Caleb Rackliffe created CASSANDRA-20100:
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Summary: Query construction is broken for SAI indexes on reversed
types with custom fixed-length encodings
Key: CASSANDRA-20100
URL: https://issues.apache.org/jira/browse/CASSANDRA-20100
Project: Cassandra
Issue Type: Bug
Components: Feature/2i Index, Feature/SAI
Reporter: Caleb Rackliffe
Assignee: Caleb Rackliffe
SAI indexes values in byte-comparable form, both in the in-memory trie that
sits alongside the Memtable, and in the on-disk SSTable-adjacent indexes. In
most cases, this means literally using {{asComparableBytes()}} from the type of
the indexed column. There are, however, a few types that use a custom
byte-comparable form, namely {{inet}}, {{bigint}}, {{varint}}, and {{decimal}},
to make sure we're dealing with a fixed-length piece of data for the numeric
(balanced tree) index.
If we index one of these types as a reversed clustering key, however, we don't
write terms as reversed comparable bytes, and this breaks some assumptions
during query construction and post-filtering, where we generally assume that
{{asComparableBytes()}} will reverse terms before they are indexed. We can make
a short-term fix here without changing anything about the on-disk format by
making sure we interpret these special types as being non-reversed (i.e.
through the lens of their base types).
In the longer term, it might make sense to standardize on indexing everything
in a non-reversed fashion in the index itself, although this might push some
complexity into post-filtering, where we are going to have to filter data
coming out of the normal read path anyway.
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