[kudu-CR] KUDU-1623. Properly handle UPSERTS that only include PK column

["Todd Lipcon (Code Review)" <ge...@cloudera.org>]

Hello Kudu Jenkins,

I'd like you to reexamine a change.  Please visit

    http://gerrit.cloudera.org:8080/4441

to look at the new patch set (#2).

Change subject: KUDU-1623. Properly handle UPSERTS that only include PK column
......................................................................

KUDU-1623. Properly handle UPSERTS that only include PK column

This fixes a bug reported by Chris George in which the tablet server
would crash when handling an UPSERT which was converted into an empty
UPDATE. For example, in pseudo-SQL:

  CREATE TABLE t (
    x INT NOT NULL PRIMARY KEY
  );

  UPSERT INTO t VALUES (1);
  UPSERT INTO t VALUES (1);

Here the second upsert would detect the primary key already existed and
convert into an update containing any non-PK columns. Since there are no
non-PK columns, the update was "empty", and ended up as an empty
RowChangeList. In DEBUG builds, this fired a DCHECK, but in RELEASE
builds, we ended up with an empty RowChangeList in the DMS. At flush
time, this would cause other assertions to fire or crash.

The fix is relatively simple: if we see that an upsert converted into an
empty update, we just drop the delta rather than continuing to insert
into the delta store. This required loosing a check at bootstrap time,
where we previously assumed that every mutation must have been recorded
in at least one store.

The test changes are much larger than the fix itself due to some
refactoring. The main gist of the change is to introduce operations in
tablet_random_access-test and fuzz-itest where we send an UPSERT which
contains only the primary key column. These tests crashed prior to the
fix and pass now.

Change-Id: Ic878f6e51ead5bf91335ddb47536e7c29de11ac4
---
M src/kudu/integration-tests/fuzz-itest.cc
A src/kudu/tablet/key_value_test_schema.h
M src/kudu/tablet/tablet.cc
M src/kudu/tablet/tablet_bootstrap.cc
M src/kudu/tablet/tablet_random_access-test.cc
5 files changed, 227 insertions(+), 73 deletions(-)


  git pull ssh://gerrit.cloudera.org:29418/kudu refs/changes/41/4441/2
-- 
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Gerrit-MessageType: newpatchset
Gerrit-Change-Id: Ic878f6e51ead5bf91335ddb47536e7c29de11ac4
Gerrit-PatchSet: 2
Gerrit-Project: kudu
Gerrit-Branch: master
Gerrit-Owner: Todd Lipcon <to...@apache.org>
Gerrit-Reviewer: David Ribeiro Alves <dr...@apache.org>
Gerrit-Reviewer: Kudu Jenkins