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ID: 520395.0, MPI für Informatik / Databases and Information Systems Group
A Framework for Reasoning about Share Equivalence and Its Integration into a Plan Generator
Authors:Neumann, Thomas; Moerkotte, Guido
Language:English
Publisher:GI
Place of Publication:Bonn, Germany
Date of Publication (YYYY-MM-DD):2009
Title of Proceedings:Datenbanksysteme in Business, Technologie und Web (BTW 2009), 13. Fachtagung des GI-Fachbereichs "Datenbanken und Informationssysteme" (DBIS)
Start Page:7
End Page:26
Title of Series:Lecture Notes in Informatics
Place of Conference/Meeting:Münster, Germany
(Start) Date of Conference/Meeting
 (YYYY-MM-DD):
2009-03-02
End Date of Conference/Meeting 
 (YYYY-MM-DD):
2009-03-06
Audience:Experts Only
Intended Educational Use:No
Abstract / Description:Very recently, Cao et al.\ presented the MAPLE approach,
which accelerates queries with multiple instances of the same relation
by sharing their scan operator.
The principal idea is to derive, in a first phase,
a non-shared tree-shaped plan via a traditional plan generator.
In a second phase, common instances of a scan are detected and shared
by turning the operator tree into an operator DAG (directed acyclic graph).

The limits of their approach are obvious.
(1) Sharing more than scans is often possible and can lead to considerable
performance benefits.
(2) As sharing influences plan costs, a separation of the optimization into
two phases comprises the danger of missing the optimal plan,
since the first optimization phase does not know about sharing.

We remedy both points by introducing a general framework for reasoning
about sharing: plans can be shared whenever they are {\em share equivalent} and
not only if they are scans of the same relation.
Second, we sketch how this framework can be integrated into a plan generator,
which then constructs optimal DAG-structured plans.
Last Change of the Resource (YYYY-MM-DD):2010-01-08
External Publication Status:published
Document Type:Conference-Paper
Communicated by:Gerhard Weikum
Affiliations:MPI für Informatik/Databases and Information Systems Group
Identifiers:LOCALID:C1256DBF005F876D-8A7DE2804C156572C1257582005424A8-...
ISBN:978-3-88579-238-3
Full Text:
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