import-export provides a ‘bulk mode’ to improve the performance of importing large datasets.
In normal operation, import-export will call
instance.save() as each row in a dataset is processed. Bulk
mode means that
instance.save() is not called, and instances are instead added to temporary lists. Once the number
of rows processed matches the
batch_size value, then either
bulk_update() is called.
batch_size is set to
bulk_update() is only called once all rows have been
Bulk deletes are also supported, by applying a
filter() to the temporary object list, and calling
the resulting query set.
- The model’s
save()method will not be called, and
post_savesignals will not be sent.
bulk_update()is only supported in Django 2.2 upwards.
- Bulk operations do not work with many-to-many relationships.
- Take care to ensure that instances are validated before bulk operations are called. This means ensuring that resource fields are declared appropriately with the correct widgets. If an exception is raised by a bulk operation, then that batch will fail. It’s also possible that transactions can be left in a corrupted state. Other batches may be successfully persisted, meaning that you may have a partially successful import.
- In bulk mode, exceptions are not linked to a row. Any exceptions raised by bulk operations are logged and returned
as critical (non-validation) errors (and re-raised if
- If you use
ForeignKeyWidgetthen this can affect performance, because it reads from the database for each row. If this is an issue then create a subclass which caches
get_queryset()results rather than reading for each invocation.
For more information, please read the Django documentation on bulk_create() and bulk_update().
Consider the following if you need to improve the performance of imports.
use_bulkfor bulk create, update and delete operations (read Caveats first).
- If your import is creating instances only (i.e. you are sure there are no updates), then set
force_init_instance = True.
- If your import is updating or creating instances, and you have a set of existing instances which can be stored in
- By default, import rows are compared with the persisted representation, and the difference is stored against each row
result. If you don’t need this diff, then disable it with
skip_diff = True.
batch_sizeto a different value is possible, but tests showed that setting this to
Nonealways resulted in worse performance in both duration and peak memory.
Scripts are provided to enable testing and benchmarking of bulk imports. See Bulk testing.