- ADD COLUMN — new field ID allocated; the column's Postgres DEFAULT is carried into Iceberg's initial-default/write-default, so existing rows read back correctly
- DROP COLUMN — removed from the current schema, existing data files untouched
- Type widening — int4→int8, float4→float8 (the changes Iceberg considers compatible)
- REPLICA IDENTITY changes
[0] https://github.com/viggy28/streambed/pull/21