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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.
Starting a Batch
Construct a Batch
object from a Database
object:
from google.cloud import spanner
client = spanner.Client()
instance = client.instance(INSTANCE_NAME)
database = instance.database(DATABASE_NAME)
batch = database.batch()
Inserting records using a Batch
Batch.insert()
adds one or more new records to a table. Fails if
any of the records already exists.
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. Fails
if any of the records does 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. Non-existent
rows do 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.
batch.commit()
Use a Batch as a Context Manager
Rather than calling Batch.commit()
manually, you can use the
Batch
instance as a context manager, and have it called automatically
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)
Next Step
Next, learn about Read-only Transactions via Snapshots.