[LUCENE-4499] Multi-word synonym filter (synonym expansion)

• Type: Improvement
• Status: Resolved
• Priority: Major
• Resolution: Duplicate
• Affects Version/s: 4.1, 6.0
• Fix Version/s: 6.0
• Component/s: core/other
• Labels: analysis multi-word synonyms
• Lucene Fields: New, Patch Available
• Assignee: Unassigned
• Reporter: Roman Chyla
• Created: 22/Oct/12 15:04
• Updated: 28/Aug/22 13:30
• Resolved: 03/Jan/17 10:50

Description

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

query time:
single-token: return only synonyms (but preserve case)
multi-token: return only 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'

You may (not) be surprised, but Lucene already supports ALL of 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 would just choose what situation they use. Please look at the unittest.

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

Issue Links

• is related to: SOLR-4381 Query-time multi-word synonym expansion
• relates to: SOLR-5379 Query-time multi-word synonym expansion