公开(公告)号：CA2374271A1

公开(公告)日：2003-09-01

申请号：CA2374271

申请日：2002-03-01

Applicant: IBM CANADA

Inventor： KOO FRED ,  LEUNG TING Y

IPC: G06F17/30

Abstract: A query rewrite optimization method for eliminating a redundant join and equivalent subquery in an SQL query before generation and selection of the optimal quer y execution plan. The method evaluates a query for a particular join of a first and second quantifier each ranging over the same table. A determination is made whether the row set produced relative to the second quantifier subsumes the row set produced relative to the first quantifier. The query ma y be reformed to eliminate the join and the second quantifier. A further determination of the removability of the second quantifier may be required such as by evaluating a of a cardinality constraint when query output cardinality is material.

公开(公告)号：CA2150745A1

公开(公告)日：1996-12-02

申请号：CA2150745

申请日：1995-06-01

Applicant: IBM CANADA

Inventor： BARU CHAITANYA ,  FECTEAU GILLES ,  KIRTON JO-ANNE ,  KOLLAR LUBOR J ,  KOO FRED

IPC: G06F16/23 ,  G06F17/30

Abstract: The invention provides a method and apparatus for distributing data of a table across a parallel data base system having a plurality of interlinked database nodes. The table is partitioned in accordance with a predetermined partitioning arrangement and data of the table is distributed across a subset of the nodes in accordance with the partitioning arrangement. The partitioning arrangement can comprise horizontal or vertical partitioning. The partitioning arrangement can comprise a partitioning map defining the relationship of partitions of the table to said subset of nodes.

公开(公告)号：CA2159269A1

公开(公告)日：1997-03-28

申请号：CA2159269

申请日：1995-09-27

Applicant: IBM CANADA

Inventor： BARU CHAITANYA K ,  KOO FRED

IPC: G06F15/167 ,  G06F17/30

Abstract: The invention provides a method and apparatus for distributing data of a table substantially uniformly across a parallel database system having a plurality of interlinked database nodes. Data of the table is distributed across a group of nodes (nodegroup) in accordance with a partitioning arrangement. Resource loading, for example, the workload or storage volume of the nodes is monitored. Data is moved from one or more nodes having higher resource loading to nodes having lower resource loading to achieve a substantially uniform distribution of the resource loading across the group of nodes concerned. In the course of moving data the selection of groups of data to be moved is performed in a manner to reduce the amount of data movement.