add: schema evolution support (Postgres → Iceberg)#21
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Automatically propagate ADD COLUMN, DROP COLUMN, ALTER TYPE (widening), and REPLICA IDENTITY changes from Postgres to Iceberg metadata. Key changes: - Decoder diffs consecutive RelationMessages by column name to detect schema changes (ADD, DROP, TYPE_CHANGE, KEY_CHANGE) - Catalog evolves Iceberg schema with stable field IDs (allocated from lastColumnID, not positional) and sets initial-default for ADD with DEFAULT - Writer flushes old-schema buffer before evolving, then updates field IDs - On restart, writer reconciles WAL columns against Iceberg metadata to detect schema drift that occurred while stopped - Second (non-replication) Postgres connection queries pg_attrdef for column default expressions - Type widening validated against allowlist (int→long, float→double) Closes #4 Co-Authored-By: Claude Opus 4.6 <[email protected]>
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Automatically propagate ADD COLUMN, DROP COLUMN, ALTER TYPE (widening), and REPLICA IDENTITY changes from Postgres to Iceberg metadata.
Key changes:
Closes #4
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