System and method for database change notification

1. A method for notifying a client of a change to data stored at a database, the method comprising:

receiving a subscription from the client, the subscription selecting a first subset of data from within a set of data;

generating a subscription plan for filtering the first subset from within the set of data;

receiving a query to be executed at the database, the query changing a second subset of data within the set of data;

generating a query plan for executing the query, the query plan for filtering the second subset from within the set of data;

matching the subscription to the query based on the set of data;

supplementing the query plan with the subscription plan;

prior to executing the supplemented query plan, evaluating the supplemented query plan whereby the subscription filters the first subset of data from within the second subset of data to form a third subset of data;

determining based on the third set of data whether or not to generate a notification of the change to the third subset of data such that the notification is generated when the third subset of data is non-empty, and the notification is not generated when the third set of data is empty; and

after evaluating the supplemented query plan, executing the query by changing the second subset of data.

2. The method of claim 1 , further comprising terminating the subscription.

3. The method of claim 1 , further comprising persisting the subscription.

4. The method of claim 1 , further comprising storing the subscription plan at a notification manager.

5. The method of claim 1 , further comprising submitting the notification to the client.

6. The method of claim 5 , further comprising changing the third subset of data at the client.

7. A computer readable medium having stored thereon computer readable instructions for performing the following steps:

receiving a subscription from a client, the subscription selecting a first subset of data from within a set of data stored at a database;

generating a subscription plan for filtering the first subset from within the set of data;

receiving a query to be executed at the database, the query changing a second subset of data within the set of data;

generating a query plan for executing the query, the query plan for filtering the second subset from within the set of data;

matching the subscription to the query based on the set of data;

supplementing the query plan with the subscription plan;

prior to executing the supplemented query plan, evaluating the supplemented query plan whereby the subscription filters the first subset of data from within the second subset of data to form a third subset of data;

determining based on the third set of data whether or not to generate a notification of the change to the third subset of data such that the notification is generated when the third subset of data is non-empty, and the notification is not generated when the third set of data is empty; and

after evaluating the supplemented query plan, executing the query by changing the second subset of data.

8. The computer readable medium of claim 7 , further comprising computer readable instructions for terminating the subscription.

9. The computer readable medium of claim 7 , further comprising computer readable instructions for persisting the subscription.

10. The computer readable medium of claim 7 , further comprising computer readable instructions for storing the subscription plan at a notification manager.

11. The computer readable medium of claim 7 , further comprising computer readable instructions for submitting the notification to the client.

12. The computer readable medium of claim 11 , further comprising computer readable instructions for changing the third subset of data data at the client.

13. A system for notifying a client of a change to data stored at a database, the system comprising:

the client comprising a cached version of data stored at the database;

the database for storing the data, the database comprising:

a database front end for:

receiving a subscription from the client, the subscription selecting a first subset of data from within a set of data;

generating a subscription plan for filtering the first subset from within the set of data;

receiving a query to be executed at the database, the query changing a second subset of data within the set of data; and

generating a query plan for executing the query, the query plan for filtering the second subset from within the set of data; and

a notification manager for:

matching the subscription to the query based on the set of data;

supplementing the query plan with the subscription plan;

prior to executing the supplemented query plan, evaluating the supplemented query plan whereby the subscription filters the first subset of data from within the second subset of data to form a third subset of data;

determining based on the third set of data whether or not to generate a notification of the change to the third subset of data such that the notification is generated when the third subset of data is non-empty, and the notification is not generated when the third set of data is empty;

an execution engine for executing the query by changing the second subset of data only after the supplemented query plan is evaluated.

14. The system of claim 13 , wherein the subscription is terminated after the notification is generated.

15. The system of claim 13 , wherein the subscription is persisted after the notification is generated.

16. The system of claim 13 , wherein the notification manager is further for storing the subscription plan.

17. The system of claim 13 , wherein the database further comprises:

an optimizer for generating an execution plan for the query based on the query plan;

and

a storage processor for maintaining data in a storage medium.

18. The system of claim 13 , wherein the notification manager is further for submitting the notification to the client.