Getting started with Cloud Spanner in PHP

Objectives

This tutorial walks you through the following steps using the Cloud Spanner client library for PHP:

  • Create a Cloud Spanner instance and database.
  • Write, read, and execute SQL queries on data in the database.
  • Update the database schema.
  • Update data using a read-write transaction.
  • Add a secondary index to the database.
  • Use the index to read and execute SQL queries on data.
  • Retrieve data using a read-only transaction.

Costs

This tutorial uses Cloud Spanner, which is a billable component of the Google Cloud. For information on the cost of using Cloud Spanner, see Pricing.

Before you begin

Complete the steps described in Set up, which cover creating and setting a default Google Cloud project, enabling billing, enabling the Cloud Spanner API, and setting up OAuth 2.0 to get authentication credentials to use the Cloud Spanner API.

In particular, make sure that you run gcloud auth application-default login to set up your local development environment with authentication credentials.

Prepare your local PHP environment

  1. Follow the steps in Service accounts to set up a service account as your Application Default Credentials. Following those steps, you should obtain both a service account key file (in JSON) and a GOOGLE_APPLICATION_CREDENTIALS environment variable that will allow you to authenticate to the Cloud Spanner API.

  2. Install the following on your development machine if they are not already installed:

  3. Clone the sample app repository to your local machine:

    git clone https://github.com/GoogleCloudPlatform/php-docs-samples

    Alternatively, you can download the sample as a zip file and extract it.

  4. Change to the directory that contains the Cloud Spanner sample code:

    cd php-docs-samples/spanner

  5. Install dependencies:

    composer install

    This will install the Cloud Spanner client library for PHP, which you can add to any project by running composer require google/cloud-spanner.

Create an instance

When you first use Cloud Spanner, you must create an instance, which is an allocation of resources that are used by Cloud Spanner databases. When you create an instance, you choose an instance configuration, which determines where your data is stored, and also the number of nodes to use, which determines the amount of serving and storage resources in your instance.

Execute the following command to create a Cloud Spanner instance in the region us-central1 with 1 node:

gcloud spanner instances create test-instance --config=regional-us-central1 \
    --description="Test Instance" --nodes=1

Note that this creates an instance with the following characteristics:

  • Instance ID test-instance
  • Display name Test Instance
  • Instance configuration regional-us-central1 (Regional configurations store data in one region, while multi-region configurations distribute data across multiple regions. Learn more in Instances.)
  • Node count of 1 (node_count corresponds to the amount of serving and storage resources available to databases in the instance. Learn more in Node count.)

You should see:

Creating instance...done.

Look through sample files

The samples repo contains a sample that shows how to use Cloud Spanner with PHP.

Take a look at the functions in src/create_database.php and src/add_column.php, which show how to create a database and modify a database schema. The data uses the example schema shown in the Schema and data model page.

Create a database

Create a database called example-db in the instance called test-instance by running the following at the command line.

php spanner.php create-database test-instance example-db

You should see:

Created database example-db on instance test-instance

You have just created a Cloud Spanner database. The following is the code that created the database.

use Google\Cloud\Spanner\SpannerClient;

/**
 * Creates a database and tables for sample data.
 * Example:
 * ```
 * create_database($instanceId, $databaseId);
 * ```
 *
 * @param string $instanceId The Spanner instance ID.
 * @param string $databaseId The Spanner database ID.
 */
function create_database($instanceId, $databaseId)
{
    $spanner = new SpannerClient();
    $instance = $spanner->instance($instanceId);

    if (!$instance->exists()) {
        throw new \LogicException("Instance $instanceId does not exist");
    }

    $operation = $instance->createDatabase($databaseId, ['statements' => [
        "CREATE TABLE Singers (
            SingerId     INT64 NOT NULL,
            FirstName    STRING(1024),
            LastName     STRING(1024),
            SingerInfo   BYTES(MAX)
        ) PRIMARY KEY (SingerId)",
        "CREATE TABLE Albums (
            SingerId     INT64 NOT NULL,
            AlbumId      INT64 NOT NULL,
            AlbumTitle   STRING(MAX)
        ) PRIMARY KEY (SingerId, AlbumId),
        INTERLEAVE IN PARENT Singers ON DELETE CASCADE"
    ]]);

    print('Waiting for operation to complete...' . PHP_EOL);
    $operation->pollUntilComplete();

    printf('Created database %s on instance %s' . PHP_EOL,
        $databaseId, $instanceId);
}

The code also defines two tables, Singers and Albums, for a basic music application. These tables are used throughout this page. Take a look at the example schema if you haven't already.

