roman created LUCENE-4499:
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Summary: Multi-word synonym filter (synonym expansion at indexing
time).
Key: LUCENE-4499
URL: https://issues.apache.org/jira/browse/LUCENE-4499
Project: Lucene - Core
Issue Type: Improvement
Components: core/other
Affects Versions: 4.1, 5.0
Reporter: roman
Priority: Minor
Fix For: 5.0
I apologize for bringing the multi-token synonym expansion up again. There is
an old, unresolved issue at LUCENE-1622 [1]
While solving the problem for our needs [2], I discovered that the current
SolrSynonym parser (and the wonderful FTS) have almost everything to
satisfactorily handle both the query and index time synonym expansion. It seems
that people often need to use the synonym filter *slightly* differently at
indexing and query time.
In our case, we must do different things during indexing and querying.
Example sentence: Mirrors of the Hubble space telescope pointed at XA5
This is what we need (comma marks position bump):
indexing: mirrors,hubble|hubble space
telescope|hst,space,telescope,pointed,xa5|astroobject#5
querying: +mirrors +(hubble space telescope | hst) +pointed
+(xa5|astroboject#5)
This translated to following needs:
indexing time:
single-token synonyms => return only synonyms
multi-token synonyms => return original tokens AND the synonyms
We need the original tokens for the proximity queries, if we indexed 'hubble
space telescope'
as one token, we cannot search for 'hubble NEAR telescope'
query time:
single-token: return only its synonyms (but preserve case)
multi-token: return only synonyms
You may (not) be surprised, but Lucene already supports ALL these requirements.
The patch is an attempt to state the problem differently. I am not sure if it
is the best option, however it works perfectly for our needs and it seems it
could work for general public too. Especially if the SynonymFilterFactory had a
preconfigured sets of SynonymMapBuilders - and people could just choose what
situation they use.
links:
[1] https://issues.apache.org/jira/browse/LUCENE-1622
[2] http://labs.adsabs.harvard.edu/trac/ads-invenio/ticket/158
[3] seems to have similar request:
http://lucene.472066.n3.nabble.com/Proposal-Full-support-for-multi-word-synonyms-at-query-time-td4000522.html
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