Include release highlight for query rewrite

docs/changelog/96161.yaml

@@ -4,3 +4,21 @@ area: "Search"
 type: enhancement
 issues:
  - 95541
+highlight:
+  title: Better indexing and search performance under concurrent indexing and search
+  body: "When a query like a match phrase query or a terms query targets a constant keyword field \
+  we can skip the query execution on shards where the query is rewritten to match no documents.\
+  We take advantage of index mappings including constant keyword fields and rewrite queries in such a way that, if\
+  a constant keyword field does not match a value defined in the index mapping we rewrite the query to match no\
+  document. This will result in the shard level request to return immediately, before the query is executed on the data\
+  node and, as a result, skipping the shard completely. In a real world scenario it is likely that index patterns or\
+  data streams include tens or hundreds of backing indices each of them with multiple shards involved. Skipping shards\
+  in such scenario might result in better query performance and better cluster resource usage. Note, anyway, that\
+  execution of the pre-filter and the corresponding \"can match\" phase where rewriting happens, depends on the overall
+  number of shards involved and on whether there is at least one of them returning a non-empty result (see\
+  'pre_filter_shard_size' setting to understand how to control this behaviour). We do the rewrite operation on the data\
+  node in the so called \"can match\" phase, taking advantage of the fact that, at that moment, we can access the index\
+  mapping and extract information about constant keyword fields and their value. This means we still \"fan-out\" the\
+  request from the coordinator node to involved data nodes. Doing the rewrite on the coordinator node is indeed not\
+  possible due to the unavailability of the index mapping."
+  notable: true