Batching Modifications¶
A Batch represents a set of data
modification operations to be performed on tables in a database. Use of a
Batch does not require creating an explicit
Snapshot or
Transaction. Until
commit() is called on a Batch,
no changes are propagated to the back-end.
Use Batch via BatchCheckout¶
Database.batch() creates a BatchCheckout
instance to use as a context manager to handle creating and committing a
Batch. The
BatchCheckout will automatically call
commit() if the with block exits
without raising an exception.
from google.cloud.spanner import KeySet
client = spanner.Client()
instance = client.instance(INSTANCE_NAME)
database = instance.database(DATABASE_NAME)
to_delete = KeySet(keys=[
('bharney@example.com',)
('nonesuch@example.com',)
])
with database.batch() as batch:
batch.insert(
'citizens', columns=['email', 'first_name', 'last_name', 'age'],
values=[
['phred@exammple.com', 'Phred', 'Phlyntstone', 32],
['bharney@example.com', 'Bharney', 'Rhubble', 31],
])
batch.update(
'citizens', columns=['email', 'age'],
values=[
['phred@exammple.com', 33],
['bharney@example.com', 32],
])
...
batch.delete('citizens', to_delete)
Inserting records using a Batch¶
Batch.insert() adds one or more new records to a table. This fails if
any of the records already exist.
batch.insert(
'citizens', columns=['email', 'first_name', 'last_name', 'age'],
values=[
['phred@exammple.com', 'Phred', 'Phlyntstone', 32],
['bharney@example.com', 'Bharney', 'Rhubble', 31],
])
Note
Ensure that data being sent for STRING columns uses a text string
(str in Python 3; unicode in Python 2).
Additionally, if you are writing data intended for a BYTES column, you
must base64 encode it.
Update records using a Batch¶
Batch.update() updates one or more existing records in a table. This fails
if any of the records do not already exist.
batch.update(
'citizens', columns=['email', 'age'],
values=[
['phred@exammple.com', 33],
['bharney@example.com', 32],
])
Note
Ensure that data being sent for STRING columns uses a text string
(str in Python 3; unicode in Python 2).
Additionally, if you are writing data intended for a BYTES column, you
must base64 encode it.
Insert or update records using a Batch¶
Batch.insert_or_update() inserts or updates one or more records in a
table. Existing rows have values for the supplied columns overwritten; other
column values are preserved.
batch.insert_or_update(
'citizens', columns=['email', 'first_name', 'last_name', 'age'],
values=[
['phred@exammple.com', 'Phred', 'Phlyntstone', 31],
['wylma@example.com', 'Wylma', 'Phlyntstone', 29],
])
Note
Ensure that data being sent for STRING columns uses a text string
(str in Python 3; unicode in Python 2).
Additionally, if you are writing data intended for a BYTES column, you
must base64 encode it.
Replace records using a Batch¶
Batch.replace() inserts or updates one or more records in a
table. Existing rows have values for the supplied columns overwritten; other
column values are set to null.
batch.replace(
'citizens', columns=['email', 'first_name', 'last_name', 'age'],
values=[
['bharney@example.com', 'Bharney', 'Rhubble', 30],
['bhettye@example.com', 'Bhettye', 'Rhubble', 30],
])
Note
Ensure that data being sent for STRING columns uses a text string
(str in Python 3; unicode in Python 2).
Additionally, if you are writing data intended for a BYTES column, you
must base64 encode it.
Delete records using a Batch¶
Batch.delete() removes one or more records from a table. Attempting to delete
rows that do not exist will not cause errors.
from google.cloud.spanner import KeySet
to_delete = KeySet(keys=[
('bharney@example.com',)
('nonesuch@example.com',)
])
batch.delete('citizens', to_delete)
Commit changes for a Batch¶
After describing the modifications to be made to table data via the
Batch.insert(), Batch.update(), Batch.insert_or_update(),
Batch.replace(), and Batch.delete() methods above, send them to
the back-end by calling Batch.commit(), which makes the Commit
API call.
You do not need to call this yourself as
BatchCheckout will call
this method automatically upon exiting the with block.
batch.commit()
Next Step¶
Next, learn about Read-only Transactions via Snapshots.
