SERVER-24981 Rewrite $limit optimization

1 files changed, 82 insertions, 0 deletions

diff --git a/jstests/sharding/agg_project_limit_pipe_split.js b/jstests/sharding/agg_project_limit_pipe_split.js
new file mode 100644
index 00000000000..010cd46c46e
--- /dev/null
+++ b/jstests/sharding/agg_project_limit_pipe_split.js
@@ -0,0 +1,82 @@
+// Tests that the correct number of results are returned when $limit is coalesced with $sort.
+(function() {
+    "use strict";
+    load("jstests/libs/analyze_plan.js");
+
+    const shardingTest = new ShardingTest({shards: 2});
+    const db = shardingTest.getDB("project_limit");
+    const coll = db.project_limit_pipe_split;
+    coll.drop();
+    assert.commandWorked(shardingTest.s0.adminCommand({enableSharding: db.getName()}));
+    assert.commandWorked(
+        shardingTest.s0.adminCommand({shardCollection: coll.getFullName(), key: {_id: "hashed"}}));
+    const bulkOp = coll.initializeOrderedBulkOp();
+    for (let i = 0; i < 400; ++i) {
+        bulkOp.insert({x: i, y: ["a", "b", "c"], z: Math.floor(i / 12)});
+    }
+    assert.writeOK(bulkOp.execute());
+
+    let agg = coll.aggregate([
+        {$match: {$or: [{z: 9}, {z: 10}]}},
+        {$sort: {x: -1}},
+        {$project: {x: 1, y: 1, z: 1, _id: 0}},
+        {$limit: 6},
+    ]);
+    assert.eq(
+        [
+          {"x": 131, "y": ["a", "b", "c"], "z": 10},
+          {"x": 130, "y": ["a", "b", "c"], "z": 10},
+          {"x": 129, "y": ["a", "b", "c"], "z": 10},
+          {"x": 128, "y": ["a", "b", "c"], "z": 10},
+          {"x": 127, "y": ["a", "b", "c"], "z": 10},
+          {"x": 126, "y": ["a", "b", "c"], "z": 10}
+        ],
+        agg.toArray());
+
+    agg = coll.aggregate([
+        {$sort: {x: 1}},
+        {$redact: "$$KEEP"},
+        {$project: {x: 1, y: 1, z: 1, _id: 0}},
+        {$limit: 6}
+    ]);
+    assert.eq(
+        [
+          {"x": 0, "y": ["a", "b", "c"], "z": 0},
+          {"x": 1, "y": ["a", "b", "c"], "z": 0},
+          {"x": 2, "y": ["a", "b", "c"], "z": 0},
+          {"x": 3, "y": ["a", "b", "c"], "z": 0},
+          {"x": 4, "y": ["a", "b", "c"], "z": 0},
+          {"x": 5, "y": ["a", "b", "c"], "z": 0}
+        ],
+        agg.toArray());
+
+    agg = coll.aggregate(
+        [{$sort: {x: -1}}, {$skip: 399}, {$project: {x: 1, y: 1, z: 1, _id: 0}}, {$limit: 6}]);
+    assert.eq([{"x": 0, "y": ["a", "b", "c"], "z": 0}], agg.toArray());
+
+    agg = coll.aggregate(
+        [{$sort: {x: -1}}, {$project: {x: 1, y: 1, z: 1, _id: 0}}, {$skip: 401}, {$limit: 6}]);
+    assert.eq(0, agg.itcount());
+
+    agg = coll.aggregate([
+        {$sort: {x: -1}},
+        {$skip: 4},
+        {$project: {x: 1, y: 1, z: 1, _id: 0}},
+        {$skip: 3},
+        {$limit: 30},
+        {$skip: 3},
+        {$limit: 6},
+    ]);
+    assert.eq(
+        [
+          {"x": 389, "y": ["a", "b", "c"], "z": 32},
+          {"x": 388, "y": ["a", "b", "c"], "z": 32},
+          {"x": 387, "y": ["a", "b", "c"], "z": 32},
+          {"x": 386, "y": ["a", "b", "c"], "z": 32},
+          {"x": 385, "y": ["a", "b", "c"], "z": 32},
+          {"x": 384, "y": ["a", "b", "c"], "z": 32}
+        ],
+        agg.toArray());
+
+    shardingTest.stop();
+})();
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