This patch modifies the Parquet scanner to resolve nested schemas, and
read and materialize collection types. The high-level modification is
to create a CollectionColumnReader that recursively materializes map-
and array-type slots.
This patch also adds many tests, most of which query a new table
called complextypestbl. This table contains hand-generated data that
is meant to expose edge cases in the scanner. The tests mostly test
the scanner, with a few tests of other functionality (e.g. array
serialization).
I ran a local benchmark comparing this scanner code to the original
scanner code on an expanded version of tpch_parquet.lineitem with
48009720 rows. My benchmark involved selecting different numbers of
columns with a single scanner thread, and I looked at the HDFS scan
node time in the query profiles. This code introduces a 10%-20%
regression in single-threaded scan time.
Change-Id: Id27fb728934e8346444f61752c9278d8010e5f3a
Reviewed-on: http://gerrit.cloudera.org:8080/576
Reviewed-by: Alex Behm <alex.behm@cloudera.com>
Tested-by: Internal Jenkins
