Enhanced Access To Data Available In A Cache

• US 20090024794A1
• Filed: 09/03/2007
• Published: 01/22/2009
• Est. Priority Date: 07/19/2007
• Status: Active Grant

• Current Assignee: Oracle International Corporation (Oracle Corporation)
• Original Assignee: Oracle International Corporation (Oracle Corporation)
• Inventors: Iyer, Shankar, Itikarlapalli, Krishna Mohan
• Granted Patent: US 8,065,484 B2
• Time in Patent Office: Days
• US Class Current: 711/118
• CPC Class Codes: G06F 12/084 with a shared cache

Abstract

Enhanced access data available in a cache. In one embodiment, a cache maintaining copies of source data is formed as a volatile memory. On receiving a request directed to the cache for a copy of a data element, the requested copy maintained in the cache is sent as a response to the request. In another embodiment used in the context of applications accessing databases in a navigational model, a cache maintains rows of data accessed by different user applications on corresponding connections. Applications may send requests directed to the cache to retrieve copies of the rows, populated potentially by other applications, while the cache restricts access to rows populated by other applications when processing requests directed to the source database system. In another embodiment, an application may direct requests to retrieve data elements caused to be populated by activity on different connections established by the same application.

Claims

1. A method of providing access to a plurality of data elements in a source system, said method being performed in a cache, said method comprising:

maintaining a copy of said plurality of data elements in a volatile memory contained in said cache;

receiving a first request directed to said cache for a copy of a data element, wherein said data element is contained in said plurality of data elements; and

sending said copy of said data element in said volatile memory as a first response to said first request.

2. The method of claim 1, further comprising:

intercepting a second request directed to said source system for said data element; and

sending said copy of said data element as a second response to said second request.

3. The method of claim 2, wherein said maintaining maintains said copy of said plurality of data elements in said volatile memory on receiving said plurality of data elements in response to a plurality of requests directed to said source system.

4. The method of claim 3, wherein said plurality of requests, said first request and said second request are received on a first connection, wherein said first connection is contained in a plurality of connections established between applications and said source system to facilitate access of said plurality of data elements, said method further comprising:

intercepting a third request directed to said source system for a second data element contained in said plurality of data elements, wherein said third request is received on a second connection contained in said plurality of connections; and

not sending a copy of said second data element contained in said volatile memory as a third response to said third request.

5. The method of claim 4, further comprising:

maintaining a partition information indicating the specific connection in said plurality of connections which caused the corresponding data element to be populated in said volatile memory, wherein said partition information indicates that said first connection caused said copy of said second data element to be stored in said volatile memory;

examining said partition information to determine to not send said copy of said second data element contained in said volatile memory as said third response.

6. The method of claim 5, wherein said first connection and said second connection are established between a same application and said source system.

7. The method of claim 5, wherein said first connection is established between a first application and said source system and said second connection is established between a second application and said source system.

8. The method of claim 5, wherein said source system comprises a database system and each of said plurality of data elements comprises a row in a table of said database system

9. The method of claim 3, wherein said plurality of requests and said second request are received from a first application and said first request is received from a second application.

10. The method of claim 9, further comprising:

intercepting a third request directed to said source system from said second application for a second data element contained in said plurality of data elements; and

not sending a copy of said second data element contained in said volatile memory as a third response to said third request.

11. The method of claim 10, further comprising:

maintaining a partition information indicating the specific application which caused the corresponding data element to be populated in said volatile memory, wherein said partition information indicates that said first application caused said copy of said second data element to be stored in said volatile memory; and

examining said partition information to determine to not send said copy of said second data element in said volatile memory as said third response.

12. The method of claim 3, further comprising:

receiving a fourth request directed to said cache for accessing copies of a set of data elements, wherein said set of data elements is contained in said plurality of data elements; and

providing said copies of said set of data elements as a fourth response to said fourth request.

13. The method of claim 12, wherein said providing provides said copies of said set of data elements in a sequential manner, said providing further comprising:

sending a copy of a first data element contained in said set of data elements;

receiving a request to access a copy of a next data element contained in said set of data elements; and

sending a copy of said next data element if a last data element of said set of data elements is not yet sent.

