Update docs for v8.17.9 release (#131142)

Author: elasticsearchmachine

docs/reference/release-notes.asciidoc

@@ -6,6 +6,7 @@
 
 This section summarizes the changes in each release.
 
+* <<release-notes-8.17.9>>
 * <<release-notes-8.17.8>>
 * <<release-notes-8.17.7>>
 * <<release-notes-8.17.6>>
@@ -91,6 +92,7 @@ This section summarizes the changes in each release.
 
 --
 
+include::release-notes/8.17.9.asciidoc[]
 include::release-notes/8.17.8.asciidoc[]
 include::release-notes/8.17.7.asciidoc[]
 include::release-notes/8.17.6.asciidoc[]

docs/reference/release-notes/8.17.9.asciidoc

@@ -0,0 +1,30 @@
+[[release-notes-8.17.9]]
+== {es} version 8.17.9
+
+coming[8.17.9]
+
+Also see <<breaking-changes-8.17,Breaking changes in 8.17>>.
+
+[[bug-8.17.9]]
+[float]
+=== Bug fixes
+
+Aggregations::
+* Aggs: Add cancellation checks to `FilterByFilter` aggregator {es-pull}130452[#130452]
+
+ES|QL::
+* Avoid O(N^2) in VALUES with ordinals grouping {es-pull}130576[#130576]
+* Avoid dropping aggregate groupings in local plans {es-pull}129370[#129370] (issues: {es-issue}129811[#129811], {es-issue}128054[#128054])
+* Fix `BytesRef2BlockHash` {es-pull}130705[#130705]
+
+Search::
+* Fix msearch request parsing when index expression is null {es-pull}130776[#130776] (issue: {es-issue}129631[#129631])
+
+[[upgrade-8.17.9]]
+[float]
+=== Upgrades
+
+Packaging::
+* Update default docker base image to Ubuntu 24.04 {es-pull}130277[#130277]
+
+