Tablestore:Configure local transaction

Prerequisites

• OTSClient is initialized. For more information, see Initialization.
• A data table is created, and data is written to the table.

Usage notes

1. Use StartLocalTransaction to create a local transaction based on the specified partition key value and obtain the ID of the local transaction.
2. Read and write data within the local transaction.

   You can call the following operations on the local transaction: GetRow, PutRow, DeleteRow, UpdateRow, BatchWriteRow, and GetRange.

3. Use CommitTransaction to commit local transactions or use AbortTransaction to abort local transactions.

Limits

• The validity period of a local transaction is up to 60 seconds.

  If a transaction is not committed or aborted within 60 seconds, the Tablestore server determines that the transaction times out and aborts the transaction.

• A transaction may be created on the Tablestore server even if a timeout error is returned. In this case, you can resend a transaction creation request after the created transaction times out.
• If a local transaction is not committed, it may become invalid. In this case, retry the operation within this transaction.
• Tablestore imposes the following limits on read and write operations on data within a local transaction:
  • The transaction ID cannot be used to access data beyond the range specified based on the partition key value that is used to create the transaction.
  • The partition key values of all write requests in the same transaction must be the same as the partition key value used to create the transaction. This limit does not apply to read requests.
  • A local transaction can be used only by one request at a time. When the transaction is in use, other operations that use the transaction ID fail.
  • The maximum interval for read and write operations on data within a transaction is 60 seconds.

    If a transaction is not read or written for more than 60 seconds, the Tablestore server determines that the transaction times out and aborts the transaction.

  • Up to 4 MB of data can be written to each transaction. The volume of data written to each transaction is calculated in the same way as a regular write request.
  • If you do not specify a version number for a cell, the Tablestore server assigns a version number to the cell in the usual way when the cell is written to the transaction (rather than when the transaction is committed).
  • If a BatchWriteRow request includes a transaction ID, all rows in the request can be written only to the table that matches the transaction ID.
  • When you use a local transaction, a write lock is added to the data of the partition key value based on which the local transaction is created. Only write requests that contain the local transaction ID and are initiated to write data within the local transaction are successful. Other non-transactional requests or write requests that contain the IDs of other local transactions and are initiated to write data within the local transaction fail. Data within the transaction is unlocked when the transaction is committed or aborted, or when the transaction times out.
  • A transaction remains valid even if a read or write request with the transaction ID is rejected. You can specify a retry rule to resend the request, or you can abort the transaction.

Parameters

Examples

1. Call the startLocalTransaction method of AsyncClient or SyncClient to create a local transaction based on a specified partition key value and obtain the ID of the created local transaction.

   PrimaryKeyBuilder primaryKeyBuilder = PrimaryKeyBuilder.createPrimaryKeyBuilder();
   primaryKeyBuilder.addPrimaryKeyColumn("pk1", PrimaryKeyValue.fromString("txnKey"));
   PrimaryKey primaryKey = primaryKeyBuilder.build();
   StartLocalTransactionRequest request = new StartLocalTransactionRequest(tableName, primaryKey);
   String txnId = client.startLocalTransaction(request).getTransactionID();

2. Read and write data within a local transaction.

   You must specify the transaction ID to read and write data within the local transaction. The read and write operations are similar to regular operations.

   • Write a row to the local transaction.

     PrimaryKeyBuilder primaryKeyBuilder = PrimaryKeyBuilder.createPrimaryKeyBuilder();
     primaryKeyBuilder.addPrimaryKeyColumn("pk1", PrimaryKeyValue.fromString("txnKey"));
     primaryKeyBuilder.addPrimaryKeyColumn("pk2", PrimaryKeyValue.fromLong("userId"));
     PrimaryKey primaryKey = primaryKeyBuilder.build();
     RowPutChange rowPutChange = new RowPutChange(tableName, primaryKey);
     rowPutChange.addColumn(new Column("Col", ColumnValue.fromLong(columnValue)));
     
     PutRowRequest request = new PutRowRequest(rowPutChange);
     request.setTransactionId(txnId);
     client.putRow(request);

   • Read the row from the local transaction.

     PrimaryKeyBuilder primaryKeyBuilder;
     primaryKeyBuilder = PrimaryKeyBuilder.createPrimaryKeyBuilder();
     primaryKeyBuilder.addPrimaryKeyColumn("pk1", PrimaryKeyValue.fromString("txnKey"));
     primaryKeyBuilder.addPrimaryKeyColumn("pk2", PrimaryKeyValue.fromLong("userId"));
     PrimaryKey primaryKey = primaryKeyBuilder.build();
     SingleRowQueryCriteria criteria = new SingleRowQueryCriteria(tableName, primaryKey);
     criteria.setMaxVersions(1); // Specify that the latest version of data is read. 
     
     GetRowRequest  request = new GetRowRequest(criteria);
     request.setTransactionId(txnId);
     GetRowResponse getRowResponse = client.getRow(request);

3. Commit or abort a local transaction.
   • Commit a local transaction so that all data modifications within the local transaction take effect.

     CommitTransactionRequest commitRequest = new CommitTransactionRequest(txnId);
     client.commitTransaction(commitRequest);

   • Abort a local transaction so that all data modifications within the local transaction do not take effect.

     AbortTransactionRequest abortRequest = new AbortTransactionRequest(txnId);
     client.abortTransaction(abortRequest);