Bug 28309 - Searching with hyphen doesn't work with Elasticsearch
Summary: Searching with hyphen doesn't work with Elasticsearch
Status: NEW
Alias: None
Product: Koha
Classification: Unclassified
Component: Searching - Elasticsearch (show other bugs)
Version: Main
Hardware: All All
: P5 - low normal
Assignee: Peter Vashchuk
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Reported: 2021-05-10 14:25 UTC by Joonas Kylmälä
Modified: 2025-05-15 05:40 UTC (History)
6 users (show)

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Description Joonas Kylmälä 2021-05-10 14:25:21 UTC
If a biblio title contains the hyphen character "–" / \xE28093 and you try to search the title as it is written with the hyphen the search produces no results. I think we need to add hyphen to the list of punctuation characters to ignore to fix this problem. The file is in admin/searchengine/elasticsearch/index_config.yaml

The issue could probably fixed also by removing hyphen in the tokenization step when storing the record to the index?
Comment 1 Esther Melander 2025-05-14 16:54:09 UTC
In Elastic Search a hyphen operates as an 'or'. Trying to search for a term like steam-boiler will return results where the term steam or boiler exists. In order to get correct search results add quotation marks "steam-boiler" to force Elastic Search to see it as a single term.

Another example is to search for U-2 boats using U2 rather than U-2. U2 is a single term but it is not returning the expected results because U2 doesn't match "U-2" or U or a 2. One option is to add U2 to a 246 varying title tag so that it appears in search results.

I think in this case Elastic Search is working the way it was designed. The question is should Koha make an exception to using the hyphen as a boolean operator?
Comment 2 Katrin Fischer 2025-05-15 05:40:26 UTC
I can see that this could be quite an issue for German as well as we do have a lot of words that are hyphenated.