In fuzz testing I have found some differences between `WHERE` and `IF` clauses
that want to get feedback from the broader community.
If you try to query with a `null` we will reject it
```
@Test
public void test() throws IOException
{
try (Cluster cluster = Cluster.build(1).start())
{
init(cluster);
cluster.schemaChange(withKeyspace("CREATE TABLE %s.tbl(pk int, ck int,
v0 int, v1 int, primary key(pk, ck))"));
var inst = cluster.coordinator(1);
inst.execute(withKeyspace("INSERT INTO %s.tbl (pk, ck, v0) VALUES (?,
?, ?)"), ConsistencyLevel.ALL, 0, 0, 0);
AssertUtils.assertRows(inst.execute(withKeyspace("SELECT * FROM %s.tbl
WHERE pk=? AND ck=? and v1=? ALLOW FILTERING"), ConsistencyLevel.ALL, 0, 0,
null),
rows());
}
}
```
This fails as follows
```
org.apache.cassandra.exceptions.InvalidRequestException: Invalid null value for
column v1
```
But if you do this in the `IF` clause it is accepted
```
@Test
public void test() throws IOException
{
try (Cluster cluster = Cluster.build(1).start())
{
init(cluster);
cluster.schemaChange(withKeyspace("CREATE TABLE %s.tbl(pk int, ck int,
v0 int, v1 int, primary key(pk, ck))"));
var inst = cluster.coordinator(1);
inst.execute(withKeyspace("UPDATE %s.tbl SET v1=0 WHERE pk=0 AND ck=0
IF v0=?"), ConsistencyLevel.QUORUM, new Object[]{null});
AssertUtils.assertRows(inst.execute(withKeyspace("SELECT * FROM %s.tbl
WHERE pk=? AND ck=?"), ConsistencyLevel.SERIAL, 0, 0, null),
rows());
}
}
```
CAS accepts this and will apply the `UPDATE` (the row doesn't exist, so `null =
null => true`; this behavior isn't consistent).
Most of the project treats `null` as something that won't ever match, which is
consistent with other DBs
```
sqlite> select * from employees;
sqlite> insert into employees (id, name, age, department) values (0, "name",
42, "cassandra");
sqlite> insert into employees (id, name, age) values (1, "name2", 42);
sqlite> select * from employees where department = null;
sqlite> sqlite> select * from employees where department is null;
id = 1
name = name2
age = 42
department = NULL
sqlite>
```
```
postgres=# select * from employees where department = null;
id | name | age | department
----+------+-----+------------
(0 rows)
postgres=# select * from employees where department is null;
id | name | age | department
----+-------+-----+------------
1 | name2 | 42 |
(1 row)
```
So I guess my main question; is this a bug or a feature?