14. The method of claim 12, further comprising sending an indication indicating that the copies of all the data elements contained in said set of data elements has been accessed, if said last data element has already been sent.

15. A computer readable medium storing one or more sequences of instructions for causing a client system to access a plurality of data elements stored in a database system, wherein execution of said one or more sequences of instructions by one or more processors contained in said client system causes said client system to perform the actions of:

sending a first request directed to a cache for a first data element, wherein said cache is implemented external to said database system and stores a copy of a subset of data elements locally, wherein said subset of data elements are contained in said plurality of data elements, said first data element being contained in said subset of data elements; and

receiving a copy of said first data element as a first response to said first request.

16. The computer readable medium of claim 15, further comprising one of more instructions for:

sending a second request directed to said database system for said first data element; and

receiving said copy of said first data element as a second response to said second request.

17. The computer readable medium of claim 16, further comprising one or more instructions for:

sending a plurality of requests directed to said database system for said subset of data elements prior to said first request; and

receiving said subset of data elements from said database system as corresponding responses to said plurality of requests,

wherein said cache stores a copy of said subset of data elements on receiving responses corresponding to said plurality of requests directed to said database system.

18. The computer readable medium of claim 17, wherein said plurality of requests, said first request and said second request are sent on a first connection, wherein said first connection is contained in a plurality of connections established between said client system and said database system to facilitate access of said plurality of data elements, further comprising one or more instructions for:

sending a third request directed to said database system for a second data element contained in said subset of data elements, wherein said third request is sent on a second connection contained in said plurality of connections; and

not receiving a copy of said second data element contained in said cache as a third response to said third request,

wherein said second data element is received from said database system as said third response to said third request.

19. A computing system comprising:

a source system to store a plurality of data elements; and

a cache comprising;

a volatile memory to store a copy of said plurality of data elements; and

a cache logic to receive a first request directed to said cache for a copy of a data element, wherein said data element is contained in said plurality of data elements and to send said copy of said data element in said volatile memory as a first response to said first request.

20. The computing system of claim 19, wherein said cache logic further comprises:

an access logic to store said copy of said plurality of data elements in said volatile memory on receiving said plurality of data elements in response to a plurality of requests directed to said source system.

wherein said access logic is also designed to intercept a second request directed to said source system for said data element and to send said copy of said data element as a second response to said second request.

21. The computing system of claim 20, wherein said plurality of requests and said second request are received from a first application and said first request is received from a second application,

wherein said access logic intercepts a third request directed to said source system from said second application for a second data element contained in said plurality of data elements and does not send a copy of said second data element contained in said volatile memory as a third response to said third request.

22. The computing system of claim 21, wherein said access logic maintains a partition information indicating the specific application which caused the corresponding data element to be populated in said volatile memory, wherein said partition information indicates that said first application caused said copy of said second data element to be stored in said volatile memory,

wherein said access logic examines said partition information to determine to not send said copy of said second data element in said volatile memory as said third response.

23. A computing system comprising:

a database system containing a plurality of tables together storing a plurality of data elements as respective rows;

a cache to maintain a copy of a subset of data elements contained in said plurality of data elements; and

a client system to retrieve said subset of data elements by sending requests directed to said cache, wherein said subset of data elements is populated in said cache in response to requests directed to said database system.

24. The computing system of claim 23, wherein a first application executing in a run time environment of said client system sends a query indicating a condition to said database system and receives a plurality of reference identifiers in response, wherein each reference identifier identifies a corresponding data element matching said condition,

said first application sending a first set of requests directed to said database system to retrieve a first set of data elements corresponding to said plurality of reference identifiers,

wherein said cache is populated with a copy of said first set of data elements on receiving responses corresponding to said first set of requests from said database system.

25. The computing system of claim 24, wherein a second application executing in said run time environment of said client system sends a second set of requests directed to said cache to retrieve said copy of said first set of data elements from said cache.