System and method for caching data for a mobile application

• US 20040015504A1
• Filed: 07/17/2002
• Published: 01/22/2004
• Est. Priority Date: 07/17/2002
• Status: Active Grant

• Current Assignee: Oracle International Corporation (Oracle Corporation)
• Original Assignee: Oracle International Corporation (Oracle Corporation)
• Inventors: Ahad, Rafiul, Rehman, Samuelson, Chiang, Jerry, Prakash, Ravindra, Kibirev, Oleg
• Granted Patent: US 6,941,310 B2
• Time in Patent Office: Days
• US Class Current: 707/100
• CPC Class Codes: G06F 16/24552 Database cache management
• CPC Class Codes: Y10S 707/99942 Manipulating data structure, e.g. compression, compaction, compilation
• CPC Class Codes: Y10S 707/99945 Object-oriented database structure processing
• CPC Class Codes: Y10S 707/99953 Recoverability

Abstract

A cache table comprises a set of access parameters and a set of data columns. One or more instances of a cache table are stored on a mobile computing device. Each instance includes an argument (a unique set of values for the access parameters) and a result set (a set of values for the data columns). Thus, each result in a result set comprises the argument and corresponding column values. Cached result sets have specified periods of validity, and may or may not be usable after becoming invalid. Valid cached data may be used regardless of whether a connection is available to a data source (e.g., data or application server). Invalid data may be used for a period of time if no connection is available to the data source. Data in a cache table may be selectively updated from a data source without synchronizing the entire local database.

Claims

1. A method of facilitating the caching of data from a data source, on a mobile computing device coupled to the data source with a discontinuously available communication link, comprising:

configuring a cache table within a database on the mobile computing device, wherein said cache table includes;

access parameters comprising a first set of columns of a dataset on a data source; and

result columns comprising a second set of columns of the dataset distinct from the first set of columns of the dataset;

generating one or more instances of said cache table within the database, wherein each said cache table instance comprises a set of rows, wherein each said row comprises;

an argument, said argument comprising a value for each column of the access parameters; and

a result set comprising a value for each column of the result columns, wherein each row in a set of rows comprises the same argument.

2. The method of claim 1, further comprising:

for each said cache table instance, storing one or more parameters for determining whether said result set of said cache table instance may be used for a data operation.

3. The method of claim 2, wherein said parameters include a response date indicating when said result set was received from the data source.

4. The method of claim 2, wherein said parameters include a last modification date indicating when said result set was last modified at the data source.

5. The method of claim 2, wherein said parameters include a time-to-live parameter configured to indicate a first period of time during which said result set is valid;

wherein said result set becomes invalid at the end of said first period of time.

6. The method of claim 5, wherein said result set is used for said data operation if said result set is valid, regardless of whether the discontinuously available communication link is available.

7. The method of claim 5, wherein a replacement result set for said result set is retrieved from the data source only if said result set is invalid.

8. The method of claim 5, wherein an update for said result set is retrieved from the data source only if said result set is invalid.

9. The method of claim 5, wherein said parameters include a staleness parameter configured to indicate a second period of time, following said first period of time, during which said result set is usable;

and

wherein said result set becomes stale at the end of said second period of time.

10. The method of claim 9, wherein said result set is used for said data operation if said result set is usable and the discontinuously available communication link is not available.

11. The method of claim 9, further comprising:

receiving a first data operation, involving a first cache table instance; and

using said result set of said first cache table instance if;

(a) said result set of said first cache table instance is valid;

or

(b) said result set of said first cache table instance is invalid and;

(1) said result set of said first cache table instance is usable; and

(2) the less than continuously available communication link is not available;

12. The method of claim 11, further comprising:

retrieving an update for said result set of said first cache table instance only if said result set of said first cache table instance is invalid.

13. The method of claim 11, further comprising:

retrieving a replacement result set for said result set of said first cache table instance only if said result set of said first cache table instance is invalid.

14. The method of claim 11, further comprising:

signaling an error if;

said result set of said first cache table instance is invalid;

said result set of said first cache table instance is stale; and

the less than continuously available communication link is not available.

15. The method of claim 1, wherein said dataset is one of a database table and a view.

16. A computer readable storage medium storing instructions that, when executed by a computer, cause the computer to perform a method of facilitating the caching of data, from a data source, on a mobile computing device coupled to the data source with a less than continuously available communication link, the method comprising:

configuring a cache table within a database on the mobile computing device, wherein said cache table includes;

access parameters comprising a first set of columns of a dataset on a data source; and

result columns comprising a second set of columns of the dataset distinct from the first set of columns of the dataset;

generating one or more instances of said cache table within the database, wherein each said cache table instance comprises a set of rows, wherein each said row comprises;

an argument, said argument comprising a value for each column of the access parameters; and

a result set comprising a value for each column of the result columns, wherein each row in a set of rows comprises the same argument.