The next step is to write data to your database.

Create a database client

To do reads and writes, you need to obtain an instance of Google\Cloud\Spanner\Database.

# Includes the autoloader for libraries installed with composer
require __DIR__ . '/vendor/autoload.php';

# Imports the Google Cloud client library
use Google\Cloud\Spanner\SpannerClient;

# Your Google Cloud Platform project ID
$projectId = 'YOUR_PROJECT_ID';

# Instantiates a client
$spanner = new SpannerClient([
    'projectId' => $projectId
]);

# Your Cloud Spanner instance ID.
$instanceId = 'your-instance-id';

# Get a Cloud Spanner instance by ID.
$instance = $spanner->instance($instanceId);

# Your Cloud Spanner database ID.
$databaseId = 'your-database-id';

# Get a Cloud Spanner database by ID.
$database = $instance->database($databaseId);

# Execute a simple SQL statement.
$results = $database->execute('SELECT "Hello World" as test');

foreach ($results as $row) {
    print($row['test'] . PHP_EOL);
}

You can think of a Database as a database connection: all of your interactions with Cloud Spanner must go through a Database. Typically you create a Database when your application starts up, then you re-use that Database to read, write, and execute transactions. Each client uses resources in Cloud Spanner.

If you create multiple clients in the same app, you should call Database::close to clean up the client's resources, including network connections, as soon as it is no longer needed.

Read more in the Database reference.

Write data with DML

You can insert data using Data Manipulation Language (DML) in a read-write transaction.

You use the executeUpdate() method to execute a DML statement.

use Google\Cloud\Spanner\SpannerClient;
use Google\Cloud\Spanner\Transaction;

/**
 * Inserts sample data into the given database with a DML statement.
 *
 * The database and table must already exist and can be created using
 * `create_database`.
 * Example:
 * ```
 * insert_data($instanceId, $databaseId);
 * ```
 *
 * @param string $instanceId The Spanner instance ID.
 * @param string $databaseId The Spanner database ID.
 */
function write_data_with_dml($instanceId, $databaseId)
{
    $spanner = new SpannerClient();
    $instance = $spanner->instance($instanceId);
    $database = $instance->database($databaseId);

    $database->runTransaction(function (Transaction $t) use ($spanner) {
        $rowCount = $t->executeUpdate(
            "INSERT Singers (SingerId, FirstName, LastName) VALUES "
            . "(12, 'Melissa', 'Garcia'), "
            . "(13, 'Russell', 'Morales'), "
            . "(14, 'Jacqueline', 'Long'), "
            . "(15, 'Dylan', 'Shaw')");
        $t->commit();
        printf('Inserted %d row(s).' . PHP_EOL, $rowCount);
    });
}

Run the sample using the write-data-with-dml command.

php spanner.php write-data-with-dml test-instance example-db

You should see:

Inserted 4 row(s).

Write data with mutations

You can also insert data using mutations.

You write data using the Database::insertBatch method. insertBatch adds new rows to a table. All inserts in a single batch are applied atomically.

This code shows how to write the data using mutations:

use Google\Cloud\Spanner\SpannerClient;

/**
 * Inserts sample data into the given database.
 *
 * The database and table must already exist and can be created using
 * `create_database`.
 * Example:
 * ```
 * insert_data($instanceId, $databaseId);
 * ```
 *
 * @param string $instanceId The Spanner instance ID.
 * @param string $databaseId The Spanner database ID.
 */
function insert_data($instanceId, $databaseId)
{
    $spanner = new SpannerClient();
    $instance = $spanner->instance($instanceId);
    $database = $instance->database($databaseId);

