This patch affects the LWT queries with IF conditions of the
following form: `IF col in :value`, i.e. if the parameter
marker is used.
When executing a prepared query with a bound value
of `(None,)` (tuple with null, example for Python driver), it is
serialized not as NULL but as "empty" value (serialization
format differs in each case).
Therefore, Scylla deserializes the parameters in the request as
empty `data_value` instances, which are, in turn, translated
to non-empty `bytes_opt` with empty byte-string value later.
Account for this case too in the CAS condition evaluation code.
Example of a problem this patch aims to fix:
Suppose we have a table `tbl` with a boolean field `test` and
INSERT a row with NULL value for the `test` column.
Then the following update query fails to apply due to the
error in IF condition evaluation code (assume `v=(null)`):
`UPDATE tbl SET test=false WHERE key=0 IF test IN :v`
returns false in `[applied]` column, but is expected to succeed.
Tests: unit(debug, dev), dtest(prepared stmt LWT tests at https://github.com/scylladb/scylla-dtest/pull/1286)
Fixes: #5710
Signed-off-by: Pavel Solodovnikov <pa.solodovnikov@scylladb.com>
Message-Id: <20200205102039.35851-1-pa.solodovnikov@scylladb.com>
(cherry picked from commit bcc4647552)
d65e2ac6af