SERVER-31394 Create passthrough of existing $changeStream tests to run against sharded collections

21 files changed, 253 insertions, 148 deletions

diff --git a/buildscripts/resmokeconfig/suites/change_streams.yml b/buildscripts/resmokeconfig/suites/change_streams.yml
index 9d616e0d4b8..89d5a1c231e 100644
--- a/buildscripts/resmokeconfig/suites/change_streams.yml
+++ b/buildscripts/resmokeconfig/suites/change_streams.yml
@@ -26,7 +26,6 @@ executor:
     class: ReplicaSetFixture
     mongod_options:
       bind_ip_all: ''
-      enableMajorityReadConcern: ''
       oplogSize: 511
       set_parameters:
         enableTestCommands: 1
diff --git a/buildscripts/resmokeconfig/suites/change_streams_mongos_passthrough.yml b/buildscripts/resmokeconfig/suites/change_streams_mongos_passthrough.yml
index 16070851739..ca94f28c281 100644
--- a/buildscripts/resmokeconfig/suites/change_streams_mongos_passthrough.yml
+++ b/buildscripts/resmokeconfig/suites/change_streams_mongos_passthrough.yml
@@ -29,7 +29,6 @@ executor:
     mongod_options:
       bind_ip_all: ''
       nopreallocj: ''
-      enableMajorityReadConcern: ''
       set_parameters:
         enableTestCommands: 1
         numInitialSyncAttempts: 1
diff --git a/buildscripts/resmokeconfig/suites/change_streams_sharded_collections_passthrough.yml b/buildscripts/resmokeconfig/suites/change_streams_sharded_collections_passthrough.yml
new file mode 100644
index 00000000000..9d0b301e992
--- /dev/null
+++ b/buildscripts/resmokeconfig/suites/change_streams_sharded_collections_passthrough.yml
@@ -0,0 +1,42 @@
+test_kind: js_test
+
+selector:
+  roots:
+  - jstests/change_streams/**/*.js
+  exclude_files:
+  # Exercises an internal detail of mongos<->mongod communication. Not expected to work on mongos.
+  - jstests/change_streams/report_latest_observed_oplog_timestamp.js
+executor:
+  config:
+    shell_options:
+      global_vars:
+        TestData:
+          defaultReadConcernLevel: majority
+          enableMajorityReadConcern: ''
+      eval: >-
+        var testingReplication = true;
+        load('jstests/libs/override_methods/set_read_and_write_concerns.js');
+        load('jstests/libs/override_methods/implicitly_shard_accessed_collections.js');
+      readMode: commands
+  hooks:
+  - class: ValidateCollections
+  - class: CleanEveryN
+    n: 20
+  fixture:
+    class: ShardedClusterFixture
+    mongos_options:
+      bind_ip_all: ''
+      set_parameters:
+        enableTestCommands: 1
+    mongod_options:
+      bind_ip_all: ''
+      nopreallocj: ''
+      set_parameters:
+        enableTestCommands: 1
+        writePeriodicNoops: 1
+        periodicNoopIntervalSecs: 1
+        numInitialSyncAttempts: 1
+    num_rs_nodes_per_shard: 1
+    num_shards: 2
+    enable_sharding:
+    - test
diff --git a/buildscripts/resmokeconfig/suites/sharded_causally_consistent_jscore_passthrough.yml b/buildscripts/resmokeconfig/suites/sharded_causally_consistent_jscore_passthrough.yml
index 24fc0eb3176..fbd53ee4dc2 100644
--- a/buildscripts/resmokeconfig/suites/sharded_causally_consistent_jscore_passthrough.yml
+++ b/buildscripts/resmokeconfig/suites/sharded_causally_consistent_jscore_passthrough.yml
@@ -17,6 +17,7 @@ selector:
   - jstests/core/compact_keeps_indexes.js  # compact.
   - jstests/core/currentop.js  # uses fsync.
   - jstests/core/auth_copydb.js # copyDatabase.
+  - jstests/core/copydatabase_no_id_index.js # copyDatabase.
   - jstests/core/copydb.js # copyDatabase.
   - jstests/core/dbadmin.js  # "local" database.
   - jstests/core/dbhash.js  # dbhash.
diff --git a/buildscripts/resmokeconfig/suites/sharded_collections_jscore_passthrough.yml b/buildscripts/resmokeconfig/suites/sharded_collections_jscore_passthrough.yml
index 03b04f5b050..c9b23f10d29 100644
--- a/buildscripts/resmokeconfig/suites/sharded_collections_jscore_passthrough.yml
+++ b/buildscripts/resmokeconfig/suites/sharded_collections_jscore_passthrough.yml
@@ -15,6 +15,7 @@ selector:
   - jstests/core/compact_keeps_indexes.js  # compact.
   - jstests/core/currentop.js  # uses fsync.
   - jstests/core/auth_copydb.js # copyDatabase.
+  - jstests/core/copydatabase_no_id_index.js # copyDatabase.
   - jstests/core/copydb.js # copyDatabase.
   - jstests/core/dbadmin.js  # "local" database.
   - jstests/core/dbhash.js  # dbhash.
diff --git a/etc/evergreen.yml b/etc/evergreen.yml
index 2370d6a155d..234d656e541 100644
--- a/etc/evergreen.yml
+++ b/etc/evergreen.yml
@@ -2892,6 +2892,17 @@ tasks:
       run_multiple_jobs: true
 
