Allocation locks and their use

• US 20050289188A1
• Filed: 06/29/2004
• Published: 12/29/2005
• Est. Priority Date: 06/29/2004
• Status: Active Grant

• Current Assignee: Microsoft Technology Licensing LLC (Microsoft Corporation)
• Original Assignee: Microsoft Corporation
• Inventors: Bailey, Steven, Nettleton, David J.
• Granted Patent: US 7,707,195 B2
• Time in Patent Office: Days
• US Class Current: 1/1
• CPC Class Codes: G06F 16/2343 Locking methods, e.g. distributed locking or locking implementation details

Abstract

Systems and methodologies are provided that employ an allocation lock, which permits only a single transaction to acquire space on a particular page at any one time. The allocation lock of the present invention facilitates operations of concurrent transactions at a subpage level (e.g., a row level), and in conjunction with a heap manager can enforce a set of conditions such that prior to a commit stage of a transaction, a space availability for a particular page can be typically assured (e.g., that transactions operating on various copies of the page do not consume all of storage space on that page), and reorganization of data around the page is mitigated (e.g., that a transaction need not move data around the page for purpose of merging various copies.)

Claims

1. A database management system comprising:

an allocation lock that permits only a single transaction to acquire space on a data page at any one time.

2. The database management system of claim 1, the data page being copied by concurrent transactions that require a modification thereof.

3. The database management system of claim 1, further comprising a heap manager component that determines an availability of space for the data page.

4. The database management system of claim 1, further comprising a lock manager that enables sub page level locking across concurrent transactions.

5. The database management system of claim 2, each of the concurrent transactions modifies a respective copy of the data page.

6. The database management system of claim 4, the sub page locking is a row level locking.

7. The system of claim 2, the heap manager component tracks an availability of space on the data page.

8. The system of claim 2, the heap manager component and the allocation lock enforce a set of conditions on a transaction that operates on a data page, such that a space availability for the data page prior to the commit stage of the transaction is assured.

9. A database engine comprising:

an allocation lock that permits only a single transaction to acquire space on a data page at any one time, the allocation lock visible across a plurality of transactions, and

a heap manager that tracks a space availability on the data page.

10. The data base engine of claim 9, each of the plurality of concurrent transactions modify a respective copy of the data page without consuming all space available on the data page.

11. The data base engine of claim 9, further comprising a lock manager that facilitates compatibility of operations across the concurrent transactions.

12. A method that facilitates synchronization in concurrent transactions comprising:

assigning an allocation lock to a data page and enable only a single transaction to acquire space on the data page at any one time; and

tracking a space availability for the data page over concurrent transactions, the concurrent transactions operating on respective copies of the data page.

13. The method of claim 12 further comprising assigning locks to a resource on the data page.

14. The method of claim 12 further comprising modifying the data page.

15. The method of claim 12 further comprising replacing a row with an inserting pointer.

16. The method of claim 15 further comprising inserting the row on a new page.

17. The method of claim 13 further comprising discarding the locks upon a roll back of a transaction.

18. The method of claim 13 further comprising discarding the locks upon committing a transaction.

19. A computer readable medium having stored thereon computer executable instructions for carrying out the method of claim 12.

20. A system for facilitating synchronization in concurrent transactions comprising:

means for permitting only one transaction that acquires additional space to operate on a datapage; and

means for tracking a space availability for the data page over all the concurrent transactions.

21. The system of claim 20 further comprising means for assuring availability of space on a data page prior to a commit stage of a transaction operating on the data page.

22. A computer-readable medium having stored thereon a data structure comprising:

a computer executable component that operates across a plurality of active transactions to permit only one transaction that acquires additional space on a datapage to operate thereon.

23. The computer readable medium of claim 22 further comprising a further computer executable component that tracks an availability of space for the data page, the data page being copied by an active transaction that requires a modification thereof.

24. The computer readable medium of claim 22 further comprising an additional computer executable component that administers logical considerations during data modification on a data page.

25. The computer readable medium of claim 24 the additional computer executable component grant locks at a row level of the data page.

26. The computer readable medium of claim 25 further comprising a forwarding pointer device that guides a query to a new location of data.

27. A system for facilitating synchronization in concurrent transactions comprising:

means for determining logical permission to insert a row on a data page during modifications thereof by concurrent transactions; and

means for determining a space availability for the data page over the concurrent transactions.

28. The system of claim 27 further comprising means for mitigating reorganization of data around the data page at the commit stage of the concurrent transactions.

29. A method for manipulating data in a data page by a transaction comprising:

copying a data page to a reserved space for the transaction;

permitting only one transaction that acquires additional space to operate on the datapage; and

tracking a space availability on the data page across a plurality of concurrent transactions working on the data page.

30. The method of claim 29 further comprising creating a new page and inserting a row therein.

31. The method of claim 29 further comprising employing a pointer in the data page to guide a query to the row in the new page.

32. The method of claim 29 further comprising locking a resource at a row level on the data page.

33. The method of claim 29 further comprising arranging a top-down lock granularity based on logical or physical granularities of objects stored in the data base.

34. The method of claim 29 further comprising acquiring an intent lock at least in one of a table level, page level and database level.

35. The method of claim 29, the permitting act further comprises defining a counter to indicate a net result of space change in the data page during a modification by a transaction.

36. The method of claim 35, further comprising acquiring an allocation lock when the counter is positive.

37. A computer readable medium having stored thereon computer executable instructions for carrying out the method of claim 29.