17. A method of facilitating data caching on a mobile computing device discontinuously coupled to a data server, the method comprising:

identifying one or more logical data tables on the data server;

for each logical data table, maintaining a table data processor configured to provide access to the logical table from the mobile computing device;

receiving an argument at the data server from the mobile computing device, wherein the argument comprises values for one or more columns of a first logical table;

identifying a set of rows of the first logical table, wherein each row in the set of rows contains the argument;

filtering the set of rows, wherein said filtering comprises;

excluding any rows that have not been modified since a last time the argument was received from the mobile computing device; and

removing from the rows the one or more columns corresponding to the argument; and

returning to the mobile computing device, in response to the argument, the filtered set of rows.

18. A computer readable storage medium storing instructions that, when executed by a computer, cause the computer to perform a method of facilitating data caching on a mobile computing device discontinuously coupled to a data server, the method comprising:

identifying one or more logical data tables on the data server;

for each logical data table, maintaining a table data processor configured to provide access to the logical table from the mobile computing device;

receiving an argument at the data server from the mobile computing device, wherein the argument comprises values for one or more columns of a first logical table;

identifying a set of rows of the first logical table, wherein each row in the set of rows contains the argument;

filtering the set of rows, wherein said filtering comprises;

excluding any rows that have not been modified since a last time the argument was received from the mobile computing device; and

removing from the rows the one or more columns corresponding to the argument; and

returning to the mobile computing device, in response to the argument, the filtered set of rows.

19. A method of caching data on a mobile computing device, wherein the mobile computing device is connectable to a data source via a discontinuously available wireless link, comprising:

receiving a first operation involving a first set of data cached on a mobile computing device;

determining whether said first set of data is valid;

if said first set of data is invalid, determining whether said discontinuously available wireless link is available;

if said first set of data is invalid and said less than continuously available wireless link is unavailable, determining whether said first set of data is usable; and

retrieving an update for said first set of data from the data source only if;

said first set of data is invalid; and

said less than continuously available wireless link is available.

20. The method of claim 19, further comprising:

determining whether said first set of data is locked by a first transaction;

wherein said first operation was initiated by said first transaction.

21. The method of claim 19, further comprising:

determining whether an active cursor is open on said first set of data by a first transaction;

wherein said first operation was initiated by said first transaction.

22. The method of claim 19, wherein said determining whether said first set of data is valid comprises:

accessing a validity parameter associated with said first set of data, wherein said validity parameter is configured to indicate a first time at which said first set of data becomes invalid; and

comparing a time of said first operation with said first time;

wherein said first set of data is valid before said first time.

23. The method of claim 22, wherein said determining whether said first set of data is usable comprises:

accessing a staleness parameter associated with said first set of data, wherein said staleness parameter is configured to indicate a second time, after said first time, when said first set of data becomes stale; and

comparing said time of said first operation with said second time;

wherein said first set of data is usable between said first time and said second time.

24. The method of claim 19, further comprising, prior to said receiving a first operation:

configuring a cache table on the mobile computing device for caching data, including said first set of data, wherein said cache table is defined by;

a set of access parameters comprising a first set of columns of a dataset on the data source; and

a second set of columns of the dataset.

25. The method of claim 24, further comprising, prior to said receiving a first operation:

generating one or more instances of said cache table, wherein each said cache table instance comprises;

an argument comprising a unique set of values for said set of access parameters; and

a result set comprising values for said second set of columns;

wherein said first set of data comprises a first result set of a first cache table instance.

26. The method of claim 24, wherein said dataset comprises one or more database tables.

27. The method of claim 24, wherein said dataset comprises one or more database views.

28. The method of claim 19, further comprising:

if said first set of data is invalid and said discontinuously available wireless link is unavailable and said first set of data is unusable, signaling an error.

29. The method of claim 19, further comprising:

using said first set of data for said first operation if;

said first set of data is valid;

or

said first set of data is invalid and said less than continuously available wireless link is unavailable and said first set of data is usable.

30. A computer readable storage medium storing instructions that, when executed by a computer, cause the computer to perform a method of caching data on a mobile computing device, wherein the mobile computing device is connectable to a data source via a discontinuously available wireless link, the method comprising:

receiving a first operation involving a first set of data cached on a mobile computing device;

determining whether said first set of data is valid;

if said first set of data is invalid, determining whether said less than continuously available wireless link is available;

if said first set of data is invalid and said discontinuously available wireless link is unavailable, determining whether said first set of data is usable; and

retrieving an update for said first set of data from the data source only if;

said first set of data is invalid; and

said less than continuously available wireless link is available.