    $operation = $database->transaction(['singleUse' => true])
        ->insertBatch('Singers', [
            ['SingerId' => 1, 'FirstName' => 'Marc', 'LastName' => 'Richards'],
            ['SingerId' => 2, 'FirstName' => 'Catalina', 'LastName' => 'Smith'],
            ['SingerId' => 3, 'FirstName' => 'Alice', 'LastName' => 'Trentor'],
            ['SingerId' => 4, 'FirstName' => 'Lea', 'LastName' => 'Martin'],
            ['SingerId' => 5, 'FirstName' => 'David', 'LastName' => 'Lomond'],
        ])
        ->insertBatch('Albums', [
            ['SingerId' => 1, 'AlbumId' => 1, 'AlbumTitle' => 'Total Junk'],
            ['SingerId' => 1, 'AlbumId' => 2, 'AlbumTitle' => 'Go, Go, Go'],
            ['SingerId' => 2, 'AlbumId' => 1, 'AlbumTitle' => 'Green'],
            ['SingerId' => 2, 'AlbumId' => 2, 'AlbumTitle' => 'Forever Hold Your Peace'],
            ['SingerId' => 2, 'AlbumId' => 3, 'AlbumTitle' => 'Terrified']
        ])
        ->commit();

    print('Inserted data.' . PHP_EOL);
}

Run the sample using the insert-data command.

php spanner.php insert-data test-instance example-db

You should see:

Inserted data.

Query data using SQL

Cloud Spanner supports a native SQL interface for reading data, which you can access on the command line using the gcloud command-line tool or programmatically using the Cloud Spanner client library for PHP.

On the command line

Execute the following SQL statement to read the values of all columns from the Albums table:

gcloud spanner databases execute-sql example-db --instance=test-instance \
    --sql='SELECT SingerId, AlbumId, AlbumTitle FROM Albums'

The result should be:

SingerId AlbumId AlbumTitle
1        1       Total Junk
1        2       Go, Go, Go
2        1       Green
2        2       Forever Hold Your Peace
2        3       Terrified

Using the Cloud Spanner client library for PHP

In addition to executing a SQL statement on the command line, you can issue the same SQL statement programmatically using the Cloud Spanner client library for PHP.

Use Database::execute() to run the SQL query.

Here's how to issue the query and access the data:

use Google\Cloud\Spanner\SpannerClient;

/**
 * Queries sample data from the database using SQL.
 * Example:
 * ```
 * query_data($instanceId, $databaseId);
 * ```
 *
 * @param string $instanceId The Spanner instance ID.
 * @param string $databaseId The Spanner database ID.
 */
function query_data($instanceId, $databaseId)
{
    $spanner = new SpannerClient();
    $instance = $spanner->instance($instanceId);
    $database = $instance->database($databaseId);

    $results = $database->execute(
        'SELECT SingerId, AlbumId, AlbumTitle FROM Albums'
    );

    foreach ($results as $row) {
        printf('SingerId: %s, AlbumId: %s, AlbumTitle: %s' . PHP_EOL,
            $row['SingerId'], $row['AlbumId'], $row['AlbumTitle']);
    }
}

Run the sample using the query-data command.

php spanner.php query-data test-instance example-db

You should see the following result:

SingerId: 2, AlbumId: 2, AlbumTitle: Forever Hold Your Peace
SingerId: 1, AlbumId: 2, AlbumTitle: Go, Go, Go
SingerId: 2, AlbumId: 1, AlbumTitle: Green
SingerId: 2, AlbumId: 3, AlbumTitle: Terrified
SingerId: 1, AlbumId: 1, AlbumTitle: Total Junk

Your results will not necessarily be in this order. If you need to ensure the ordering of the result, use an ORDER BY clause, as documented in SQL best practices.

Query using a SQL parameter

You can include custom values in SQL statements using supported SQL types.

Here is an example of using @lastName as a parameter in the WHERE clause to query records containing a specific value for LastName.

use Google\Cloud\Spanner\SpannerClient;

/**
 * Queries sample data from the database using SQL with a parameter.
 * Example:
 * ```
 * query_data_with_parameter($instanceId, $databaseId);
 * ```
 *
 * @param string $instanceId The Spanner instance ID.
 * @param string $databaseId The Spanner database ID.
 */
function query_data_with_parameter($instanceId, $databaseId)
{
    $spanner = new SpannerClient();
    $instance = $spanner->instance($instanceId);
    $database = $instance->database($databaseId);

    $results = $database->execute(
        'SELECT SingerId, FirstName, LastName FROM Singers ' .
        'WHERE LastName = @lastName',
        ['parameters' => ['lastName' => 'Garcia']]
    );

    foreach ($results as $row) {
        printf('SingerId: %s, FirstName: %s, LastName: %s' . PHP_EOL,
            $row['SingerId'], $row['FirstName'], $row['LastName']);
    }
}

Run the sample using the query-data-with-parameter command.

php spanner.php query-data-with-parameter test-instance example-db

You should see the following result:

SingerId: 12, FirstName: Melissa, LastName: Garcia

Read data using the read API

In addition to Cloud Spanner's SQL interface, Cloud Spanner also supports a read interface.

