emkornfield commented on code in PR #258: URL: https://github.com/apache/parquet-format/pull/258#discussion_r1628168052
########## CONTRIBUTING.md: ########## @@ -29,3 +29,78 @@ Recommendations and requirements for how to best contribute to Parquet. We striv ### License By contributing your code, you agree to license your contribution under the terms of the APLv2: https://github.com/apache/parquet-format/blob/master/LICENSE + +### Additions/Changes to the Format + +The general steps for adding features to the format are as follows: + +1. Discuss changes on on the developer mailing list ([email protected]). Often times it is helpful to link to a draft pull request to make the discussion concrete. This step is complete when there lazy consensus. + +2. One a change has lazy consensus two implementations of the feature +demonstrating interopability must also be provided. One implementation MUST be [parquet-java](http://github.com/apache/parquet-java). It is preferred that the second implementation be [parquet-cpp](https://github.com/apache/arrow) or [parquet-rs](https://github.com/apache/arrow-rs), however at the discretion of the PMC any +open source Parquet implementation may be acceptable. + +3. After the first two steps are complete a formal vote is held on the Parquet mailing list to officially +ratify the feature. After the vote passes the format change is merged into the parquet-format repository +and it is expected the change in step 2 will also be merged soon after. + +#### General guidelines/preferences on additions. + +1. To the greatest extent possible changes should have an option for forwards compatibility + (old readers can still read files). +2. New encodings should be fully specified in this repository and ideally not rely on an external + dependencies for implementation (i.e. Parquet is the source of truth for the encoding) +3. New compression mechanisms must have a pure Java implementation that can be used as dependency + in parquet-java. + +### Releases + +The Parquet community aims to do releases of the format package only as needed when new features are introduced. +If multiple new features are being proposed simultaneously some features might be consolidated into the same release. Guidance is provided below on when implementations should enable features added to the specification. +Do to confusion in the past over parquet versioning it is not expected that there will be a 3.0 release of the specification in the foreseeable future. + +### Compatibility and Feature Enablement + +For the purposes of this discussion we classify features into the following buckets: + +1. Backwards compatible. A file written by an older version of a library can be read by a newer version of the +library. + +2. Forwards compatible. A file written by a new version of the library can be read by an older version +of the library. + +3. Forwards compatible with suboptimal performance. A file written by a new version of the library can +be read an older version of the library but performance might be suboptimal (e.g. statistics might be missing +from the older reader's perspective). + +4. Forwards incompatible. A file written with a new version of the library cannot be read by an older version +of the library. + +Backwards compatibility is the concern of implementations but given the ubiquity of Parquet and the length +of time it has been used, libraries SHOULD always support reading older format versions. + +The Parquet PMC recommends the following guidance for using features defined in the specification. + +1. Forwards compatible changes MAY be used by default in implementations once the parquet-format containing +those changes has been formally released. These features SHOULD be turned on 1 year after the parquet-java Review Comment: I'll clarify but I mean turned on by default. I hope implementations add the features soon after introduction. -- 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]
