[GitHub] [iceberg] rdblue commented on pull request #2957: Core: add TableMetadata update builder

[GitBox <gi...@apache.org>]

rdblue commented on pull request #2957:
URL: https://github.com/apache/iceberg/pull/2957#issuecomment-920477110


   I was imagining the builder would work a little differently. There's definitely some value in the regular builder pattern where you can mostly copy fields and just make calls to change values. But I think adding a builder could bring more value if we actually moved the implementations of the `TableMetadata` modifications into the builder. So what I was thinking was to basically move all of the methods like `replaceCurrentSnapshot` and `removeSnapshotsIf` into the builder itself.
   
   That approach allows us to make more than one change without adding special handling for `upgradeToFormatVersion`. We could chain changes to produce a new `TableMetadata` because the methods keep track of table state.
   
   A second benefit that I'm interested in is tracking the high-level changes the led to a new `TableMetadata` object. We're building a REST-based catalog and I think this is the first step to an update that posts just what changed. For example, `replaceCurrentSnapshot` could produce a new `TableMetadata`, but also keep track of the facts that (1) a new snapshot was added and (2) the current snapshot was set to that snapshot's ID. Those granular changes make a REST protocol much more efficient.
   
   Does that motivation make sense?


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