ESQL: More specific index pattern in testMultipleBatchesWithLookupJoin (#130006)

* Specific idx in testMultipleBatchesWithLookupJoin

Do not use `from *` in the test, be more specifc - otherwise other tests
can affect the output if they leave indices behind, affecting the column
count.

* Remove column count validation

That doesn't really tell us much in this test, anyway.

Author: alex-spies

x-pack/plugin/esql/qa/server/src/main/java/org/elasticsearch/xpack/esql/qa/rest/RestEsqlTestCase.java

@@ -1014,21 +1014,22 @@ public void testMultipleBatchesWithLookupJoin() throws IOException {
         // Create more than 10 indices to trigger multiple batches of data node execution.
         // The sort field should be missing on some indices to reproduce NullPointerException caused by duplicated items in layout
         for (int i = 1; i <= 20; i++) {
-            createIndex("idx" + i, randomBoolean(), "\"mappings\": {\"properties\" : {\"a\" : {\"type\" : \"keyword\"}}}");
+            createIndex("no_sort_field_idx" + i, randomBoolean(), "\"mappings\": {\"properties\" : {\"a\" : {\"type\" : \"keyword\"}}}");
         }
         bulkLoadTestDataLookupMode(10);
         // lookup join with and without sort
         for (String sort : List.of("", "| sort integer")) {
-            var query = requestObjectBuilder().query(format(null, "from * | lookup join {} on integer {}", testIndexName(), sort));
+            var query = requestObjectBuilder().query(
+                format(null, "from {},no_sort_field_idx* | lookup join {} on integer {}", testIndexName(), testIndexName(), sort)
+            );
             Map<String, Object> result = runEsql(query);
             var columns = as(result.get("columns"), List.class);
-            assertEquals(22, columns.size());
             var values = as(result.get("values"), List.class);
             assertEquals(10, values.size());
         }
         // clean up
         for (int i = 1; i <= 20; i++) {
-            assertThat(deleteIndex("idx" + i).isAcknowledged(), is(true));
+            assertThat(deleteIndex("no_sort_field_idx" + i).isAcknowledged(), is(true));
         }
     }