[GitHub] [cassandra] adelapena commented on pull request #1892: CASSANDRA-17941 trunk: CQL data masking functions

[GitBox <gi...@apache.org>]

adelapena commented on PR #1892:
URL: https://github.com/apache/cassandra/pull/1892#issuecomment-1358045881

   Thanks for the review. I have rebased the branch and tried to address the suggestions on an additional commit. CI:
   
   * https://app.circleci.com/pipelines/github/adelapena/cassandra/2531/workflows/0c22bed2-ed42-4d96-985d-df23a36d846f
   * https://app.circleci.com/pipelines/github/adelapena/cassandra/2531/workflows/d78e875e-ec27-4a93-935d-1f9233065e19
   
   As discussed on Slack, the proposed functions are taken into account in the `ResultSet` metadata when the functions are used as regular function calls in a `SELECT` query. That metadata will be comprised by functions calls with the adequate type. Thus, using functions that return a data type different to their input shouldn't be a problem when directly using the functions in queries, like for example `SELECT mask_hash(v) FROM t`. In that example, the `ResultSet` metadata will contain a column named `mask_hash(v)` of type `blob`. That shouldn't surprise the user running the query. 
   
   However, we should take those return types into account during CASSANDRA-18068. On that ticket we will allow to attach the utility masking functions to table columns on `CREATE/ALTER TABLE`. That can be problematic because in that case the user query is not explicitly invoking the function, and the name and type of the column don't change on the `ResultSet`.
   
   Probably we will need to just forbid attaching type-altering masking functions to column definitions on `CREATE/ALTER TABLE`. We could also forbid them by default but have a config property that allows that kind of mapping, if we see any value to it. However, there doesn't seem to be a reason to forbid the explicit use of those functions on regular `SELECT` queries.


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