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https://issues.apache.org/jira/browse/ARROW-11077?page=com.atlassian.jira.plugin.system.issuetabpanels:all-tabpanel
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Ben Sully updated ARROW-11077:
------------------------------
Attachment: small-nested-lists.parquet
> [Rust] ParquetFileArrowReader panicks when trying to read nested list
> ---------------------------------------------------------------------
>
> Key: ARROW-11077
> URL: https://issues.apache.org/jira/browse/ARROW-11077
> Project: Apache Arrow
> Issue Type: Bug
> Components: Rust
> Reporter: Ben Sully
> Priority: Major
> Attachments: small-nested-lists.parquet
>
>
> I think this is documented in the code, but I can't be 100% sure.
> When trying to execute a DataFusion query over a Parquet file where one field
> is a struct with a nested list, the thread panicks due to unwrapping on an
> `Option::None` [at this
> point|https://github.com/apache/arrow/blob/36d80e37373ab49454eb47b2a89c10215ca1b67e/rust/parquet/src/arrow/array_reader.rs#L1334-L1337]
>
> [.|https://github.com/apache/arrow/blob/36d80e37373ab49454eb47b2a89c10215ca1b67e/rust/parquet/src/arrow/array_reader.rs#L1334-L1337].]
> This `None` is returned by
> [`visit_primitive`|https://github.com/apache/arrow/blob/master/rust/parquet/src/arrow/array_reader.rs#L1243-L1245],
> but I can't quite make sense of _why_ it returns a `None` rather than an
> error?
> I added a couple of dbg! calls to see what the item_type and list_type are:
> {code}
> [/home/ben/repos/rust/arrow/rust/parquet/src/arrow/array_reader.rs:1339]
> &item_type = PrimitiveType {
> basic_info: BasicTypeInfo {
> name: "item",
> repetition: Some(
> OPTIONAL,
> ),
> logical_type: UTF8,
> id: None,
> },
> physical_type: BYTE_ARRAY,
> type_length: -1,
> scale: -1,
> precision: -1,
> }
> [/home/ben/repos/rust/arrow/rust/parquet/src/arrow/array_reader.rs:1340]
> &list_type = GroupType {
> basic_info: BasicTypeInfo {
> name: "tags",
> repetition: Some(
> OPTIONAL,
> ),
> logical_type: LIST,
> id: None,
> },
> fields: [
> GroupType {
> basic_info: BasicTypeInfo {
> name: "list",
> repetition: Some(
> REPEATED,
> ),
> logical_type: NONE,
> id: None,
> },
> fields: [
> PrimitiveType {
> basic_info: BasicTypeInfo {
> name: "item",
> repetition: Some(
> OPTIONAL,
> ),
> logical_type: UTF8,
> id: None,
> },
> physical_type: BYTE_ARRAY,
> type_length: -1,
> scale: -1,
> precision: -1,
> },
> ],
> },
> ],
> }{code}
> I guess we should at least use `.expect` here instead of `.unwrap` so it's
> more clear why this is happening!
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