Allocation locks and their use

• US 7,707,195 B2
• Filed: 06/29/2004
• Issued: 04/27/2010
• 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.
• Primary Examiner(s): Cottingham; John R.
• Assistant Examiner(s): Khakhar; Nirav K
• Application Number:
  US10/879,664
• Publication Number:
  US 20050289188A1
• Time in Patent Office: 2,128 Days
• Field of Search: None
• US Class Current: 707/704
• 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 that manages a database including a database data page, the database data page providing sub-page storage space, the database management system further managing a plurality of concurrent database transaction requiring a modification of the database data page and storing a respective copy of the database data page in a separate space, the database management system comprising:

a processor; and

one or more physical computer readable storage media operatively coupled to the processor, the computer-readable storage media having stored thereon computer executable instructions that, when executed by the processor, implement the database management system, including;

a database engine that employs an allocation lock to facilitate operations of the concurrent database transactions at a sub-page level during modification of the database data page, the database engine comprising;

a lock manage component that facilitates compatibility of operations across the concurrent database transactions, including sub-page locking, and that grants one of the concurrent database transactions an exclusive lock on a first sub-page of the database data page when the one of the concurrent database transactions requests to modify the first sub-page, the exclusive lock permits the one of concurrent database transactions to modify a copy of the first sub-page in its respective copy of the database data page while restricting others of the concurrent database transactions from modifying corresponding copies of the first sub-page in their respective copies of the database data page, but allows the others of the concurrent database transactions to modify other sub-pages, the lock manager component further comprising;

an allocation lock component that grants the one of the concurrent database transactions an allocation lock on the database data page when the one of the concurrent database transactions seeks additional space to modify the database data page, wherein the allocation lock permits the one of the concurrent database transactions to acquire additional space on the database data page and to use the additional space in its respective copy of the database data page and allows the others of the concurrent database transactions that do not require additional space on the database data page to effect modifications to their respective copies of the database data page, but prevents the others of the concurrent database transactions from acquiring additional space on the database data page, wherein the allocation lock is distinguished from the exclusion lock;

a heap manager component that tracks storage space availability on the database data page to ensure that the concurrent database transactions do not consume all of the storage space on the database data page; and

acquiring an intent lock at least in one of a table level, a page level and a database level.

2. The database management system of claim 1, wherein the heap manager component determines whether sufficient space is available to perform a part of a transaction on the database data page.

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

4. The database management system of claim 1, the sub-page locking is a row level locking.

5. The database management system of claim 1, the heap manager component and the allocation lock component enforce a set of conditions on any transaction that operate on the database data page, such that reorganization of data around the database data page at a commit stage of the concurrent database transactions is mitigated while merging of various copies of the database data page during the commit operation.

6. A method that facilitates synchronization of concurrent database transactions in a database management system that manages a database having a database data page that provides sub-page row storage space, the database management system further managing a plurality of concurrent database transactions, each of the concurrent database transactions requiring a modification of the database data page, the method comprising:

creating a copy of the database data page for each of the concurrent database transactions, each of the concurrent database transactions storing its respective copy of the database data page in a separate reserved space to facilitate modifying the database data page;

assigning an exclusive row level lock on a first row of the database data page to one of the concurrent database transaction when the one of the concurrent database transactions requests to modify the first row, the exclusive lock permits the one of the concurrent database transactions to modify a copy of the first row in its respective copy of the database data page while restricting others of the concurrent database transactions from modifying corresponding copies of the first row in their respective copies of the database data page, but allows the others of the concurrent database transactions to modify other rows;

assigning an allocation lock on the database data page to the one of the concurrent database transactions when the one of the concurrent database transactions seeks additional space to modify the database data page, the allocation lock permits the one of the concurrent database transactions to acquire additional space on the database data page and to use the additional space in its respective copy of the database data page and allows the others of the concurrent database transaction that do not require additional space on the database data page to effect modifications to their respective copies of the database data page, but prevents the others of the concurrent database transactions from acquiring additional space on the database data page;

each of the concurrent database transactions modifying its respective copy of the database data page using row level operations to facilitate modifying the database data page;

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

ensuring that the concurrent database transactions do not consume all of storage space on the database data page based in part on the tracked space availability; and

acquiring an intent lock at least in one of a table level, a page level and a database level.

7. The method of claim 6 further comprising assigning a disparate lock to a resource on the database data page.

8. The method of claim 6 further comprising replacing a row with an inserting pointer that guides a query to a row in a new database data page.

9. The method of claim 8 further comprising inserting the row on the new database data page.

10. The method of claim 7 further comprising discarding the locks upon a roll back of a transaction.

11. The method of claim 7 further comprising discarding the locks upon committing a transaction.

12. A computer program product comprising one or more physical computer readable storage media having stored thereon computer executable instructions that, when executed by a processor, perform the method of claim 6.

13. The method of claim 6 further comprising assuring availability of space on the database data page prior to a commit stage of a transaction operating on the database data page.

14. The method of claim 13 further comprising mitigating reorganization of data around the database data page at the commit stage of the concurrent database transactions while merging of various copies of the database data page during the commit operation.

15. The method of claim 6 further comprising arranging a top-down lock granularity based on logical or physical granularities of objects stored in the database.

16. The method of claim 6, the lock manager component further comprises a counter to indicate a net result of space change in the database data page during a modification by the concurrent database transactions.

17. The method of claim 16, further comprising acquiring an allocation lock when the counter is positive.