I have indexed all wikipedia pages on elasticsearch, and now I would like to search through them according to a list of keywords that I have created. The documents on elasticsearch have only three fields: id for the page id, title for the page title and content for the page content (already clean of wikipedia markup).
My goal is to reproduce the mediawiki query api as much as possible, with parameters action=query and list=search. For instance, given the keywords "non riemannian metric spaces", a call to
https://en.wikipedia.org/w/api.php?action=query&list=search&format=json&srlimit=10&srprop=&srsearch=non%20riemannian%20metric%20spaces
gives a list of the most relevant pages for those keywords.
So far I have been using rather simple elasticsearch search queries, like for instance
POST _search
{
"query": {
"bool" : {
"must" : {
"match" : {
"content": {
"query": "non riemannian metric spaces"
}
}
},
"should" : {
"match" : {
"title": {
"query": "non riemannian metric spaces",
"boost": x
}
}
}
}
}
}
for several values of boost, like 1, 2 or 0.5. This gives already some decent results, in the sense that the pages I obtain are relevant to the keywords, but sometimes they are not quite the same I get with the mediawiki api.
I would be glad to hear some suggestions on how to fine-tune the elasticsearch query to mimic more accurately the mediawiki api behavior. Or even, since the mediawiki api itself is built with elasticsearch and cirrussearch, I would like to know whether the actual elasticsearch query for the entry point above with those specific parameters is openly available.
Thank you in advance!
UPDATE (after Robis Koopmans' answer): Seeing the actual query with cirrusDumpQuery has indeed been very useful. I do however have some followup questions concerning the query:
The query has a set of similar multi_match clauses searching my keywords in fields like ["title.plain^1", "title^3"]. While I understand the ^n boost, I ignore what .plain refers to. Does it have to do with elasticsearch itself (i.e. is it a field derived from title at index time?) or is it something that has to do with the specific mediawiki mapping they use? In any case, I would appreciate some more information about this.
At some other point in the query, there is a {"match": {"all": {...}}} clause. What exactly is the all key here? Is it a document field? Is it related with the match_all clause?
What is the suggest field that appears in the query? In the score explanation it seems to be associated with synonyms. How are those handled in this case?
To be performed after the search, there is a rescore clause with two other score functions. One of them uses the popularity_score of a wikipedia page. What is that?
And finally, the most relevant score that ends up ranking the pages is the output of the sltr clause. In it, there is a "model": "enwiki-20220421-20180215-query_explorer", and in the score explanation it is identified with a LtrModel: naive_additive_decision_tree. I understand that this model is some stored LTR model. However, since it seems to be the most relevant number in the final sorting of the results, what exactly is that model and is it openly available?
Please feel free to answer whichever question you know the answer to, and again thanks a lot!
The query has a set of similar multi_match clauses searching my keywords in fields like ["title.plain^1", "title^3"]. While I understand the ^n boost, I ignore what .plain refers to. Does it have to do with elasticsearch itself (i.e. is it a field derived from title at index time?) or is it something that has to do with the specific mediawiki mapping they use? In any case, I would appreciate some more information about this.
The .plain fields are generated as part of the elasticsearch mapping. The current settings and mappings are available to see how exactly they work. mediawiki.org includes a search glossary entry on the plain field as well. In general the top level field contains a highly processed form of the text, and the plain field uses minimal analysis.
At some other point in the query, there is a {"match": {"all": {...}}} clause. What exactly is the all key here? Is it a document field? Is it related with the match_all clause?
mediawiki.org also contains an (incomplete) CirrusSearch schema that gives a brief description of these fields and the various analysis chain components used. The all field is an optimization to give a strong first-pass filter against the search index.
What is the suggest field that appears in the query? In the score explanation it seems to be associated with synonyms. How are those handled in this case?
Suggest field contains shingles (word ngrams) of the articles title and redirects, essentially a pre-calculation of phrase queries. The suggest might look like synonyms in the explain output, and they often contain those, but it also includes misspellings, translations, and numerous other reasons editors have for creating redirects. Matches on redirects are generally a strong relevance signal.
To be performed after the search, there is a rescore clause with two other score functions. One of them uses the popularity_score of a wikipedia page. What is that?
This is the fraction of page views on the wiki that go to that article.
And finally, the most relevant score that ends up ranking the pages is the output of the sltr clause. In it, there is a "model": "enwiki-20220421-20180215-query_explorer", and in the score explanation it is identified with a LtrModel: naive_additive_decision_tree. I understand that this model is some stored LTR model. However, since it seems to be the most relevant number in the final sorting of the results, what exactly is that model and is it openly available?
