Lars Hofhansl created PHOENIX-3156:
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Summary: Bug in DistinctPrefixFilter
Key: PHOENIX-3156
URL: https://issues.apache.org/jira/browse/PHOENIX-3156
Project: Phoenix
Issue Type: Bug
Reporter: Lars Hofhansl
Priority: Blocker
Fix For: 4.8.0
There's a corner case I found where a DISTINCT and GROUP BY query along a
prefix of a compound row key might return incorrect results.
The filter relies on seeing the _0 column absolutely last, and not seeing all
Cells that should be filtered. That break in two scenarios:
# we have a table with key (key1, key2, key3) and columns (c1 and c2). Now
construct a WHERE <a clause that always matches c1>, <a clause that filters by
c2) GROUP BY key1, key2. Now the filter would mis-skip when it sees the Cell
for c1.
# we force lower key column names. In that case those would sort after the _0
column. The DistinctPrefixFilter would see the _0 column first and skip.
I can fix #1 (by ignoring all Cells other than then _0 one). I do not know how
to fix case #2.
I think this is a blocker and we may have to undo the entire DISTINCT and GROUP
BY prefix optimization.
[~an...@apache.org], [~giacomotaylor], [~samarthjain].
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