5 files changed, 160 insertions, 0 deletions
diff --git a/jstests/core/explain_agg_write_concern.js b/jstests/core/explain_agg_write_concern.js
new file mode 100644
index 00000000000..3a70040a525
--- /dev/null
+++ b/jstests/core/explain_agg_write_concern.js
@@ -0,0 +1,64 @@
+/**
+ * Tests related to the aggregate commands behavior with writeConcern and writeConcern + explain.
+ */
+(function() {
+    "use strict";
+
+    let coll = db[jsTest.name()];
+    let outColl = db[jsTest.name() + "_out"];
+    coll.drop();
+    outColl.drop();
+
+    assert.writeOK(coll.insert({_id: 1}));
+
+    // Agg should accept write concern if the last stage is a $out.
+    assert.commandWorked(db.runCommand({
+        aggregate: coll.getName(),
+        pipeline: [{$out: outColl.getName()}],
+        cursor: {},
+        writeConcern: {w: 1}
+    }));
+    assert.eq(1, outColl.find().itcount());
+    outColl.drop();
+
+    // Agg should reject writeConcern if the last stage is not an $out.
+    assert.commandFailed(
+        db.runCommand({aggregate: coll.getName(), pipeline: [], cursor: {}, writeConcern: {w: 1}}));
+
+    // Agg should succeed if the last stage is an $out and the explain flag is set.
+    assert.commandWorked(db.runCommand({
+        aggregate: coll.getName(),
+        pipeline: [{$out: outColl.getName()}],
+        explain: true,
+    }));
+    assert.eq(0, outColl.find().itcount());
+    outColl.drop();
+
+    // Agg should fail if the last stage is an $out and both the explain flag and writeConcern are
+    // set.
+    assert.commandFailed(db.runCommand({
+        aggregate: coll.getName(),
+        pipeline: [{$out: outColl.getName()}],
+        explain: true,
+        writeConcern: {w: 1}
+    }));
+
+    // Agg explain helpers with all verbosities (or verbosity omitted) should fail if the last stage
+    // is an $out and writeConcern is set.
+    assert.throws(function() {
+        coll.explain().aggregate([{$out: outColl.getName()}], {writeConcern: {w: 1}});
+    });
+    assert.throws(function() {
+        coll.explain("queryPlanner").aggregate([{$out: outColl.getName()}], {writeConcern: {w: 1}});
+    });
+    assert.throws(function() {
+        coll.explain("executionStats").aggregate([{$out: outColl.getName()}], {
+            writeConcern: {w: 1}
+        });
+    });
+    assert.throws(function() {
+        coll.explain("allPlansExecution").aggregate([{$out: outColl.getName()}], {
+            writeConcern: {w: 1}
+        });
+    });
+}());
diff --git a/jstests/core/views/views_aggregation.js b/jstests/core/views/views_aggregation.js
index 4a7e141a49f..a0c5392deb4 100644
--- a/jstests/core/views/views_aggregation.js
+++ b/jstests/core/views/views_aggregation.js
@@ -119,6 +119,48 @@
             {aggregate: "largeView", pipeline: [{$sort: {x: -1}}], cursor: {}, allowDiskUse: true}),
         "Expected aggregate to succeed since 'allowDiskUse' was specified");
 
