# Synonyms result scoring **URL:** \ **Category:** Elasticsearch\ **Created:** [October 15, 2018, 3:18pm UTC](https://discuss.elastic.co/t/synonyms-result-scoring/152523 "2018-10-15T15:18:51Z")\ **Posts on this page:** 6\ **Page:** 1
**Author:** ![Bilal](https://avatars.discourse-cdn.com/v4/letter/b/3ab097/32.png) [@Bilal](https://discuss.elastic.co/u/Bilal)\ **Post date:** [October 15, 2018, 3:18pm UTC](https://discuss.elastic.co/t/synonyms-result-scoring/152523/1 "2018-10-15T15:18:52Z")
I'm reading [this article](https://opensourceconnections.com/blog/2016/12/02/solr-elasticsearch-synonyms-better-patterns-keyphrases/) about Patterns for Synonyms in Elasticsearch and I have some questions about the results that I got, here is the mappings and settings I used: ``` PUT wheat_syn { "mappings": { "wheat": { "properties": { "description": { "type": "text", "analyzer": "syn_text", "fields": { "keyword": { "type": "keyword", "ignore_above": 256 } } } } } }, "settings": { "analysis": { "filter": { "autophrase_syn": { "type": "synonym", "synonyms": ["triticum aestivum => triticum_aestivum", "bread wheat => bread_wheat"] }, "wheat_syn": { "type": "synonym", "tokenizer": "keyword", "synonyms": ["triticum_aestivum, bread_wheat, wheat"] } }, "analyzer": { "syn_text": { "tokenizer": "standard", "filter": ["lowercase", "autophrase_syn", "wheat_syn"] } } } } } ``` The Documents: ``` PUT wheat_syn/wheat/_bulk { "index" : { "_id" : "1" } } { "description": "Wheat is a grass widely cultivated for its seed, a cereal grain which is a worldwide staple food." } { "index" : { "_id" : "2" } } { "description": "The scientific name is Triticum aestivum." } { "index" : { "_id" : "3" } } { "description": "bread wheat is good for health." } ``` The query: ``` GET wheat_syn/wheat/_search { "query": { "match": { "description": "wheat" } } } ``` After executing the query, I got the following result: ``` { "took": 2, "timed_out": false, "_shards": { "total": 5, "successful": 5, "skipped": 0, "failed": 0 }, "hits": { "total": 3, "max_score": 0.48155478, "hits": [ { "_index": "wheat_syn", "_type": "wheat", "_id": "2", "_score": 0.48155478, "_source": { "description": "The scientific name is Triticum aestivum." } }, { "_index": "wheat_syn", "_type": "wheat", "_id": "3", "_score": 0.48155478, "_source": { "description": "bread wheat is good for health." } }, { "_index": "wheat_syn", "_type": "wheat", "_id": "1", "_score": 0.46197122, "_source": { "description": "Wheat is a grass widely cultivated for its seed, a cereal grain which is a worldwide staple food." } } ] } } ``` Now, my questions are: 1. I was expecting to get the sentence `Wheat is a grass widely cultivated for its seed, a cereal grain which is a worldwide staple food` first since the user was looking for this word, why isn't the case ? 2. Why there is a difference in the score and if it's depend on the position of the queried sentence/word in the description field, the third sentence in the results should be first right ? (this is a simple example, the more documents I add the higher difference of score is). Thank you ! ---
**Author:** ![abdon](https://sea2.discourse-cdn.com/elastic/user_avatar/discuss.elastic.co/abdon/32/9195_2.png) [@abdon](https://discuss.elastic.co/u/abdon)\ **Post date:** [October 15, 2018, 4:34pm UTC](https://discuss.elastic.co/t/synonyms-result-scoring/152523/2 "2018-10-15T16:34:32Z")
Great questions! 1. Synonyms score the same as an exact match. There is no automatic preference for exact matches. 2. The length of a field is an important factor that determines the score: shorter fields score higher than longer fields. What you're seeing is that the documents with a shorter field (6 terms) score higher than the document with a longer field (18 terms). If you want to understand how a score is calculated, you can add `"explain": true` to a search request, and Elasticsearch will tell you exactly how the score for each hit was calculated: ```auto GET wheat_syn/wheat/_search { "explain": true, "query": { "match": { "description": "wheat" } } } ``` Some suggestions: if you are looking at scores for a small dataset like this, consider creating the index with one shard (instead of the default 5). Otherwise the scoring may be unexpected as explained [here](https://www.elastic.co/guide/en/elasticsearch/guide/current/relevance-is-broken.html). Also, consider indexing the data twice: once with synonyms and once without synonyms. You can do that by using [multi-fields](https://www.elastic.co/guide/en/elasticsearch/reference/current/multi-fields.html). Your index creation command would become: ```auto PUT wheat_syn { "mappings": { "wheat": { "properties": { "description": { "type": "text", "fields": { "synonyms": { "type": "text", "analyzer": "syn_text" }, "keyword": { "type": "keyword", "ignore_above": 256 } } } } } }, "settings": { "number_of_shards": 1, "analysis": { "filter": { "autophrase_syn": { "type": "synonym", "synonyms": [ "triticum aestivum => triticum_aestivum", "bread wheat => bread_wheat" ] }, "wheat_syn": { "type": "synonym", "tokenizer": "keyword", "synonyms": [ "triticum_aestivum, bread_wheat, wheat" ] } }, "analyzer": { "syn_text": { "tokenizer": "standard", "filter": [ "lowercase", "autophrase_syn", "wheat_syn" ] } } } } } ``` Now, you can use a `bool` query to search simultaneously with and without synonyms: ```auto GET wheat_syn/wheat/_search { "query": { "bool": { "must": [ { "match": { "description.synonyms": "wheat" } } ], "should": [ { "match": { "description": { "query": "wheat" } } } ] } } } ``` Those documents that contain the exact term are the only ones that match the `should` clause (which does not use synonyms). As a result, those docs will get a higher score and rank at the top of the results. Synonyms can be tricky to set up correctly. We will soon launch an [on-demand training course about synonyms](https://www.elastic.co/training/specializations/elasticsearch-advanced-search/improving-search-with-synonyms) that covers topics like this. ---
