4. Deleting a record

To delete a record or records in a database table you make use of the following functions:

1. delete_by_pk()

2. delete_one()

3. delete_bulk()

1. delete_by_pk()

Using the delete_by_pk() method, you can delete a record in a database based on the primary-key value.

affected_rows = mysql_loom.delete_by_pk(instance=User, pk=1)

The above take the following as arguments:

Argument	Description	Type	Default	Required
instance	The model class from which to delete the instance.	Model		Yes
pk	The primary key value of the instance to delete.	Any		Yes

2. delete_one()

You can also use filters to delete a record in a database. The delete_one() function enables you to delete a single record in a database that matches a filter.

affected_rows = mysql_loom.delete_one(
    instance=User, filters=[Filter(column="username", value="@miller")]
)

The method takes in the following arguments:

Argument	Description	Type	Default	Required
instance	The model class from which to delete the instance(s).	Model		Yes
filters	Filter or collection of filters to apply to the deletion query.	Filter or list[Filter] or None	None	No
offset	Number of instances to skip before deleting.	int or None	No
order	Collection of Order or as single Order to order the instances by before deletion.	list[Order] or Order``or ``None	[]	No

3. delete_bulk()

You can also use the delete_bulk() method to delete a multitude of records that match a given filter:

affected_rows = mysql_loom.delete_bulk(
    instance=User, filters=[Filter(column="username", value="@miller")]
)

The method takes the following as arguments:

Argument	Description	Type	Default	Required
instance	The model class from which to delete instances.	Model		Yes
filters	Filter or collection of filters to apply to the deletion query.	Filter or list[Filter] or None	None	No
limit	Maximum number of instances to delete.	int or None	No
offset	Number of instances to skip before deleting.	int or None	No
order	Collection of Order or a single Order to order the instances by before deletion.	list[Order] or Order``or ``None	[]	No

Warning: Potential Risk with delete_bulk()

Warning

When using the delete_bulk() function, exercise caution as it can be aggressive. If the filter is not explicitly provided, there is a risk of mistakenly deleting all records in the table.

Guidelines for Safe Usage

To mitigate the potential risks associated with delete_bulk(), follow these guidelines:

1. Always Provide a Filter:

   • When calling delete_bulk(), make sure to provide a filter to specify the subset of records to be deleted. This helps prevent unintentional deletions.

   # Example: Delete records where 'status' is 'inactive'
   affected_rows = mysql_loom.delete_bulk(
       instance=User,
       filters=Filter(column="status",  value='inactive'),
   )
   

2. Consider Usage When Necessary:

• When contemplating data deletion, it is advisable to consider more targeted methods before resorting to delete_bulk(). Prioritize the use of delete_one() or delete_by_pk() methods to remove specific records based on your needs. This ensures a more precise and controlled approach to data deletion.

3. Use limit and offsets options

• You can consider using the limit and offset options during invocation of delete_bulk

affected_rows = mysql_loom.delete_bulk(
    instance=Post,
    order=[Order(column="id", order="DESC"), Order(column="createdAt", order="ASC")],
    filters=[Filter(column="id", operator="gt", value=0)],
    offset=0,
    limit=10,
)

By following these guidelines, you can use the delete_bulk() function safely and minimize the risk of unintended data loss. Always exercise caution and adhere to best practices when performing bulk deletion operations.