+    // Test explain modes on a view.
+    let explainPlan = assert.commandWorked(
+        viewsDB.popSortedView.explain("queryPlanner").aggregate([{$limit: 1}, {$match: {pop: 3}}]));
+    assert.eq(explainPlan.stages[0].$cursor.queryPlanner.namespace, "views_aggregation.coll");
+    assert(!explainPlan.stages[0].$cursor.hasOwnProperty("executionStats"));
+
+    explainPlan = assert.commandWorked(viewsDB.popSortedView.explain("executionStats")
+                                           .aggregate([{$limit: 1}, {$match: {pop: 3}}]));
+    assert.eq(explainPlan.stages[0].$cursor.queryPlanner.namespace, "views_aggregation.coll");
+    assert(explainPlan.stages[0].$cursor.hasOwnProperty("executionStats"));
+    assert.eq(explainPlan.stages[0].$cursor.executionStats.nReturned, 1);
+    assert(!explainPlan.stages[0].$cursor.executionStats.hasOwnProperty("allPlansExecution"));
+
+    explainPlan = assert.commandWorked(viewsDB.popSortedView.explain("allPlansExecution")
+                                           .aggregate([{$limit: 1}, {$match: {pop: 3}}]));
+    assert.eq(explainPlan.stages[0].$cursor.queryPlanner.namespace, "views_aggregation.coll");
+    assert(explainPlan.stages[0].$cursor.hasOwnProperty("executionStats"));
+    assert.eq(explainPlan.stages[0].$cursor.executionStats.nReturned, 1);
+    assert(explainPlan.stages[0].$cursor.executionStats.hasOwnProperty("allPlansExecution"));
+
+    // Passing a value of true for the explain option to the aggregation command, without using the
+    // shell explain helper, should continue to work.
+    explainPlan = assert.commandWorked(
+        viewsDB.popSortedView.aggregate([{$limit: 1}, {$match: {pop: 3}}], {explain: true}));
+    assert.eq(explainPlan.stages[0].$cursor.queryPlanner.namespace, "views_aggregation.coll");
+    assert(!explainPlan.stages[0].$cursor.hasOwnProperty("executionStats"));
+
+    // Test allPlansExecution explain mode on the base collection.
+    explainPlan = assert.commandWorked(
+        viewsDB.coll.explain("allPlansExecution").aggregate([{$limit: 1}, {$match: {pop: 3}}]));
+    assert.eq(explainPlan.stages[0].$cursor.queryPlanner.namespace, "views_aggregation.coll");
+    assert(explainPlan.stages[0].$cursor.hasOwnProperty("executionStats"));
+    printjson(explainPlan.stages[0].$cursor.executionStats);
+    assert.eq(explainPlan.stages[0].$cursor.executionStats.nReturned, 5);
+    assert(explainPlan.stages[0].$cursor.executionStats.hasOwnProperty("allPlansExecution"));
+
+    // The explain:true option should not work when paired with the explain shell helper.
+    assert.throws(function() {
+        viewsDB.popSortedView.explain("executionStats")
+            .aggregate([{$limit: 1}, {$match: {pop: 3}}], {explain: true});
+    });
+
     // The remaining tests involve $lookup and $graphLookup. We cannot lookup into sharded
     // collections, so skip these tests if running in a sharded configuration.
     let isMasterResponse = assert.commandWorked(viewsDB.runCommand("isMaster"));
diff --git a/jstests/core/views/views_count.js b/jstests/core/views/views_count.js
index ddf97ce0bb2..932021e899f 100644
--- a/jstests/core/views/views_count.js
+++ b/jstests/core/views/views_count.js
@@ -53,6 +53,26 @@
     assert.commandWorked(explainPlan);
     assert.eq(explainPlan["stages"][0]["$cursor"]["queryPlanner"]["namespace"], "views_count.coll");
 
+    // Count with explicit explain modes works on a view.
+    explainPlan =
+        assert.commandWorked(lessThanSevenView.explain("queryPlanner").count({x: {$gte: 5}}));
+    assert.eq(explainPlan.stages[0].$cursor.queryPlanner.namespace, "views_count.coll");
+    assert(!explainPlan.stages[0].$cursor.hasOwnProperty("executionStats"));
+
+    explainPlan =
+        assert.commandWorked(lessThanSevenView.explain("executionStats").count({x: {$gte: 5}}));
+    assert.eq(explainPlan.stages[0].$cursor.queryPlanner.namespace, "views_count.coll");
+    assert(explainPlan.stages[0].$cursor.hasOwnProperty("executionStats"));
+    assert.eq(explainPlan.stages[0].$cursor.executionStats.nReturned, 2);
+    assert(!explainPlan.stages[0].$cursor.executionStats.hasOwnProperty("allPlansExecution"));
+
+    explainPlan =
+        assert.commandWorked(lessThanSevenView.explain("allPlansExecution").count({x: {$gte: 5}}));
+    assert.eq(explainPlan.stages[0].$cursor.queryPlanner.namespace, "views_count.coll");
+    assert(explainPlan.stages[0].$cursor.hasOwnProperty("executionStats"));
+    assert.eq(explainPlan.stages[0].$cursor.executionStats.nReturned, 2);
+    assert(explainPlan.stages[0].$cursor.executionStats.hasOwnProperty("allPlansExecution"));
+
     // Count with hint works on a view.
     assert.commandWorked(viewsDB.runCommand({count: "identityView", hint: "_id_"}));
 
