{"id":106417,"date":"2023-01-19T18:48:11","date_gmt":"2023-01-19T16:48:11","guid":{"rendered":"https:\/\/prohoster.info\/?p=106417"},"modified":"2023-01-24T13:52:43","modified_gmt":"2023-01-24T11:52:43","slug":"razrabotchiki-sqlite-razvivayut-bekend-hc-tree-s-podderzhkoj-parallelnyh-operaczij-zapisi","status":"publish","type":"post","link":"https:\/\/prohoster.info\/en\/blog\/news\/razrabotchiki-sqlite-razvivayut-bekend-hc-tree-s-podderzhkoj-parallelnyh-operaczij-zapisi","title":{"rendered":"SQLite developers enhance the HC-tree backend with support for parallel write operations","gt_translate_keys":[{"key":"rendered","format":"text"}]},"content":{"rendered":"
The developers of the SQLite project have started testing an experimental backend called HCtree, which supports row-level locking and provides a high level of parallelism in processing requests. The new backend aims to improve the efficiency of SQLite usage in client-server systems that handle a large number of simultaneous write requests to the database. <\/p>\n
The b-tree structures originally used in SQLite for data storage are not designed for such load, which limits SQLite to writing in a single thread. As an experiment, the developers have begun to develop an alternative solution using the HC-tree structure for storage, which is better suited for parallelizing write operations. <\/p>\n
To enable simultaneous execution of multiple operations in HCtree, a transaction partitioning mechanism is applied, utilizing page-level locking and resembling MVCC (multi-version concurrency control), but using transaction checks based on keys and key ranges instead of page sets. Read and write operations are tied to a database snapshot, with changes becoming visible in the main database only after the transaction is completed. <\/p>\n
Clients can use three operations to open transactions: <\/p>\n
\n
\u00abBEGIN\u00bb \u2014 transactions do not take into account the access data of other clients. If write operations are performed within the transaction, it can only be committed if there were no other write operations in the database during its execution.\n
\u00abBEGIN CONCURRENT\u00bb \u2014 transactions collect information about the access of other clients. If write operations are performed within the transaction, it can be committed if other transactions have been committed in the database since the snapshot was created.\n
\u00abBEGIN EXCLUSIVE\u00bb \u2014 after opening, the transaction blocks operations from other transactions until it is completed. <\/ul>\n
HCtree supports master-slave style replication, allowing transactions to be transferred to another database and keeping secondary databases in sync with the primary. HCtree also removes the limit on database size \u2014 instead of 32-bit data page identifiers, HCtree uses 48-bit identifiers, which increases the maximum database size from 16 tebibytes to 1 exbibyte (one million tebibytes). The performance of SQLite with the HCtree backend is expected to be no less than that of the classic single-threaded backend. SQLite clients supporting HCtree will be able to access both HC-tree based databases and old SQLite databases. \n Source: opennet.ru<\/a> <\/p>","protected":false,"gt_translate_keys":[{"key":"rendered","format":"html"}]},"excerpt":{"rendered":"