cql-pytest: test for secondary-index on empty-string value
cql-pytest: test for secondary-index on empty-string value

When a string column is indexed with a secondary index, the empty value
for this column (an empty string '') is perfectly legal, and should be
indexed as well. This is not the same as an unset (null) value which
isn't indexed.

The following test demonstrates that this case works in Cassandra, but
does not in Scylla (so the test is marked "xfail"). In Scylla, a query
that returns the expected results with ALLOW FILTERING suddenly returns
a different (and wrong) result when an index is added on the table.

This test reproduces issue #9364.

Refs #9364.

Signed-off-by: Nadav Har'El <625169824b719df98706d88646d0aae6f368ae4d@scylladb.com>
Message-Id: <20210922121510.291826-1-625169824b719df98706d88646d0aae6f368ae4d@scylladb.com>

scylladb/scylla,scylladb/scylla,scylladb/scylla,scylladb/scylla