paul-rogers commented on issue #1870: DRILL-7359: Add support for DICT type in RowSet Framework URL: https://github.com/apache/drill/pull/1870#issuecomment-541442192 On, read, we can access the `DICT` as a dictionary and as an array. This means we need to be a bit clever about designing the `DictReader()` interface. We can get our `DictReader` similar to the write case: ``` DictReader dictReader = rowReader.dict("myDict"); ``` Now, we have two ways to proceed. Either we want key/value lookups, or array access. For array access, we want an iterator, much like the `ArrayReader`, but that gives us access to both the key and value. Something like: ``` interface DictReader ... ScalarReader key(); ObjectReader value(); boolean next(); ``` For key/value, we have a challenge. We need a way to specify the key that is type-specific. Then, we need to access the key in a type-specific way. This is the first time we've had such an issue. Maybe we can build this on the array iterator. In addition to the `next()` method, we can provide a `findFoo()` method, with one for each supported key type. ``` int findString(String key); int findInt(int key); ... ``` The semantics might be that the array index is set to the (first) index of the requested value, and that index is returned. If not found, the return value is -1 and the array index is one past the end of the array. ``` DictReader dictReader = ... if (dictReader.findString("barney")) { value = dictReader.value().scalar().getDouble(); } ``` There are probably other variations. Think how you expect to use the reader (for testing, yes, but what other operations)?
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