Enhanced access to data available in a cache

• US 8,065,484 B2
• Filed: 09/03/2007
• Issued: 11/22/2011
• 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 Venkata
• Primary Examiner(s): RUTZ, JARED IAN
• Application Number:
  US11/849,311
• Publication Number:
  US 20090024794A1
• Time in Patent Office: 1,541 Days
• Field of Search: 711/129, 711/163, 711/118, 709/215, 709/219
• 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 stored in a source system, said method comprising:

sending from a user application a plurality of requests directed to said source system by having an address of said source system specified as the target of each request, wherein said plurality of requests are sent based on execution of a first set of instructions constituting a part of said user application;

populating a cache with a copy of said plurality of data elements based on examination of said plurality of requests, sending from said user application a first request for a copy of a data element, said first request being directed to said cache by having an address of said cache specified as the target of said first request,

wherein said data element is contained in said plurality of data elements and said first request is sent by executing a second set of instructions forming another part of said user application;

receiving, by said cache, said first request directed to said cache for said copy of said data element,

sending by said cache to said user application, said copy of said data element in said cache as a first response to said first request directed to said cache;

intercepting, by said cache, a second request directed to said source system for said data element, said second request being directed to said source system by having the address of said source system as the target; and

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

2. The method of claim 1, wherein each of said address of said source system and said cache is an Internet Protocol (IP) address and wherein said user application is implemented in a same single client system having said IP address of said cache.

3. The method of claim 2, 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.

4. The method of claim 3, 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.

5. The method of claim 3, 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.

6. The method of claim 1, wherein said plurality of requests, said first request and said second request are received by said cache on a first connection, whereby said second response is sent in view of having received on the same connection as on which the request causing the cache to be populated is also received,

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 stored in said cache, 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 cache as a response to said third request in view of having received said third request on a different connection compared to the request causing the cache to be populated.

7. The method of claim 6, 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 cache, wherein said partition information indicates that said first connection caused said copy of said second data element to be stored in said cache;

examining said partition information to determine whether said second data element is populated in response to requests received on said second connection, wherein it is determined to not send said copy of said second data element contained in said cache as said third response in view of said partition information indicating that said second data element is populated in response to requests received on said first connection.

8. The method of claim 7, wherein said first connection and said second connection are established between said user application and said source system,

wherein each request directed to said cache contains an identifier of a connection associated the data item sought to be retrieved from said cache,

wherein the requested data item is sent in corresponding response only if the partition information indicates that the requested data item has been populated based on requests received on the same connection as that identified by said identifier associated with the requested data item;

wherein said first request directed to said cache contains a first identifier of said first connection thereby causing said copy of said data element to be sent as a response by said cache.

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

10. The method of claim 7, 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.

11. The method of claim 1, 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 cache as a response to said third request in view of said third request being received from a different application compared to the application that caused said second data element to be populated in said cache.

12. The method of claim 11, further comprising:

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

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

13. A computer readable medium storing one or more sequences of instructions for causing a client system to access data elements stored in a source 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 from a user application a plurality of requests directed to said source system by having an address of said source system specified as the target of each request, wherein said plurality of requests are sent based on execution of a first set of instructions constituting a part of said user application;

receiving corresponding responses in said user application, wherein said plurality of requests cause a cache to be populated with a copy of a plurality of data elements,

wherein said cache is implemented external to said source system and stores a copy of said plurality of data elements locally;

sending from said user application a first request for a copy of a first data element, said first request being directed to said cache by having an address of said cache specified as the target of said first request, wherein said first request is sent based on execution of a second set of instructions constituting another part of said user application, wherein said first data element is contained in said plurality of data elements; and

receiving in said user application from said cache, a copy of said first data element as a first response to said first request.

14. The computer readable medium of claim 13, further comprising one of more instructions for:

sending from said user application, a second request for said first data element directed to said source system by having an address of said source system specified as the target of said second request; and

receiving in said user application from said cache, said copy of said first data element as a second response to said second request.

15. The computer readable medium of claim 14, wherein said source system is a database system which stores data elements in tables in the form of rows, 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 plurality 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 response to said third request,

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

16. A computing system comprising:

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

a client system to execute an application, said client system also comprising a cache, said user application operable to;

send a plurality of requests directed to said source system by having an address of said source system specified as the target of each request, and receive corresponding responses in said application, wherein said plurality of requests cause said cache to be populated with a copy of a plurality of data elements,

wherein said cache is implemented external to said database system and stores a copy of said plurality of data elements locally;

send a first request for a copy of a first data element, said first request being directed to said cache by having an address of said cache specified as the target of said first request, wherein said first data element is contained in said plurality of data elements; and

receive from said cache, a copy of said first data element as a first response to said first request;

said cache comprising;

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

a cache logic to receive said first request and to send said copy of said data element in said volatile memory as a first response to said first request.

17. The computing system of claim 16, 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 said 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.

18. The computing system of claim 17, wherein said plurality of requests and said second request are received from said user application,

wherein said access logic intercepts a third request directed to said source system from a 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 response to said third request in view of said third request being received from an application different from the application causing said second data element to be populated in said cache.

19. The computing system of claim 18, 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 user 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 response to said third request.

20. 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 first receive a plurality of requests for a subset of data elements contained in said plurality of data elements, each of said plurality of requests being directed to said database system by having the address of the database specified as the target of the request, said cache to maintain a copy of said subset of data elements in response to examining said plurality of requests; and

a client system to execute a first user application which is operable to;

send said plurality of requests and receive said subset of data elements as corresponding responses;

retrieve said subset of data elements by sending requests directed to said cache by having an address of said cache specified as the target of each request.

21. The computing system of claim 20, wherein said first user 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 user 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.

22. The computing system of claim 21, 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.

23. A method of allowing access to data elements stored in a source system, said method being performed in a client system, said method comprising:

sending from a user application a plurality of requests directed to said source system by having an address of said source system specified as the target of each request, wherein said plurality of requests are sent based on execution of a first set of instructions constituting a part of said user application;

receiving corresponding responses in said user application, wherein said plurality of requests cause a cache to be populated with a copy of a plurality of data elements,

wherein said cache is implemented external to said source system and stores a copy of said plurality of data elements locally;

sending from said user application a first request for a copy of a first data element, said first request being directed to said cache by having an address of said cache specified as the target of said first request, wherein said first request is sent based on execution of a second set of instructions constituting another part of said user application, wherein said first data element is contained in said plurality of data elements; and

receiving in said user application from said cache, a copy of said first data element as a first response to said first request.

24. The method of claim 23, further comprising one of more instructions for:

sending from said user application, a second request for said first data element directed to said source system by having an address of said source system specified as the target of said second request; and

receiving in said user application from said cache, said copy of said first data element as a second response to said second request.

25. The method of claim 24, wherein said source system is a database system which stores data elements in tables in the form of rows, 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 plurality 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 response to said third request,

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