[TYPO3-Solr] The way spelling corrections in the synonyms.txt file work...

[Jigal van Hemert]

Hi,

In the synonyms.txt file you can define synonyms and spelling 
corrections. The description [1] of the SynonymFilterFactory advices to 
use them only at index time because of two potential issues and a 
counter intuitive issue with idf differences.

This is how it's configured in EXT:solr too.

The problem which I see "in the wild" is that if visitors search for a 
word that is on the left side in the spelling correction list there will 
be no results at all. Only if a misspelled word exists in the indexed 
documents it will be included in the results when you search for the 
correctly spelled word.

Could it be a solution to enable the SynonymFilterFactory at query time 
with the following restrictions? :
- a separate synonyms file with only spelling corrections
- no multiple word spelling corrections
Of course these restrictions can't be automated, but at least there is a 
possibility to improve the search experience for people with bad 
spelling habits.

1) is it correct that spelling corrections do not work on search terms 
entered by visitors?
2) is the extra synonyms file a usable solution for custom cases?
3) is this useful to be included in EXT:solr?

[1] 
http://wiki.apache.org/solr/AnalyzersTokenizersTokenFilters#solr.SynonymFilterFactory

-- 
Jigal van Hemert
TYPO3 CMS Active Contributor

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