docs(spanner): snippet for setting read lock mode #2495
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| // Copyright 2026 Google LLC | ||
| // | ||
| // Licensed under the Apache License, Version 2.0 (the "License"); | ||
| // you may not use this file except in compliance with the License. | ||
| // You may obtain a copy of the License at | ||
| // | ||
| // http://www.apache.org/licenses/LICENSE-2.0 | ||
| // | ||
| // Unless required by applicable law or agreed to in writing, software | ||
| // distributed under the License is distributed on an "AS IS" BASIS, | ||
| // WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. | ||
| // See the License for the specific language governing permissions and | ||
| // limitations under the License. | ||
|
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| // sample-metadata: | ||
| // title: Performs a read-write transaction with read lock mode option | ||
| // usage: node read-lock-mode.js <INSTANCE_ID> <DATABASE_ID> <PROJECT_ID> | ||
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| 'use strict'; | ||
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| function main( | ||
| instanceId = 'my-instance', | ||
| databaseId = 'my-database', | ||
| projectId = 'my-project-id', | ||
| ) { | ||
| // [START spanner_read_lock_mode] | ||
| // Imports the Google Cloud Spanner client library | ||
| const {Spanner, protos} = require('@google-cloud/spanner'); | ||
| // The read lock mode specified at the client-level will be applied | ||
| // to all RW transactions. | ||
| const readLockModeOptionsForClient = { | ||
| defaultTransactionOptions: { | ||
| readLockMode: | ||
| protos.google.spanner.v1.TransactionOptions.ReadWrite.ReadLockMode | ||
| .OPTIMISTIC, | ||
| }, | ||
| }; | ||
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| // Instantiates a client with defaultTransactionOptions | ||
| const spanner = new Spanner({ | ||
| projectId: projectId, | ||
| defaultTransactionOptions: readLockModeOptionsForClient, | ||
| }); | ||
|
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There was a problem hiding this comment. The const defaultTransactionOptions = {
readLockMode:
protos.google.spanner.v1.TransactionOptions.ReadWrite.ReadLockMode
.OPTIMISTIC,
};
// Instantiates a client with defaultTransactionOptions
const spanner = new Spanner({
projectId: projectId,
defaultTransactionOptions,
}); |
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| function runTransactionWithReadLockMode() { | ||
| // Gets a reference to a Cloud Spanner instance and database | ||
| const instance = spanner.instance(instanceId); | ||
| const database = instance.database(databaseId); | ||
| // The read lock mode specified at the request-level takes precedence over | ||
| // the read lock mode configured at the client-level. | ||
| const readLockModeOptionsForTransaction = { | ||
| readLockMode: | ||
| protos.google.spanner.v1.TransactionOptions.ReadWrite.ReadLockMode | ||
| .PESSIMISTIC, | ||
| }; | ||
|
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| database.runTransaction( | ||
| readLockModeOptionsForTransaction, | ||
| async (err, transaction) => { | ||
| if (err) { | ||
| console.error(err); | ||
| return; | ||
| } | ||
| try { | ||
| const query = | ||
| 'SELECT AlbumTitle FROM Albums WHERE SingerId = 2 AND AlbumId = 1'; | ||
| const results = await transaction.run(query); | ||
| // Gets first album's title | ||
| const rows = results[0].map(row => row.toJSON()); | ||
| const albumTitle = rows[0].AlbumTitle; | ||
| console.log(`previous album title ${albumTitle}`); | ||
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| const update = | ||
| "UPDATE Albums SET AlbumTitle = 'New Album Title' WHERE SingerId = 2 AND AlbumId = 1"; | ||
| const [rowCount] = await transaction.runUpdate(update); | ||
| console.log( | ||
| `Successfully updated ${rowCount} record in Albums table.`, | ||
| ); | ||
| await transaction.commit(); | ||
| console.log( | ||
| 'Successfully executed read-write transaction with readLockMode option.', | ||
| ); | ||
| } catch (err) { | ||
| console.error('ERROR:', err); | ||
| } finally { | ||
| transaction.end(); | ||
|
There was a problem hiding this comment. The |
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| // Close the database when finished. | ||
| await database.close(); | ||
| } | ||
| }, | ||
| ); | ||
| } | ||
| runTransactionWithReadLockMode(); | ||
| // [END spanner_read_lock_mode] | ||
| } | ||
| process.on('unhandledRejection', err => { | ||
| console.error(err.message); | ||
| process.exitCode = 1; | ||
| }); | ||
| main(...process.argv.slice(2)); | ||
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There are some extra newlines here that make the formatting inconsistent with the rest of the file. Please remove the extra blank lines for consistency.