[GitHub] [iceberg] wypoon commented on pull request #2275: Core: add schema id to snapshot and history entry

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

wypoon commented on pull request #2275:
URL: https://github.com/apache/iceberg/pull/2275#issuecomment-792958633


   I have some questions:
   When we switch from v1 format to v2, and a new metadata file is written for an existing table, what schemas are written to the `schemas` list? And in the `snapshot-log`, what `schema-id` is written for the previous snapshots? (Is it not written, i.e., is null? or is it 0?)
   In general, if we see a schema id of 0, does that ever represent a specific schema, or does that always represent some undetermined schema? Let me elaborate: (1) Will we ever see a `schema-id` of 0 in a metadata file and if so, does that refer to a unique schema? (2) In code, if a have an instance of a schema and its schemaId is 0, what are the semantics of that schemaId?


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