit: maybe, store it by value?


http://gerrit.cloudera.org:8080/#/c/17547/3/src/kudu/tablet/diff_scan-test.cc@233
PS3, Line 233: ASSERT_OK
nit: could it ever fail?  If yes, then it'd necessary to join the thread since 
line 234 wouldn't be reachable


http://gerrit.cloudera.org:8080/#/c/17547/3/src/kudu/tablet/diff_scan-test.cc@243
PS3, Line 243:   opts.order = ORDERED;;
             :   opts.include_deleted_rows = true;
How crucial are these custom settings for the reproduction of the issue?  It 
would be nice to add a comment about that.


http://gerrit.cloudera.org:8080/#/c/17547/3/src/kudu/tablet/diff_scan-test.cc@246
PS3, Line 246: static const bool
nit: as for 'kRowKey', could use constexpr here as well (just for uniformity)



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Gerrit-Project: kudu
Gerrit-Branch: master
Gerrit-MessageType: comment
Gerrit-Change-Id: Iccfc518999d36679f85ed901ba65cf7b4894cd55
Gerrit-Change-Number: 17547
Gerrit-PatchSet: 3
Gerrit-Owner: Andrew Wong <[email protected]>
Gerrit-Reviewer: Alexey Serbin <[email protected]>
Gerrit-Reviewer: Andrew Wong <[email protected]>
Gerrit-Reviewer: Bankim Bhavsar <[email protected]>
Gerrit-Reviewer: Grant Henke <[email protected]>
Gerrit-Reviewer: Kudu Jenkins (120)
Gerrit-Reviewer: Tidy Bot (241)
Gerrit-Comment-Date: Mon, 07 Jun 2021 20:17:42 +0000
Gerrit-HasComments: Yes

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