Ensure STATS is working after RERANK / COMPLETION

Author: afoucret

x-pack/plugin/esql/qa/testFixtures/src/main/resources/completion.csv-spec

@@ -59,3 +59,17 @@ title:text                      | completion:keyword
 War and Peace                   | THIS IS A PROMPT: WAR AND PEACE
 War and Peace (Signet Classics) | THIS IS A PROMPT: WAR AND PEACE (SIGNET CLASSICS)
 ;                                                                                                                       
+
+completion followed by stats
+required_capability: completion
+required_capability: match_operator_colon
+
+FROM books METADATA _score
+| WHERE title:"war and peace" AND author:"Tolstoy"
+| COMPLETION CONCAT("This is a prompt: ", title) WITH { "inference_id" : "test_completion" }
+| STATS count=COUNT(*), avg_completion_length = AVG(LENGTH(completion))
+;
+
+count:long | avg_completion_length:double
+4          | 50.75
+;

x-pack/plugin/esql/qa/testFixtures/src/main/resources/rerank.csv-spec

@@ -294,3 +294,18 @@ The Lord of the Rings - Boxed Set                                | 3.76885509490
 Return of the King Being the Third Part of The Lord of the Rings | 3.6248698234558105 | 9.000900317914784E-4 | 0.001396648003719747
 // end::combine-result[]
 ;
+
+reranker followed by stats
+required_capability: rerank
+required_capability: match_operator_colon
+
+FROM books METADATA _score
+| WHERE title:"war and peace" AND author:"Tolstoy"
+| SORT _score DESC, book_no ASC
+| RERANK "war and peace" ON title WITH { "inference_id" : "test_reranker" }
+| STATS count_book = COUNT(*) WHERE _score >= 0.03
+;
+
+count_book:long
+2
+;