docs: add paragraph about using `percolate` query in a filter context

docs/reference/query-dsl/percolate-query.asciidoc

@@ -144,6 +144,42 @@ In that case the `document` parameter can be substituted with the following para
 `preference`:: Optionally, preference to be used to fetch document to percolate.
 `version`:: Optionally, the expected version of the document to be fetched.
 
+[float]
+==== Percolating in a filter context
+
+In case you are not interested in the score, better performance can be expected by wrapping
+the percolator query in a `bool` query's filter clause or in a `constant_score` query:
+
+[source,js]
+--------------------------------------------------
+GET /my-index/_search
+{
+    "query" : {
+        "constant_score": {
+            "filter": {
+                "percolate" : {
+                    "field" : "query",
+                    "document" : {
+                        "message" : "A new bonsai tree in the office"
+                    }
+                }
+            }
+        }
+    }
+}
+--------------------------------------------------
+// CONSOLE
+// TEST[continued]
+
+At index time terms are extracted from the percolator query and the percolator
+can often determine whether a query matches just by looking at those extracted
+terms. However, computing scores requires to deserialize each matching query
+and run it against the percolated document, which is a much more expensive
+operation. Hence if computing scores is not required the `percolate` query
+should be wrapped in a `constant_score` query or a `bool` query's filter clause.
+
+Note that the `percolate` query never gets cached by the query cache.
+
 [float]
 ==== Percolating multiple documents