spelling.suggestion_threshold (collection.cfg setting)
This option specifies a frequency threshold when considering whether words should be added to the spelling suggestion index. The range is 1 to 100 with a default of 1. Increasing this value reduces overhead but may reduce the quality of spelling suggestions.
The default setting is 1, which specifies that any word that appears at least once in the lexicon (list of words from indexed documents) should be included in the spelling index:
The threshold value is also used when deciding whether annotations (anchortext, clicks etc.) should be included in the spelling index based on their weight.
If you believe that the spelling index is too large or is increasing query response time you may decide to change the setting to 5:
This will mean that only words that occur at least 5 times in the lexicon will be included in the spelling index.
When altering the spelling suggestion threshold, you may also wish to adjust the spelling_fullmatch_trigger_const setting which controls the maximum number of full matches for a result set beyond which spelling suggestions will not be given. See query processor options for more information.