Use Database::read() to read rows from the database. Use a KeySet object to define a collection of keys and key ranges to read.

Here's how to read the data:

use Google\Cloud\Spanner\SpannerClient;

/**
 * Reads sample data from the database.
 * Example:
 * ```
 * read_data($instanceId, $databaseId);
 * ```
 *
 * @param string $instanceId The Spanner instance ID.
 * @param string $databaseId The Spanner database ID.
 */
function read_data($instanceId, $databaseId)
{
    $spanner = new SpannerClient();
    $instance = $spanner->instance($instanceId);
    $database = $instance->database($databaseId);

    $keySet = $spanner->keySet(['all' => true]);
    $results = $database->read(
        'Albums',
        $keySet,
        ['SingerId', 'AlbumId', 'AlbumTitle']
    );

    foreach ($results->rows() as $row) {
        printf('SingerId: %s, AlbumId: %s, AlbumTitle: %s' . PHP_EOL,
            $row['SingerId'], $row['AlbumId'], $row['AlbumTitle']);
    }
}

Run the sample using the read-data command.

php spanner.php read-data test-instance example-db

You should see output similar to:

SingerId: 1, AlbumId: 1, AlbumTitle: Total Junk
SingerId: 1, AlbumId: 2, AlbumTitle: Go, Go, Go
SingerId: 2, AlbumId: 1, AlbumTitle: Green
SingerId: 2, AlbumId: 2, AlbumTitle: Forever Hold your Peace
SingerId: 2, AlbumId: 3, AlbumTitle: Terrified

Update the database schema

Assume you need to add a new column called MarketingBudget to the Albums table. Adding a new column to an existing table requires an update to your database schema. Cloud Spanner supports schema updates to a database while the database continues to serve traffic. Schema updates do not require taking the database offline and they do not lock entire tables or columns; you can continue writing data to the database during the schema update. Read more about supported schema updates and schema change performance in Schema updates.

Add a column

You can add a column on the command line using the gcloud command-line tool or programmatically using the Cloud Spanner client library for PHP.

On the command line

Use the following ALTER TABLE command to add the new column to the table:

gcloud spanner databases ddl update example-db --instance=test-instance \
    --ddl='ALTER TABLE Albums ADD COLUMN MarketingBudget INT64'

You should see:

Schema updating...done.

Using the Cloud Spanner client library for PHP

Use Database::updateDdl to modify the schema:

use Google\Cloud\Spanner\SpannerClient;

/**
 * Adds a new column to the Albums table in the example database.
 * Example:
 * ```
 * add_column($instanceId, $databaseId);
 * ```
 *
 * @param string $instanceId The Spanner instance ID.
 * @param string $databaseId The Spanner database ID.
 */
function add_column($instanceId, $databaseId)
{
    $spanner = new SpannerClient();
    $instance = $spanner->instance($instanceId);
    $database = $instance->database($databaseId);

    $operation = $database->updateDdl(
        'ALTER TABLE Albums ADD COLUMN MarketingBudget INT64'
    );

    print('Waiting for operation to complete...' . PHP_EOL);
    $operation->pollUntilComplete();

    printf('Added the MarketingBudget column.' . PHP_EOL);
}

Run the sample using the add-column command.

php spanner.php add-column test-instance example-db

You should see:

Added the MarketingBudget column.

Write data to the new column

The following code writes data to the new column. It sets MarketingBudget to 100000 for the row keyed by Albums(1, 1) and to 500000 for the row keyed by Albums(2, 2).

use Google\Cloud\Spanner\SpannerClient;

/**
 * Updates sample data in the database.
 *
 * This updates the `MarketingBudget` column which must be created before
 * running this sample. You can add the column by running the `add_column`
 * sample or by running this DDL statement against your database:
 *
 *     ALTER TABLE Albums ADD COLUMN MarketingBudget INT64
 *
 * Example:
 * ```
 * update_data($instanceId, $databaseId);
 * ```
 *
 * @param string $instanceId The Spanner instance ID.
 * @param string $databaseId The Spanner database ID.
 */
function update_data($instanceId, $databaseId)
{
    $spanner = new SpannerClient();
    $instance = $spanner->instance($instanceId);
    $database = $instance->database($databaseId);

