alamb commented on a change in pull request #1149:
URL: https://github.com/apache/arrow-rs/pull/1149#discussion_r782430643
##########
File path: arrow/src/json/writer.rs
##########
@@ -486,6 +486,41 @@ fn set_column_for_json_rows(
.expect("cannot cast dictionary to underlying values");
set_column_for_json_rows(rows, row_count, &hydrated, col_name)
}
+ DataType::Map(_, _) => {
+ let maparr = as_map_array(array);
+
+ let keys = maparr.keys();
+ let values = maparr.values();
+
+ // Keys have to be strings to convert to json.
+ if !matches!(keys.data_type(), DataType::Utf8) {
+ panic!("Unsupported datatype: {:#?}", array.data_type());
Review comment:
it would be much nicer if this code did not `panic` when there was an
unsupported datatype. However, I see that the the signature for
`set_column_for_json_rows` does not return a Result 😢
I'll file a follow on ticket and see if someone in the community is
interesting in improving this
##########
File path: arrow/src/json/writer.rs
##########
@@ -1312,6 +1347,65 @@ mod tests {
{}
{"list":[{}]}
{"list":[{}]}
+"#
+ );
+ }
+
+ #[test]
+ fn json_writer_map() {
+ let keys_array =
+ super::StringArray::from(vec!["foo", "bar", "baz", "qux", "quux"]);
+ let values_array = super::Int64Array::from(vec![10, 20, 30, 40, 50]);
+
+ let keys = Field::new("keys", DataType::Utf8, false);
+ let values = Field::new("values", DataType::Int64, false);
+ let entry_struct = StructArray::from(vec![
+ (keys, Arc::new(keys_array) as ArrayRef),
+ (values, Arc::new(values_array) as ArrayRef),
+ ]);
+
+ let map_data_type = DataType::Map(
+ Box::new(Field::new(
+ "entries",
+ entry_struct.data_type().clone(),
+ true,
+ )),
+ false,
+ );
+
+ // [{"foo": 10}, null, {}, {"bar": 20, "baz": 30, "qux": 40}, {"quux":
50}, {}]
Review comment:
It would be great to have a better / nicer way to contruct `MapArrays`
-- again not for this PR but eventually it would be nice to have something like
https://docs.rs/arrow/6.5.0/arrow/array/struct.StructArray.html
I will file another ticket
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