etseidl commented on PR #9011: URL: https://github.com/apache/arrow-rs/pull/9011#issuecomment-3671317464
> Unfortunately dictionary encoding is best effort, and writers will fallback to different encodings if the dictionary gets too large. The result is you need to know if all the pages are dictionary encoded in order to be able to make this optimisation - iirc this information is not encoded anywhere but the page header itself... This is why the page encoding stats exist in the column metadata. This will tell you if all pages in a given chunk are dictionary encoded. (See https://github.com/apache/arrow-rs/blob/116ae12f2a200579025400c0f1d871d0e3fb0d47/parquet/src/file/metadata/mod.rs#L1072-L1083) That said, I'm not nuts about duplicating the logic to decode the dictionary page, and just for the async reader. If we're going down this path, then I think all readers should have access. Perhaps this could be in `ArrowReaderBuilder` or even `ParquetMetaData` 🤷 -- This is an automated message from the Apache Git Service. To respond to the message, please log on to GitHub and use the URL above to go to the specific comment. To unsubscribe, e-mail: [email protected] For queries about this service, please contact Infrastructure at: [email protected]
