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docs(spanner): snippet for setting read lock mode (#1473) · googleapis/python-spanner@7e79920 · GitHub

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skuruppu
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docs(spanner): snippet for setting read lock mode (#1473)
Snippet shows how to set the read lock mode at the client-level and how to override the option at the transaction-level.
1 parent 2c5eb96 commit 7e79920

3 files changed

Lines changed: 69 additions & 4 deletions

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‎samples/samples/requirements.txt‎

Lines changed: 1 addition & 1 deletion
Original file line numberDiff line numberDiff line change
@@ -1,2 +1,2 @@
1-
google-cloud-spanner==3.57.0
1+
google-cloud-spanner==3.58.0
22
futures==3.4.0; python_version < "3"

‎samples/samples/snippets.py‎

Lines changed: 60 additions & 2 deletions
Original file line numberDiff line numberDiff line change
@@ -3186,14 +3186,13 @@ def isolation_level_options(
31863186
instance_id,
31873187
database_id,
31883188
):
3189-
from google.cloud.spanner_v1 import TransactionOptions, DefaultTransactionOptions
3190-
31913189
"""
31923190
Shows how to run a Read Write transaction with isolation level options.
31933191
"""
31943192
# [START spanner_isolation_level]
31953193
# instance_id = "your-spanner-instance"
31963194
# database_id = "your-spanner-db-id"
3195+
from google.cloud.spanner_v1 import TransactionOptions, DefaultTransactionOptions
31973196

31983197
# The isolation level specified at the client-level will be applied to all RW transactions.
31993198
isolation_options_for_client = TransactionOptions.IsolationLevel.SERIALIZABLE
@@ -3232,6 +3231,60 @@ def update_albums_with_isolation(transaction):
32323231
# [END spanner_isolation_level]
32333232

32343233

3234+
def read_lock_mode_options(
3235+
instance_id,
3236+
database_id,
3237+
):
3238+
"""
3239+
Shows how to run a Read Write transaction with read lock mode options.
3240+
"""
3241+
# [START spanner_read_lock_mode]
3242+
# instance_id = "your-spanner-instance"
3243+
# database_id = "your-spanner-db-id"
3244+
from google.cloud.spanner_v1 import TransactionOptions, DefaultTransactionOptions
3245+
3246+
# The read lock mode specified at the client-level will be applied to all
3247+
# RW transactions.
3248+
read_lock_mode_options_for_client = TransactionOptions.ReadWrite.ReadLockMode.OPTIMISTIC
3249+
3250+
# Create a client that uses Serializable isolation (default) with
3251+
# optimistic locking for read-write transactions.
3252+
spanner_client = spanner.Client(
3253+
default_transaction_options=DefaultTransactionOptions(
3254+
read_lock_mode=read_lock_mode_options_for_client
3255+
)
3256+
)
3257+
instance = spanner_client.instance(instance_id)
3258+
database = instance.database(database_id)
3259+
3260+
# The read lock mode specified at the request level takes precedence over
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# the read lock mode configured at the client level.
3262+
read_lock_mode_options_for_transaction = (
3263+
TransactionOptions.ReadWrite.ReadLockMode.PESSIMISTIC
3264+
)
3265+
3266+
def update_albums_with_read_lock_mode(transaction):
3267+
# Read an AlbumTitle.
3268+
results = transaction.execute_sql(
3269+
"SELECT AlbumTitle from Albums WHERE SingerId = 2 and AlbumId = 1"
3270+
)
3271+
for result in results:
3272+
print("Current Album Title: {}".format(*result))
3273+
3274+
# Update the AlbumTitle.
3275+
row_ct = transaction.execute_update(
3276+
"UPDATE Albums SET AlbumTitle = 'A New Title' WHERE SingerId = 2 and AlbumId = 1"
3277+
)
3278+
3279+
print("{} record(s) updated.".format(row_ct))
3280+
3281+
database.run_in_transaction(
3282+
update_albums_with_read_lock_mode,
3283+
read_lock_mode=read_lock_mode_options_for_transaction
3284+
)
3285+
# [END spanner_read_lock_mode]
3286+
3287+
32353288
def set_custom_timeout_and_retry(instance_id, database_id):
32363289
"""Executes a snapshot read with custom timeout and retry."""
32373290
# [START spanner_set_custom_timeout_and_retry]
@@ -3856,6 +3909,9 @@ def add_split_points(instance_id, database_id):
38563909
subparsers.add_parser(
38573910
"isolation_level_options", help=isolation_level_options.__doc__
38583911
)
3912+
subparsers.add_parser(
3913+
"read_lock_mode_options", help=read_lock_mode_options.__doc__
3914+
)
38593915
subparsers.add_parser(
38603916
"set_custom_timeout_and_retry", help=set_custom_timeout_and_retry.__doc__
38613917
)
@@ -4018,6 +4074,8 @@ def add_split_points(instance_id, database_id):
40184074
directed_read_options(args.instance_id, args.database_id)
40194075
elif args.command == "isolation_level_options":
40204076
isolation_level_options(args.instance_id, args.database_id)
4077+
elif args.command == "read_lock_mode_options":
4078+
read_lock_mode_options(args.instance_id, args.database_id)
40214079
elif args.command == "set_custom_timeout_and_retry":
40224080
set_custom_timeout_and_retry(args.instance_id, args.database_id)
40234081
elif args.command == "create_instance_with_autoscaling_config":

‎samples/samples/snippets_test.py‎

Lines changed: 8 additions & 1 deletion
Original file line numberDiff line numberDiff line change
@@ -993,12 +993,19 @@ def test_set_custom_timeout_and_retry(capsys, instance_id, sample_database):
993993

994994

995995
@pytest.mark.dependency(depends=["insert_data"])
996-
def test_isolated_level_options(capsys, instance_id, sample_database):
996+
def test_isolation_level_options(capsys, instance_id, sample_database):
997997
snippets.isolation_level_options(instance_id, sample_database.database_id)
998998
out, _ = capsys.readouterr()
999999
assert "1 record(s) updated." in out
10001000

10011001

1002+
@pytest.mark.dependency(depends=["insert_data"])
1003+
def test_read_lock_mode_options(capsys, instance_id, sample_database):
1004+
snippets.read_lock_mode_options(instance_id, sample_database.database_id)
1005+
out, _ = capsys.readouterr()
1006+
assert "1 record(s) updated." in out
1007+
1008+
10021009
@pytest.mark.dependency(
10031010
name="add_proto_types_column",
10041011
)

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