Hello Lars Volker, Gabor Kaszab, Alex Behm,
I'd like you to reexamine a change. Please visit
to look at the new patch set (#16).
Change subject: IMPALA-4167: Support insert plan hints for CREATE TABLE AS
IMPALA-4167: Support insert plan hints for CREATE TABLE AS SELECT
This change adds support for "clustered", "noclustered", "shuffle" and
"noshuffle" hints in CTAS statement.
create /*+ clustered,noshuffle */ table t partitioned by (year, month)
as select * from functional.alltypes
The effect of these hints are the same as in insert statements:
Sort locally by partition expression before insert to ensure that only
one partition is written at a time. The goal is to reduce the number of
files kept open / buffers kept in memory simultaneously.
Do not sort by primary key before insert to Kudu table. No effect on HDFS
tables currently, as this is their default behavior.
Forces the planner to add an exchange node that repartitions by the
partition expression of the output table. This means that a partition
will be written only by a single node, which minimizes the global
number of simultaneous writes.
If only one partition is written (because all partitioning columns
are constant or the target table is not partitioned), then the shuffle
hint leads to a plan where all rows are merged at the coordinator where
the table sink is executed.
Do not add exchange node before insert to partitioned tables.
The parser needed some modifications to be able to differentiate between
CREATE statements that allow hints (CTAS), and CREATE statements that
do not (every other type of CREATE statements). As a result, KW_CREATE
was moved from tbl_def_without_col_defs to statement rules.
The parser tests mirror the tests of INSERT, while analysis and planner
tests are minimal, as the underlying logic is the same as for INSERT.
Query tests are not created, as the hints have no effect on
the DDL part of CTAS, and the actual query ran is the same as in
the insert case.
9 files changed, 210 insertions(+), 64 deletions(-)
git pull ssh://gerrit.cloudera.org:29418/Impala-ASF refs/changes/00/8400/16
To view, visit http://gerrit.cloudera.org:8080/8400
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Gerrit-Owner: Csaba Ringhofer <csringho...@cloudera.com>
Gerrit-Reviewer: Alex Behm <alex.b...@cloudera.com>
Gerrit-Reviewer: Csaba Ringhofer <csringho...@cloudera.com>
Gerrit-Reviewer: Gabor Kaszab <gaborkas...@cloudera.com>
Gerrit-Reviewer: Lars Volker <l...@cloudera.com>