TableAlterer

deltalake.table.TableAlterer

TableAlterer(table: DeltaTable)

API for various table alteration commands.

add_constraint

add_constraint(constraints: Dict[str, str], custom_metadata: Optional[Dict[str, str]] = 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]]	custom metadata that will be added to the transaction commit.	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'}
```

drop_constraint

drop_constraint(name: str, raise_if_not_exists: bool = True, custom_metadata: Optional[Dict[str, str]] = 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]]	custom metadata that will be added to the transaction commit.	None

Example:

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

**Drop the constraint**
```python
dt.alter.drop_constraint(name = "value_gt_5")
```

**Configuration after dropping**
```python
dt.metadata().configuration
{}
```