DATABASE SYSTEM
FIG. 1 illustrates a database system 1 including a storage device 2 . Device 2 stores table data 3 indicative of a plurality of rows 4 . A source access module 5 is assigned to access one of rows 4 , this particular row being designated by reference numeral 6 . Module 5 is responsive to a command 7 for reading row 6 from device 2 . Subsequently, module 5 writes row 6 to device 2 in a packet accessible by a target module 8 , this packet presently taking the form of a shared spool file 9.
1 . A database system including:
a storage device for storing table data indicative of a plurality of rows;
a source access module assigned to access one of the rows, the source module being responsive to a command for:
reading the row from the storage device; and
writing the row to the storage device in a packet accessible by a target access module.
2 . A system according to claim 1 wherein the command is indicative of the target module.
3 . A system according to claim 2 wherein the command is either of:
a row redistribution command to redistribute the row to the target module; or
a row duplication command to duplicate the row to the target module.
4 . A system according to claim 2 wherein the command is indicative of a plurality of target modules and the packet is accessible by the plurality of target modules.
5 . A system according to claim 1 wherein a source node carries the source module and a target node carries the target module.
6 . A system according to claim 5 wherein node sharing of spools is enabled such that when a given module carried by a given node reads a spool, one or more further modules carried by that given node share a common memory copy of the spool.
7 . A system according to claim 5 wherein the source and target nodes belong to a single clique.
8 . A system according to claim 7 wherein clique sharing of spools is enabled such that a clique shared spool file is accessible by any module carried by any node in the clique.
9 . A system according to claim 5 wherein the row is maintained in a source storage location of the storage device, the source storage location maintaining a portion of the table data assigned to the source node.
10 . A system according to claim 9 wherein the row is written to a shared storage location of the storage device, the shared storage location selectively maintaining one or more portions of the table data respectively assigned to one or more nodes of the system.
11 . A system according to claim 1 wherein the storage device includes a shared storage location for maintaining the packet.
12 . A system according to claim 1 wherein the packet is a clique shared spool file accessible by the target module.
13 . A system according to claim 12 wherein the command is a row redistribution command and the clique shared spool file maintains the row for consumption by the target module such that the row is redistributed to the target module.
14 . A system according to claim 13 wherein only the target module reads the clique shared spool file.
15 . A system according to claim 14 wherein there is a plurality of target modules and a clique shared spool maintaining the row is provided for each target module.
16 . A system according to claim 12 wherein the command is a row duplication command and the clique shared spool file maintains the row for consumption by the target module such that the row is duplicated to the target module.
17 . A system according to claim 16 wherein there is a plurality of target modules and the clique shared spool file is available for consumption by each of the target modules such that the row is duplicated to each of the target modules.
18 . A method for row redistribution in a database system, the method including the steps of:
reading the row from a source storage location using a source access module; and
writing the row to a second storage location using the source access module such that the row is accessible to a target access module thereby to redistribute the row to the target module.
19 . A method for row duplication in a database system, the method including the steps of:
reading the row from a source storage location using a source access module; and
writing the row to a second storage location using the source access module such that the row is accessible to a plurality of target access modules thereby to duplicate the row to the plurality of target access modules.
20 . A database system including:
a plurality of nodes for accessing data; and
a plurality of primary storage locations each for maintaining a portion of the data, each portion being maintained for access by a respective associated one of the nodes; and
a secondary storage location for selectively maintaining one or more portions of the data for access by a predetermined one or more of the nodes.