Fixup lookup

Author: nik9000

x-pack/plugin/esql/compute/src/main/java/org/elasticsearch/compute/lucene/read/ValuesSourceReaderOperator.java

@@ -43,6 +43,12 @@ public class ValuesSourceReaderOperator extends AbstractPageMappingToIteratorOpe
      * @param docChannel the channel containing the shard, leaf/segment and doc id
      */
     public record Factory(List<FieldInfo> fields, List<ShardContext> shardContexts, int docChannel) implements OperatorFactory {
+        public Factory {
+            if (fields.isEmpty()) {
+                throw new IllegalStateException("ValuesSourceReaderOperator doesn't support empty fields");
+            }
+        }
+
         @Override
         public Operator get(DriverContext driverContext) {
             return new ValuesSourceReaderOperator(driverContext.blockFactory(), fields, shardContexts, docChannel);
@@ -96,6 +102,9 @@ public record ShardContext(IndexReader reader, Supplier<SourceLoader> newSourceL
      * @param docChannel the channel containing the shard, leaf/segment and doc id
      */
     public ValuesSourceReaderOperator(BlockFactory blockFactory, List<FieldInfo> fields, List<ShardContext> shardContexts, int docChannel) {
+        if (fields.isEmpty()) {
+            throw new IllegalStateException("ValuesSourceReaderOperator doesn't support empty fields");
+        }
         this.fields = fields.stream().map(FieldWork::new).toArray(FieldWork[]::new);
         this.shardContexts = shardContexts;
         this.docChannel = docChannel;

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

@@ -350,8 +350,14 @@ private void doLookup(T request, CancellableTask task, ActionListener<List<Page>
                 warnings
             );
             releasables.add(queryOperator);
-            var extractFieldsOperator = extractFieldsOperator(shardContext.context, driverContext, request.extractFields);
-            releasables.add(extractFieldsOperator);
+
+            List<Operator> operators = new ArrayList<>();
+            if (request.extractFields.isEmpty() == false) {
+                var extractFieldsOperator = extractFieldsOperator(shardContext.context, driverContext, request.extractFields);
+                releasables.add(extractFieldsOperator);
+                operators.add(extractFieldsOperator);
+            }
+            operators.add(finishPages);
 
             /*
              * Collect all result Pages in a synchronizedList mostly out of paranoia. We'll
@@ -373,7 +379,7 @@ private void doLookup(T request, CancellableTask task, ActionListener<List<Page>
                 driverContext,
                 request::toString,
                 queryOperator,
-                List.of(extractFieldsOperator, finishPages),
+                operators,
                 outputOperator,
                 Driver.DEFAULT_STATUS_INTERVAL,
                 Releasables.wrap(shardContext.release, localBreaker)