Anchor for database synchronization excluding uncommitted transaction modifications

• US 20080109494A1
• Filed: 11/03/2006
• Published: 05/08/2008
• Est. Priority Date: 11/03/2006
• Status: Active Grant

• Current Assignee: Microsoft Technology Licensing LLC (Microsoft Corporation)
• Original Assignee: Microsoft Corporation
• Inventors: Robeal, Rafik, Chitre, Sudarshan A., Zhou, Shaoyu
• Granted Patent: US 7,653,664 B2
• Time in Patent Office: Days
• US Class Current: 707/201
• CPC Class Codes: G06F 16/27 Replication, distribution or synchronisation of data between databases or within a distributed database system; Distributed database system architectures therefor

Abstract

Described is a technology in which an anchor value is determined, for example to synchronize a destination database or data store with modifications made to a source database. The new anchor value is determined in a manner that excludes modifications corresponding to any uncommitted transactions. The new anchor value may be based on a counter value or a date and time value stored with each modification. The new anchor value may be determined by comparing a first set of committed modifications that do not include uncommitted modifications against a second set of modifications that includes committed modifications and uncommitted modifications. Alternatively, the new anchor value may be determined from the earliest start date and time among the modifications that are part of any uncommitted transactions. The anchor may be used (e.g., via queries) to enumerate modifications for synchronization, and also for detecting conflicts between the source and destination databases.

Claims

1. In a computing environment in which a destination database or data store is synchronized with a source database to apply modifications made to the source database to the destination database or data store, a method comprising:

determining a new anchor value, including determining an anchor value that excludes any modification or modifications corresponding to an uncommitted transaction; and

using the new anchor value to enumerate modifications that were made to the source database.

2. The method of claim 1 wherein determining the new anchor value comprises computing the new anchor value based on a datatype value stored with each modification.

3. The method of claim 2 wherein the datatype value comprises an increasing counter value or corresponds to a date and time value stored with each modification.

4. The method of claim 1 wherein determining the new anchor value comprises, obtaining a first set of committed modifications that do not include uncommitted modifications, obtaining a second set of modifications that includes committed modifications and uncommitted modifications, and establishing the new anchor value based on a minimum value that exists in the second set but not in the first set.

5. The method of claim 1 wherein determining the new anchor value comprises, accessing data corresponding to one or more active transactions, in which the data includes a start date and time associated with each active transaction, and establishing the new anchor value based on a minimum start date and time.

6. The method of claim 1 further comprising, synchronizing the destination database or data store to the source database, including synchronizing a range of modifications based on the new anchor value and a last anchor value.

7. The method of claim 6 further comprising, setting the last anchor value to the new anchor value after synchronizing.

8. The method of claim 6 further comprising, synchronizing at least one other modification outside the range that does not include any modification detected as part of an uncommitted transaction.

9. The method of claim 1 wherein the destination comprises an updateable database, and further comprising, detecting a conflict between the source database and destination database based on the new anchor value.

10. The method of claim 1 further comprising providing at least one query of a set of possible queries that use the new anchor value, the set of possible queries comprising:

incrementally enumerate inserts, incrementally enumerate updates, incrementally enumerate deletes, apply inserts, apply updates with conflict detection, or apply deletes with conflict detection.

11. In a computing environment, a system comprising:

a source database that receives modifications;

a destination database or data store that is synchronized with the modifications received at the source database; and

a synchronization mechanism coupled to the source database and destination database or data store that computes a new anchor value for synchronizing the destination database or data store with a range of modifications, the new anchor value based upon the lowest value that is used to track a modification that is part of an uncommitted transaction.

12. The system of claim 11 wherein the new anchor value corresponds to a counter value that is stored in association with each modification and adjusted with each modification.

13. The system of claim 11 wherein the new anchor value corresponds to date and time data that is stored in association with each modification.

14. The system of claim 11 wherein the synchronization mechanism computes the new anchor value by comparing a first set of committed modifications that do not include uncommitted modifications against a second set of modifications that includes committed modifications and uncommitted modifications.

15. The system of claim 11 wherein the synchronization mechanism computes the new anchor value by determining a minimum start date and time value from among start date and time values associated with active transactions.

16. A computer-readable medium having computer-executable instructions, which when executed perform steps, comprising:

evaluating tracking data associated with at least one modification made to a source database that corresponds to an uncommitted transaction;

determining a new anchor value for the source database based on the tracking data; and

using the new anchor value to enumerate modifications that were made to the source database with respect to a previous anchor value.

17. The computer-readable medium of claim 16 wherein the tracking data includes table data in the source database, and wherein evaluating the tracking data includes comparing a first set of committed modifications that do not include uncommitted modifications against a second set of modifications that includes committed modifications, and wherein determining the new anchor value comprises selecting from the tracking data a minimum value that exists in the second set but not in the first set.

18. The computer-readable medium of claim 16 wherein the tracking data includes active transaction information in a system table that tracks each active transaction and has a start date and time associated with each active transaction, wherein evaluating the tracking data includes accessing the system table, and wherein determining the new anchor value comprises finding in the system table the earliest start date and time of any active transaction.

19. The computer-readable medium of claim 16 having further computer-executable instructions comprising, synchronizing a destination database or data store with a range of modifications based on the new anchor value and the previous anchor value.

20. The computer-readable medium of claim 16 having further computer-executable instructions comprising, detecting a conflict between the source database and a destination database based on the new anchor value.