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This patch provides replan support for multiple executor group sets.
Each executor group set is associated with a distinct number of nodes
and a threshold for estimated memory per host in bytes that can be
denoted as [<group_name_prefix>:<#nodes>, <threshold>].
In the patch, a query of type EXPLAIN, QUERY or DML can be compiled
more than once. In each attempt, per host memory is estimated and
compared with the threshold of an executor group set. If the estimated
memory is no more than the threshold, the iteration process terminates
and the final plan is determined. The executor group set with the
threshold is selected to run the query.
A new query option 'enable_replan', default to 1 (enabled), is added.
It can be set to 0 to disable this patch and to generate the distributed
plan for the default executor group.
To avoid long compilation time, the following enhancement is enabled.
Note 1) can be disabled when relevant meta-data change is
detected.
1. Authorization is performed only for the 1st compilation;
2. openTransaction() is called for transactional queries in 1st
compilation and the saved transactional info is used in
subsequent compilations. Similar logic is applied to Kudu
transactional queries.
To facilitate testing, the patch imposes an artificial two executor
group setup in FE as follows.
1. [regular:<#nodes>, 64MB]
2. [large:<#nodes>, 8PB]
This setup is enabled when a new query option 'test_replan' is set
to 1 in backend tests, or RuntimeEnv.INSTANCE.isTestEnv() is true as
in most frontend tests. This query option is set to 0 by default.
Compilation time increases when a query is compiled in several
iterations, as shown below for several TPCDs queries. The increase
is mostly due to redundant work in either single node plan creation
or recomputing value transfer graph phase. For small queries, the
increase can be avoided if they can be compiled in single iteration
by properly setting the smallest threshold among all executor group
sets. For example, for the set of queries listed below, the smallest
threshold can be set to 320MB to catch both q15 and q21 in one
compilation.
Compilation time (ms)
Queries Estimated Memory 2-iterations 1-iteration Percentage of
increase
q1 408MB 60.14 25.75 133.56%
q11 1.37GB 261.00 109.61 138.11%
q10a 519MB 139.24 54.52 155.39%
q13 339MB 143.82 60.08 139.38%
q14a 3.56GB 762.68 312.92 143.73%
q14b 2.20GB 522.01 245.13 112.95%
q15 314MB 9.73 4.28 127.33%
q21 275MB 16.00 8.18 95.59%
q23a 1.50GB 461.69 231.78 99.19%
q23b 1.34GB 461.31 219.61 110.05%
q4 2.60GB 218.05 105.07 107.52%
q67 5.16GB 694.59 334.24 101.82%
Testing:
1. Almost all FE and BE tests are now run in the artificial two
executor setup except a few where a specific cluster configuration
is desirable;
2. Ran core tests successfully;
3. Added a new observability test and a new query assignment test;
4. Disabled concurrent insert test (test_concurrent_inserts) and
failing inserts (test_failing_inserts) test in local catalog mode
due to flakiness. Reported both in IMPALA-11189 and IMPALA-11191.
Change-Id: I75cf17290be2c64fd4b732a5505bdac31869712a
Reviewed-on: http://gerrit.cloudera.org:8080/18178
Reviewed-by: Qifan Chen <qchen@cloudera.com>
Tested-by: Qifan Chen <qchen@cloudera.com>
103 KiB
103 KiB