From 26ee6582c87299114d070e13b3af1f11a63041c7 Mon Sep 17 00:00:00 2001
From: Tara Drwenski <tdrwenski@ucar.edu>
Date: Mon, 15 Apr 2024 13:30:00 +0200
Subject: [PATCH] Fix renamed dimension in aggregations where refGroup may be
 null

---
 .../src/main/java/ucar/nc2/internal/ncml/NcmlReader.java    | 6 ++++--
 1 file changed, 4 insertions(+), 2 deletions(-)

diff --git a/cdm/core/src/main/java/ucar/nc2/internal/ncml/NcmlReader.java b/cdm/core/src/main/java/ucar/nc2/internal/ncml/NcmlReader.java
index 9d316d9d02..df76a96854 100644
--- a/cdm/core/src/main/java/ucar/nc2/internal/ncml/NcmlReader.java
+++ b/cdm/core/src/main/java/ucar/nc2/internal/ncml/NcmlReader.java
@@ -810,9 +810,11 @@ private void readDim(Group.Builder groupBuilder, @Nullable Group refGroup, Eleme
 
     String nameInFile = dimElem.getAttributeValue("orgName") != null ? dimElem.getAttributeValue("orgName") : name;
 
-    // LOOK this is wrong, groupBuilder may already have the dimension.
     // see if it already exists
-    Dimension dim = (refGroup == null) ? null : refGroup.findDimension(nameInFile);
+    Optional<Dimension> dimFromAgg = groupBuilder.findDimension(nameInFile);
+    Dimension dim =
+        (refGroup == null || dimFromAgg.isPresent()) ? dimFromAgg.orElse(null) : refGroup.findDimension(nameInFile);
+
     if (dim == null) { // nope - create it
       String lengthS = dimElem.getAttributeValue("length");
       if (lengthS == null) {