 - <<: *task_template
+  name: change_streams_sharded_collections_passthrough_WT
+  depends_on:
+  - name: change_streams_WT
+  commands:
+  - func: "do setup"
+  - func: "run tests"
+    vars:
+      resmoke_args: --suites=change_streams_sharded_collections_passthrough --storageEngine=wiredTiger
+      run_multiple_jobs: true
+
+- <<: *task_template
   name: dbtest
   commands:
   - func: "do setup"
@@ -4918,6 +4929,7 @@ buildvariants:
   - name: change_streams_WT
   - name: change_streams_mongos_passthrough_WT
   - name: change_streams_secondary_reads_WT
+  - name: change_streams_sharded_collections_passthrough_WT
   - name: dbtest_WT
   - name: disk_WT
   - name: failpoints
@@ -5037,6 +5049,7 @@ buildvariants:
   - name: causally_consistent_jscore_passthrough_auth_WT
   - name: change_streams_WT
   - name: change_streams_mongos_passthrough_WT
+  - name: change_streams_sharded_collections_passthrough_WT
   - name: concurrency_WT
   - name: concurrency_replication_WT
   - name: concurrency_sharded_WT
@@ -6004,6 +6017,7 @@ buildvariants:
   - name: sharded_causally_consistent_jscore_passthrough_WT
   - name: change_streams_WT
   - name: change_streams_mongos_passthrough_WT
+  - name: change_streams_sharded_collections_passthrough_WT
   - name: dbtest_WT
   - name: disk_WT
   - name: failpoints
@@ -6513,6 +6527,7 @@ buildvariants:
   - name: sharded_causally_consistent_jscore_passthrough_WT
   - name: change_streams_WT
   - name: change_streams_mongos_passthrough_WT
+  - name: change_streams_sharded_collections_passthrough_WT
   - name: concurrency_WT
   - name: concurrency_replication_WT
   - name: concurrency_sharded_WT
@@ -6755,6 +6770,7 @@ buildvariants:
   - name: sharded_causally_consistent_jscore_passthrough_WT
   - name: change_streams_WT
   - name: change_streams_mongos_passthrough_WT
+  - name: change_streams_sharded_collections_passthrough_WT
   - name: concurrency_WT
   - name: concurrency_replication_WT
   - name: concurrency_sharded_WT
@@ -6932,6 +6948,7 @@ buildvariants:
   - name: change_streams_WT
   - name: change_streams_mongos_passthrough_WT
   - name: change_streams_secondary_reads_WT
+  - name: change_streams_sharded_collections_passthrough_WT
   - name: concurrency_WT
   - name: concurrency_replication_WT
   - name: concurrency_sharded_WT
@@ -8650,6 +8667,7 @@ buildvariants:
   - name: sharded_causally_consistent_jscore_passthrough_WT
   - name: change_streams_WT
   - name: change_streams_mongos_passthrough_WT
+  - name: change_streams_sharded_collections_passthrough_WT
   - name: concurrency
     distros:
     - rhel62-large  # Some workloads require a lot of memory, use a bigger machine for this suite.
@@ -9042,6 +9060,7 @@ buildvariants:
   - name: change_streams_WT
   - name: change_streams_mongos_passthrough_WT
   - name: change_streams_secondary_reads_WT
+  - name: change_streams_sharded_collections_passthrough_WT
   - name: concurrency_WT
   - name: concurrency_replication_WT
   - name: concurrency_sharded_WT
@@ -9190,6 +9209,7 @@ buildvariants:
   - name: change_streams_WT
   - name: change_streams_mongos_passthrough_WT
   - name: change_streams_secondary_reads_WT
+  - name: change_streams_sharded_collections_passthrough_WT
   - name: concurrency_WT
   - name: concurrency_replication_WT
   - name: concurrency_sharded_WT
diff --git a/jstests/change_streams/change_stream.js b/jstests/change_streams/change_stream.js
index c1415a2a1f5..80356aa3b48 100644
--- a/jstests/change_streams/change_stream.js
+++ b/jstests/change_streams/change_stream.js
@@ -2,13 +2,14 @@
 (function() {
     "use strict";
 
+    load("jstests/libs/collection_drop_recreate.js");  // For assert[Drop|Create]Collection.
     load("jstests/libs/change_stream_util.js");
     load('jstests/libs/uuid_util.js');
 
     let cst = new ChangeStreamTest(db);
 
     jsTestLog("Testing single insert");
-    db.t1.drop();
+    assertDropCollection(db, "t1");
     let cursor = cst.startWatchingChanges({pipeline: [{$changeStream: {}}], collection: db.t1});
     // Test that if there are no changes, we return an empty batch.
     assert.eq(0, cursor.firstBatch.length, "Cursor had changes: " + tojson(cursor));
@@ -40,7 +41,7 @@
 
     jsTestLog("Testing update");
     cursor = cst.startWatchingChanges({pipeline: [{$changeStream: {}}], collection: db.t1});
-    assert.writeOK(db.t1.update({_id: 0}, {a: 3}));
+    assert.writeOK(db.t1.update({_id: 0}, {_id: 0, a: 3}));
     expected = {
         documentKey: {_id: 0},
         fullDocument: {_id: 0, a: 3},
@@ -51,7 +52,7 @@
 
     jsTestLog("Testing update of another field");
     cursor = cst.startWatchingChanges({pipeline: [{$changeStream: {}}], collection: db.t1});
-    assert.writeOK(db.t1.update({_id: 0}, {b: 3}));
+    assert.writeOK(db.t1.update({_id: 0}, {_id: 0, b: 3}));
     expected = {
         documentKey: {_id: 0},
         fullDocument: {_id: 0, b: 3},
@@ -62,7 +63,7 @@
 
     jsTestLog("Testing upsert");
     cursor = cst.startWatchingChanges({pipeline: [{$changeStream: {}}], collection: db.t1});
-    assert.writeOK(db.t1.update({_id: 2}, {a: 4}, {upsert: true}));
+    assert.writeOK(db.t1.update({_id: 2}, {_id: 2, a: 4}, {upsert: true}));
     expected = {
         documentKey: {_id: 2},
         fullDocument: {_id: 2, a: 4},
@@ -94,6 +95,7 @@
     cst.assertNextChangesEqual({cursor: cursor, expectedChanges: [expected]});
 
     jsTestLog("Testing intervening write on another collection");
+    assertDropCollection(db, "t2");
     cursor = cst.startWatchingChanges({pipeline: [{$changeStream: {}}], collection: db.t1});
     let t2cursor = cst.startWatchingChanges({pipeline: [{$changeStream: {}}], collection: db.t2});
     assert.writeOK(db.t2.insert({_id: 100, c: 1}));
@@ -109,25 +111,28 @@
 
     jsTestLog("Testing drop of unrelated collection");
     assert.writeOK(db.dropping.insert({}));
-    db.dropping.drop();
+    assertDropCollection(db, db.dropping.getName());
     // Should still see the previous change from t2, shouldn't see anything about 'dropping'.
 
