[Impala-CR](cdh5-trunk) IMPALA-3148. Fix selectivity computation for pushed Kudu predicates

["Casey Ching (Code Review)" <ge...@cloudera.org>]

Casey Ching has uploaded a new patch set (#2).

Change subject: IMPALA-3148. Fix selectivity computation for pushed Kudu predicates
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IMPALA-3148. Fix selectivity computation for pushed Kudu predicates

This follows up on a TODO from the Kudu merge and also fixes a bug:
IMPALA-976 changed the computation of selectivities for a combined
list of conjuncts to better handle expressions with no selectivity
estimate. The Kudu implementation was forked from before this change
and thus did not have an equivalent change.

This refactors the algorithm to a new static method and calls it from
both PlanNode and KuduScanNode so that the selectivity estimate
behavior is the same regardless of whether Kudu can evaluate the
predicate server-side.

Todd tested this on TPCH 3TB and verified that the plans are reasonable
now where they used to be nonsense.

Change-Id: Id507077b577ed5804fc80517f33ea185f2bff41a
---
M fe/src/main/java/com/cloudera/impala/planner/KuduScanNode.java
M fe/src/main/java/com/cloudera/impala/planner/PlanNode.java
M testdata/workloads/functional-planner/queries/PlannerTest/kudu-selectivity.test
3 files changed, 73 insertions(+), 16 deletions(-)


  git pull ssh://gerrit.cloudera.org:29418/Impala refs/changes/28/2628/2
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Gerrit-MessageType: newpatchset
Gerrit-Change-Id: Id507077b577ed5804fc80517f33ea185f2bff41a
Gerrit-PatchSet: 2
Gerrit-Project: Impala
Gerrit-Branch: cdh5-trunk
Gerrit-Owner: Todd Lipcon <to...@apache.org>
Gerrit-Reviewer: Alex Behm <al...@cloudera.com>
Gerrit-Reviewer: Casey Ching <ca...@cloudera.com>
Gerrit-Reviewer: Todd Lipcon <to...@apache.org>