diff --git a/jstests/core/views/views_distinct.js b/jstests/core/views/views_distinct.js
index b53a8e9e871..0a0b6002b15 100644
--- a/jstests/core/views/views_distinct.js
+++ b/jstests/core/views/views_distinct.js
@@ -68,6 +68,23 @@
     assert.eq(explainPlan["stages"][0]["$cursor"]["queryPlanner"]["namespace"],
               "views_distinct.coll");
 
+    // Distinct with explicit explain modes works on a view.
+    explainPlan = assert.commandWorked(largePopView.explain("queryPlanner").distinct("pop"));
+    assert.eq(explainPlan.stages[0].$cursor.queryPlanner.namespace, "views_distinct.coll");
+    assert(!explainPlan.stages[0].$cursor.hasOwnProperty("executionStats"));
+
+    explainPlan = assert.commandWorked(largePopView.explain("executionStats").distinct("pop"));
+    assert.eq(explainPlan.stages[0].$cursor.queryPlanner.namespace, "views_distinct.coll");
+    assert(explainPlan.stages[0].$cursor.hasOwnProperty("executionStats"));
+    assert.eq(explainPlan.stages[0].$cursor.executionStats.nReturned, 2);
+    assert(!explainPlan.stages[0].$cursor.executionStats.hasOwnProperty("allPlansExecution"));
+
+    explainPlan = assert.commandWorked(largePopView.explain("allPlansExecution").distinct("pop"));
+    assert.eq(explainPlan.stages[0].$cursor.queryPlanner.namespace, "views_distinct.coll");
+    assert(explainPlan.stages[0].$cursor.hasOwnProperty("executionStats"));
+    assert.eq(explainPlan.stages[0].$cursor.executionStats.nReturned, 2);
+    assert(explainPlan.stages[0].$cursor.executionStats.hasOwnProperty("allPlansExecution"));
+
     // Distinct commands fail when they try to change the collation of a view.
     assert.commandFailedWithCode(
         viewsDB.runCommand({distinct: "identityView", key: "state", collation: {locale: "en_US"}}),
diff --git a/jstests/core/views/views_find.js b/jstests/core/views/views_find.js
index c196e980ce5..da555e454b7 100644
--- a/jstests/core/views/views_find.js
+++ b/jstests/core/views/views_find.js
@@ -72,6 +72,23 @@
     // Views support find with explain.
     assert.commandWorked(viewsDB.identityView.find().explain());
 
+    // Find with explicit explain modes works on a view.
+    let explainPlan = assert.commandWorked(viewsDB.identityView.find().explain("queryPlanner"));
+    assert.eq(explainPlan.stages[0].$cursor.queryPlanner.namespace, "views_find.coll");
+    assert(!explainPlan.stages[0].$cursor.hasOwnProperty("executionStats"));
+
+    explainPlan = assert.commandWorked(viewsDB.identityView.find().explain("executionStats"));
+    assert.eq(explainPlan.stages[0].$cursor.queryPlanner.namespace, "views_find.coll");
+    assert(explainPlan.stages[0].$cursor.hasOwnProperty("executionStats"));
+    assert.eq(explainPlan.stages[0].$cursor.executionStats.nReturned, 5);
+    assert(!explainPlan.stages[0].$cursor.executionStats.hasOwnProperty("allPlansExecution"));
+
+    explainPlan = assert.commandWorked(viewsDB.identityView.find().explain("allPlansExecution"));
+    assert.eq(explainPlan.stages[0].$cursor.queryPlanner.namespace, "views_find.coll");
+    assert(explainPlan.stages[0].$cursor.hasOwnProperty("executionStats"));
+    assert.eq(explainPlan.stages[0].$cursor.executionStats.nReturned, 5);
+    assert(explainPlan.stages[0].$cursor.executionStats.hasOwnProperty("allPlansExecution"));
+
     // Only simple 0 or 1 projections are allowed on views.
     assert.writeOK(viewsDB.coll.insert({arr: [{x: 1}]}));
     assert.commandFailedWithCode(