Question about schema evolution and partition spec evolution

[Saisai Shao <sa...@gmail.com>]

Hi team,

I have some newbie questions about schema evolution and partition
evolution. From the design spec, Iceberg supports schema evolution and
partition spec evolution, my questions are:

1. If a new column is added, are we going to rewrite the whole data, if not
how do we support it?
2. Do we support partition spec evolution to add new partition column? If
so, does it require data rewrite, since the directories may be different?
3. Do we support changing partition strategy during partition spec
evolution, say from identity to bucket? If so, I think it requires data
rewrite, am I correct? Also do we need to keep old data, so that historical
revisit will get a correct result.

Sorry about newbie questions, since Iceberg is a mutable table, which makes
problem more complicated, and I'm doing bucketing support, so I'm thinking
about schema evolution which potentially affects bucketing.

Best regards,
Saisai