Martin Durant created ARROW-3247:
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Summary: Support spark array and map types
Key: ARROW-3247
URL: https://issues.apache.org/jira/browse/ARROW-3247
Project: Apache Arrow
Issue Type: Improvement
Components: Python
Reporter: Martin Durant
As far I understand, there is already some support for nested
array/dict/structs in arrow. However, spark Map and List types are structured
one level deeper (I believe to allow for both NULL and empty entries).
Surprisingly, fastparquet can load these. I do not know the plan for arbitrary
nested object support, but it should be made clear.
Schema of spark-generated file from the fastparquet test suite (please see in
text mode):
- spark_schema:
| - map_op_op: MAP, OPTIONAL
| - key_value: REPEATED
| | - key: BYTE_ARRAY, UTF8, REQUIRED
| - value: BYTE_ARRAY, UTF8, OPTIONAL
| - map_op_req: MAP, OPTIONAL
| - key_value: REPEATED
| | - key: BYTE_ARRAY, UTF8, REQUIRED
| - value: BYTE_ARRAY, UTF8, REQUIRED
| - map_req_op: MAP, REQUIRED
| - key_value: REPEATED
| | - key: BYTE_ARRAY, UTF8, REQUIRED
| - value: BYTE_ARRAY, UTF8, OPTIONAL
| - map_req_req: MAP, REQUIRED
| - key_value: REPEATED
| | - key: BYTE_ARRAY, UTF8, REQUIRED
| - value: BYTE_ARRAY, UTF8, REQUIRED
| - arr_op_op: LIST, OPTIONAL
| - list: REPEATED
| - element: BYTE_ARRAY, UTF8, OPTIONAL
| - arr_op_req: LIST, OPTIONAL
| - list: REPEATED
| - element: BYTE_ARRAY, UTF8, REQUIRED
| - arr_req_op: LIST, REQUIRED
| - list: REPEATED
| - element: BYTE_ARRAY, UTF8, OPTIONAL
- arr_req_req: LIST, REQUIRED
- list: REPEATED
- element: BYTE_ARRAY, UTF8, REQUIRED
(please forgive that some of this has already been mentioned elsewhere; this is
one of the entries in the list at
https://github.com/dask/fastparquet/issues/374 as a feature that is useful in
fastparquet)
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