uk.ac.ic.doc.rodex.qproc
Class MiniConQueryRewriterAdaptive

java.lang.Object
  uk.ac.ic.doc.rodex.qproc.QueryRewriter
      uk.ac.ic.doc.rodex.qproc.MiniConQueryRewriter
          uk.ac.ic.doc.rodex.qproc.MiniConQueryRewriterAdaptive

public class MiniConQueryRewriterAdaptive
extends MiniConQueryRewriter

MiniConQueryRewriterAdaptive.java Differs from MiniConQueryWriter in that this considers views which are only partially matched with the join sub-goals of the query. Instead of discarding these views, this algorithm keeps them with the partially matched (join) sub-goals for further check. If there exist other views which are mappable to the remaining sub-goals, then these views are then combined to make an MCD.

Author:

Duc M Le dmle@doc.ic.ac.uk

Nested Class Summary

Nested classes/interfaces inherited from class uk.ac.ic.doc.rodex.qproc.MiniConQueryRewriter

MiniConQueryRewriter.MiniConDescription

Field Summary

Fields inherited from class uk.ac.ic.doc.rodex.qproc.MiniConQueryRewriter

mcds, queryAnalyser, viewAnalysers

Fields inherited from class uk.ac.ic.doc.rodex.qproc.QueryRewriter

_qa, query, views

Constructor Summary

MiniConQueryRewriterAdaptive(ASG query, java.util.List views)
Creates a new instance of QueryRewriterForFiltering

MiniConQueryRewriterAdaptive(ASG query, QueryAnalyser[] viewMetadata)

Method Summary

protected java.util.List	getMinimumCoverage(java.util.List sharedVars, QueryAnalyser view, java.util.Map invmap) Check that a query contains certain variables in its head and if not it must contains all related sub-goals
QueryRewriterResult	rewrite() Implements method in QueryWriter abstract parent class Rewrite query using views based on the MiniCon algorithm following a two-phase process:

Methods inherited from class uk.ac.ic.doc.rodex.qproc.MiniConQueryRewriter

analyse, checkComparisonPredicates, checkConstants, contains, createConjunctiveQueries, createQueryFromSubGoals, getLeastRestrictiveMapping, getMinimumCoverage, getQueryAnalyser, getSharedVariables, refineConjunctiveQueries, subtractList

Methods inherited from class uk.ac.ic.doc.rodex.qproc.QueryRewriter

getQueryRewriterInstance, getQueryRewriterInstance, getQueryRewriterInstance, getQueryRewriterInstance

Methods inherited from class java.lang.Object

clone, equals, finalize, getClass, hashCode, notify, notifyAll, toString, wait, wait, wait

Constructor Detail

MiniConQueryRewriterAdaptive

public MiniConQueryRewriterAdaptive(ASG query,
                                    java.util.List views)

Creates a new instance of QueryRewriterForFiltering

MiniConQueryRewriterAdaptive

public MiniConQueryRewriterAdaptive(ASG query,
                                    QueryAnalyser[] viewMetadata)

Method Detail

rewrite

public QueryRewriterResult rewrite()
                            throws QueryRewriterException

Description copied from class: MiniConQueryRewriter

Implements method in QueryWriter abstract parent class
Rewrite query using views based on the MiniCon algorithm following a two-phase process:

Phase 1: For each view we check to see if there is a mapping between any of the query
subgoals and the view's. If a mapping exists and there are shared variables
in the query subgoal which are also in the query's head but not in the view's head,
a further check is carried out to find the mininum set of query sub-goals containing
the shared variables that the view need to cover.

If there are any comparison predicates in the query (e.g. >, <, = etc.) and they
are mutually consistent with those found in a view mentioned above then an MCD can be created
for that view.

Phase 2: Identify disjoint sets of MCDs found in phase 1 with each set covering all query's subgoals.
Combine MCDs in each set to produce a conjunctive rewriting of the query.
The final query re-writing is the union of all conjunctive rewritten queries.

Overrides:

rewrite in class MiniConQueryRewriter

Throws:

QueryRewriterException

getMinimumCoverage

protected java.util.List getMinimumCoverage(java.util.List sharedVars,
                                            QueryAnalyser view,
                                            java.util.Map invmap)

Check that a query contains certain variables in its head and if not it
must contains all related sub-goals

Parameters:

sharedVars - a List of shared variables to check

view - a QueryAnalyser object containing having the data structure
of the view that needs to be checked

Returns:

List a minimum list of view's sub-goals (if any) that cover

the shared variables; null if view fails to cover.