Monish Gupta

US Patent:

20070118547, May 24, 2007

Filed:

Nov 22, 2005

Appl. No.:

11/285340

Inventors:

Monish Gupta - Santa Clara CA, US
Scott Lashley - Portland OR, US
Daniel Wood - Fremont CA, US

International Classification:

G06F 7/00

US Classification:

707101000

Abstract:

A method and system are provided for maintaining a database index version. The database index includes a secondary node affiliated with each leaf node of the index. The secondary node stores version information for each leaf node. A pointer in a header section of the leaf node connects the leaf node to the secondary node. In addition, a status list is maintained to identify each transaction. At such time as a scan of a database index is conducted and an index item is returned, a computation is conducted using the transaction identifiers in the secondary node, the delete flag in the leaf node, and the status list contents for the scanning transaction. The computation and associated logic will determine whether to accept or reject an item. The method results in returning a correct version of the item as existed at the time of start of the scanning transaction.

US Patent:

20080077591, Mar 27, 2008

Filed:

Sep 22, 2006

Appl. No.:

11/534564

Inventors:

Monish Gupta - Santa Clara CA, US
Scott David Lashley - Portland OR, US

International Classification:

G06F 17/30

US Classification:

707 8

Abstract:

The present invention expounds upon the ANSI “read committed” isolation level by allowing readers to read committed data without waiting for a concurrent writer to the data to finish. The method returns a last committed version of the data as it existed prior to changes made by the concurrent writer. Only two versions of any data record are required to be stored in the record data store, the last committed version and the current version. The last committed version may be generated from an undo log record. Locating the appropriate undo log record may be accomplished by storing a log sequence number in a lock data structure associated with the requested data record. A transaction flag may also stored in the lock data structure to facilitate generating the last committed version. The method may also utilize one or more locks to detect a concurrent writer to the requested data.