Elasticsearch difference between MUST and SHOULD bool query

Question

What is the difference between MUST and SHOULD bool query in ES   If I ONLY want results that contain my terms should I then use must    I have a query that should only contain certain values  and also no results that has a lower date timestamp than todays time date - NOW  Also  Can i use multiple filters inside a must like the code bellow    filtered      filter      bool               must                   term       type    1                term       totals    14                term       groupId    3                range                       expires                           gte    now

User · Accepted Answer

must means  The clause  query  must appear in matching documents  These clauses must match  like logical AND   should means  At least one of these clauses must match  like logical OR   Basically they are used like logical operators AND and OR  See this   Now in a bool query   must means  Clauses that must match for the document to be included   should means  If these clauses match  they increase the  score  otherwise  they have no effect  They are simply used to refine the relevance score for each document     Yes you can use multiple filters inside must

User · Answer

As said in the documentation      Must  The clause  query  must appear in matching documents       Should  The clause  query  should appear in the matching document  In a boolean query with no must clauses  one or more should clauses must match a document  The minimum number of should clauses to match can be set using the minimum should match parameter    In other words  results will have to be matched by all the queries present in the must clause   or match at least one of the should clauses if there is no must clause   Since you want your results to satisfy all the queries  you should use must     You can indeed use filters inside a boolean query

User · Answer

Since this is a popular question  I would like to add that in Elasticsearch version 2 things changed a bit   Instead of filtered query  one should use bool query in the top level   If you don t care about the score of must parts  then put those parts into filter key  No scoring means faster search  Also  Elasticsearch will automatically figure out  whether to cache them  etc  must not is equally valid for caching   Reference  https   www elastic co guide en elasticsearch reference current query-dsl-bool-query html  Also  mind that  gte    now  cannot be cached  because of millisecond granularity  Use two ranges in a must clause  one with now 1h and another with now so that the first can be cached for a while and the second for precise filtering accelerated on a smaller result set

[elasticsearch] Elasticsearch difference between MUST and SHOULD bool query

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