abhiaagarwal opened a new issue, #6783:
URL: https://github.com/apache/arrow-rs/issues/6783
**Is your feature request related to a problem or challenge? Please describe
what you are trying to do.**
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I'm attempting to read Arrow IPC data from a Go source that uses
Delta-encoded dictionaries. Arrow-rs does not seem to be able to parse and
properly resolve it.
```
+----+----------+-------------------------+-----------------------------+-------------------------+----------------------------------+------------------+------------------+-------------------+------+--------+
| id | resource | scope | start_time_unix_nano |
duration_time_unix_nano | trace_id | span_id |
parent_span_id | name | kind | status |
+----+----------+-------------------------+-----------------------------+-------------------------+----------------------------------+------------------+------------------+-------------------+------+--------+
| 0 | {id: 0} | {id: 0, name: __main__} | 2024-11-24T02:32:12.701141Z |
PT161220S | 4333035c6fc2b2575203f7eb736d1a61 | 4f13686daef62ace |
f1a5af7c58d5b29c | child_operation_0 | 1 | {} |
| 1 | {id: 0} | {id: 0, name: __main__} | 2024-11-24T02:32:14.147818Z |
PT126185S | 456cdc4641073bee3599f703649a04f5 | 9704fb28a544a987 |
1a30f9660037c951 | child_operation_0 | 1 | {} |
| 1 | {id: 0} | {id: 0, name: __main__} | 2024-11-24T02:32:15.666419Z |
PT132589S | 930a2ef4cefd8ce990a388bfd6f72ee6 | 735d38465f4d7739 |
c6ab1841b8cd7d99 | child_operation_0 | 1 | {} |
| 1 | {id: 0} | {id: 0, name: __main__} | 2024-11-24T02:32:12.863028Z |
PT108051S | 4333035c6fc2b2575203f7eb736d1a61 | b63c63b739fa2268 |
f1a5af7c58d5b29c | child_operation_1 | 1 | {} |
```
```
Field { name: "id", data_type: UInt16, nullable: true, dict_id: 0,
dict_is_ordered: false, metadata: {"encoding": "delta"} }, Field { name:
"resource", data_type: Struct([Field { name: "id", data_type: UInt16, nullable:
true, dict_id: 0, dict_is_ordered: false, metadata: {"encoding": "delta"} }]),
nullable: true, dict_id: 0, dict_is_ordered: false, metadata: {} }, Field {
name: "scope", data_type: Struct([Field { name: "id", data_type: UInt16,
nullable: true, dict_id: 0, dict_is_ordered: false, metadata: {"encoding":
"delta"} }, Field { name: "name", data_type: Dictionary(UInt8, Utf8), nullable:
true, dict_id: 0, dict_is_ordered: false, metadata: {"dictId": "1"} }]),
nullable: true, dict_id: 0, dict_is_ordered: false, metadata: {} }, Field {
name: "start_time_unix_nano", data_type: Timestamp(Nanosecond, Some("UTC")),
nullable: false, dict_id: 0, dict_is_ordered: false, metadata: {} }, Field {
name: "duration_time_unix_nano", data_type: Dictionary(UInt8,
Duration(Millisecond)), nul
lable: false, dict_id: 1, dict_is_ordered: false, metadata: {"dictId": "4"} },
Field { name: "trace_id", data_type: FixedSizeBinary(16), nullable: false,
dict_id: 0, dict_is_ordered: false, metadata: {} }, Field { name: "span_id",
data_type: FixedSizeBinary(8), nullable: false, dict_id: 0, dict_is_ordered:
false, metadata: {} }, Field { name: "parent_span_id", data_type:
FixedSizeBinary(8), nullable: true, dict_id: 0, dict_is_ordered: false,
metadata: {} }, Field { name: "name", data_type: Dictionary(UInt8, Utf8),
nullable: false, dict_id: 2, dict_is_ordered: false, metadata: {"dictId": "6"}
}, Field { name: "kind", data_type: Dictionary(UInt8, Int32), nullable: true,
dict_id: 3, dict_is_ordered: false, metadata: {"dictId": "7"} }, Field { name:
"status", data_type: Struct([]), nullable: true, dict_id: 0, dict_is_ordered:
false, metadata: {} }
```
Since delta encoding is not supported, the id column is not incrementing.
**Describe the solution you'd like**
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Arrow-rs should support Delta encoded dictionaries.
**Describe alternatives you've considered**
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you've considered.
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**Additional context**
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Prior work:
https://github.com/apache/arrow-go/blob/e112ad0de5ca66133256f2db71bda4dd2d1731f5/arrow/internal/dictutils/dict.go/https://github.com/apache/arrow-go/blob/e112ad0de5ca66133256f2db71bda4dd2d1731f5/arrow/ipc/file_reader.go#L763
#5488 for a similar implementation for Arrow Flight
I've started to try solving this problem, mimicking the go implementation by
modifying the private function `fn read_dictionary_impl`.
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