    $operation = $database->transaction(['singleUse' => true])
        ->updateBatch('Albums', [
            ['SingerId' => 1, 'AlbumId' => 1, 'MarketingBudget' => 100000],
            ['SingerId' => 2, 'AlbumId' => 2, 'MarketingBudget' => 500000],
        ])
        ->commit();

    print('Updated data.' . PHP_EOL);
}

Run the sample using the update-data command.

php spanner.php update-data test-instance example-db

You should see:

Updated data.

You can also execute a SQL query or a read call to fetch the values that you just wrote.

Here's the code to execute the query:

use Google\Cloud\Spanner\SpannerClient;

/**
 * Queries sample data from the database using SQL.
 * This sample uses the `MarketingBudget` column. You can add the column
 * by running the `add_column` sample or by running this DDL statement against
 * your database:
 *
 *      ALTER TABLE Albums ADD COLUMN MarketingBudget INT64
 *
 * Example:
 * ```
 * query_data_with_new_column($instanceId, $databaseId);
 * ```
 *
 * @param string $instanceId The Spanner instance ID.
 * @param string $databaseId The Spanner database ID.
 */
function query_data_with_new_column($instanceId, $databaseId)
{
    $spanner = new SpannerClient();
    $instance = $spanner->instance($instanceId);
    $database = $instance->database($databaseId);

    $results = $database->execute(
        'SELECT SingerId, AlbumId, MarketingBudget FROM Albums'
    );

    foreach ($results as $row) {
        printf('SingerId: %s, AlbumId: %s, MarketingBudget: %d' . PHP_EOL,
            $row['SingerId'], $row['AlbumId'], $row['MarketingBudget']);
    }
}

To execute this query, run the sample using the query-data-with-new-column argument.

php spanner.php query-data-with-new-column test-instance example-db

You should see:

SingerId: 1, AlbumId: 1, MarketingBudget: 100000
SingerId: 1, AlbumId: 2, MarketingBudget: 0
SingerId: 2, AlbumId: 1, MarketingBudget: 0
SingerId: 2, AlbumId: 2, MarketingBudget: 500000
SingerId: 2, AlbumId: 3, MarketingBudget: 0

Update data

You can update data using DML in a read-write transaction.

You use the executeUpdate() method to execute a DML statement.

use Google\Cloud\Spanner\SpannerClient;
use Google\Cloud\Spanner\Transaction;

/**
 * Performs a read-write transaction to update two sample records in the
 * database.
 *
 * This will transfer 200,000 from the `MarketingBudget` field for the second
 * Album to the first Album. If the `MarketingBudget` for the second Album is
 * too low, it will raise an exception.
 *
 * Before running this sample, you will need to run the `update_data` sample
 * to populate the fields.
 * Example:
 * ```
 * write_data_with_dml_transaction($instanceId, $databaseId);
 * ```
 *
 * @param string $instanceId The Spanner instance ID.
 * @param string $databaseId The Spanner database ID.
 */
function write_data_with_dml_transaction($instanceId, $databaseId)
{
    $spanner = new SpannerClient();
    $instance = $spanner->instance($instanceId);
    $database = $instance->database($databaseId);

    $database->runTransaction(function (Transaction $t) use ($spanner) {
        // Transfer marketing budget from one album to another. We do it in a transaction to
        // ensure that the transfer is atomic.
        $transferAmount = 200000;

        $results = $t->execute(
            "SELECT MarketingBudget from Albums WHERE SingerId = 2 and AlbumId = 2"
        );
        $resultsRow = $results->rows()->current();
        $album2budget = $resultsRow['MarketingBudget'];

        // Transaction will only be committed if this condition still holds at the time of
        // commit. Otherwise it will be aborted and the callable will be rerun by the
        // client library.
        if ($album2budget >= $transferAmount) {
            $results = $t->execute(
                "SELECT MarketingBudget from Albums WHERE SingerId = 1 and AlbumId = 1"
            );
            $resultsRow = $results->rows()->current();
            $album1budget = $resultsRow['MarketingBudget'];

            $album2budget -= $transferAmount;
            $album1budget += $transferAmount;

