[#SES-700] Further reduce duplicate statements in SPARQL-construct query results

Issue Details [XML]

Key:	SES-700
Type:	Improvement
Status:	Resolved
Resolution:	Fixed
Priority:	Minor
Assignee:	Arjohn Kampman
Reporter:	James Leigh
Votes:	0
Watchers:	0

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Further reduce duplicate statements in SPARQL-construct query results

Created: 07/Jan/10 12:11 PM Updated: 07/Jan/10 02:30 PM

Component/s:

SPARQL, SeRQL

Affects Version/s:

None

Fix Version/s:

2.3.1

File Attachments:

multiprojection.patch (3 kb)

Issue Links:

Related

This issue is related to:
	~~SES-385~~ duplicate statements in SPARQL-constr...

Description

CONSTRUCT queries should be reduced further. Currently only consecutive duplicates are removed, however, larger construct clauses repeat a pattern (over and over).

The MultiProjectionIterator should not repeat projections that were also produced from the previous nested BindingSet.

This does not have a big impact when the repository is embedded, but when the repository is remote and the result is serialized by the Sesame Server the duplicates have a noticeable impact on performance. A common construct query I have been using was serialized to 47K over HTTP using RDF/XML, by reducing the number of duplicates this could be reduced to 9.1K.

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Change History

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Comment by Arjohn Kampman [07/Jan/10 12:14 PM]

Here is a patch that reduces duplicates from consecutive multi-projections (construct clause pattern sets).

[ Permlink ]

Comment by Arjohn Kampman [07/Jan/10 02:30 PM]

Supplied patch was applied and then modified to reduce processing overhead. MultiProjectionIterator now compares results with the previous result from the same projection instead of with the previous results of all projections, but this probably works in most cases.