Add accessors for List and Map type #101
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Similar to `Row`, this adds accessors to `List` and `Map` type. For the former, type-safe accessors are added to get the `i`th element in the list. For the latter, `getKeys` and `getValues` are added to get the map keys and values, respectively.
| // TODO: implement `getKeys`, `getValues`, etc., for `Map`. | ||
| /// Trait for type-safe access of an index for a `Map` | ||
| pub trait MapAccessor { | ||
| fn get_keys<'a>(&'a self) -> Box<ListAccessor + 'a>; |
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Would you consider returning Vec<Field> or &[Field] for keys and values? It might result in less code.
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Now the question is whether or not it is possible to get struct from map value if we return &[Field]. In this case we would have to map to Group(Row), and then use one of the accessors. So yes, it may be functionally correct to return ListAccessor.
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Yes, we are only exposing Row, List and Map at the moment, and each of them offers accessors. So, here we need to return ListAccessor instead of list of Field which is not exposed.
I'm also hesitant on whether the RowIter should return Box<RowAccessor> instead of Row. In future if we implement a batch-oriented record reader, we may want to return a Row from the current RowBatch, whose implementation may be different from what we have right now.
Also, it might better to rename the RowAccessor to Row, and the current Row to RowImpl or something.
Just some random thought 😀 .
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Sounds good, I would suggest we keep the current implementation for now.
| fn get_values<'a>(&'a self) -> Box<ListAccessor + 'a>; | ||
| } | ||
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| struct MapList<'a> { |
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Will API work if this struct is private?
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I think we don't need to export MapList, but only the accessors.
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Merged. Thanks @sadikovi for the review! |
Similar to
Row, this adds accessors toListandMaptype. For theformer, type-safe accessors are added to get the
ith element in thelist. For the latter,
getKeysandgetValuesare added to get the mapkeys and values, respectively.