-    jsTestLog("Testing rename");
-    db.t3.drop();
-    t2cursor = cst.startWatchingChanges({pipeline: [{$changeStream: {}}], collection: db.t2});
-    assert.writeOK(db.t2.renameCollection("t3"));
-    expected = {operationType: "invalidate"};
-    cst.assertNextChangesEqual(
-        {cursor: t2cursor, expectedChanges: [expected], expectInvalidate: true});
+    // Test collection renaming. Sharded collections cannot be renamed.
+    if (!db.t2.stats().sharded) {
+        jsTestLog("Testing rename");
+        assertDropCollection(db, "t3");
+        t2cursor = cst.startWatchingChanges({pipeline: [{$changeStream: {}}], collection: db.t2});
+        assert.writeOK(db.t2.renameCollection("t3"));
+        expected = {operationType: "invalidate"};
+        cst.assertNextChangesEqual(
+            {cursor: t2cursor, expectedChanges: [expected], expectInvalidate: true});
+    }
 
     jsTestLog("Testing insert that looks like rename");
-    db.dne1.drop();
-    db.dne2.drop();
+    assertDropCollection(db, "dne1");
+    assertDropCollection(db, "dne2");
     const dne1cursor =
         cst.startWatchingChanges({pipeline: [{$changeStream: {}}], collection: db.dne1});
     const dne2cursor =
         cst.startWatchingChanges({pipeline: [{$changeStream: {}}], collection: db.dne2});
-    assert.writeOK(db.t3.insert({_id: 101, renameCollection: "test.dne1", to: "test.dne2"}));
+    assert.writeOK(db.t2.insert({_id: 101, renameCollection: "test.dne1", to: "test.dne2"}));
     cst.assertNextChangesEqual({cursor: dne1cursor, expectedChanges: []});
     cst.assertNextChangesEqual({cursor: dne2cursor, expectedChanges: []});
 
@@ -144,8 +149,7 @@
     }
 
     jsTestLog("Testing resumability");
-    db.resume1.drop();
-    assert.commandWorked(db.createCollection("resume1"));
+    assertDropAndRecreateCollection(db, "resume1");
 
     // Note we do not project away 'id.ts' as it is part of the resume token.
     let resumeCursor = cst.startWatchingChanges(
diff --git a/jstests/change_streams/change_stream_ban_from_lookup.js b/jstests/change_streams/change_stream_ban_from_lookup.js
index f17be0ecef1..08bc600ad55 100644
--- a/jstests/change_streams/change_stream_ban_from_lookup.js
+++ b/jstests/change_streams/change_stream_ban_from_lookup.js
@@ -4,16 +4,17 @@
 (function() {
     "use strict";
 
-    load("jstests/aggregation/extras/utils.js");  // For assertErrorCode.
+    load("jstests/aggregation/extras/utils.js");       // For assertErrorCode.
+    load("jstests/libs/collection_drop_recreate.js");  // For assert[Drop|Create]Collection.
 
-    const coll = db.change_stream_ban_from_lookup;
-    coll.drop();
+    const coll = assertDropAndRecreateCollection(db, "change_stream_ban_from_lookup");
+    const foreignColl = "unsharded";
 
     assert.writeOK(coll.insert({_id: 1}));
 
     // Verify that we cannot create a $lookup using a pipeline which begins with $changeStream.
     assertErrorCode(coll,
-                    [{$lookup: {from: coll.getName(), as: 'as', pipeline: [{$changeStream: {}}]}}],
+                    [{$lookup: {from: foreignColl, as: 'as', pipeline: [{$changeStream: {}}]}}],
                     ErrorCodes.IllegalOperation);
 
     // Verify that we cannot create a $lookup if its pipeline contains a sub-$lookup whose pipeline
@@ -22,14 +23,11 @@
         coll,
         [{
            $lookup: {
-               from: coll.getName(),
+               from: foreignColl,
                as: 'as',
                pipeline: [
                    {$match: {_id: 1}},
-                   {
-                     $lookup:
-                         {from: coll.getName(), as: 'subas', pipeline: [{$changeStream: {}}]}
-                   }
+                   {$lookup: {from: foreignColl, as: 'subas', pipeline: [{$changeStream: {}}]}}
                ]
            }
         }],
diff --git a/jstests/change_streams/change_stream_ban_from_views.js b/jstests/change_streams/change_stream_ban_from_views.js
index b2789e72155..643df54bd74 100644
--- a/jstests/change_streams/change_stream_ban_from_views.js
+++ b/jstests/change_streams/change_stream_ban_from_views.js
@@ -4,29 +4,30 @@
 (function() {
     "use strict";
 
-    const collName = "change_stream_ban_from_views";
+    load("jstests/libs/collection_drop_recreate.js");  // For assert[Drop|Create]Collection.
+
+    const coll = assertDropAndRecreateCollection(db, "change_stream_ban_from_views");
+    assert.writeOK(coll.insert({_id: 1}));
+
     const normalViewName = "nonChangeStreamView";
     const csViewName = "changeStreamView";
 
-    db[normalViewName].drop();
-    db[csViewName].drop();
-    db[collName].drop();
-
-    assert.writeOK(db[collName].insert({_id: 1}));
+    assertDropCollection(db, normalViewName);
+    assertDropCollection(db, csViewName);
 
     const csPipe = [{$changeStream: {}}];
 
     // Create one valid view for testing purposes.
-    assert.commandWorked(
-        db.runCommand({create: normalViewName, viewOn: collName, pipeline: [{$match: {_id: 1}}]}));
+    assert.commandWorked(db.runCommand(
+        {create: normalViewName, viewOn: coll.getName(), pipeline: [{$match: {_id: 1}}]}));
 
     // Verify that we cannot create a view using a pipeline which begins with $changeStream.
     assert.commandFailedWithCode(
-        db.runCommand({create: csViewName, viewOn: collName, pipeline: csPipe}),
+        db.runCommand({create: csViewName, viewOn: coll.getName(), pipeline: csPipe}),
         ErrorCodes.OptionNotSupportedOnView);
 
     // We also cannot update an existing view to use a $changeStream pipeline.
     assert.commandFailedWithCode(
-        db.runCommand({collMod: normalViewName, viewOn: collName, pipeline: csPipe}),
+        db.runCommand({collMod: normalViewName, viewOn: coll.getName(), pipeline: csPipe}),
         ErrorCodes.OptionNotSupportedOnView);
 })();
diff --git a/jstests/change_streams/change_stream_collation.js b/jstests/change_streams/change_stream_collation.js
index 5093bbe4ed0..314e7b08954 100644
--- a/jstests/change_streams/change_stream_collation.js
+++ b/jstests/change_streams/change_stream_collation.js
@@ -1,20 +1,18 @@
 /**
  * Tests that a change stream can use a user-specified, or collection-default collation.
- *
- * This test assumes that it will be able to drop and then re-create a collection with non-default
- * options.
- * @tags: [assumes_no_implicit_collection_creation_after_drop]
  */
 (function() {
     "use strict";
 
