RussellSpitzer opened a new pull request, #13769: URL: https://github.com/apache/iceberg/pull/13769
A Proof of Concept pr to show what allowing writing to Parquet Manifests might look like as well as the illuminate the rough edges we will need to work around to get this into the project. I'm collecting some thoughts on the work in the document below: https://docs.google.com/document/d/13TeFu20jhkUFbb-FaaGQWFiXKO6kKyy_nX1QyFgoUoU/edit?usp=sharing Implementation issues ### Empty Structs Parquet does not support an empty struct in the schema but our current definition of the manifest has a required “partition” struct. For an unpartitioned table this means an empty struct is required in the schema. POC Work - I work around this by just putting in a dummy placeholder struct instead. ### Public API from Manifest Reader Reliance on Manifest Metadata Currently the Manifest Reader attempts to extract table’s Specs information from inside the avro metadata. This isn’t actually required by any of our code and there is basically never a time in production where we read a manifest and don’t already have the specs. The tests are a different case and require a lot of rewriting. There is unfortunately one major exception to this, Snapshot provides several apis like (addedFiles(FileIO io)) which reads manifests directly with a FileIO to produce their entries, this creates a manifest group directly but without setting specById. In this context we also do not have access to the table, we probably will need to change this interface if we want to remove reliance on file metadata. POC Work - Originally I focused on just fixing all the test references after skimming and trying to determine if there were any real production uses of the API. Once I discovered the issue with BaseSnapshot I tried to determine exactly the scope, 30 of the above test failures are related to this issue. Many are test related (checking snapshot contents) but there are some public usages in cherry-pick snapshot. ### Refactoring of Parquet InternalReader Implementation The current parquet InternalReader API returns a reader function before we are able to get arguments for custom classes. ManifestReader needs to be able to read into custom classes (ManifestEntry, DataFile, etc ..) so the custom classes need to be created prior to the reader function being generated. POC Work - Bit of a sloppy fix here but we move the reader into the Parquet class itself so that we can modify the function before it is built. ### Use of Immutables in BaseFile Parquet readers using a reusable container fail because BaseFile returns an immutable representation of the splitOffset list. POC Work - Just return a mutable list for now ### Determining Manifest Type Based on Extension In order to have different behaviors for different types but allow reading both avro and parquet manifests, we need to rely on extensions. Most likely not a problem in the wild, but many of our tests use manifest file names without a type extension. POC Work - Just fixing tests -- 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] --------------------------------------------------------------------- To unsubscribe, e-mail: [email protected] For additional commands, e-mail: [email protected]
