1 files changed, 64 insertions, 0 deletions
diff --git a/jstests/noPassthrough/server_status_query_exec_stats.js b/jstests/noPassthrough/server_status_query_exec_stats.js
new file mode 100644
index 00000000000..3a5a050d428
--- /dev/null
+++ b/jstests/noPassthrough/server_status_query_exec_stats.js
@@ -0,0 +1,64 @@
+/**
+ * Tests for serverStatus metrics.queryExecutor stats.
+ */
+(function() {
+    "use strict";
+
+    if (jsTest.options().storageEngine === "mobile") {
+        print("Skipping test because storage engine isn't mobile");
+        return;
+    }
+
+    const conn = MongoRunner.runMongod();
+    assert.neq(null, conn, "mongod was unable to start up");
+    const db = conn.getDB(jsTest.name());
+    const coll = db[jsTest.name()];
+
+    let getCollectionScans = () => {
+        return db.serverStatus().metrics.queryExecutor.collectionScans.total;
+    };
+    let getCollectionScansNonTailable = () => {
+        return db.serverStatus().metrics.queryExecutor.collectionScans.nonTailable;
+    };
+
+    // Create and populate a capped collection so that we can run tailable queries.
+    const nDocs = 32;
+    coll.drop();
+    assert.commandWorked(db.createCollection(jsTest.name(), {capped: true, size: nDocs * 100}));
+
+    for (let i = 0; i < nDocs; i++) {
+        assert.commandWorked(coll.insert({a: i}));
+    }
+
+    // Test nontailable collection scans update collectionScans counters appropriately.
+    for (let i = 0; i < nDocs; i++) {
+        assert.eq(coll.find({a: i}).itcount(), 1);
+        assert.eq(i + 1, getCollectionScans());
+        assert.eq(i + 1, getCollectionScansNonTailable());
+    }
+
+    // Test tailable collection scans update collectionScans counters appropriately.
+    for (let i = 0; i < nDocs; i++) {
+        assert.eq(coll.find({a: i}).tailable().itcount(), 1);
+        assert.eq(nDocs + i + 1, getCollectionScans());
+        assert.eq(nDocs, getCollectionScansNonTailable());
+    }
+
+    // Run a query which will require the client to fetch multiple batches from the server. Ensure
+    // that the getMore commands don't increment the counter of collection scans.
+    assert.eq(coll.find({}).batchSize(2).itcount(), nDocs);
+    assert.eq((nDocs * 2) + 1, getCollectionScans());
+    assert.eq(nDocs + 1, getCollectionScansNonTailable());
+
+    // Create index to test that index scans don't up the collection scan counter.
+    assert.commandWorked(coll.createIndex({a: 1}));
+    // Run a bunch of index scans.
+    for (let i = 0; i < nDocs; i++) {
+        assert.eq(coll.find({a: i}).itcount(), 1);
+    }
+    // Assert that the number of collection scans hasn't increased.
+    assert.eq((nDocs * 2) + 1, getCollectionScans());
+    assert.eq(nDocs + 1, getCollectionScansNonTailable());
+
+    MongoRunner.stopMongod(conn);
+}());