-    load("jstests/libs/change_stream_util.js");  // For 'ChangeStreamTest'.
+    load("jstests/libs/collection_drop_recreate.js");  // For assert[Drop|Create]Collection.
+    load("jstests/libs/change_stream_util.js");        // For 'ChangeStreamTest'.
 
     let cst = new ChangeStreamTest(db);
 
     const caseInsensitive = {locale: "en_US", strength: 2};
-    const caseInsensitiveCollection = db.change_stream_case_insensitive;
-    caseInsensitiveCollection.drop();
+
+    let caseInsensitiveCollection = "change_stream_case_insensitive";
+    assertDropCollection(db, caseInsensitiveCollection);
 
     // Test that you can open a change stream before the collection exists, and it will use the
     // simple collation.
@@ -23,8 +21,8 @@
 
     // Create the collection with a non-default collation - this should invalidate the stream we
     // opened before it existed.
-    assert.commandWorked(
-        db.runCommand({create: caseInsensitiveCollection.getName(), collation: caseInsensitive}));
+    caseInsensitiveCollection =
+        assertCreateCollection(db, caseInsensitiveCollection, {collation: caseInsensitive});
     cst.assertNextChangesEqual({
         cursor: simpleCollationStream,
         expectedChanges: [{operationType: "invalidate"}],
@@ -60,10 +58,8 @@
         {cursor: explicitCaseInsensitiveStream, expectedChanges: [{docId: 0}, {docId: 1}]});
 
     // Test that the collation does not apply to the scan over the oplog.
-    const similarNameCollection = db.cHaNgE_sTrEaM_cAsE_iNsEnSiTiVe;
-    similarNameCollection.drop();
-    assert.commandWorked(
-        db.runCommand({create: similarNameCollection.getName(), collation: {locale: "en_US"}}));
+    const similarNameCollection = assertDropAndRecreateCollection(
+        db, "cHaNgE_sTrEaM_cAsE_iNsEnSiTiVe", {collation: {locale: "en_US"}});
 
     assert.writeOK(similarNameCollection.insert({_id: 0, text: "aBc"}));
 
@@ -79,15 +75,15 @@
     // Test that creating a collection without a collation does not invalidate any change streams
     // that were opened before the collection existed.
     (function() {
-        const noCollationCollection = db.change_stream_no_collation;
-        noCollationCollection.drop();
+        let noCollationCollection = "change_stream_no_collation";
+        assertDropCollection(db, noCollationCollection);
 
         const streamCreatedBeforeNoCollationCollection = cst.startWatchingChanges({
             pipeline: [{$changeStream: {}}, {$project: {docId: "$documentKey._id"}}],
             collection: noCollationCollection
         });
 
-        assert.commandWorked(db.runCommand({create: noCollationCollection.getName()}));
+        noCollationCollection = assertCreateCollection(db, noCollationCollection);
         assert.writeOK(noCollationCollection.insert({_id: 0}));
 
         cst.assertNextChangesEqual(
@@ -97,16 +93,16 @@
     // Test that creating a collection and explicitly specifying the simple collation does not
     // invalidate any change streams that were opened before the collection existed.
     (function() {
-        const simpleCollationCollection = db.change_stream_simple_collation;
-        simpleCollationCollection.drop();
+        let simpleCollationCollection = "change_stream_simple_collation";
+        assertDropCollection(db, simpleCollationCollection);
 
         const streamCreatedBeforeSimpleCollationCollection = cst.startWatchingChanges({
             pipeline: [{$changeStream: {}}, {$project: {docId: "$documentKey._id"}}],
             collection: simpleCollationCollection
         });
 
-        assert.commandWorked(db.runCommand(
-            {create: simpleCollationCollection.getName(), collation: {locale: "simple"}}));
+        simpleCollationCollection =
+            assertCreateCollection(db, simpleCollationCollection, {collation: {locale: "simple"}});
         assert.writeOK(simpleCollationCollection.insert({_id: 0}));
 
         cst.assertNextChangesEqual(
@@ -116,8 +112,8 @@
     // Test that creating a change stream with a non-default collation, then creating a collection
     // with the same collation will not invalidate the change stream.
     (function() {
-        const frenchCollection = db.change_stream_french_collation;
-        frenchCollection.drop();
+        let frenchCollection = "change_stream_french_collation";
+        assertDropCollection(db, frenchCollection);
 
         const frenchChangeStream = cst.startWatchingChanges({
             pipeline: [{$changeStream: {}}, {$project: {docId: "$documentKey._id"}}],
@@ -125,8 +121,8 @@
             collection: frenchCollection
         });
 
-        assert.commandWorked(
-            db.runCommand({create: frenchCollection.getName(), collation: {locale: "fr"}}));
+        frenchCollection =
+            assertCreateCollection(db, frenchCollection, {collation: {locale: "fr"}});
         assert.writeOK(frenchCollection.insert({_id: 0}));
 
         cst.assertNextChangesEqual({cursor: frenchChangeStream, expectedChanges: [{docId: 0}]});
@@ -135,8 +131,8 @@
     // Test that creating a change stream with a non-default collation, then creating a collection
     // with *a different* collation will not invalidate the change stream.
     (function() {
-        const germanCollection = db.change_stream_german_collation;
-        germanCollection.drop();
+        let germanCollection = "change_stream_german_collation";
+        assertDropCollection(db, germanCollection);
 
         const englishCaseInsensitiveStream = cst.startWatchingChanges({
             pipeline: [
@@ -148,8 +144,8 @@
             collection: germanCollection
         });
 
-        assert.commandWorked(
-            db.runCommand({create: germanCollection.getName(), collation: {locale: "de"}}));
+        germanCollection =
+            assertCreateCollection(db, germanCollection, {collation: {locale: "de"}});
         assert.writeOK(germanCollection.insert({_id: 0, text: "aBc"}));
 
         cst.assertNextChangesEqual(
@@ -159,10 +155,8 @@
     // Test that creating a change stream with a non-default collation against a collection that has
     // a non-simple default collation will use the collation specified on the operation.
     (function() {
-        const caseInsensitiveCollection = db.change_stream_case_insensitive;
-        caseInsensitiveCollection.drop();
-        assert.commandWorked(db.runCommand(
-            {create: caseInsensitiveCollection.getName(), collation: caseInsensitive}));
+        const caseInsensitiveCollection = assertDropAndRecreateCollection(
+            db, "change_stream_case_insensitive", {collation: caseInsensitive});
 
