Impala already supported RLE encoding for levels and dictionary pages, so
the only task was to integrate it into BoolColumnReader.
A new benchmark, rle-benchmark.cc is added to test the speed of RLE
decoding for different bit widths and run lengths.
There might be a small performance impact on PLAIN encoded booleans,
because of the additional branch when the cache of BoolColumnReader is
filled. As the cache size is 128, I considered this to be outside the
"hot loop".
Testing:
As Impala cannot write RLE encoded bool columns at the moment, parquet-mr
was used to create a test file, testdata/data/rle_encoded_bool.parquet
tests/query_test/test_scanners.py#test_rle_encoded_bools creates a table
that uses this file, and tries to query from it.
Change-Id: I4644bf8cf5d2b7238b05076407fbf78ab5d2c14f
Reviewed-on: http://gerrit.cloudera.org:8080/9403
Reviewed-by: Tim Armstrong <tarmstrong@cloudera.com>
Tested-by: Impala Public Jenkins
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