`table.update_schema()` continues to commit when exist with an exception

[jiakai-li]

Apache Iceberg version

0.8.1 (latest release)

Please describe the bug 🐞

While working on the issue of #1493 I noticed when running below code, the field of field_should_not_exist will still be added to the table.

from pyiceberg.catalog.sql import SqlCatalog
from pyiceberg.schema import Schema
from pyiceberg.types import IntegerType, NestedField, StringType

WAREHOUSE_PATH = "/workspaces/iceberg-python/warehouse"
catalog = SqlCatalog(
    "default",
    uri=f"sqlite:///{WAREHOUSE_PATH}/pyiceberg_catalog.db", warehouse=f"file://{WAREHOUSE_PATH}",
)
catalog.create_namespace_if_not_exists("default")

try:
    catalog.drop_table("default.test")
except:
    pass

schema = Schema(
    NestedField(1, "field1", StringType(), required=False)
)

table = catalog.create_table("default.test", schema)

with table.update_schema() as update:
    update.add_column("field_should_not_exist", IntegerType())
    raise Exception("Error!")

The behaviour is a bit confuse to me. Due to an exception is raised within the context manager, I would expect the transaction to be aborted. But seems commit is currently the only option to exit the context manager:

class UpdateTableMetadata(ABC, Generic[U]):
    _transaction: Transaction

    def __init__(self, transaction: Transaction) -> None:
        self._transaction = transaction

    @abstractmethod
    def _commit(self) -> UpdatesAndRequirements: ...

    def commit(self) -> None:
        self._transaction._apply(*self._commit())

    def __exit__(self, _: Any, value: Any, traceback: Any) -> None:
        """Close and commit the change."""
        self.commit()  # <----- we currently ignore the exc_type

    def __enter__(self) -> U:
        """Update the table."""
        return self  # type: ignore

Willingness to contribute

• I can contribute a fix for this bug independently
• I would be willing to contribute a fix for this bug with guidance from the Iceberg community
• I cannot contribute a fix for this bug at this time

[kevinjqliu]

Hey @jiakai-li thanks for raising this issue!
The root cause is the same as the one i raised in #1253 and #1497

Specifically, when using UpdateSchema as a "transaction" and a context manager, I expect the transaction to be atomic

with table.update_schema() as update:
    update.add_column("field_should_not_exist", IntegerType())
    raise Exception("Error!")

This example shows that the first add_column is processed, even though the transaction errored and should not apply any updates.

The core issue is from setting Transaction's autocommit=True in UpdateSchema (source)
This will cause every update to be "applied"/"flushed" as soon as possible (source)

As mentioned in #1253, i think we should get rid of autocommit ASAP, as there are new table update PRs trying to use it. (#1500 #1285)

[jiakai-li]

Thank you @kevinjqliu , I'm closing this issue to avoid duplicates then. Let's keep the discussion at #1253

[kevinjqliu]

I like the example you have above! Do you mind transferring it to #1253?