SERVER-61284: Support simple projection optimization for simple exclusion projections

2 files changed, 12 insertions, 9 deletions

diff --git a/jstests/aggregation/bugs/exclusion_projection_does_not_affect_field_order.js b/jstests/aggregation/bugs/exclusion_projection_does_not_affect_field_order.js
index 4bc45bccef5..09d2239389a 100644
--- a/jstests/aggregation/bugs/exclusion_projection_does_not_affect_field_order.js
+++ b/jstests/aggregation/bugs/exclusion_projection_does_not_affect_field_order.js
@@ -2,6 +2,10 @@
 // changes.
 //
 // This is designed as a regression test for SERVER-37791.
+// @tags: [
+//   do_not_wrap_aggregations_in_facets,
+//   requires_fcv_62,
+// ]
 (function() {
 "use strict";
 
@@ -13,13 +17,14 @@ assert.commandWorked(coll.insert({_id: 2, c: 1}));
 assert.commandWorked(coll.insert({_id: 3, y: 1, z: 1}));
 
 // We expect $addFields to retain the position of pre-existing fields, and then append new fields in
-// the order that they are specified in the query. This rule should not be impacted by the presence
-// of a preceding exclusion projection.
+// the order that they are specified in the query. This rule should not be impacted by exclusion
+// projection on non-existent fields. However, depending on projection implementation, excluding a
+// field that already exists can affect $addFields behaviour: an excluded field can be put in
+// the original place or appended to the end of the document.
 assert.eq(
     [
         {_id: 1, x: 3, y: 4, b: 5, c: 6, a: 7},
-        // Here "c" retains the position that it had prior to being excluded.
-        {_id: 2, c: 6, x: 3, y: 4, b: 5, a: 7},
+        {_id: 2, x: 3, y: 4, b: 5, c: 6, a: 7},
         {_id: 3, y: 4, z: 1, x: 3, b: 5, c: 6, a: 7}
     ],
     coll.aggregate([
diff --git a/jstests/aggregation/optimize_away_pipeline.js b/jstests/aggregation/optimize_away_pipeline.js
index 36921f42c34..d08bde70f5d 100644
--- a/jstests/aggregation/optimize_away_pipeline.js
+++ b/jstests/aggregation/optimize_away_pipeline.js
@@ -690,13 +690,11 @@ projStage = getAggPlanStage(explain, "PROJECTION_SIMPLE");
 assert.neq(null, projStage, explain);
 assertTransformByShape({a: 1, b: 1, _id: 0}, projStage.transformBy, explain);
 
-// Test that an exclusion projection at the front of the pipeline is not pushed down, if there no
+// Test that an exclusion projection at the front of the pipeline is pushed down if there is no
 // finite dependency set.
 pipeline = [{$project: {x: 0}}];
-assertPipelineUsesAggregation({pipeline: pipeline, expectedStages: ["COLLSCAN"]});
-explain = coll.explain().aggregate(pipeline);
-assert(!planHasStage(db, explain, "PROJECTION_SIMPLE"), explain);
-assert(!planHasStage(db, explain, "PROJECTION_DEFAULT"), explain);
+assertPipelineDoesNotUseAggregation(
+    {pipeline: pipeline, expectedStages: ["PROJECTION_SIMPLE", "COLLSCAN"]});
 
 // Test that a computed projection at the front of the pipeline is pushed down, even if there's no
 // finite dependency set.