test/cql-pytest: add a couple of tests for static columns
test/cql-pytest: add a couple of tests for static columns

This patch adds two tests for two interesting edge cases in the behavior
of static columns in Scylla. We already have a lot of tests for static
columns in other frameworks (C++ unit tests, cql and dtest), but the two
cases here are issues where specifically we weren't sure how Cassandra
behaves in those cases - and this can most easily be checked in the
test/cql-pytest framework.

The first test, test_static_not_selected, is a reproducer for issue #10091.
This issue was reported by a user @aohotnik, who was surprised by the
fact that Scylla returns empty values, instead of nothing, when selecting
regular columns of a non-existent row if the partition has a static
column set. The test demonstrates a difference between Scylla and
Cassandra, so it is marked "xfail" - it passes on Cassandra and fails on
Scylla. If later we decide that both Scylla's and Cassandra's behaviours
are reasonable and both can be considered "correct", we can change this
test to except Scylla's result as well and it will beging to pass.

The second test, test_missing_row_with_static, shows that SELECT of a
non-existent row returns nothing - even if the partition has a static
column. The behavior in this case is identical in Scylla and Cassandra,
so this test passes. This contrasts with the analogous situation in LWT
UPDATE from issue #10081, where the IF condition is expected to see the
static column value.

Refs #10081
Refs #10091

Signed-off-by: Nadav Har'El <625169824b719df98706d88646d0aae6f368ae4d@scylladb.com>
Message-Id: <20220220120418.831540-1-625169824b719df98706d88646d0aae6f368ae4d@scylladb.com>

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