         const englishCaseSensitiveStream = cst.startWatchingChanges({
             pipeline: [
@@ -185,9 +179,8 @@
     // Test that creating a change stream with a non-default collation against a collection that has
     // a simple default collation will use the collation specified on the operation.
     (function() {
-        const noCollationCollection = db.change_stream_no_collation;
-        noCollationCollection.drop();
-        assert.commandWorked(db.runCommand({create: noCollationCollection.getName()}));
+        const noCollationCollection =
+            assertDropAndRecreateCollection(db, "change_stream_no_collation");
 
         const cursor = noCollationCollection.watch(
             [
@@ -198,7 +191,7 @@
         assert(!cursor.hasNext());
         assert.writeOK(noCollationCollection.insert({_id: 0, text: "aBc"}));
         assert.writeOK(noCollationCollection.insert({_id: 1, text: "abc"}));
-        assert(cursor.hasNext());
+        assert.soon(() => cursor.hasNext());
         assert.docEq(cursor.next(), {docId: 0});
         assert(cursor.hasNext());
         assert.docEq(cursor.next(), {docId: 1});
diff --git a/jstests/change_streams/change_stream_invalidation.js b/jstests/change_streams/change_stream_invalidation.js
index c442b1dcecf..7f3a1c0529b 100644
--- a/jstests/change_streams/change_stream_invalidation.js
+++ b/jstests/change_streams/change_stream_invalidation.js
@@ -6,6 +6,7 @@
     load("jstests/libs/change_stream_util.js");
     load('jstests/libs/uuid_util.js');
     load('jstests/replsets/libs/two_phase_drops.js');  // For 'TwoPhaseDropCollectionTest'.
+    load("jstests/libs/collection_drop_recreate.js");  // For assert[Drop|Create]Collection.
 
     let cst = new ChangeStreamTest(db);
 
@@ -13,7 +14,7 @@
 
     // Write a document to the collection and test that the change stream returns it
     // and getMore command closes the cursor afterwards.
-    const collGetMore = db.change_stream_getmore_invalidations;
+    const collGetMore = assertDropAndRecreateCollection(db, "change_stream_getmore_invalidations");
     // We awaited the replication of the first write, so the change stream shouldn't return it.
     // Use { w: "majority" } to deal with journaling correctly, even though we only have one node.
     assert.writeOK(collGetMore.insert({_id: 0, a: 1}, {writeConcern: {w: "majority"}}));
@@ -47,8 +48,7 @@
     });
 
     jsTestLog("Testing aggregate command closes cursor for invalidate entries");
-    const collAgg = db.change_stream_agg_invalidations;
-    db.createCollection(collAgg.getName());
+    const collAgg = assertDropAndRecreateCollection(db, "change_stream_agg_invalidations");
     const collAggUuid = getUUIDFromListCollections(db, collAgg.getName());
     // Get a valid resume token that the next aggregate command can use.
     aggcursor = cst.startWatchingChanges(
@@ -61,7 +61,7 @@
 
     // It should not possible to resume a change stream after a collection drop, even if the
     // invalidate has not been received.
-    assert(collAgg.drop());
+    assertDropCollection(db, collAgg.getName());
     // Wait for two-phase drop to complete, so that the UUID no longer exists.
     assert.soon(function() {
         return !TwoPhaseDropCollectionTest.collectionIsPendingDropInDatabase(db, collAgg.getName());
@@ -75,13 +75,14 @@
     // Test that it is possible to open a new change stream cursor on a collection that does not
     // exist.
     jsTestLog("Testing aggregate command on nonexistent collection");
-    const collDoesNotExist = db.change_stream_agg_invalidations_does_not_exist;
-    db.runCommand({drop: collDoesNotExist.getName(), writeConcern: {j: true}});
+    const collDoesNotExistName = "change_stream_agg_invalidations_does_not_exist";
+    assertDropCollection(db, collDoesNotExistName);
 
     // Cursor creation succeeds, but there are no results.
     aggcursor = cst.startWatchingChanges({
-        collection: collDoesNotExist,
+        collection: collDoesNotExistName,
         pipeline: [{$changeStream: {}}],
+        includeToken: true,
     });
 
     // We explicitly test getMore, to ensure that the getMore command for a non-existent collection
@@ -91,7 +92,8 @@
     assert.eq(aggcursor.nextBatch.length, 0, tojson(aggcursor.nextBatch));
 
     // After collection creation, we see oplog entries for the collection.
-    assert.writeOK(collDoesNotExist.insert({_id: 0}, {writeConcern: {j: true}}));
+    const collNowExists = assertCreateCollection(db, collDoesNotExistName);
+    assert.writeOK(collNowExists.insert({_id: 0}, {writeConcern: {j: true}}));
     change = cst.getOneChange(aggcursor);
     assert.eq(change.operationType, "insert", tojson(change));
 
diff --git a/jstests/change_streams/change_stream_shell_helper.js b/jstests/change_streams/change_stream_shell_helper.js
index 4e972e0fd6f..58d20645ae1 100644
--- a/jstests/change_streams/change_stream_shell_helper.js
+++ b/jstests/change_streams/change_stream_shell_helper.js
@@ -3,12 +3,12 @@
 (function() {
     "use strict";
 
-    const collName = "change_stream_shell_helper";
-    const coll = db[collName];
-    coll.drop();
+    load("jstests/libs/collection_drop_recreate.js");  // For assert[Drop|Create]Collection.
+
+    const coll = assertDropAndRecreateCollection(db, "change_stream_shell_helper");
 
     function checkNextChange(cursor, expected) {
-        assert(cursor.hasNext());
+        assert.soon(() => cursor.hasNext());
         assert.docEq(cursor.next(), expected);
     }
 
