Hello Alex Behm,
I'd like you to reexamine a change. Please visit
http://gerrit.cloudera.org:8080/10119
to look at the new patch set (#3).
Change subject: IMPALA-6821: Push down limits into Kudu
......................................................................
IMPALA-6821: Push down limits into Kudu
This patch takes advantage of a recent change in Kudu (KUDU-16) that
exposes the ability to set limits on KuduScanners. Since each
KuduScanner corresponds to a scan token, and there will be multiple
scan tokens per query, this is just a performance optimization in
cases where the limit is smaller than the number of rows per token,
and Impala still needs to apply the limit on our side for cases where
the limit is greater than the number of rows per token.
Testing:
- Added e2e tests for various situations where limits are applied at
a Kudu scan node.
- For the query 'select * from tpch_kudu.lineitem limit 1', a best
case perf scenario for this change where the limit is highly
effective, the time spent in the Kudu scan node was reduced from
6.107ms to 3.498ms (avg over 3 runs).
- For the query 'select count(*) from (select * from
tpch_kudu.lineitem limit 1000000) v', a worst case perf scenario for
this change where the limit is ineffective, the time spent in the
Kudu scan node was essentially unchanged, 32.815ms previously vs.
29.532ms (avg over 3 runs).
Change-Id: Ibe35e70065d8706b575e24fe20902cd405b49941
---
M be/src/exec/kudu-scanner.cc
A testdata/workloads/functional-query/queries/QueryTest/kudu_limit.test
M tests/query_test/test_kudu.py
3 files changed, 68 insertions(+), 0 deletions(-)
git pull ssh://gerrit.cloudera.org:29418/Impala-ASF refs/changes/19/10119/3
--
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Gerrit-Project: Impala-ASF
Gerrit-Branch: master
Gerrit-MessageType: newpatchset
Gerrit-Change-Id: Ibe35e70065d8706b575e24fe20902cd405b49941
Gerrit-Change-Number: 10119
Gerrit-PatchSet: 3
Gerrit-Owner: Thomas Tauber-Marshall <tmarsh...@cloudera.com>
Gerrit-Reviewer: Alex Behm <alex.b...@cloudera.com>
Gerrit-Reviewer: Thomas Tauber-Marshall <tmarsh...@cloudera.com>
