Abstract: Techniques and solutions are provided for performing transactions within a database system that stores database data using a row store and a column store. For example, a transaction that performs operations to update data in both the row store and the column store can use the same transaction object. The state of the transaction can be atomically changed. For example, the state of the transaction object can be atomically changed from uncommitted to committed (e.g., set to a commit identifier to represent the committed state).

Abstract: Disclosed herein are system, method, and computer program product embodiments for synchronizing lost change between a source table and a replica table. An embodiment operates by detecting a restart at a source node or a replica node. Row-ID values of replication log entries are then compared to row-ID column values of rows at a replica table of the replica node. Replication errors at a source table or the replica table are then determined based on the row-ID comparison. The rows of the source table and the replica table are then updated based on the determination.

Abstract: Disclosed herein are system, method, and computer program product embodiments for utilizing a transaction control block for providing reader-writer access to transaction commit status. An embodiment operates by receiving a row read request and determining that the row is versioned. The system determines that a first timestamp information for a row destroy transaction associated with the row exists in a transaction control block and retrieves the first timestamp information from the transaction control block.

Abstract: Disclosed herein are system, method, and computer program product embodiments for removing a deadlock during replication from distributed source tables to a replica node. An embodiment operates by detecting a deadlock at a parallel log replayer at a replica node. A first replication log entry from a queue at the parallel log replayer is then selected based on whether removing the first replication log entry from the queue removes the deadlock. The first replication log entry is then forwarded to a waiting queue. A second replication log entry is then replayed at the parallel log replayer. After replaying the second replication log entry, the first replication log entry is replayed at the parallel log replayer.

Abstract: Disclosed herein are system, method, and computer program product embodiments for replicating a database transaction to a replica table. An embodiment operates by receiving a replication log entry and an associated transaction commit log entry for a database transaction to be replayed to a row at a replica table. A row-ID value of the replication log entry is compared to a row-ID column value of the row at the replica table. The replication log entry is then replayed at a parallel log replayer based on the comparison. The database transaction is then committed to the replica table by replaying the associated transaction commit log entry at a transaction log replayer.

Abstract: Techniques and solutions are provided for performing transactions within a database system that stores database data using a row store and a column store. For example, a transaction that performs operations to update data in both the row store and the column store can use the same transaction object. The state of the transaction can be atomically changed. For example, the state of the transaction object can be atomically changed from uncommitted to committed (e.g., set to a commit identifier to represent the committed state).

Abstract: Systems, methods and computer program product embodiments for providing version garbage collection using snapshot lists are disclosed herein. Version garbage collection using snapshot lists includes storing, by at least one processor, versions of a record in a database table, the record comprising a record value and a version timestamp, storing, by the at least one processor, active snapshots in two levels of active snapshot lists, an active snapshot comprising a transaction identifier and a snapshot timestamp, determining, by the at least one processor, a minimum active snapshot from the active snapshots in the two levels of active snapshot lists and deleting, by the at least one processor, versions of the record having a version timestamp earlier than a snapshot timestamp of the minimum active snapshot.

Abstract: Methods, systems and computer-readable storage mediums encoded with computer programs executed by one or more processors for providing a compressed representation of a transaction token are disclosed. In an embodiment, upon a receipt of a request for a write transaction at a slave server it is determined whether there exists an unassigned transaction identifier (TID) stored locally at the slave server as provided by a master server to the slave server prior to the receipt of the write request by the slave server. If there exists an unassigned TID at the slave server, the slave server is configured to assign the unassigned TID to the write transaction, otherwise the slave server is configured to request a plurality of unassigned TIDs from the master server, receive the plurality of unassigned TIDs, and assign one of the received unassigned TIDs to the write transaction. The write transaction is processed.

Abstract: Systems, methods and computer program product embodiments for providing version garbage collection using snapshot lists are disclosed herein. Version garbage collection using snapshot lists includes storing, by at least one processor, versions of a record in a database table, the record comprising a record value and a version timestamp, storing, by the at least one processor, active snapshots in two levels of active snapshot lists, an active snapshot comprising a transaction identifier and a snapshot timestamp, determining, by the at least one processor, a minimum active snapshot from the active snapshots in the two levels of active snapshot lists and deleting, by the at least one processor, versions of the record having a version timestamp earlier than a snapshot timestamp of the minimum active snapshot.

Abstract: Methods, systems and computer-readable storage mediums encoded with computer programs executed by one or more processors for providing a compressed representation of a transaction token are disclosed. In an embodiment, a transaction token maintains statues of transaction to a database in a first data structure and a second data structure. The first data structure includes a plurality of identifiers respectively corresponding to the transactions to the database and a corresponding status of each identifier indicating whether a given transaction is open or closed, wherein the plurality of identifiers is maintained below a threshold number of identifiers. The second data structure includes a plurality of identifiers of transactions to the database beyond the threshold and whose status is open.