@@ -41,13 +41,13 @@
     let cursor = coll.watch();
     assert(!cursor.hasNext());
     assert.writeOK(coll.insert({_id: 0, x: 1}));
-    assert(cursor.hasNext());
+    assert.soon(() => cursor.hasNext());
     let change = cursor.next();
     assert(!cursor.hasNext());
     let expected = {
         documentKey: {_id: 0},
         fullDocument: {_id: 0, x: 1},
-        ns: {db: "test", coll: collName},
+        ns: {db: "test", coll: coll.getName()},
         operationType: "insert",
     };
     assert("_id" in change, "Got unexpected change: " + tojson(change));
@@ -72,7 +72,7 @@
     expected = {
         documentKey: {_id: 0},
         fullDocument: {_id: 0, x: 10},
-        ns: {db: "test", coll: collName},
+        ns: {db: "test", coll: coll.getName()},
         operationType: "update",
         updateDescription: {removedFields: [], updatedFields: {x: 10}},
     };
@@ -135,15 +135,15 @@
     expected = {
         documentKey: {_id: 2},
         fullDocument: {_id: 2, x: 1},
-        ns: {db: "test", coll: collName},
+        ns: {db: "test", coll: coll.getName()},
         operationType: "insert",
     };
     checkNextChange(cursor, expected);
     assert(!cursor.hasNext());
     assert(!cursor.isClosed());
     assert(!cursor.isExhausted());
-    coll.drop();
-    assert(cursor.hasNext());
+    assertDropCollection(db, coll.getName());
+    assert.soon(() => cursor.hasNext());
     assert(cursor.isClosed());
     assert(!cursor.isExhausted());
     expected = {operationType: "invalidate"};
diff --git a/jstests/change_streams/change_stream_whitelist.js b/jstests/change_streams/change_stream_whitelist.js
index 817dd35fef4..12848e1e9e7 100644
--- a/jstests/change_streams/change_stream_whitelist.js
+++ b/jstests/change_streams/change_stream_whitelist.js
@@ -5,11 +5,13 @@
 (function() {
     "use strict";
 
-    load('jstests/aggregation/extras/utils.js');  // For assertErrorCode().
+    load('jstests/aggregation/extras/utils.js');       // For assertErrorCode.
+    load("jstests/libs/collection_drop_recreate.js");  // For assert[Drop|Create]Collection.
+
+    const coll = assertDropAndRecreateCollection(db, "change_stream_whitelist");
 
     // Bare-bones $changeStream pipeline which will be augmented during tests.
     const changeStream = [{$changeStream: {}}];
-    const coll = db[jsTestName()];
 
     // List of non-$changeStream stages which are explicitly whitelisted.
     const whitelist = [
diff --git a/jstests/change_streams/lookup_post_image.js b/jstests/change_streams/lookup_post_image.js
index 0f75ad073e9..bba5021e393 100644
--- a/jstests/change_streams/lookup_post_image.js
+++ b/jstests/change_streams/lookup_post_image.js
@@ -6,12 +6,11 @@
     "use strict";
 
     load("jstests/libs/change_stream_util.js");
+    load("jstests/libs/collection_drop_recreate.js");  // For assert[Drop|Create]Collection.
     load("jstests/replsets/libs/two_phase_drops.js");  // For 'TwoPhaseDropCollectionTest'.
 
     let cst = new ChangeStreamTest(db);
-    const coll = db.change_post_image;
-
-    coll.drop();
+    const coll = assertDropAndRecreateCollection(db, "change_post_image");
 
     jsTestLog("Testing change streams without 'fullDocument' specified");
     // Test that not specifying 'fullDocument' does include a 'fullDocument' in the result for an
@@ -124,7 +123,7 @@
         collection: coll,
         pipeline: [
             {$changeStream: {fullDocument: "updateLookup", resumeAfter: deleteDocResumePoint}},
-            {$match: {operationType: "update"}}
+            {$match: {operationType: {$ne: "delete"}}}
         ],
         aggregateOptions: {cursor: {batchSize: 0}}
     });
@@ -134,19 +133,35 @@
         collection: coll,
         pipeline: [
             {$changeStream: {fullDocument: "updateLookup", resumeAfter: deleteDocResumePoint}},
-            {$match: {operationType: "update"}}
+            {$match: {operationType: {$ne: "delete"}}}
         ],
         aggregateOptions: {cursor: {batchSize: 0}}
     });
 
+    // Retrieve the 'insert' operation from the latter stream. This is necessary on a sharded
+    // collection so that the documentKey is retrieved before the collection is recreated;
+    // otherwise, per SERVER-31691, a uassert will occur.
+    // TODO SERVER-31847: all remaining operations on the old UUID should be visible even if we have
+    // not retrieved the first oplog entry before the collection is recreated.
+    latestChange = cst.getOneChange(cursorBeforeDrop);
+    assert.eq(latestChange.operationType, "insert");
+    assert(latestChange.hasOwnProperty("fullDocument"));
+    assert.eq(latestChange.fullDocument, {_id: "fullDocument is lookup 2"});
+
     // Drop the collection and wait until two-phase drop finishes.
-    coll.drop();
+    assertDropCollection(db, coll.getName());
     assert.soon(function() {
         return !TwoPhaseDropCollectionTest.collectionIsPendingDropInDatabase(db, coll.getName());
     });
 
-    // Check the next $changeStream entry; this is the test document inserted above. The collection
-    // has been dropped, so our attempt to look up the post-image results in a null document.
+    // Check the next $changeStream entry; this is the test document inserted above.
+    latestChange = cst.getOneChange(cursor);
+    assert.eq(latestChange.operationType, "insert");
+    assert(latestChange.hasOwnProperty("fullDocument"));
+    assert.eq(latestChange.fullDocument, {_id: "fullDocument is lookup 2"});
+
+    // The next entry is the 'update' operation. Because the collection has been dropped, our
+    // attempt to look up the post-image results in a null document.
     latestChange = cst.getOneChange(cursor);
     assert.eq(latestChange.operationType, "update");
     assert(latestChange.hasOwnProperty("fullDocument"));
@@ -166,10 +181,10 @@
     // Test that looking up the post image of an update after the collection has been dropped and
     // created again will result in 'fullDocument' with a value of null. This must be done using
     // getMore because new cursors cannot be established after a collection drop.
-    //
+
     // Insert a document with the same _id, verify the change stream won't return it due to
     // different UUID.
-    assert.commandWorked(db.createCollection(coll.getName()));
+    assertCreateCollection(db, coll.getName());
     assert.writeOK(coll.insert({_id: "fullDocument is lookup 2"}));
 
     // Confirm that the next entry's post-image is null since new collection has a different UUID.
@@ -179,19 +194,18 @@
     assert.eq(latestChange.fullDocument, null);
 