            // Update the albums
            $t->executeUpdate(
                "UPDATE Albums "
                . "SET MarketingBudget = @AlbumBudget "
                . "WHERE SingerId = 1 and AlbumId = 1",
                [
                    'parameters' => [
                        'AlbumBudget' => $album1budget
                    ]
                ]
            );
            $t->executeUpdate(
                "UPDATE Albums "
                . "SET MarketingBudget = @AlbumBudget "
                . "WHERE SingerId = 2 and AlbumId = 2",
                [
                    'parameters' => [
                        'AlbumBudget' => $album2budget
                    ]
                ]
            );

            $t->commit();

            print('Transaction complete.' . PHP_EOL);
        }
    });
}

Run the sample using the write-data-with-dml-transaction command.

php spanner.php write-data-with-dml-transaction test-instance example-db

You should see:

Transaction complete.

Use a secondary index

Suppose you wanted to fetch all rows of Albums that have AlbumTitle values in a certain range. You could read all values from the AlbumTitle column using a SQL statement or a read call, and then discard the rows that don't meet the criteria, but doing this full table scan is expensive, especially for tables with a lot of rows. Instead you can speed up the retrieval of rows when searching by non-primary key columns by creating a secondary index on the table.

Adding a secondary index to an existing table requires a schema update. Like other schema updates, Cloud Spanner supports adding an index while the database continues to serve traffic. Cloud Spanner automatically backfills the index with your existing data. Backfills might take a few minutes to complete, but you don't need to take the database offline or avoid writing to the indexed table during this process. For more details, see index backfilling.

After you add a secondary index, Cloud Spanner automatically uses it for SQL queries that are likely to run faster with the index. If you use the read interface, you must specify the index that you want to use.

Add a secondary index

You can add an index on the command line using the gcloud command line tool or programmatically using the Cloud Spanner client library for PHP.

On the command line

Use the following CREATE INDEX command to add an index to the database:

gcloud spanner databases ddl update example-db --instance=test-instance \
    --ddl='CREATE INDEX AlbumsByAlbumTitle ON Albums(AlbumTitle)'

You should see:

Schema updating...done.

Using the Cloud Spanner client library for PHP

Use Database::updateDdl to add an index:

use Google\Cloud\Spanner\SpannerClient;

/**
 * Adds a simple index to the example database.
 * Example:
 * ```
 * create_index($instanceId, $databaseId);
 * ```
 *
 * @param string $instanceId The Spanner instance ID.
 * @param string $databaseId The Spanner database ID.
 */
function create_index($instanceId, $databaseId)
{
    $spanner = new SpannerClient();
    $instance = $spanner->instance($instanceId);
    $database = $instance->database($databaseId);

    $operation = $database->updateDdl(
        'CREATE INDEX AlbumsByAlbumTitle ON Albums(AlbumTitle)'
    );

    print('Waiting for operation to complete...' . PHP_EOL);
    $operation->pollUntilComplete();

    printf('Added the AlbumsByAlbumTitle index.' . PHP_EOL);
}

Run the sample using the create-index command.

php spanner.php create-index test-instance example-db

Adding an index can take a few minutes. After the index is added, you should see:

Added the AlbumsByAlbumTitle index.

Read using the index

For SQL queries, Cloud Spanner automatically uses an appropriate index. In the read interface, you must specify the index in your request.

To use the index in the read interface, use the Database::read method.

use Google\Cloud\Spanner\SpannerClient;

/**
 * Reads sample data from the database using an index.
 *
 * The index must exist before running this sample. You can add the index
 * by running the `add_index` sample or by running this DDL statement against
 * your database:
 *
 *     CREATE INDEX AlbumsByAlbumTitle ON Albums(AlbumTitle)
 *
 * Example:
 * ```
 * read_data_with_index($instanceId, $databaseId);
 * ```
 *
 * @param string $instanceId The Spanner instance ID.
 * @param string $databaseId The Spanner database ID.
 */
function read_data_with_index($instanceId, $databaseId)
{
    $spanner = new SpannerClient();
    $instance = $spanner->instance($instanceId);
    $database = $instance->database($databaseId);

    $keySet = $spanner->keySet(['all' => true]);
    $results = $database->read(
        'Albums',
        $keySet,
        ['AlbumId', 'AlbumTitle'],
        ['index' => 'AlbumsByAlbumTitle']
    );

    foreach ($results->rows() as $row) {
        printf('AlbumId: %s, AlbumTitle: %s' . PHP_EOL,
            $row['AlbumId'], $row['AlbumTitle']);
    }
}

