Browse Prior Art Database

Enforcement of Uniqueness Constraints in Partitioned Tables

IP.com Disclosure Number: IPCOM000109427D
Original Publication Date: 1992-Aug-01
Included in the Prior Art Database: 2005-Mar-24
Document File: 1 page(s) / 45K

Publishing Venue

IBM

Related People

Malkemus, TR: AUTHOR

Abstract

In a parallel database management system (PDB) that maintains local indexes, a unique index would not be adequate to enforce uniqueness for an entire table: uniqueness would be enforced at each partition, but the same key value could appear in more than one partition of the table, thereby violating the constraint. This invention provides a method of global enforcement of a uniqueness constraint for partitioned tables.

This text was extracted from an ASCII text file.
This is the abbreviated version, containing approximately 88% of the total text.

Enforcement of Uniqueness Constraints in Partitioned Tables

      In a parallel database management system (PDB) that maintains
local indexes, a unique index would not be adequate to enforce
uniqueness for an entire table: uniqueness would be enforced at each
partition, but the same key value could appear in more than one
partition of the table, thereby violating the constraint.  This
invention provides a method of global enforcement of a uniqueness
constraint for partitioned tables.

      When a row is inserted into a partitioned table, it is placed
in one of the table's partitions.  The choice of partition for a
given row is determined by the PDB in a manner that is immaterial to
this invention. The invention enforcing uniqueness constraints is as
follows:
1.   From the nodes receiving new rows, all the rows' unique key
values are broadcast through a table queue to the other nodes that
contain partitions of the table.
2.   When rows' unique key values are updated (changed), the new
values are broadcast through a table queue to the other nodes that
contain partitions of the table.
3.   At each node, those key values are read from the table queue.
4.   The unique index partition at each node is searched for each
value.
5.   If one of the values is found, an error is indicated and the
operation fails:  all modifications to the database for the request
are undone (rolled back).
6.   The unique index partition at a row's home node enforces the
uniquenes...