smaheshwar-pltr commented on code in PR #3220:
URL: https://github.com/apache/iceberg-python/pull/3220#discussion_r3261579754
##########
pyiceberg/table/__init__.py:
##########
@@ -1009,6 +1012,148 @@ def commit_transaction(self) -> Table:
return self._table
+class ReplaceTableTransaction(Transaction):
+ """A transaction that replaces an existing table's schema, spec, sort
order, location, and properties.
+
+ The existing table UUID, snapshots, snapshot log, metadata log, and
history are preserved.
+ The "main" branch ref is removed (current-snapshot-id set to -1), and new
+ schema/spec/sort-order/location/properties are applied.
+ """
+
+ def __init__(
+ self,
+ table: StagedTable,
+ new_schema: Schema,
+ new_spec: PartitionSpec,
+ new_sort_order: SortOrder,
+ new_location: str,
+ new_properties: Properties,
+ ) -> None:
+ super().__init__(table, autocommit=False)
+ self._initial_changes(table.metadata, new_schema, new_spec,
new_sort_order, new_location, new_properties)
+
+ def _initial_changes(
+ self,
+ table_metadata: TableMetadata,
+ new_schema: Schema,
+ new_spec: PartitionSpec,
+ new_sort_order: SortOrder,
+ new_location: str,
+ new_properties: Properties,
+ ) -> None:
+ """Set the initial changes that transform the existing table into the
replacement.
+
+ Always emits `SetCurrentSchema` / `SetDefaultPartitionSpec` /
`SetDefaultSortOrder`
+ (even when the resulting id is reused) so the request body
unambiguously signals a
+ replace. Bumps `format-version` when the new properties request it.
+ """
+ # Upgrade format-version if requested via properties.
+ requested_format_version_str =
new_properties.get(TableProperties.FORMAT_VERSION)
+ if requested_format_version_str is not None:
+ requested_format_version = int(requested_format_version_str)
+ if requested_format_version > table_metadata.format_version:
+ self._updates +=
(UpgradeFormatVersionUpdate(format_version=requested_format_version),)
+
+ # Remove the main branch ref to clear the current snapshot.
+ self._updates += (RemoveSnapshotRefUpdate(ref_name=MAIN_BRANCH),)
+
+ # Schema: reuse an existing schema_id if structurally identical, else
add a new one
+ # with a fresh schema_id (max + 1, matching UpdateSchema's convention).
+ existing_schema_id = self._find_matching_schema_id(table_metadata,
new_schema)
+ if existing_schema_id is not None:
+ self._updates +=
(SetCurrentSchemaUpdate(schema_id=existing_schema_id),)
+ else:
+ next_schema_id = max((s.schema_id for s in
table_metadata.schemas), default=-1) + 1
+ schema_with_fresh_id = new_schema.model_copy(update={"schema_id":
next_schema_id})
+ self._updates += (
+ AddSchemaUpdate(schema_=schema_with_fresh_id),
+ SetCurrentSchemaUpdate(schema_id=-1),
+ )
+
+ # Partition spec: same reuse-or-add pattern. Assign a fresh spec_id on
add to avoid
+ # collisions with existing specs (AddPartitionSpecUpdate refuses
duplicate IDs).
+ effective_spec = UNPARTITIONED_PARTITION_SPEC if
new_spec.is_unpartitioned() else new_spec
+ existing_spec_id = self._find_matching_spec_id(table_metadata,
effective_spec)
+ if existing_spec_id is not None:
+ self._updates += (SetDefaultSpecUpdate(spec_id=existing_spec_id),)
+ else:
+ next_spec_id = max((s.spec_id for s in
table_metadata.partition_specs), default=-1) + 1
+ spec_with_fresh_id = PartitionSpec(*effective_spec.fields,
spec_id=next_spec_id)
+ self._updates += (
+ AddPartitionSpecUpdate(spec=spec_with_fresh_id),
+ SetDefaultSpecUpdate(spec_id=-1),
+ )
+
+ # Sort order: same reuse-or-add pattern with fresh order_id on add.
+ effective_sort_order = UNSORTED_SORT_ORDER if
new_sort_order.is_unsorted else new_sort_order
+ existing_order_id = self._find_matching_sort_order_id(table_metadata,
effective_sort_order)
+ if existing_order_id is not None:
+ self._updates +=
(SetDefaultSortOrderUpdate(sort_order_id=existing_order_id),)
+ else:
+ next_order_id = max((o.order_id for o in
table_metadata.sort_orders), default=-1) + 1
+ sort_order_with_fresh_id = SortOrder(*effective_sort_order.fields,
order_id=next_order_id)
+ self._updates += (
+ AddSortOrderUpdate(sort_order=sort_order_with_fresh_id),
+ SetDefaultSortOrderUpdate(sort_order_id=-1),
+ )
+
+ # Set location if changed.
+ if new_location != table_metadata.location:
+ self._updates += (SetLocationUpdate(location=new_location),)
+
+ # Merge properties (SetPropertiesUpdate merges onto existing
properties).
+ if new_properties:
+ self._updates += (SetPropertiesUpdate(updates=new_properties),)
+
+ @staticmethod
+ def _find_matching_schema_id(table_metadata: TableMetadata, schema:
Schema) -> int | None:
Review Comment:
Supports the case Fokko walked through in [#433
(comment)](https://github.com/apache/iceberg-python/pull/433#discussion_r1524529502):
`CREATE OR REPLACE` back to a previously-seen schema reuses its `schema_id`
and does not append a duplicate. Same logic for spec and sort order — see
`_find_matching_spec_id` and `_find_matching_sort_order_id` below.
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