Run the sample using the read-data-with-index command.

php spanner.php read-data-with-index test-instance example-db

You should see:

AlbumId: 2, AlbumTitle: Forever Hold your Peace
AlbumId: 2, AlbumTitle: Go, Go, Go
AlbumId: 1, AlbumTitle: Green
AlbumId: 3, AlbumTitle: Terrified
AlbumId: 1, AlbumTitle: Total Junk

Add an index with a STORING clause

You might have noticed that the read example above did not include reading the MarketingBudget column. This is because Cloud Spanner's read interface does not support the ability to join an index with a data table to look up values that are not stored in the index.

Create an alternate definition of AlbumsByAlbumTitle that stores a copy of MarketingBudget in the index.

On the command line

gcloud spanner databases ddl update example-db --instance=test-instance \
    --ddl='CREATE INDEX AlbumsByAlbumTitle2 ON Albums(AlbumTitle) STORING (MarketingBudget)'

Adding an index can take a few minutes. After the index is added, you should see:

Schema updating...done.

Using the Cloud Spanner client library for PHP

Use Database::updateDdl to add an index with a STORING clause:

use Google\Cloud\Spanner\SpannerClient;

/**
 * Adds an storing index to the example database.
 *
 * This sample uses the `MarketingBudget` column. You can add the column
 * by running the `add_column` sample or by running this DDL statement against
 * your database:
 *
 *     ALTER TABLE Albums ADD COLUMN MarketingBudget INT64
 *
 * Example:
 * ```
 * create_storing_index($instanceId, $databaseId);
 * ```
 *
 * @param string $instanceId The Spanner instance ID.
 * @param string $databaseId The Spanner database ID.
 */
function create_storing_index($instanceId, $databaseId)
{
    $spanner = new SpannerClient();
    $instance = $spanner->instance($instanceId);
    $database = $instance->database($databaseId);

    $operation = $database->updateDdl(
        'CREATE INDEX AlbumsByAlbumTitle2 ON Albums(AlbumTitle) ' .
        'STORING (MarketingBudget)'
    );

    print('Waiting for operation to complete...' . PHP_EOL);
    $operation->pollUntilComplete();

    printf('Added the AlbumsByAlbumTitle2 index.' . PHP_EOL);
}

Run the sample using the create-storing-index command.

php spanner.php create-storing-index test-instance example-db

You should see:

Added the AlbumsByAlbumTitle2 index.

Now you can execute a read that fetches all AlbumId, AlbumTitle, and MarketingBudget columns from the AlbumsByAlbumTitle2 index:

use Google\Cloud\Spanner\SpannerClient;

/**
 * Reads sample data from the database using an index with a storing
 * clause.
 *
 * The index must exist before running this sample. You can add the index
 * by running the `add_storing_index` sample or by running this DDL statement
 * against your database:
 *
 *     CREATE INDEX AlbumsByAlbumTitle2 ON Albums(AlbumTitle)
 *     STORING (MarketingBudget)
 *
 * Example:
 * ```
 * read_data_with_storing_index($instanceId, $databaseId);
 * ```
 *
 * @param string $instanceId The Spanner instance ID.
 * @param string $databaseId The Spanner database ID.
 */
function read_data_with_storing_index($instanceId, $databaseId)
{
    $spanner = new SpannerClient();
    $instance = $spanner->instance($instanceId);
    $database = $instance->database($databaseId);

    $keySet = $spanner->keySet(['all' => true]);
    $results = $database->read(
        'Albums',
        $keySet,
        ['AlbumId', 'AlbumTitle', 'MarketingBudget'],
        ['index' => 'AlbumsByAlbumTitle2']
    );

    foreach ($results->rows() as $row) {
        printf('AlbumId: %s, AlbumTitle: %s, MarketingBudget: %d' . PHP_EOL,
            $row['AlbumId'], $row['AlbumTitle'], $row['MarketingBudget']);
    }
}

Run the sample using the read-data-with-storing-index command.

php spanner.php read-data-with-storing-index test-instance example-db

You should see output similar to:

AlbumId: 2, AlbumTitle: Forever Hold your Peace, MarketingBudget: 300000
AlbumId: 2, AlbumTitle: Go, Go, Go, MarketingBudget: 0
AlbumId: 1, AlbumTitle: Green, MarketingBudget: 0
AlbumId: 3, AlbumTitle: Terrified, MarketingBudget: 0
AlbumId: 1, AlbumTitle: Total Junk, MarketingBudget: 300000

Retrieve data using read-only transactions

Suppose you want to execute more than one read at the same timestamp. Read-only transactions observe a consistent prefix of the transaction commit history, so your application always gets consistent data. Use a Snapshot object for executing read-only transactions. Use the Database::snapshot method to get a Snapshot object.

