Csaba Ringhofer has uploaded this change for review. ( 
http://gerrit.cloudera.org:8080/10683


Change subject: IMPALA-7417: Remove DCHECKs with unnecessary constraint on 
dictionary encoding bit width
......................................................................

IMPALA-7417: Remove DCHECKs with unnecessary constraint on dictionary encoding 
bit width

Reading dictionary encoded Parquet data pages where the bit width is
larger than the encoded type's size (e.g. coding 8 bit TINYINT with
16 bit dictionary indices) led to DCHECK error in debug builds.
Impala does not create such parquet files (an N bit type can have
maximum 2^N distinct values, so N bit dictionary indices are enough
for a dictionary that contains every possible value), but the Parquet
standard does not forbid to do so.

These DCHECKs were probably introduced by a copy paste error (similar
checks exist in the non-dictionary encoded bit reader functions,
where they are valid).

Testing:
- a new test is added to check that these data pages can be decoded
  correctly

Change-Id: I9ff3b00cbcab09dec11b3607d7d9a9c2c0025e1a
---
M be/src/util/bit-packing.inline.h
M be/src/util/bit-stream-utils.inline.h
M testdata/data/README
A testdata/data/dict_encoding_with_large_bit_width.parquet
M tests/query_test/test_scanners.py
5 files changed, 21 insertions(+), 3 deletions(-)



  git pull ssh://gerrit.cloudera.org:29418/Impala-ASF refs/changes/83/10683/1
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Gerrit-Project: Impala-ASF
Gerrit-Branch: master
Gerrit-MessageType: newchange
Gerrit-Change-Id: I9ff3b00cbcab09dec11b3607d7d9a9c2c0025e1a
Gerrit-Change-Number: 10683
Gerrit-PatchSet: 1
Gerrit-Owner: Csaba Ringhofer <csringho...@cloudera.com>

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