[[query-dsl-regexp-query]] === Regexp Query The `regexp` query allows you to use regular expression term queries. See <> for details of the supported regular expression language. The "term queries" in that first sentence means that Elasticsearch will apply the regexp to the terms produced by the tokenizer for that field, and not to the original text of the field. *Note*: The performance of a `regexp` query heavily depends on the regular expression chosen. Matching everything like `.*` is very slow as well as using lookaround regular expressions. If possible, you should try to use a long prefix before your regular expression starts. Wildcard matchers like `.*?+` will mostly lower performance. [source,js] -------------------------------------------------- GET /_search { "query": { "regexp":{ "name.first": "s.*y" } } } -------------------------------------------------- // CONSOLE Boosting is also supported [source,js] -------------------------------------------------- GET /_search { "query": { "regexp":{ "name.first":{ "value":"s.*y", "boost":1.2 } } } } -------------------------------------------------- // CONSOLE You can also use special flags [source,js] -------------------------------------------------- GET /_search { "query": { "regexp":{ "name.first": { "value": "s.*y", "flags" : "INTERSECTION|COMPLEMENT|EMPTY" } } } } -------------------------------------------------- // CONSOLE Possible flags are `ALL` (default), `ANYSTRING`, `COMPLEMENT`, `EMPTY`, `INTERSECTION`, `INTERVAL`, or `NONE`. Please check the http://lucene.apache.org/core/4_9_0/core/org/apache/lucene/util/automaton/RegExp.html[Lucene documentation] for their meaning Regular expressions are dangerous because it's easy to accidentally create an innocuous looking one that requires an exponential number of internal determinized automaton states (and corresponding RAM and CPU) for Lucene to execute. Lucene prevents these using the `max_determinized_states` setting (defaults to 10000). You can raise this limit to allow more complex regular expressions to execute. [source,js] -------------------------------------------------- GET /_search { "query": { "regexp":{ "name.first": { "value": "s.*y", "flags" : "INTERSECTION|COMPLEMENT|EMPTY", "max_determinized_states": 20000 } } } } -------------------------------------------------- // CONSOLE include::regexp-syntax.asciidoc[]