[LUCENE-6400] SynonymParser should encode 'expand' correctly.

• Type: Bug
• Status: Closed
• Priority: Major
• Resolution: Fixed
• Fix Version/s: 5.2, 6.0
• Lucene Fields: New
• Assignee: Unassigned
• Reporter: Robert Muir
• Created: 06/Apr/15 21:58
• Updated: 28/Aug/22 14:30
• Resolved: 16/Apr/15 21:53

Description

Today SolrSynonymParser encodes something like A, B, C with 'expand=true' like this:
A -> A, B, C (includeOrig=false)
B -> B, A, C (includeOrig=false)
C -> C, A, B (includeOrig=false)

This gives kinda buggy output (synfilter sees it all as replacements, and makes all the terms with type synonym, positionLength isnt supported, etc) and it wastes space in the FST (includeOrig is just one bit).

Example with "spiderman, spider man" and analysis on 'spider man'

Trunk:
term=spider,startOffset=0,endOffset=6,positionIncrement=1,positionLength=1,type=SYNONYM
term=spiderman,startOffset=0,endOffset=10,positionIncrement=0,positionLength=1,type=SYNONYM
term=man,startOffset=7,endOffset=10,positionIncrement=1,positionLength=1,type=SYNONYM

You can see this is confusing, all the words have type SYNONYM, because spider and man got deleted, and totally replaced by new terms (Which happen to have the same text).

Patch:
term=spider,startOffset=0,endOffset=6,positionIncrement=1,positionLength=1,type=word
term=spiderman,startOffset=0,endOffset=10,positionIncrement=0,positionLength=2,type=SYNONYM
term=man,startOffset=7,endOffset=10,positionIncrement=1,positionLength=1,type=word