SECOND LEVEL DATABASE FILE CACHE FOR ROW INSTANTIATION

• US 20150269179A1
• Filed: 03/20/2014
• Published: 09/24/2015
• Est. Priority Date: 03/20/2014
• Status: Active Grant

• Current Assignee: Sybase Incorporated (SAP SE)
• Original Assignee: Sybase Incorporated (SAP SE)
• Inventors: McClements, Tim, Vander Ploeg, Michael
• Granted Patent: US 10,558,571 B2
• Time in Patent Office: Days
• US Class Current: 1/1
• CPC Class Codes: G06F 12/084 with a shared cache
• CPC Class Codes: G06F 12/0871 Allocation or management of cache space
• CPC Class Codes: G06F 16/24552 Database cache management
• CPC Class Codes: G06F 2212/3042 being part of a memory device, e.g. cache DRAM
• CPC Class Codes: G06F 2212/311 In host system
• CPC Class Codes: G06F 2212/465 Structured object, e.g. database record

Abstract

In an example embodiment, one or more pages from a database are stored in a page cache stored in a shared memory, the one or more pages stored in a packed format. One or more rows from the database are stored in a row cache stored in the shared memory, the one or more rows stored in an unpacked format. A request for a row of the database is received. Then, the row cache is searched for the row. In response to a determination that the row cannot be found in the row cache, the page cache is searched for the row. Finally, the row is returned.

Claims

1. A method for managing a shared memory for a database, the method comprising:

storing one or more pages from the database in a page cache stored in the shared memory, the one or more pages stored in a packed format;

storing one or more rows from the database in a row cache stored in the shared memory, the one or more rows stored in an unpacked format, wherein the row cache is coupled to a page cache stored in the shared memory;

receiving a request for a row of the database;

identifying the row in the row cache; and

returning the row in the unpacked format from the row cache.

2. The method of claim 1, further comprising, in response to a determination that the row cannot be found in the page cache, retrieving a page containing the row from the database.

3. The method of claim 2, further comprising, in response to retrieving the page from the database, storing the page in the page cache in a packed format and storing the row from the page in the row cache in an unpacked format.

4. The method of claim 1, further comprising, in response to a determination that the row is found in the page cache, retrieving the row from the page cache, unpacking the row, and storing the unpacked row in the row cache.

5. The method of claim 4, wherein the storing the unpacked row in the row cache includes compressing the unpacked row and storing offsets and distances to be used to decompress the unpacked row in the row cache along with the compressed unpacked row.

6. The method of claim 3, wherein the storing the row in the row cache includes requesting a memory segment from a global memory manager and receiving a denial if the shared memory is full.

7. The method of claim 3, wherein the storing the page in the page cache includes requesting a memory segment from a global memory manager, and the global memory manager requesting that the row cache return a memory segment if the shared memory is full.

8. A system comprising:

a database;

a shared memory; and

a caching component executable by a processor and configured to;

store one or more pages from the database in a page cache stored in the shared memory, the one or more pages stored in a packed format;

store one or more rows from the database in a row cache stored in the shared memory, the one or more rows stored in an unpacked format, wherein the row cache is coupled to a page cache stored in the shared memory;

receive a request for a row of the database;

identify the row in the row cache; and

return the row in the unpacked format from the row cache.

9. The system of claim 8, wherein the system operates on a mobile device.

10. The system of claim 8, wherein the database synchronizes with a consolidated database on a server computer.

11. The system of claim 8, wherein the caching component is further configured to, in response to a determination that the row cannot be found in the page cache, retrieve a page containing the row from the database.

12. The system of claim 11, wherein the caching component is further configured to, in response to retrieving the page from the database, store the page in the page cache in a packed format and store the row from the page in the row cache in an unpacked format.

13. The system of claim 8, wherein the caching component is further configured to, in response to a determination that the row is found in the page cache, retrieve the row from the page cache, unpack it, and store the unpacked row in the row cache.

14. The system of claim 12, wherein the storing the unpacked row in the row cache includes compressing the unpacked row and storing offsets and distances to be used to decompress the unpacked row in the row cache along with the compressed unpacked row.

15. The system of claim 12, wherein the storing the row in the row cache includes requesting a memory segment from a global memory manager and receiving a denial if the shared memory is full.

16. The system of claim 12, wherein the storing the page in the page cache includes requesting a memory segment from a global memory manager, and the global memory manager requesting that the row cache return a memory segment if the shared memory is full.

17. A non-transitory machine-readable storage medium comprising instructions, which when implemented by one or more machines, cause the one or more machines to perform operations comprising:

storing one or more pages from the database in a page cache stored in the shared memory, the one or more pages stored in a packed format;

storing one or more rows from the database in a row cache stored in the shared memory, the one or more rows stored in an unpacked format, wherein the row cache is coupled to a page cache stored in the shared memory;

receiving a request for a row of the database;

identifying the row in the row cache; and

returning the row in the unpacked format from the row cache.

18. The non-transitory machine-readable storage medium of claim 17, wherein the operations further comprise, in response to a determination that the row cannot be found in the page cache, retrieving a page containing the row from the database.

19. The non-transitory machine-readable storage medium of claim 18, wherein the operations further comprise, in response to retrieving the page from the database, storing the page in the page cache in a packed format and storing the row from the page in the row cache in an unpacked format.

20. The non-transitory machine-readable storage medium of claim 17, wherein the operations further comprise, in response to a determination that the row is found in the page cache, retrieving the row from the page cache, unpacking it, and storing the unpacked row in the row cache.