Interface BatchReadOnlyTransaction

Version 6.14.1

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public interface BatchReadOnlyTransaction extends ReadOnlyTransaction

BatchReadOnlyTransaction can be configured to read at timestamps in the past and allows for exporting arbitrarily large amounts of data from Cloud Spanner databases. This is a read only transaction which additionally allows to partition a read or query request. Read/query request can then be executed independently over each partition while observing the same snapshot of the database. BatchReadOnlyTransaction can also be shared across multiple processes/machines by passing around the BatchTransactionId and then recreating the transaction using BatchClient#batchReadOnlyTransaction(BatchTransactionId).

Unlike locking read-write transactions, BatchReadOnlyTransaction never abort. They can fail if the chosen read timestamp is garbage collected; however any read or query activity within an hour on the transaction avoids garbage collection and most applications do not need to worry about this in practice.

To execute a BatchReadOnlyTransaction, specify a TimestampBound, which tells Cloud Spanner how to choose a read timestamp.

Implements

ReadOnlyTransaction

Methods

execute(Partition partition)

public abstract ResultSet execute(Partition partition)

Execute the partition to return ResultSet. The result returned could be zero or more rows. The row metadata may be absent if no rows are returned.

 final BatchReadOnlyTransaction txn =
     batchClient.batchReadOnlyTransaction(TimestampBound.strong());
 List

Parameter

Name	Description
partition	Partition

Returns

Type	Description
ResultSet

Exceptions

Type	Description
SpannerException

getBatchTransactionId()

public abstract BatchTransactionId getBatchTransactionId()

Returns a BatchTransactionId to be re-used across several machines/processes. This BatchTransactionId guarantees the subsequent read/query to be executed at the same timestamp.

Returns

Type	Description
BatchTransactionId

partitionQuery(PartitionOptions partitionOptions, Statement statement, Options.QueryOption[] options)

public abstract List<Partition> partitionQuery(PartitionOptions partitionOptions, Statement statement, Options.QueryOption[] options)

Returns a list of Partition to execute a query against the database.

These partitions can be executed across multiple processes, even across different machines. The partition size and count can be configured using PartitionOptions. Though it may not necessarily be honored depending on the query and options in the request.

Parameters

Name	Description
partitionOptions	PartitionOptions configuration for size and count of partitions returned
statement	Statement the query statement to execute
options	QueryOption[] the options to configure the query final BatchReadOnlyTransaction txn = batchClient.batchReadOnlyTransaction(TimestampBound.strong()); List <!--SNIPPET partition_query-->

Returns

Type	Description
List<Partition>

Exceptions

Type	Description
SpannerException

partitionRead(PartitionOptions partitionOptions, String table, KeySet keys, Iterable<String> columns, Options.ReadOption[] options)

public abstract List<Partition> partitionRead(PartitionOptions partitionOptions, String table, KeySet keys, Iterable<String> columns, Options.ReadOption[] options)

Returns a list of Partition to read zero or more rows from a database.

These partitions can be executed across multiple processes, even across different machines. The partition size and count hints can be configured using PartitionOptions.

Parameters

Name	Description
partitionOptions	PartitionOptions configuration for size and count of partitions returned
table	String the name of the table to read
keys	KeySet the keys and ranges of rows to read. Regardless of ordering in keys, rows are returned in their natural key order.
columns	Iterable<String> the columns to read
options	ReadOption[] the options to configure the read, supported values are Options#prefetchChunks() final BatchReadOnlyTransaction txn = batchClient.batchReadOnlyTransaction(TimestampBound.strong()); List <!--SNIPPET partition_read-->

Returns

Type	Description
List<Partition>

Exceptions

Type	Description
SpannerException

partitionReadUsingIndex(PartitionOptions partitionOptions, String table, String index, KeySet keys, Iterable<String> columns, Options.ReadOption[] options)

public abstract List<Partition> partitionReadUsingIndex(PartitionOptions partitionOptions, String table, String index, KeySet keys, Iterable<String> columns, Options.ReadOption[] options)

Returns a list of Partition to read zero or more rows from a database using an index.

These partitions can be executed across multiple processes, even across different machines. The partition size and count can be configured using PartitionOptions. Though it may not necessarily be honored depending on the parameters in the request.

Parameters

Name	Description
partitionOptions	PartitionOptions configuration for size and count of partitions returned
table	String the name of the table to read
index	String the name of the index on table to use
keys	KeySet the keys and ranges of index rows to read. Regardless of ordering in keys, rows are returned in the natural key order of the index.
columns	Iterable<String> the columns to read
options	ReadOption[] the options to configure the read final BatchReadOnlyTransaction txn = batchClient.batchReadOnlyTransaction(TimestampBound.strong()); List <!--SNIPPET partition_read_using_index-->

Returns

Type	Description
List<Partition>

Exceptions

Type	Description
SpannerException