Interface BatchReadOnlyTransaction (6.83.0)

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.

Closes the session as part of the cleanup. It is the responsibility of the caller to make a call to this method once the transaction completes execution across all the channels (which is understandably hard to identify). It is okay if the caller does not call the method because the backend will anyways clean up the unused session.

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<Partition> partitions = txn.partitionQuery(PartitionOptions.getDefaultInstance(),
     Statement.of("SELECT SingerId, FirstName, LastName FROM Singers"));

 for (final Partition p : partitions) {
   try (ResultSet results = txn.execute(p)) {
     while (results.next()) {
       long singerId = results.getLong(0);
       String firstName = results.getString(1);
       String lastName = results.getString(2);
       System.out.println("[" + singerId + "] " + firstName + " " + lastName);
     }
   }
 }
 

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 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.

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.

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.