     // Test that invalidate entries don't have 'fullDocument' even if 'updateLookup' is specified.
-    db.collInvalidate.drop();
-    assert.commandWorked(db.createCollection(db.collInvalidate.getName()));
+    const collInvalidate = assertDropAndRecreateCollection(db, "collInvalidate");
     cursor = cst.startWatchingChanges({
-        collection: db.collInvalidate,
+        collection: collInvalidate.getName(),
         pipeline: [{$changeStream: {fullDocument: "updateLookup"}}],
         aggregateOptions: {cursor: {batchSize: 0}}
     });
-    assert.writeOK(db.collInvalidate.insert({_id: "testing invalidate"}));
-    db.collInvalidate.drop();
+    assert.writeOK(collInvalidate.insert({_id: "testing invalidate"}));
+    assertDropCollection(db, collInvalidate.getName());
     // Wait until two-phase drop finishes.
     assert.soon(function() {
         return !TwoPhaseDropCollectionTest.collectionIsPendingDropInDatabase(
-            db, db.collInvalidate.getName());
+            db, collInvalidate.getName());
     });
     latestChange = cst.getOneChange(cursor);
     assert.eq(latestChange.operationType, "insert");
@@ -202,9 +216,7 @@
     // TODO(russotto): Can just use "coll" here once read majority is working.
     // For now, using the old collection results in us reading stale data sometimes.
     jsTestLog("Testing full document lookup with a real getMore");
-    const coll2 = db.real_get_more;
-    coll2.drop();
-    assert.commandWorked(db.createCollection(coll2.getName()));
+    const coll2 = assertDropAndRecreateCollection(db, "real_get_more");
     assert.writeOK(coll2.insert({_id: "getMoreEnabled"}));
 
     cursor = cst.startWatchingChanges({
diff --git a/jstests/change_streams/only_wake_getmore_for_relevant_changes.js b/jstests/change_streams/only_wake_getmore_for_relevant_changes.js
index f7d909f039f..84f4d0ae979 100644
--- a/jstests/change_streams/only_wake_getmore_for_relevant_changes.js
+++ b/jstests/change_streams/only_wake_getmore_for_relevant_changes.js
@@ -4,7 +4,8 @@
     "use strict";
 
     load('jstests/libs/uuid_util.js');
-    load("jstests/libs/fixture_helpers.js");  // For 'FixtureHelpers'.
+    load("jstests/libs/fixture_helpers.js");           // For 'FixtureHelpers'.
+    load("jstests/libs/collection_drop_recreate.js");  // For assert[Drop|Create]Collection.
 
     /**
      * Uses a parallel shell to execute the javascript function 'event' at the same time as an
@@ -20,11 +21,13 @@
         // the getMore to run. To prevent this from happening, the main thread waits for an insert
         // into "sentinel", to signal that the parallel shell has started and is waiting for the
         // getMore to appear in currentOp.
-        const shellSentinelCollection = db.shell_sentinel;
-        shellSentinelCollection.drop();
+        const shellSentinelCollection = assertDropAndRecreateCollection(db, "shell_sentinel");
 
-        const awaitShellDoingEventDuringGetMore =
-            startParallelShell(`
+        const port =
+            (collection.stats().sharded ? collection.getMongo().port
+                                        : FixtureHelpers.getPrimaryForNodeHostingDatabase(db).port);
+
+        const awaitShellDoingEventDuringGetMore = startParallelShell(`
 // Signal that the parallel shell has started.
 assert.writeOK(db.getCollection("${ shellSentinelCollection.getName() }").insert({}));
 
@@ -34,12 +37,12 @@ assert.soon(function() {
                  op: "getmore",
                  "command.collection": "${collection.getName()}",
                  "originatingCommand.comment": "${identifyingComment}",
-             }).inprog.length === 1;
+             }).inprog.length > 0;
 });
 
 const eventFn = ${ event.toString() };
 eventFn();`,
-                               FixtureHelpers.getPrimaryForNodeHostingDatabase(db).port);
+                                                                     port);
 
         // Wait for the shell to start.
         assert.soon(() => shellSentinelCollection.findOne() != null);
@@ -104,9 +107,7 @@ eventFn();`,
         return result;
     }
 
-    const changesCollection = db.changes;
-    changesCollection.drop();
-    assert.commandWorked(db.createCollection(changesCollection.getName()));
+    const changesCollection = assertDropAndRecreateCollection(db, "changes");
 
     // Start a change stream cursor.
     const wholeCollectionStreamComment = "change stream on entire collection";
@@ -130,7 +131,6 @@ eventFn();`,
         event: () => assert.writeOK(db.changes.insert({_id: "wake up"}))
     });
     assert.eq(getMoreResponse.cursor.nextBatch.length, 1);
-    const changesCollectionUuid = getUUIDFromListCollections(db, changesCollection.getName());
     assert.docEq(getMoreResponse.cursor.nextBatch[0], {
         documentKey: {_id: "wake up"},
         fullDocument: {_id: "wake up"},
@@ -140,7 +140,7 @@ eventFn();`,
 
     // Test that an insert to an unrelated collection will not cause the change stream to wake up
     // and return an empty batch before reaching the maxTimeMS.
-    db.unrelated_collection.drop();
+    assertDropCollection(db, "unrelated_collection");
     assertEventDoesNotWakeCursor({
         collection: changesCollection,
         awaitDataCursorId: changeCursorId,
diff --git a/jstests/change_streams/report_latest_observed_oplog_timestamp.js b/jstests/change_streams/report_latest_observed_oplog_timestamp.js
index 6c5b92f0392..e75c50794a1 100644
--- a/jstests/change_streams/report_latest_observed_oplog_timestamp.js
+++ b/jstests/change_streams/report_latest_observed_oplog_timestamp.js
@@ -4,18 +4,16 @@
 (function() {
     "use strict";
 
-    const testName = "report_latest_observed_oplog_timestamp";
-    const cursorCollection = db.getCollection(testName);
-    const otherCollection = db.getCollection("unrelated_" + testName);
+    load("jstests/libs/collection_drop_recreate.js");  // For assert[Drop|Create]Collection.
 
-    // Drop collections to assure a clean run.  Collections may not exist so do not check result.
-    cursorCollection.drop();
-    otherCollection.drop();
+    // Drop and recreate collections to assure a clean run.
+    const testName = "report_latest_observed_oplog_timestamp";
+    const cursorCollection = assertDropAndRecreateCollection(db, testName);
+    const otherCollection = assertDropAndRecreateCollection(db, "unrelated_" + testName);
 
     // Get a resume point.
     jsTestLog("Getting a resume point.");
     const batchSize = 2;
-    assert.commandWorked(db.createCollection(cursorCollection.getName()));
     const firstResponse = assert.commandWorked(cursorCollection.runCommand(
         {aggregate: testName, pipeline: [{$changeStream: {}}], cursor: {batchSize: batchSize}}));
     assert.eq(0, firstResponse.cursor.firstBatch.length);
diff --git a/jstests/change_streams/required_as_first_stage.js b/jstests/change_streams/required_as_first_stage.js
index 3d5bbb1ea6c..d84d7e4c127 100644
--- a/jstests/change_streams/required_as_first_stage.js
+++ b/jstests/change_streams/required_as_first_stage.js
@@ -1,10 +1,11 @@
 // Tests that the $changeStream stage can only be present as the first stage in the pipeline.
 (function() {
     "use strict";
-    load("jstests/aggregation/extras/utils.js");  // For assertErrorCode.
 
