Query DSL
editQuery DSL
editElasticsearch provides a full Query DSL (Domain Specific Language) based on JSON to define queries. Think of the Query DSL as an AST (Abstract Syntax Tree) of queries, consisting of two types of clauses:
- Leaf query clauses
-
Leaf query clauses look for a particular value in a particular field, such as the
match
,term
orrange
queries. These queries can be used by themselves. - Compound query clauses
-
Compound query clauses wrap other leaf or compound queries and are used to combine
multiple queries in a logical fashion (such as the
bool
ordis_max
query), or to alter their behaviour (such as theconstant_score
query).
Query clauses behave differently depending on whether they are used in query context or filter context.
- Allow expensive queries
-
Certain types of queries will generally execute slowly due to the way they are implemented, which can affect the stability of the cluster. Those queries can be categorised as follows:
-
Queries that need to do linear scans to identify matches:
-
script
queries - queries on numeric, date, boolean, ip, geo_point or keyword fields that are not indexed but have doc values enabled
-
-
Queries that have a high up-front cost:
-
fuzzy
queries (except onwildcard
fields) -
regexp
queries (except onwildcard
fields) -
prefix
queries (except onwildcard
fields or those withoutindex_prefixes
) -
wildcard
queries (except onwildcard
fields) -
range
queries ontext
andkeyword
fields
-
- Joining queries
-
Queries that may have a high per-document cost:
-
The execution of such queries can be prevented by setting the value of the search.allow_expensive_queries
setting to false
(defaults to true
).