[ES|QL] Compare query builders using identity (#139080) (#139136)

(cherry picked from commit afa1ea9)

# Conflicts:
#	x-pack/plugin/esql/src/main/java/org/elasticsearch/xpack/esql/expression/function/fulltext/SingleFieldFullTextFunction.java

Author: Mikep86

docs/changelog/139080.yaml

@@ -0,0 +1,5 @@
+pr: 139080
+summary: "[ES|QL] Compare query builders using identity"
+area: "ES|QL"
+type: bug
+issues: []

x-pack/plugin/esql/src/main/java/org/elasticsearch/xpack/esql/expression/function/fulltext/FullTextFunction.java

@@ -149,7 +149,7 @@ public String functionType() {
 
     @Override
     public int hashCode() {
-        return Objects.hash(super.hashCode(), query, queryBuilder);
+        return Objects.hash(super.hashCode(), query, System.identityHashCode(queryBuilder));
     }
 
     @Override
@@ -158,7 +158,9 @@ public boolean equals(Object obj) {
             return false;
         }
 
-        return Objects.equals(queryBuilder, ((FullTextFunction) obj).queryBuilder) && Objects.equals(query, ((FullTextFunction) obj).query);
+        // Compare query builders using identity because that's how they are compared during query rewriting
+        FullTextFunction other = (FullTextFunction) obj;
+        return queryBuilder == other.queryBuilder && Objects.equals(query, other.query);
     }
 
     @Override