paul-rogers commented on issue #1945: DRILL-7502: Invalid codegen for typeof() with UNION URL: https://github.com/apache/drill/pull/1945#issuecomment-570762571 Another thing to note is that we may want to go though one more round of sorting out the type functions. In normal SQL, there is just one level of type: a columns is an `INT` or a `DOUBLE`. In Sqllite (IIRC) there is the `Variant` type: so a column can be `Variant` but the values can be `INT` or `DOUBLE`. The "variant" name comes from Visual Basic. In Drill, the variant is called `UNION`. In Drill, we also have structured types: `ARRAY<INTEGER>` or `DICT<STRING,DOUBLE>`. We've been trying to handle all these cases with originally one function (`typeof()`), then later three (adding `sqlTypeOf()` and `drillTypeOf()`). We probably want four variations. Two forms of the type: * The full type description: `ARRAY<ARRAY<MAP<a: INTEGER, b: VARCHAR>>>` say, or `UNION<DOUBLE, INTEGER>`. * The short type of the vector itself: `LIST`, `UNION`. For Variant types (`UNION`, `LIST`) we then want two forms: * The vector itself. (`DICT`, `MAP`, `UNION`, `LIST`) * The value: (`INTEGER`, `DOUBLE`). Of course, the value can itself be structured: a `UNION` which has a `LIST` of `UNION` types. So, for both the vector and the value, we'd want both the simple and verbose forms. And, now that @arina-ielchiieva added the nice type description system, we have no function which returns the full description, including the `NOT NULL` attribute, as it appears in the schema file: `INTEGER NOT NULL`. The present fix gets us closer, but it is hard to solve four or five cases with three functions. I suspect we could do better. Suggestions welcomed!
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