**Author:** ![Bilal](https://avatars.discourse-cdn.com/v4/letter/b/3ab097/32.png) [@Bilal](https://discuss.elastic.co/u/Bilal)\ **Post date:** [October 16, 2018, 9:51am UTC](https://discuss.elastic.co/t/synonyms-result-scoring/152523/3 "2018-10-16T09:51:56Z")
Thank you for the detailed answer, the example you provided worked perfectly, now I understand why I had this unexpected results. In the link you provided ([Relevence is Broken !](https://www.elastic.co/guide/en/elasticsearch/guide/current/relevance-is-broken.html#relevance-is-broken)) it says: > In practice, this is not a problem. The differences between local and global IDF diminish the more documents that you add to the index. With real-world volumes of data, the local IDFs soon even out. The problem is not that relevance is broken but that there is too little data. Which explains a lot ! so in case I have a large dataset, Can your suggestions still be applied ? I mean, I can increase the number of shards and index my data twice without problems ? are there anythings that I shall take into account ? ---
**Author:** ![abdon](https://sea2.discourse-cdn.com/elastic/user_avatar/discuss.elastic.co/abdon/32/9195_2.png) [@abdon](https://discuss.elastic.co/u/abdon)\ **Post date:** [October 16, 2018, 10:16am UTC](https://discuss.elastic.co/t/synonyms-result-scoring/152523/4 "2018-10-16T10:16:45Z")
Yes, all of this should scale to however much data you have, and however many shards you have. I was just pointing out that with just three documents it does not make sense to have more than one shard. 🙂 ---
**Author:** ![softwaredoug](https://sea2.discourse-cdn.com/elastic/user_avatar/discuss.elastic.co/softwaredoug/32/22681_2.png) [@softwaredoug](https://discuss.elastic.co/u/softwaredoug)\ **Post date:** [November 10, 2018, 2:02pm UTC](https://discuss.elastic.co/t/synonyms-result-scoring/152523/5 "2018-11-10T14:02:53Z")
> [@abdon](#): > > - Synonyms score the same as an exact match. There is no automatic preference for exact matches. Just one note, this is a good default. But it's not always a good idea to assume that synonyms should be scored as equivalent. There's a set of practices that have built up in the search relevance community around using synonyms for a variety of reasons, including expansion to broadening terms which people want to score lower. I've put together a PR to make this behavior configurable in match / multi\_match queries (similar to a Solr patch accepted a while back - which makes this behavior configurable) > > > In Lucene, SynonymQuery became the default behavior for single term synonym quer…ies, which ES 6.0 inherited. While this is a good default, it interferes with other legitimate uses of synonyms. You don't always want to blend document frequencies of the terms. > > It's common to want to expand a term to a broadening term, but maintaining the specificity of the original term. (ie \`jeans =\> jeans, trousers\`). I and others have written about \[these techniques\](https://opensourceconnections.com/blog/2016/12/23/elasticsearch-synonyms-patterns-taxonomies/) for implementing hierarchical vocabularies. In these cases blending ends up doing more harm, so this PR makes this behavior configurable. > > This PR introduces an option to the match query, \`synonym\_query\_style\` which can have the values \`blended\` (default), \`most\_terms\`, or \`best\_terms\`. > > \`\`\` > { > "match": { > "text": { > "query": "blue jeans", > "synonym\_query\_style": "most\_terms" > } > } > } > \`\`\` > > with a synonym file \`jeans, trousers\` would turn into a search: \`text:jeans text:trousers\`. This is basically the pre 6.0 behavior. > > Using \`best\_terms\` changes the synonym query to a dismax \`text:jeans | text:trousers\` which tends to ignore the broader term in the narrower term is present. > > One note on this PR, > \- tests seem to be failing locally for me for unrelated functionality (transport client stuff...) > \- any feedback on where to place a test is greatly appreciated. I looked for how other match query options were tested and did not find anything. ---
**Author:** ![system](https://us1.discourse-cdn.com/elastic/original/3X/1/a/1ac57faf039f6b580b3f104ef42a2a89e41014de.png) [@system](https://discuss.elastic.co/u/system)\ **Post date:** [December 8, 2018, 2:02pm UTC](https://discuss.elastic.co/t/synonyms-result-scoring/152523/6 "2018-12-08T14:02:54Z")
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