-    const coll = db.change_stream_required_as_first_stage;
-    coll.drop();
+    load("jstests/aggregation/extras/utils.js");       // For assertErrorCode.
+    load("jstests/libs/collection_drop_recreate.js");  // For assert[Drop|Create]Collection.
+
+    const coll = assertDropAndRecreateCollection(db, "change_stream_required_as_first_stage");
 
     assertErrorCode(coll, [{$indexStats: {}}, {$changeStream: {}}], 40602);
     assertErrorCode(
diff --git a/jstests/libs/change_stream_util.js b/jstests/libs/change_stream_util.js
index cbaf69fdedf..aea8aa3a1a5 100644
--- a/jstests/libs/change_stream_util.js
+++ b/jstests/libs/change_stream_util.js
@@ -30,10 +30,14 @@ function ChangeStreamTest(_db, name = "ChangeStreamTest") {
             pipeline.push(self.oplogProjection);
         }
 
+        // The 'collection' argument may be either a collection name or DBCollection object.
+        assert(collection instanceof DBCollection || typeof collection === "string");
+        const collName = (collection instanceof DBCollection ? collection.getName() : collection);
+
         let res = assert.commandWorked(_db.runCommand(
-            Object.merge({aggregate: collection.getName(), pipeline: pipeline}, aggregateOptions)));
+            Object.merge({aggregate: collName, pipeline: pipeline}, aggregateOptions)));
         assert.neq(res.cursor.id, 0);
-        _allCursors.push({db: _db.getName(), coll: collection.getName(), cursorId: res.cursor.id});
+        _allCursors.push({db: _db.getName(), coll: collName, cursorId: res.cursor.id});
         return res.cursor;
     };
 
@@ -41,10 +45,9 @@ function ChangeStreamTest(_db, name = "ChangeStreamTest") {
      * Issues a 'getMore' on the provided cursor and returns the cursor returned.
      */
     self.getNextBatch = function(cursor) {
-        let collection = _db.getMongo().getCollection(cursor.ns);
+        const collName = cursor.ns.split(/\.(.+)/)[1];
         return assert
-            .commandWorked(_db.runCommand(
-                {getMore: cursor.id, collection: collection.getName(), batchSize: 1}))
+            .commandWorked(_db.runCommand({getMore: cursor.id, collection: collName, batchSize: 1}))
             .cursor;
     };
 
diff --git a/jstests/libs/collection_drop_recreate.js b/jstests/libs/collection_drop_recreate.js
new file mode 100644
index 00000000000..9d2888ce6d8
--- /dev/null
+++ b/jstests/libs/collection_drop_recreate.js
@@ -0,0 +1,29 @@
+/**
+ * Attempts to drop the given collection and asserts either that the drop succeeded or the
+ * collection did not exist. Avoids automatically recreating the collection in the case of test
+ * suites where accessing or dropping the collection implicitly recreates it.
+ */
+function assertDropCollection(db, collName) {
+    var cmdRes = db.runCommand({drop: collName});
+    assert(cmdRes.ok === 1 || cmdRes.code === ErrorCodes.NamespaceNotFound, tojson(cmdRes));
+}
+
+/**
+ * Attempts to create a collection with the given name and options, if any, and asserts on failure.
+ * Returns the newly-created collection on success. When running under a sharded collections
+ * passthrough, the new collection will be implicitly sharded.
+ */
+function assertCreateCollection(db, collName, collOpts) {
+    assert.commandWorked(db.createCollection(collName, collOpts));
+    return db.getCollection(collName);
+}
+
+/**
+ * Attempts to drop a collection with the given name and recreate it with the specified options, if
+ * any. Asserts if either step fails. Returns the newly-created collection on success. When running
+ * under a sharded collections passthrough, the new collection will be implicitly sharded.
+ */
+function assertDropAndRecreateCollection(db, collName, collOpts) {
+    assertDropCollection(db, collName);
+    return assertCreateCollection(db, collName, collOpts);
+}
\ No newline at end of file
diff --git a/jstests/libs/override_methods/implicitly_shard_accessed_collections.js b/jstests/libs/override_methods/implicitly_shard_accessed_collections.js
index 3f1f8b24a55..e8ebf477167 100644
--- a/jstests/libs/override_methods/implicitly_shard_accessed_collections.js
+++ b/jstests/libs/override_methods/implicitly_shard_accessed_collections.js
@@ -45,7 +45,8 @@
             assert.commandWorked(res, "enabling sharding on the '" + dbName + "' db failed");
         }
 
-        res = db.adminCommand({shardCollection: fullName, key: {_id: 'hashed'}});
+        res = db.adminCommand(
+            {shardCollection: fullName, key: {_id: 'hashed'}, collation: {locale: "simple"}});
         if (res.ok === 0 && testMayRunDropInParallel) {
             // We ignore ConflictingOperationInProgress error responses from the
             // "shardCollection" command if it's possible the test was running a "drop" command
@@ -64,9 +65,10 @@
     DB.prototype.getCollection = function() {
         var collection = originalGetCollection.apply(this, arguments);
 
-        // If the collection exists, there must have been a previous call to getCollection
-        // where we sharded the collection so there's no need to do it again.
-        if (collection.exists()) {
+        const collStats = this.runCommand({collStats: collection.getName()});
+
+        // If the collection is already sharded or is non-empty, do not attempt to shard.
+        if (collStats.sharded || collStats.count > 0) {
             return collection;
         }
 
diff --git a/src/mongo/shell/db.js b/src/mongo/shell/db.js
index 8ef40760efa..f417f40060d 100644
--- a/src/mongo/shell/db.js
+++ b/src/mongo/shell/db.js
@@ -325,10 +325,8 @@ var DB;
         var options = opt || {};
 
         // We have special handling for the 'flags' field, and provide sugar for specific flags. If
-        // the
-        // user specifies any flags we send the field in the command. Otherwise, we leave it blank
-        // and
-        // use the server's defaults.
+        // the user specifies any flags we send the field in the command. Otherwise, we leave it
+        // blank and use the server's defaults.
         var sendFlags = false;
         var flags = 0;
         if (options.usePowerOf2Sizes != undefined) {