cql3: create tokens out of null values properly

Method reponsible for creating a token of given values is not meant to be
used with empty optionals. Thus, having requested a token of the columns
containing null values resulted with an exception being thrown. This kind
of behaviour was not compatible with the one applied in cassandra.

To fix this, before the computation of a token, it is checked whether
no null value is contained. If any value in the processed vector is null,
null value is returned.

Fixes:  #10594

Closes #10942

cql3/functions/token_fct.hh

@@ -32,6 +32,9 @@ public:
     }
 
     bytes_opt execute(cql_serialization_format sf, const std::vector<bytes_opt>& parameters) override {
+        if (std::any_of(parameters.cbegin(), parameters.cend(), [](const auto& param){ return !param; })) {
+            return std::nullopt;
+        }
         auto key = partition_key::from_optional_exploded(*_schema, parameters);
         auto tok = dht::get_token(*_schema, key);
         warn(unimplemented::cause::VALIDATION);

test/cql/token_from_null_test.cql

@@ -0,0 +1,14 @@
+-- single null value
+CREATE KEYSPACE reproducer WITH replication = {'class': 'SimpleStrategy', 'replication_factor': 1};
+CREATE TABLE reproducer.t(pk int PRIMARY KEY, v int);
+INSERT INTO reproducer.t (pk) VALUES (1);
+SELECT TOKEN(v) FROM reproducer.t;
+
+-- multiple null values
+CREATE TABLE reproducer.t2(pk int PRIMARY KEY, a int, b int);
+INSERT INTO reproducer.t2 (pk) VALUES (1);
+SELECT TOKEN(pk, a, b) FROM reproducer.t2;
+SELECT TOKEN(pk, b) FROM reproducer.t2;
+SELECT TOKEN(a, b) FROM reproducer.t2;
+
+DROP KEYSPACE reproducer;

test/cql/token_from_null_test.result

@@ -0,0 +1,39 @@
+> -- single null value
+> CREATE KEYSPACE reproducer WITH replication = {'class': 'SimpleStrategy', 'replication_factor': 1};
+OK
+> CREATE TABLE reproducer.t(pk int PRIMARY KEY, v int);
+OK
+> INSERT INTO reproducer.t (pk) VALUES (1);
+OK
+> SELECT TOKEN(v) FROM reproducer.t;
++-------------------+
+| system.token(v)   |
+|-------------------|
+| null              |
++-------------------+
+> 
+> -- multiple null values
+> CREATE TABLE reproducer.t2(pk int PRIMARY KEY, a int, b int);
+OK
+> INSERT INTO reproducer.t2 (pk) VALUES (1);
+OK
+> SELECT TOKEN(pk, a, b) FROM reproducer.t2;
++--------------------------+
+| system.token(pk, a, b)   |
+|--------------------------|
+| null                     |
++--------------------------+
+> SELECT TOKEN(pk, b) FROM reproducer.t2;
++-----------------------+
+| system.token(pk, b)   |
+|-----------------------|
+| null                  |
++-----------------------+
+> SELECT TOKEN(a, b) FROM reproducer.t2;
++----------------------+
+| system.token(a, b)   |
+|----------------------|
+| null                 |
++----------------------+
+> 
+> DROP KEYSPACE reproducer;OK