TableAlterer

deltalake.table.TableAlterer

TableAlterer(table: DeltaTable)

API for various table alteration commands.

add_columns

add_columns(fields: Union[DeltaField, List[DeltaField]], custom_metadata: Optional[Dict[str, str]] = None, commit_properties: Optional[CommitProperties] = None, post_commithook_properties: Optional[PostCommitHookProperties] = None) -> None

Add new columns and/or update the fields of a stuctcolumn

Parameters:

Name	Type	Description	Default
fields	Union[Field, List[Field]]	fields to merge into schema	required
commit_properties	Optional[CommitProperties]	properties of the transaction commit. If None, default values are used.	None
post_commithook_properties	Optional[PostCommitHookProperties]	properties for the post commit hook. If None, default values are used.	None

Example

from deltalake.schema import Field, PrimitiveType, StructType
dt = DeltaTable("test_table")
new_fields = [
    Field("baz", StructType([Field("bar", PrimitiveType("integer"))])),
    Field("bar", PrimitiveType("integer"))
]
dt.alter.add_columns(
    new_fields
)

add_constraint

add_constraint(constraints: Dict[str, str], custom_metadata: Optional[Dict[str, str]] = None, post_commithook_properties: Optional[PostCommitHookProperties] = None, commit_properties: Optional[CommitProperties] = None) -> None

Add constraints to the table. Limited to single constraint at once.

Parameters:

Name	Type	Description	Default
constraints	Dict[str, str]	mapping of constraint name to SQL-expression to evaluate on write	required
custom_metadata	Optional[Dict[str, str]]	Deprecated and will be removed in future versions. Use commit_properties instead.	None
post_commithook_properties	Optional[PostCommitHookProperties]	properties for the post commit hook. If None, default values are used.	None
commit_properties	Optional[CommitProperties]	properties of the transaction commit. If None, default values are used.	None

Example

from deltalake import DeltaTable
dt = DeltaTable("test_table_constraints")
dt.alter.add_constraint({
    "value_gt_5": "value > 5",
})

Check configuration

dt.metadata().configuration
{'delta.constraints.value_gt_5': 'value > 5'}

add_feature

add_feature(feature: Union[TableFeatures, List[TableFeatures]], allow_protocol_versions_increase: bool = False, commit_properties: Optional[CommitProperties] = None, post_commithook_properties: Optional[PostCommitHookProperties] = None) -> None

Enable a table feature.

Parameters:

Name	Type	Description	Default
feature	Union[TableFeatures, List[TableFeatures]]	Table Feature e.g. Deletion Vectors, Change Data Feed	required
allow_protocol_versions_increase	bool	Allow the protocol to be implicitily bumped to reader 3 or writer 7	False
commit_properties	Optional[CommitProperties]	properties of the transaction commit. If None, default values are used.	None
post_commithook_properties	Optional[PostCommitHookProperties]	properties for the post commit hook. If None, default values are used.	None

Example

from deltalake import DeltaTable
dt = DeltaTable("test_table")
dt.alter.add_feature(TableFeatures.AppendOnly)

Check protocol

dt.protocol()
ProtocolVersions(min_reader_version=1, min_writer_version=7, writer_features=['appendOnly'], reader_features=None)

drop_constraint

drop_constraint(name: str, raise_if_not_exists: bool = True, custom_metadata: Optional[Dict[str, str]] = None, post_commithook_properties: Optional[PostCommitHookProperties] = None, commit_properties: Optional[CommitProperties] = None) -> None

Drop constraints from a table. Limited to single constraint at once.

Parameters:

Name	Type	Description	Default
name	str	constraint name which to drop.	required
raise_if_not_exists	bool	set if should raise if not exists.	True
custom_metadata	Optional[Dict[str, str]]	Deprecated and will be removed in future versions. Use commit_properties instead.	None
post_commithook_properties	Optional[PostCommitHookProperties]	properties for the post commit hook. If None, default values are used.	None
commit_properties	Optional[CommitProperties]	properties of the transaction commit. If None, default values are used.	None

Example

from deltalake import DeltaTable
dt = DeltaTable("test_table_constraints")
dt.metadata().configuration
{'delta.constraints.value_gt_5': 'value > 5'}

Drop the constraint

dt.alter.drop_constraint(name = "value_gt_5")

Configuration after dropping

dt.metadata().configuration
{}

set_column_metadata

set_column_metadata(column: str, metadata: dict[str, str], commit_properties: Optional[CommitProperties] = None, post_commithook_properties: Optional[PostCommitHookProperties] = None) -> None

Update a field's metadata in a schema. If the metadata key does not exist, the entry is inserted.

If the column name doesn't exist in the schema - an error is raised.

:param column: name of the column to update metadata for. :param metadata: the metadata to be added or modified on the column. :param commit_properties: properties of the transaction commit. If None, default values are used. :param post_commithook_properties: properties for the post commit hook. If None, default values are used. :return:

set_table_properties

set_table_properties(properties: Dict[str, str], raise_if_not_exists: bool = True, custom_metadata: Optional[Dict[str, str]] = None, commit_properties: Optional[CommitProperties] = None) -> None

Set properties from the table.

Parameters:

Name	Type	Description	Default
properties	Dict[str, str]	properties which set	required
raise_if_not_exists	bool	set if should raise if not exists.	True
custom_metadata	Optional[Dict[str, str]]	Deprecated and will be removed in future versions. Use commit_properties instead.	None
commit_properties	Optional[CommitProperties]	properties of the transaction commit. If None, default values are used.	None

Example

from deltalake import write_deltalake, DeltaTable
import pandas as pd
df = pd.DataFrame(
    {"id": ["1", "2", "3"],
    "deleted": [False, False, False],
    "price": [10., 15., 20.]
    })
write_deltalake("tmp", df)

dt = DeltaTable("tmp")
dt.alter.set_table_properties({"delta.enableChangeDataFeed": "true"})