Batches

Create / interact with a batch of updates / deletes.

Batches provide the ability to execute multiple operations in a single request to the Cloud Datastore API.

See https://cloud.google.com/datastore/docs/concepts/entities#batch_operations

class google.cloud.datastore.batch.Batch(client)

Bases: object

An abstraction representing a collected group of updates / deletes.

Used to build up a bulk mutation.

For example, the following snippet of code will put the two save operations and the delete operation into the same mutation, and send them to the server in a single API request:

>>> entity1 = datastore.Entity(client.key('EntityKind', 1234))
>>> entity2 = datastore.Entity(client.key('EntityKind', 2345))
>>> key3 = client.key('EntityKind', 3456)
>>> batch = client.batch()
>>> batch.begin()
>>> batch.put(entity1)
>>> batch.put(entity2)
>>> batch.delete(key3)
>>> batch.commit()

You can also use a batch as a context manager, in which case commit() will be called automatically if its block exits without raising an exception:

>>> with client.batch() as batch:
...     batch.put(entity1)
...     batch.put(entity2)
...     batch.delete(key3)

By default, no updates will be sent if the block exits with an error:

>>> def do_some_work(batch):
...    return
>>> with client.batch() as batch:
...     do_some_work(batch)
...     raise Exception()  # rolls back
Traceback (most recent call last):
  ...
Exception

begin()

Begins a batch.

This method is called automatically when entering a with statement, however it can be called explicitly if you don’t want to use a context manager.

Overridden by google.cloud.datastore.transaction.Transaction.

  • Raises

    ValueError if the batch has already begun.

commit(retry=None, timeout=None)

Commits the batch.

This is called automatically upon exiting a with statement, however it can be called explicitly if you don’t want to use a context manager.

  • Parameters

    • retry (google.api_core.retry.Retry) – A retry object used to retry requests. If None is specified, requests will be retried using a default configuration.

    • timeout (float) – Time, in seconds, to wait for the request to complete. Note that if retry is specified, the timeout applies to each individual attempt.

  • Raises

    ValueError if the batch is not in progress.

current()

Return the topmost batch / transaction, or None.

delete(key)

Remember a key to be deleted during commit().

  • Parameters

    key (google.cloud.datastore.key.Key) – the key to be deleted.

  • Raises

    ValueError if the batch is not in progress, if key is not complete, or if the key’s project does not match ours.

property mutations()

Getter for the changes accumulated by this batch.

Every batch is committed with a single commit request containing all the work to be done as mutations. Inside a batch, calling put() with an entity, or delete() with a key, builds up the request by adding a new mutation. This getter returns the protobuf that has been built-up so far.

  • Return type

    iterable

  • Returns

    The list of datastore_pb2.Mutation protobufs to be sent in the commit request.

property namespace()

Getter for namespace in which the batch will run.

  • Return type

    str

  • Returns

    The namespace in which the batch will run.

property project()

Getter for project in which the batch will run.

  • Return type

    str

  • Returns

    The project in which the batch will run.

put(entity)

Remember an entity’s state to be saved during commit().

NOTE: Any existing properties for the entity will be replaced by those currently set on this instance. Already-stored properties which do not correspond to keys set on this instance will be removed from the datastore.

NOTE: Property values which are “text” (‘unicode’ in Python2, ‘str’ in Python3) map to ‘string_value’ in the datastore; values which are “bytes” (‘str’ in Python2, ‘bytes’ in Python3) map to ‘blob_value’.

When an entity has a partial key, calling commit() sends it as an insert mutation and the key is completed. On return, the key for the entity passed in is updated to match the key ID assigned by the server.

  • Parameters

    entity (google.cloud.datastore.entity.Entity) – the entity to be saved.

  • Raises

    ValueError if the batch is not in progress, if entity has no key assigned, or if the key’s project does not match ours.

rollback()

Rolls back the current batch.

Marks the batch as aborted (can’t be used again).

Overridden by google.cloud.datastore.transaction.Transaction.

  • Raises

    ValueError if the batch is not in progress.