31. A database for caching data on a mobile device, the database comprising:

a cache table defined by;

a set of access parameters corresponding to a first set of attributes of a data source accessible through a wireless communication connection; and

a second set of attributes of the data source;

wherein the database is discontinuously connected to the central data source through the wireless communication connection; and

one or more instances of said cache table, wherein each said cache table instance comprises;

an argument, said argument comprising a unique set of values for said access parameters; and

a result set comprising values for said second set of attributes; and

for each said cache table instance, information for determining a period of time during which said result set is usable on the mobile device.

32. The database of claim 31, wherein said period of time during which said result set is usable comprises:

a first period of time during which said result set is valid.

33. The database of claim 32, wherein said first period of time is specified by the data source.

34. The database of claim 32, wherein the database is configured to not retrieve said result set from the central data source during said first period of time.

35. The database of claim 32, wherein said period of time during which said result set is usable further comprises:

a second period of time during which said result set is invalid but not yet stale;

wherein said second period of time immediately follows said first period of time.

36. The database of claim 35, wherein said result set is not usable by a database transaction after said second period time unless:

said result set is locked by the database transaction;

or the database transaction has an active cursor open on said result set.

37. The database of claim 31, wherein said information comprises:

a first parameter configured to indicate when said result set becomes invalid; and

a second parameter configured to indicate when said result set becomes stale.

38. The database of claim 31, further comprising:

a queue configured to store operations on said one or more cache table instances prior to transmission of the operations to the data source;

wherein the operations are stored in said queue when the data source is not accessible through the wireless communication connection.

39. A system for caching data on a mobile computing device connectable to a central data source through a wireless link, comprising:

a database configured to selectively operate in either of an on-line mode and an off-line mode with respect to a central data source;

within the database, a cache table defined by;

a set of access parameters corresponding to a first set of attributes of the data source; and

a second set of attributes of the central data source;

within the database, one or more instances of said cache table, wherein each said cache table instance comprises;

an argument comprising a value for each of said access parameters; and

a set of results, wherein each said result comprises a value for each of said second set of attributes of the data source; and

for each said cache table instance, information for determining whether said result set is usable.

40. The system of claim 39, wherein said information for a first result set of a first cache table instance comprises one or more of:

a response-date parameter configured to indicate when said first result set was last provided to the database from the data source;

a last-modified-date parameter configured to indicate when said first result set was last modified at the data source;

a time-to-live parameter configured to indicate a first period of time during which said first result set is valid, wherein said first result set is usable if said first result set is valid; and

a staleness parameter configured to indicate a second period of time, starting at the expiration of said first period of time, during which said first result set may be usable.

41. The system of claim 40, wherein:

a first operation involving said first cache table instance is received at a time O;

said first period of time ends at a time V;

said second period of time ends at a time U; and

said result set is usable for said first operation if;

O is earlier than V;

or

O is later than V and O is earlier than U and said database is operated in the off-line mode with respect to the data source.

42. The system of claim 39, wherein said database operates in the on-line mode with the central data source to receive a first result set for a first cache table instance only when:

said first result set does not exist in the database;

or

said first result set exists in the database, but is not usable.

43. The system of claim 39, wherein:

if a first result set of a first cache table instance is valid, said database operates in the off-line mode during an operation involving said first cache table instance regardless of whether the wireless link to the central data source is available.

44. A system for caching data on a mobile computing device, wherein the mobile computing device is configured for connection to a central data source on a discontinuous basis, the system comprising:

a cache table configured to cache data, from the central data source, on the mobile computing device;

one or more entries in said cache table, each said entry comprising a set of data from the central data source;

for each entry in said cache table, a validity parameter for determining a period of time during which said set of data is valid;

for each entry in said cache table, a usability parameter for determining whether said set of data is usable after said period of time during which said set of data is valid; and

a communication module configured to connect the mobile computing device to the central data source on a less than continuous basis.

45. The system of claim 44, wherein said validity parameter is configured to identify a first time at which said set of data becomes invalid;

wherein, until said first time, said set of data is used for an operation involving said cache table entry, regardless of whether the mobile computing device is connected to the central data source.

47. The system of claim 44, wherein said communication module is configured to connect the mobile computing device to the central data source for a maximum of one cache table entry operation at a time.

48. The system of claim 47, wherein the mobile computing device is not connected to the central data source for an operation involving a cache table entry that is valid.

46. The system of claim 46, wherein said usability parameter is configured to identify a second time at which said set of data becomes stale;

wherein, after said first time and until said second time, said set of data is used for an operation involving said cache table entry, only if the mobile computing device is not connected to the central data source.