[role="xpack"]
[testenv="basic"]
[[eql-limitations]]
== EQL limitations
++++
<titleabbrev>Limitations</titleabbrev>
++++

dev::[]

[discrete]
[[eql-nested-fields]]
=== EQL search on nested fields is not supported

You cannot use EQL to search the values of a <<nested,`nested`>> field or the
sub-fields of a `nested` field. However, indices containing `nested` field
mappings are otherwise supported.

[discrete]
[[eql-unsupported-syntax]]
=== Unsupported syntax

{es} supports a subset of {eql-ref}/index.html[EQL syntax]. {es} cannot run EQL
queries that contain:

* Array functions:
** {eql-ref}/functions.html#arrayContains[`arrayContains`]
** {eql-ref}/functions.html#arrayCount[`arrayCount`]
** {eql-ref}/functions.html#arraySearch[`arraySearch`]

* {eql-ref}/joins.html[Joins]

* {eql-ref}/basic-syntax.html#event-relationships[Lineage-related keywords]:
** `child of`
** `descendant of`
** `event of`

* The following {eql-ref}/pipes.html[pipes]:
** {eql-ref}/pipes.html#count[`count`]
** {eql-ref}/pipes.html#filter[`filter`]
** {eql-ref}/pipes.html#sort[`sort`]
** {eql-ref}/pipes.html#unique[`unique`]
** {eql-ref}/pipes.html#unique-count[`unique_count`]

* {eql-ref}/sequences.html[State and timespan-related sequence keywords]:
** `with maxspan`
** `until`