Granted Patent B2

US 7,792,885 · App. 11/248,147 · Granted Sep 7, 2010

Assignee: Alcatel Lucent

Abstract

Claims (39)

1. A method of providing a plurality of processes with access to data stored in a cache, comprising:

copying the data from a database to the cache in a shared memory, the shared memory being directly accessible by each process of the plurality of processes without using a database server;

maintaining synchronicity between the database and the cache, wherein any alteration of the database triggers creation of a message comprising a table identifier (ID) of a table within the database, a row ID, and an action flag, wherein the action flag signifies one of addition, deletion, and update in the database;

when the action flag signifies either deletion or update, setting a row status flag to the table ID and the row ID that correspond to the action flag in the cache as update pending or deletion pending;

modifying the cache in response to the message, wherein the action flag specifies the modification performed in a row identified by the table ID and row ID;

providing each process with an Application Program Interface (API) that allows each process to access the data within the cache; and

preventing said API from accessing said data from within the cache when the row status flag of an accessed row is marked as update pending or deletion pending.

2. The method of claim 1 , further comprising:

using a plurality of worker threads to copy the data from the database to the cache, wherein the cache comprises: for each table in the database, at least one linked list of data segments storing data from the table,

a plurality of control segments in the cache, wherein each control segment stores an address of a different first data segment in each linked list, and each data segment corresponds to a unique worker thread, whereby the worker thread corresponding to a second data segment copies data from the database into the second data segment in the cache once the first data segment is full, except that a last entry in a last data segment in the linked list of data segments stores an invalid address, and

a master segment containing a plurality of entries within the cache, wherein each master segment entry stores an address for a different control segment.

3. The method of claim 1 , further comprising:

rowlocking a portion of the data in the cache when a corresponding row and table in the database is deleted or modified until the deletion or modification in the database is verified, thereby preventing the processes from accessing the portion of the data while deletions or modifications in the database are being synchronized with the cache.

4. The method of claim 1 , further comprising:

creating at least one worker thread, each worker thread assigned a task of modifying a portion of the cache;

creating a notification group object (NGO);

upon completion of each worker thread of its assigned task, destroying the NGO; and

upon destruction of the NGO, removing any rowlock for the portion of the cache identified by the message.

5. A cache that stores data from a database having a plurality of tables, the cache having a data structure stored on a computer-readable medium, wherein the computer-readable medium is a shared memory that is directly accessible by a plurality of processes without using a database server, the data structure comprising:

for each table of the plurality of tables, at least one linked list of data segments storing data from the table, wherein each first data segment corresponds to a unique worker thread and has an address of a second data segment as its last entry, whereby the worker thread corresponding to the second data segment copies the data from the database to the second data segment in the cache once the first data segment is full, except that a last entry in a last data segment in the linked list of data segments stores an invalid address, wherein any alteration of the database triggers creation of a message comprising a table identifier (ID) of a table within the database, a row ID, and an action flag, wherein the action flag signifies one of addition, deletion, and update in the database;

a plurality of control segments, wherein each control segment stores an address of a different first data segment in each linked list of data segments;

a master segment containing a plurality of entries, wherein each master segment entry stores an address for a different control segment; and

row status flags that block access to data in the cache in a specified row of each table when said row status flags are marked as update pending or deletion pending, wherein the row status flags are set to corresponding table IDs and row IDs in the cache as update pending or deletion pending when the action flag signifies either deletion or update.

6. The method of claim 1 , wherein the message is three integers in length, each integer respectively corresponding to the table ID, the row ID, and the action flag.

7. The method of claim 1 , wherein a controller sets the row status flag, deletes the message from a first queue, and forwards the message to a second queue.

8. The method of claim 1 , further comprising:

determining that an action in the database is neither deletion, addition, nor update; and

in response to the determination, discarding the message and generating an error report.

9. The method of claim 4 , wherein the NGO is an object oriented programming object.

10. The method of claim 4 , wherein the NGO comprises at least one of a group status, a request count, a completed request count, a blocked status, and a condition variable.

11. A method of providing a plurality of processes with access to data stored in a cache, comprising:

copying the data from a database to the cache in a shared memory, the shared memory being directly accessible by each process of the plurality of processes without using a database server;

maintaining synchronicity between the database and the cache, wherein any alteration of the database triggers creation of a message comprising a table identifier (ID) of a table within the database, a row ID, and an action flag, wherein the action flag signifies one of addition, deletion, and update in the database;

when the action flag signifies either deletion or update, setting a row status flag to the table ID and the row ID that correspond to the action flag in the cache as update pending or deletion pending;

modifying the cache in response to the message, wherein the action flag specifies the modification performed in a row identified by the table ID and row ID;

providing each process with an Application Program Interface (API) that allows each process to access the data within the cache;

preventing said API from accessing said data from within the cache when the row status flag of an accessed row is marked as update pending or deletion pending;

determining that an action in the database is neither deletion, addition, nor update; and in response to the determination, discarding the message and generating an error report; and

using a plurality of worker threads to copy the data from the database to the cache, wherein the cache comprises: for each table in the database, at least one linked list of data segments storing data from the table, a plurality of control segments in the cache, wherein each control segment stores an address of a different first data segment in each linked list, and each data segment corresponds to a unique worker thread, whereby the worker thread corresponding to a second data segment copies data from the database into the second data segment in the cache once the first data segment is full, except that a last entry in a last data segment in the linked list of data segments stores an invalid address, and a master segment containing a plurality of entries within the cache, wherein each master segment entry stores an address for a different control segment, the message is three integers in length, each integer respectively corresponding to the table ID, the row ID, and the action flag, a controller sets the row status flag, deletes the message from a first queue, and forwards the message to a second queue

Assignments (9)

Priority Claims (1)

Continuity (1)