[Discover] Restore context documentation

docs/discover/context.asciidoc

@@ -0,0 +1,62 @@
+[[discover-document-context]]
+== View a document in context
+
+Once you've narrowed your search to a specific event,
+you might want to inspect the documents that occurred
+immediately before and after the event. With the Context view,
+you can do just that for index patterns that contain time-based events.
+
+To open the Context view, click the expand icon (>) in the document table, and then click
+*View surrounding documents.*
+
+The documents are sorted by the time field specified in the index pattern 
+and displayed using the same set of columns as the *Discover* view from which 
+the context was opened. The anchor document is highlighted in blue.
+
+
+[role="screenshot"]
+image::images/Discover-ContextView.png[Image showing context view feature, with anchor documents highlighted in blue]
+
+[float]
+[[filter-context]]
+=== Filter the context
+
+The filters you applied in *Discover* are carried over to the Context view. 
+Pinned filters remain active, while normal filters are copied in a disabled state. 
+You can re-enable these filters to refine your context view.
+
+If the Context view contains a large number of documents not related to the event under
+investigation, you can use filters to restrict the documents to display.
+
+[float]
+[[change-context-size]]
+=== Change the number of surrounding documents
+
+By default, the five newest and oldest
+documents are listed. To increase the number of documents that surround the anchor document,
+click *Load*. Five documents are added with each click.
+
+[float]
+[[configure-context-ContextView]]
+=== Configure the context view
+
+To configure the Context view, use these settings in <<advanced-options,
+Advanced Settings>>.
+
+[horizontal]
+`context:defaultSize`:: The number of documents to display by default.
+`context:step`:: The default number of documents to load with each button click.
+`context:tieBreakerFields`:: The field to use for tiebreaking in case of equal time field values.
+The default is the `_doc` field.
++
+You can enter a comma-separated list of field
+names, which is checked in sequence for suitability when a context is
+displayed. The first suitable field is used as the tiebreaking
+field. A field is suitable if the field exists and is sortable in the index
+pattern the context is based on.
++
+Although not required, it is recommended to only
+use fields that have {ref}/doc-values.html[doc values] enabled to achieve
+good performance and avoid unnecessary {ref}/modules-fielddata.html[field
+data] usage. Common examples for suitable fields include log line numbers,
+monotonically increasing counters and high-precision timestamps.

docs/user/discover.asciidoc

@@ -161,7 +161,8 @@ image:images/document-table-expanded.png[Table view with document expanded]
 . Scan through the fields and their values. If you find a field of interest,
 hover of its name for filters and other controls.
 
-. To view documents that occurred before or after the event you are looking at, click **View surrounding documents**.
+. To view documents that occurred before or after the event you are looking at, click
+<<discover-document-context, View surrounding documents>>.
 
 . For direct access to a particular document, click **View single document**.
 +
@@ -216,3 +217,7 @@ include::{kib-repo-dir}/management/index-patterns.asciidoc[]
 include::{kib-repo-dir}/discover/set-time-filter.asciidoc[]
 
 include::{kib-repo-dir}/discover/search.asciidoc[]
+
+include::{kib-repo-dir}/discover/context.asciidoc[]
+
+