Reference documentation and code samples for the Cloud Spanner Client class BatchClient.
Provides Batch APIs used to read data from a Cloud Spanner database.
Batch Clients are useful when one wants to read or query a large amount of data from Cloud Spanner across multiple processes, even across multiple machines. It allows creation of partitions of a Cloud Spanner database in order to facilitate reading or querying of each partition independently at the same snapshot.
Example:
use Google\Cloud\Spanner\SpannerClient;
$spanner = new SpannerClient();
$batch = $spanner->batch('instance-id', 'database-id');
// Using Cloud Pub/Sub to share partitions with workers
use Google\Cloud\PubSub\PubSubClient;
$pubsub = new PubSubClient();
$topic = $pubsub->topic('partition-queries');
$snapshot = $batch->snapshot();
// Executing a partition query will return a list of Partitions.
$partitions = $snapshot->partitionQuery('SELECT * FROM Users WHERE firstName = %s AND location = %s', [
'parameters' => [
'firstName' => 'John',
'location' => 'USA'
]
]);
// Each partition is published to Cloud Pub/Sub, where it can be executed by
// a worker.
foreach ($partitions as $partition) {
$topic->publish([
'attributes' => [
'snapshot' => $snapshot->serialize(),
'partition' => $partition->serialize()
]
]);
}
// Once all workers have finished, we will close the snapshot.
// The logic to determine whether the snapshot is no longer needed will vary
// and is not implemented here.
do {
$finished = areWorkersDone();
if ($finished) {
$snapshot->close();
}
} while(!$finished);
// Using Cloud Pub/Sub to consume a partition and return a result.
use Google\Cloud\PubSub\PubSubClient;
$pubsub = new PubSubClient();
$subscription = $pubsub->subscription('partition-query-consumer');
$messages = $subscription->pull([
'returnImmediately' => true,
'maxMessages' => 1
]);
if ($messages) {
$message = $messages[0];
$snapshot = $batch->snapshotFromString($message->attribute('snapshot'));
$partition = $batch->partitionFromString($message->attribute('partition'));
// Do something with the query result.
processResult($snapshot->executePartition($partition));
}
Namespace
Google \ Cloud \ Spanner \ BatchMethods
__construct
Parameters | |
---|---|
Name | Description |
operation |
Google\Cloud\Spanner\Operation
A Cloud Spanner Operations wrapper. |
databaseName |
string
The database name to which the batch client instance is scoped. |
options |
array
Configuration options. |
↳ databaseRole |
string
The user created database role which creates the session. |
snapshot
Create a batch snapshot.
Example:
$snapshot = $batch->snapshot();
Parameters | |
---|---|
Name | Description |
options |
array
Configuration Options
|
↳ transactionOptions |
bool
.strong Read at a timestamp where all previously committed transactions are visible. |
↳ transactionOptions |
Timestamp
.readTimestamp Executes all reads at the given timestamp. |
↳ transactionOptions |
Duration
.exactStaleness Represents a number of seconds. Executes all reads at a timestamp that is $exactStaleness old. |
↳ sessionOptions |
array
Configuration options for session creation. |
Returns | |
---|---|
Type | Description |
Google\Cloud\Spanner\Batch\BatchSnapshot |
snapshotFromString
Create a Google\Cloud\Spanner\Batch\BatchSnapshot from a snapshot identifier.
This method can be used to deserialize a snapshot which is shared across multiple servers or processes.
Example:
$snapshot = $batch->snapshotFromString($snapshotString);
Parameter | |
---|---|
Name | Description |
identifier |
string
A stringified representation of Google\Cloud\Spanner\Batch\BatchSnapshot. |
Returns | |
---|---|
Type | Description |
Google\Cloud\Spanner\Batch\BatchSnapshot |
partitionFromString
Create a Google\Cloud\Spanner\Batch\PartitionInterface instance.
This method can be used to deserialize a partition which is shared across multiple servers or processes.
Example:
$partition = $batch->partitionFromString($partitionString);
Parameter | |
---|---|
Name | Description |
partition |
string
Partition data |
Returns | |
---|---|
Type | Description |
Google\Cloud\Spanner\Batch\PartitionInterface |
Constants
PARTITION_TYPE_KEY
Value: '__partitionTypeName'