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https://issues.apache.org/jira/browse/LUCENE-2454?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=13052436#comment-13052436
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Mark Harwood commented on LUCENE-2454:
--------------------------------------
bq. This overlaps with the BlockJoinQuery of LUCENE-3171, this issue might even
be closed as duplicate of that one. Which one is preferred?
We need to look at the likely use cases. 2454 was created to service a use case
which I expect to be a very common pattern and I'm not sure if LUCENE-3171
satisfies this need. Apps commonly need to return a selection of both matching
and non-matching children along with the "best" parents. Why? - it's a very
similar rationale to the way that highlighting returns a summary of text - it
doesn't just return the matched words, it also returns surrounding text as
useful context when displaying results to users. However, some texts can be
very large and there's a need to limit what context is brought back.
If we apply this logic to 2454 we can see that for the top parents it is common
to also want some non-matching children (e.g. for a resume return a person's
employment history - not just the employments that matched the original search)
but it is also necessary to summarize some parent's history (e.g. the
contractor who listed a gazillion positions in his employment history needs
summarising). A common pattern is for solutions to ask for the best 11 children
for the best parents and display only 10 - that way the app knows that for
certain parents there is more data available (i.e. those with 11 matches) and
can offer a "more" button to retrieve the extra children for parents of
interest. 2454 satisfies this use case as follows:
# Use a NestedDocumentQuery to get best parents with child criteria expressed
as a "must"
# Use a PerParentLimitedQuery to get a selection of children per top parent
where MUST belong to a top parent (tested using primary key) and use the child
criteria again but this time as a "SHOULD" clause to relevance rank the
selection of children returned
It's worth considering this sort of use case carefully before making any code
decisions.
> Nested Document query support
> -----------------------------
>
> Key: LUCENE-2454
> URL: https://issues.apache.org/jira/browse/LUCENE-2454
> Project: Lucene - Java
> Issue Type: New Feature
> Components: core/search
> Affects Versions: 3.0.2
> Reporter: Mark Harwood
> Assignee: Mark Harwood
> Priority: Minor
> Attachments: LUCENE-2454.patch, LUCENE-2454.patch,
> LuceneNestedDocumentSupport.zip
>
>
> A facility for querying nested documents in a Lucene index as outlined in
> http://www.slideshare.net/MarkHarwood/proposal-for-nested-document-support-in-lucene
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