This model is generated by mjolnir and essentially overwrites the score from the rest of the query. There is some information in wikitech (found there as it is more specific to the WMF deployment of mediawiki than mediawiki itself), also a slide deck called From Clicks to Models might give some insight into whats happening in that code base. Perhaps important to know mjolnir only applies to bag of words queries, queries invoking phrases or other expert functionality skip the ML model.
Noone had asked for the models before, if they might be useful i dumped the current models from the ranking plugin. This contains both the feature definitions used and the decision trees generated by xgboost.
I didn't find an excuse to link it above, but maybe the draft page at CirrusSearch/Scoring that mentions some of the factors that go into retrieval and scoring, particularly for queries that can't be run through mjolnir models, might help as well.
You can add cirrusDumpQuery to your query
example:
https://en.wikipedia.org/w/index.php?title=Special:Search&cirrusDumpQuery=&search=cat+dog+chicken&ns0=1
more information:
https://www.mediawiki.org/wiki/Extension:CirrusSearch#API
You can't make Elasticsearch queries to Wikipedia directly, but CirrusSearch can generate many types of queries beyond fulltext search. It's not clear from your question exactly what type of query you are looking for, but it might be worth to look at sorting options, if you prefer to weight results by text similarity only, and not things like page views.
We have a requirement that we think is a candidate for a Multi-Search query but we are not sure.
Say we are selling clothes.
The user can enter a type of clothing such as Shirts and we bring back all the shirts using a filter.
We would also like to provide the user with an option of them typing in a keyword such as "formal" or "beach" etc. But this keyword should not effect the results but identify with a flag which items in the results these keywords appear.
Any suggestion would be greatly appreciated.
What about using Named Queries?
The ideas is that this feature of Elasticsearch allows users to mark each clause in the query with a _name value identifying the particular clause. If the particular clauses, say a clause with "formal" keyword or a clause with "beach" keyword", are matched, the response will include a matched_queries prop with each result noting which particular item was matched.
Another option might be to use Highlights. The feature does allow you to specify a separate highlighting query. However, the response format here may not be as straightforward or meet your requirements.
What I'm trying to accomplish on a high level is an autocomplete input field which queries both customers and orders on multiple fields, with customers ranking higher for customer name searches.
It seems to me that there are various ways to approach this problem with the tools that elasticsearch provides.
The way that I have approached this is to use multi_match queries with prefix_phrase type in order to get partial queries to work across multiple fields.
For example, "bo" should return back matches for "Bob Smith" as well as "Adam Boss". I'm indexing fullname as a separate field from firstname and lastname, so that "adam boss" will return a valid prefix match as well.
In addition, I'd like to boost customer results - trying to do that with a boost param on the multi_match, but that doesn't seem to be working the way I'd expect it to.
What would be a straight forward way to tackle this problem?
One of the challenges I'm facing with the elasticsearch docs is that it's not always clear which properties and features apply to which others. For example, the multi_match documentation doesn't talk about using a custom boost, other than on a field-level.
I think the best way is using completion suggester of ES (v0.90.3+), please refer here for a real use case:
http://www.elasticsearch.org/blog/you-complete-me/
http://www.elasticsearch.org/guide/en/elasticsearch/reference/current/search-suggesters-completion.html
I'm integrating elasticsearch into an asset tracking application. When I setup the mapping initially, I envisioned the 'brand' field being a single-term field like 'Hitachi', or 'Ford'. Instead, I'm finding that the brand field in the actual data contains multiple terms like: "MB 7 A/B", "B-7" or even "Brush Bull BB72X".
I have an autocomplete component setup now that I configured to do autocomplete against an edgeNGram field, and perform the actual search against an nGram field. It's completely useless the way I set it up because users expect the search results to be restricted to what the autocomplete matches.
Any suggestions on the best way to setup my mapping to support autocomplete and subsequent searches against a multiple term field like this? I'm considering a terms query against a keyword field, or possibly a match query with 'and' as the operator? I also have to deal with hyphens like "B-7".
you can use phrase suggest, the guide is here:
http://www.elasticsearch.org/guide/en/elasticsearch/reference/current/search-suggesters.html
the phrase suggest guide is here:
http://www.elasticsearch.org/guide/en/elasticsearch/reference/current/search-suggesters-phrase.html
I have googled a lot and also searched in stackoverflow.com about how to sort search results based on a Field Value in Lucene 3.0.2, but not found any useful data. I'm getting the search results from the index, based on the user query but not able to sort the results based on field like id or date.
I have pasted my code here for searching lucene index- http://pastie.org/1033974.
Please help me to solve this problem. If you provide me some example code or links where i can find that will be better.
Thanks
The IndexSearcher class has a couple of search methods that takes a Sort Object that you have to use. A Sort object is basically a wrapper around one or more SortField objects which hold details on what field to sort on and how.
Note that a field must be indexed to be used for sorting.