The following shows how to run a query and perform a read in the same read-only transaction:

use Google\Cloud\Spanner\SpannerClient;

/**
 * Reads data inside of a read-only transaction.
 *
 * Within the read-only transaction, or "snapshot", the application sees
 * consistent view of the database at a particular timestamp.
 * Example:
 * ```
 * read_only_transaction($instanceId, $databaseId);
 * ```
 *
 * @param string $instanceId The Spanner instance ID.
 * @param string $databaseId The Spanner database ID.
 */
function read_only_transaction($instanceId, $databaseId)
{
    $spanner = new SpannerClient();
    $instance = $spanner->instance($instanceId);
    $database = $instance->database($databaseId);

    $snapshot = $database->snapshot();
    $results = $snapshot->execute(
        'SELECT SingerId, AlbumId, AlbumTitle FROM Albums'
    );
    print('Results from the first read:' . PHP_EOL);
    foreach ($results as $row) {
        printf('SingerId: %s, AlbumId: %s, AlbumTitle: %s' . PHP_EOL,
            $row['SingerId'], $row['AlbumId'], $row['AlbumTitle']);
    }

    // Perform another read using the `read` method. Even if the data
    // is updated in-between the reads, the snapshot ensures that both
    // return the same data.
    $keySet = $spanner->keySet(['all' => true]);
    $results = $database->read(
        'Albums',
        $keySet,
        ['SingerId', 'AlbumId', 'AlbumTitle']
    );

    print('Results from the second read:' . PHP_EOL);
    foreach ($results->rows() as $row) {
        printf('SingerId: %s, AlbumId: %s, AlbumTitle: %s' . PHP_EOL,
            $row['SingerId'], $row['AlbumId'], $row['AlbumTitle']);
    }
}

Run the sample using the read-only-transaction command.

php spanner.php read-only-transaction test-instance example-db

You should see output similar to:

Results from first read:
SingerId: 2, AlbumId: 2, AlbumTitle: Forever Hold Your Peace
SingerId: 1, AlbumId: 2, AlbumTitle: Go, Go, Go
SingerId: 2, AlbumId: 1, AlbumTitle: Green
SingerId: 2, AlbumId: 3, AlbumTitle: Terrified
SingerId: 1, AlbumId: 1, AlbumTitle: Total Junk
Results from second read:
SingerId: 1, AlbumId: 1, AlbumTitle: Total Junk
SingerId: 1, AlbumId: 2, AlbumTitle: Go, Go, Go
SingerId: 2, AlbumId: 1, AlbumTitle: Green
SingerId: 2, AlbumId: 2, AlbumTitle: Forever Hold Your Peace
SingerId: 2, AlbumId: 3, AlbumTitle: Terrified

Cleanup

To avoid incurring additional charges to your Cloud Billing account for the resources used in this tutorial, drop the database and delete the instance that you created.

Delete the database

If you delete an instance, all databases within it are automatically deleted. This step shows how to delete a database without deleting an instance (you would still incur charges for the instance).

On the command line

gcloud spanner databases delete example-db --instance=test-instance

Using the Cloud Console

  1. Go to the Cloud Spanner Instances page in the Google Cloud Console.

    Go to the Instances page

  2. Click the instance.

  3. Click the database that you want to delete.

  4. In the Database details page, click Delete.

  5. Confirm that you want to delete the database and click Delete.

Delete the instance

Deleting an instance automatically drops all databases created in that instance.

On the command line

gcloud spanner instances delete test-instance

Using the Cloud Console

  1. Go to the Cloud Spanner Instances page in the Google Cloud Console.

    Go to the Instances page

  2. Click your instance.

  3. Click Delete.

  4. Confirm that you want to delete the instance and click Delete.

What's next