31 results about "Multiversion concurrency control" patented technology

Various embodiments include one or more of systems, methods, software, and data structures that allow dual access to concurrent data in a database management system including uncommitted updated data. Some embodiments include a dual snapshot of data in a multi-version concurrency control style database, but the embodiments described herein are equally applicable to virtually any other type of database and database management system.

A transaction creates a wait for dependency on a version in a main memory database implementing a multi-version concurrency control scheme. The wait for dependency allows the transaction to update the version while other transactions are reading the version. The multi-version concurrency control scheme also allows commit dependencies to be implementing concurrently with wait for dependencies. Commit dependencies allow a transaction to read an updated version before the updated version is committed.

The invention discloses a multi-version concurrency control method and device for a database, a server and a storage medium. The method comprises the steps of blocking a transaction number of a current transaction in an exclusive lock mode when the current transaction is started; if a current operation of the current transaction is a write operation, generating a transaction save point; searchingfor a target data page corresponding to the write operation, and locking the target data page in the exclusive lock mode; executing the current operation according to a preset rule. Through this blocking mechanism, the number of locks is not directly related to the number of records modified by transactions, the number of the locks can be greatly decreased, blocking conflicts and blocking resourceconsumption are reduced, and the concurrency efficiency of a database management system is improved.

The invention discloses a distributed transaction processing system using a multi-type replica in a decentralized schema. The distributed transaction processing system comprises a transaction interface module, a transaction processing module and a transaction memory module, wherein the transaction interface module comprises an outward interface sub-module and a transaction preprocessing sub-module, the transaction processing module comprises a multi-type replica sub-module, a read transaction processing module, a replica group transaction state sub-module, a read request distribution sub-module, a replica repair sub-module, a multiversion concurrency control (MVCC) read sub-module, a local writing transaction processing sub-module, a local writing transaction paxos replica consistency sub-module, a local writing transaction commit sub-module, a global writing transaction processing sub-module, a main sub-transaction paxos replica consistency sub-module, a secondary sub-transaction paxos replica consistency sub-module and a global writing transaction commit sub-module. The distributed transaction processing system can solve the problems in an existing system that the reading and writing environment is limited, reading and writing availability can not be configured autonomously according to requirements of application, a global transaction depends on locking and cost is high.

The invention provides a database operation method and device. The method includes the steps that prediction execution data generated when prediction execution is conducted on a to-be-executed event is obtained, wherein the prediction execution data includes a primary key value of target data required by the to-be-executed event and a value, adopted in the prediction execution process, of the target data; according to the primary key value of the target data, the current value of the target data is loaded from a target sub-database corresponding to the to-be-executed event; when the current value of the target data is different from the value, adopted in the prediction execution process, of the target data, whether the current value of the target data affects the business logic of the to-be-executed event is judged; if the current value of the target data does not affect the business logic of the to-be-executed event, the current value of the target data serves as version data corresponding to the to-be-executed event, and the version data is recorded in the target sub-database. According to the method and the device, the storage cost of multi-version concurrency control can be saved, and the disk capacity required by the database is reduced.

Embodiments of the present invention disclose a multi-version concurrency control method in a database and a database system, which are mainly applied to the field of database technologies. The database system sets a data page link of a page, where the data page link includes a page pointer of each version page of the page, and a page pointer of a version page is used to point to another version page prior to a last operation on the version page. In this way, when a page in the database is read, if a timestamp of a current version page is greater than a timestamp of a read transaction included in a data reading request, page-level rollback may be directly performed according to a data page link of the page that is requested to read to roll back to a page that needs to be read, which helps a user to know a page in the database at any time, that is, which facilitates queries for data on each version page in the database. Further, the database system may implement record rollback efficiently by combining a data page link and a record link, thereby realizing consistent reading.

The related compression storage method for great much data comprises: detecting CPU type to select matched storage strategy; saving one piece of record with integral information in website as the reference for other records; noting the reference record difference by increment means; removing the last-version data in history to realize the dynamic conversion for history and active data; according to frequency of data value, recoding data to calculate without decoding. This invention can improve query efficiency with less storage space.

The invention discloses a multi-version concurrency control method and system based on virtual global clock synchronization. The method comprises the following steps: reading data; calculating and verifying a version timestamp; and writing the value written into a tuple in a set into a tuple storage position in a database, and updating the read timestamp and the write timestamp of the related tuple. The system comprises: a data reading module used for reading and copying all tuples involved in a current transaction; a timestamp calculation module used for calculating a submission timestamp ofthe current transaction according to the currently designed tuple read timestamp and write timestamp; a timestamp verification module used for verifying whether the timestamp obtained through calculation is valid or not; and a data writing module used for writing the successfully verified timestamp and the modified tuple into the database storage. The method has the following beneficial effects: the access tuples are checked, and the timestamp of each transaction is inertially calculated when the transaction is submitted, so that the limited sorting condition can be avoided.

The invention discloses a trusted log recording method based on blockchain, provides an overall framework suitable for a distributed log system based on blockchain, and provides each module and each log in the overall architecture. Layered specific design; especially in the consensus layer of the distributed accounting module, the traditional practical Byzantine fault-tolerant algorithm is improved by combining multi-version concurrency control methods, random algorithms and event monitoring mechanisms. The invention is used to solve the lack of trusted log function for further consensus verification of the correctness of the log generated by the node and the operation authority of the node in the existing distributed system, and to improve the problem of large communication volume of the traditional practical Byzantine fault tolerance algorithm.

Throughput is preserved in a distributed system while maintaining concurrency by pushing a commit wait period to client commit paths and to future readers. As opposed to servers performing commit waits, the servers assign timestamps, which are used to ensure that causality is preserved. When a server executes a transaction that writes data to a distributed database, the server acquires a user-level lock, and assigns the transaction a timestamp equal to a current time plus an interval corresponding to bounds of uncertainty of clocks in the distributed system. After assigning the timestamp, the server releases the user-level lock. Any client devices, before performing a read of the written data, must wait until the assigned timestamp is in the past.