Merge pull request #1183 from girder/reduce-pipeline-memory

Reduce memory use in a mongo aggregation pipeline
girder · May 30, 2023 · 7b20a92 · 7b20a92
2 parents 037e9dc + 0064a9b
commit 7b20a92
Show file tree

Hide file tree

Showing 2 changed files with 16 additions and 2 deletions.
diff --git a/CHANGELOG.md b/CHANGELOG.md
@@ -1,5 +1,10 @@
 # Change Log
 
+## 1.22.1
+
+### Improvements
+- Reduce memory use in a mongo aggregation pipeline ([#1183](../../pull/1183))
+
 ## 1.22.0
 
 ### Features

diff --git a/girder_annotation/girder_large_image_annotation/rest/annotation.py b/girder_annotation/girder_large_image_annotation/rest/annotation.py
@@ -630,8 +630,17 @@ def getFolderAnnotations(self, id, recurse, user, limit=False, offset=False, sor
         pipeline = recursivePipeline + [
             {'$lookup': {
                 'from': 'item',
-                'localField': '_id',
-                'foreignField': 'folderId',
+                # We have to use a pipeline to use a projection to reduce the
+                # data volume, so instead of specifying localField and
+                # foreignField, we set the localField to a variable, then match
+                # it in a pipeline and project to exclude everything but id.
+                # 'localField': '_id',
+                # 'foreignField': 'folderId',
+                'let': {'fid': '$_id'},
+                'pipeline': [
+                    {'$match': {'$expr': {'$eq': ['$$fid', '$folderId']}}},
+                    {'$project': {'_id': 1}}
+                ],
                 'as': '__items'
             }},
             {'$lookup': {