GraphQL API doesn't support inserting null values for some types

[marksurnin]

We noticed that GraphQL API throws an exception when we try to insert null for some data types: list, map, tuple and udt.

For example, if there's a table such as

CREATE TABLE type_test.test (
    a int PRIMARY KEY,
    b list<int>,
    c map<int, text>,
    d frozen<tuple<int, int>>,
    e custom_udt
)

the schema for testInput is the following, note that the types are nullable:

input testInput {
  a: Int
  b: [Int]
  c: [EntryIntKeyStringValueInput]
  d: TupleIntIntInput
  e: custom_udtUdtInput
}

When we pass null as the value for the list type:

mutation {
  inserttest(value:{a: 4, b: null}) {
    applied
  }
}

we get the following exception:

WARN  [2021-10-18 14:31:33,337] notprivacysafe.graphql.execution.SimpleDataFetcherExceptionHandler: Exception while fetching data (/inserttest) : null
java.lang.NullPointerException: null
! at io.stargate.graphql.schema.cqlfirst.dml.fetchers.DataTypeMapping.convertCollection(DataTypeMapping.java:70)
! at io.stargate.graphql.schema.cqlfirst.dml.fetchers.DataTypeMapping.toDBValue(DataTypeMapping.java:45)
! at io.stargate.graphql.schema.cqlfirst.dml.fetchers.DmlFetcher.toDBValue(DmlFetcher.java:224)

This happens when inserting null for columns c, d, and e as well.

Would the fix be to make methods such as convertCollection, convertMap, etc. in DataTypeMapping return null when graphQLValue is null or is there more to this?

---

For context, we're migrating some use cases to Stargate that insert null values to remove existing values, which is why we'd like to maintain parity with CQL.

cqlsh> insert into type_test.test(a, b, c, d, e) VALUES (2, null, null, null, null);
cqlsh> select * from type_test.test ;
 a | b    | c        | d      | e
---+------+----------+--------+------------------
 1 |  [2] | {3: '3'} | (4, 4) | {one: 1, two: 2}
 2 | null |     null |   null |             null

We're aware that we could insert null if we omit this field from a mutation but this doesn't work for upserts where we'd like to overwrite existing values with null. Thanks!

[dougwettlaufer]

@olim7t what are your thoughts here?

[olim7t]

Yes we need to fix that.
For lists I think passing an empty list would achieve the same effect since CQL considers empty list and null the same, but it will be more user-friendly to accept null as well.