Fix failing UTs part 2

Author: julian-elastic

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

@@ -5163,6 +5163,9 @@ FROM multi_column_joinable
 | LIMIT 20
 ;
 
+warning:Line 2:3: evaluation of [LOOKUP JOIN multi_column_joinable_lookup ON id_int, is_active_bool] failed, treating result as null. Only first 20 failures recorded.
+warning:Line 2:3: java.lang.IllegalArgumentException: LOOKUP JOIN encountered multi-value
+
 id_int:integer | name_str:keyword | extra1:keyword | other1:keyword | other2:integer
 4              | David            | qux            | zeta           | 6000
 5              | Eve              | quux           | eta            | 7000
@@ -5188,6 +5191,9 @@ FROM multi_column_joinable
 | LIMIT 20
 ;
 
+warning:Line 2:3: evaluation of [LOOKUP JOIN multi_column_joinable_lookup ON id_int, is_active_bool] failed, treating result as null. Only first 20 failures recorded.
+warning:Line 2:3: java.lang.IllegalArgumentException: LOOKUP JOIN encountered multi-value
+
 id_int:integer | name_str:keyword | extra1:keyword | other1:keyword | other2:integer
 4              | David            | qux            | zeta           | 6000
 5              | Eve              | quux           | eta            | 7000
@@ -5242,6 +5248,11 @@ FROM multi_column_joinable
 | LIMIT 20
 ;
 
+warning:Line 2:3: evaluation of [LOOKUP JOIN multi_column_joinable_lookup ON id_int, is_active_bool] failed, treating result as null. Only first 20 failures recorded.
+warning:Line 2:3: java.lang.IllegalArgumentException: LOOKUP JOIN encountered multi-value
+warning:Line 3:23: evaluation of [id_int + 5000] failed, treating result as null. Only first 20 failures recorded.
+warning:Line 3:23: java.lang.IllegalArgumentException: single-value function encountered multi-value
+
 id_int:integer | name_str:keyword | extra1:keyword | other1:keyword | other2:integer
 4              | David            | qux            | zeta           | 6000
 5              | Eve              | quux           | eta            | 7000
@@ -5267,6 +5278,11 @@ lookupJoinWithMixJoinAndNonJoinColumnsPushable
  | LIMIT 20
  ;
 
+warning:Line 2:3: evaluation of [LOOKUP JOIN multi_column_joinable_lookup ON id_int, is_active_bool] failed, treating result as null. Only first 20 failures recorded.
+warning:Line 2:3: java.lang.IllegalArgumentException: LOOKUP JOIN encountered multi-value
+warning:Line 3:18: evaluation of [id_int + 5000] failed, treating result as null. Only first 20 failures recorded.
+warning:Line 3:18: java.lang.IllegalArgumentException: single-value function encountered multi-value
+ 
  id_int:integer | name_str:keyword | extra1:keyword | other1:keyword | other2:integer
  4              | David            | qux            | zeta           | 6000
  5              | Eve              | quux           | eta            | 7000
@@ -5291,6 +5307,9 @@ lookupJoinWithMixJoinAndNonJoinColumnsPushable
  | LIMIT 20
  ;
 
+warning:Line 3:9: evaluation of [id_int > 7] failed, treating result as null. Only first 20 failures recorded.
+warning:Line 3:9: java.lang.IllegalArgumentException: single-value function encountered multi-value
+ 
 id_int:integer | name_str:keyword | extra1:keyword | other1:keyword | other2:integer
 8              | Hank             | garply         | lambda         | 11000
 9              | null             | waldo          | null           | null
@@ -5316,6 +5335,9 @@ lookupJoinWithExpressionOfOtherFields
       NEED TO DEBUG WHY THE FILTER IS NOT PUSHED TO THE RIGHT SIDE OF THE LOOKUP JOIN
    */
   ;
+
+warning:Line 2:3: evaluation of [LOOKUP JOIN multi_column_joinable_lookup ON id_int, is_active_bool] failed, treating result as null. Only first 20 failures recorded.
+warning:Line 2:3: java.lang.IllegalArgumentException: LOOKUP JOIN encountered multi-value
 
 id_int:integer | name_str:keyword | extra1:keyword | other1:keyword | other2:integer
 5              | Eve              | quux           | eta            | 7000

x-pack/plugin/esql/src/main/java/org/elasticsearch/xpack/esql/enrich/ExpressionQueryList.java

@@ -55,7 +55,7 @@ public ExpressionQueryList(
 
     private void buildPrePostJoinFilter(PhysicalPlan rightPreJoinPlan, ClusterService clusterService) {
         // we support a FilterExec as the pre-join filter
-        // if we filter Exec is not translatable to a QueryBuilder, we will apply it after the join
+        // if the filter Exec is not translatable to a QueryBuilder, we will apply it after the join
         if (rightPreJoinPlan instanceof FilterExec filterExec) {
             try {
                 LucenePushdownPredicates lucenePushdownPredicates = LucenePushdownPredicates.from(

x-pack/plugin/esql/src/main/java/org/elasticsearch/xpack/esql/enrich/LookupFromIndexService.java

@@ -277,9 +277,11 @@ public void writeTo(StreamOutput out) throws IOException {
             }
             if (out.getTransportVersion().onOrAfter(TransportVersions.ESQL_LOOKUP_JOIN_PRE_JOIN_FILTER)) {
                 planOut.writeOptionalNamedWriteable(rightPreJoinPlan);
-            } else if (rightPreJoinPlan != null) {
-                throw new EsqlIllegalArgumentException("LOOKUP JOIN with pre-join filter is not supported on remote node");
             }
+            // JULIAN TODO: need a better way to indicate that the filter does not need to be applied here
+            /*else if (rightPreJoinPlan != null) {
+                throw new EsqlIllegalArgumentException("LOOKUP JOIN with pre-join filter is not supported on remote node");
+            }*/
         }
 
         @Override