Github user HeartSaVioR commented on the issue:
https://github.com/apache/storm/pull/1714
@arunmahadevan
Let me summary regarding nested map/array support.
* accessing nested element in nested map/array works without modifying
Calcite.
* it should be defined as ANY. Specifying MAP's value type to MAP doesn't
seem to work. I don't understand this behavior but it works anyway.
* We need to wrap value with CAST if we need to use value in expression.
* For example, `MAPFIELD['a'] = 2` doesn't work but `CAST(MAPFIELD['a']
AS INTEGER) = 2` works.
* Using value in projection (fields of SELECT) doesn't need to be wrapped
with CAST.
* NOTE: this is NOT a safe operation, and errors are shown in runtime.
* If value is null in any chance, comparing it to other will **throw
RuntimeException** in runtime.
* value itself could be null.
* value could be null when we access array with wrong index or map with
non-exist key.
* If we access array with index out of bound, it will **throw
ArrayIndexOutOfBoundException** in runtime.
So there's a way to support current feature with adding some inconveniences
(CAST), but it is no longer safe operation. Since user can't handle errors
manually, this can make worker continuously crashed.
I asked Calcite dev. group about this and didn't get answer yet.
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