Python Client for Cloud Spanner¶
Cloud Spanner is the world’s first fully managed relational database service to offer both strong consistency and horizontal scalability for mission-critical online transaction processing (OLTP) applications. With Cloud Spanner you enjoy all the traditional benefits of a relational database; but unlike any other relational database service, Cloud Spanner scales horizontally to hundreds or thousands of servers to handle the biggest transactional workloads.
Quick Start¶
In order to use this library, you first need to go through the following steps:
Installation¶
Install this library in a virtualenv using pip. virtualenv is a tool to create isolated Python environments. The basic problem it addresses is one of dependencies and versions, and indirectly permissions.
With virtualenv, it’s possible to install this library without needing system install permissions, and without clashing with the installed system dependencies.
Supported Python Versions¶
Python >= 3.5
Deprecated Python Versions¶
Python == 2.7. Python 2.7 support will be removed on January 1, 2020.
Mac/Linux¶
pip install virtualenv
virtualenv <your-env>
source <your-env>/bin/activate
<your-env>/bin/pip install google-cloud-spanner
Windows¶
pip install virtualenv
virtualenv <your-env>
<your-env>\Scripts\activate
<your-env>\Scripts\pip.exe install google-cloud-spanner
Example Usage¶
Executing Arbitrary SQL in a Transaction¶
Generally, to work with Cloud Spanner, you will want a transaction. The
preferred mechanism for this is to create a single function, which executes
as a callback to database.run_in_transaction:
# First, define the function that represents a single "unit of work"
# that should be run within the transaction.
def update_anniversary(transaction, person_id, unix_timestamp):
# The query itself is just a string.
#
# The use of @parameters is recommended rather than doing your
# own string interpolation; this provides protections against
# SQL injection attacks.
query = """SELECT anniversary FROM people
WHERE id = @person_id"""
# When executing the SQL statement, the query and parameters are sent
# as separate arguments. When using parameters, you must specify
# both the parameters themselves and their types.
row = transaction.execute_sql(
query=query,
params={'person_id': person_id},
param_types={
'person_id': types.INT64_PARAM_TYPE,
},
).one()
# Now perform an update on the data.
old_anniversary = row[0]
new_anniversary = _compute_anniversary(old_anniversary, years)
transaction.update(
'people',
['person_id', 'anniversary'],
[person_id, new_anniversary],
)
# Actually run the `update_anniversary` function in a transaction.
database.run_in_transaction(update_anniversary,
person_id=42,
unix_timestamp=1335020400,
)
Select records using a Transaction¶
Once you have a transaction object (such as the first argument sent to
run_in_transaction), reading data is easy:
# Define a SELECT query.
query = """SELECT e.first_name, e.last_name, p.telephone
FROM employees as e, phones as p
WHERE p.employee_id == e.employee_id"""
# Execute the query and return results.
result = transaction.execute_sql(query)
for row in result.rows:
print(row)
Insert records using Data Manipulation Language (DML) with a Transaction¶
Use the execute_update() method to execute a DML statement:
spanner_client = spanner.Client()
instance = spanner_client.instance(instance_id)
database = instance.database(database_id)
def insert_singers(transaction):
row_ct = transaction.execute_update(
"INSERT Singers (SingerId, FirstName, LastName) "
" VALUES (10, 'Virginia', 'Watson')"
)
print("{} record(s) inserted.".format(row_ct))
database.run_in_transaction(insert_singers)
Insert records using Mutations with a Transaction¶
To add one or more records to a table, use insert:
transaction.insert(
'citizens',
columns=['email', 'first_name', 'last_name', 'age'],
values=[
['phred@exammple.com', 'Phred', 'Phlyntstone', 32],
['bharney@example.com', 'Bharney', 'Rhubble', 31],
],
)
Update records using Data Manipulation Language (DML) with a Transaction¶
spanner_client = spanner.Client()
instance = spanner_client.instance(instance_id)
database = instance.database(database_id)
def update_albums(transaction):
row_ct = transaction.execute_update(
"UPDATE Albums "
"SET MarketingBudget = MarketingBudget * 2 "
"WHERE SingerId = 1 and AlbumId = 1"
)
print("{} record(s) updated.".format(row_ct))
database.run_in_transaction(update_albums)
Update records using Mutations with a Transaction¶
Transaction.update updates one or more existing records in a table. Fails
if any of the records does not already exist.
transaction.update(
'citizens',
columns=['email', 'age'],
values=[
['phred@exammple.com', 33],
['bharney@example.com', 32],
],
)
Next Steps¶
See the Client Library Documentation to learn how to connect to Cloud Spanner using this Client Library.
Read the Product documentation to learn more about the product and see How-to Guides.
