SERVER-18198 fix incorrect logic for applying read pref to aggregate command

1 files changed, 42 insertions, 0 deletions

diff --git a/jstests/aggregation/bugs/server18198.js b/jstests/aggregation/bugs/server18198.js
new file mode 100644
index 00000000000..6d8d827e416
--- /dev/null
+++ b/jstests/aggregation/bugs/server18198.js
@@ -0,0 +1,42 @@
+// SERVER-18198 check read pref is only applied when there is no $out stage
+// in aggregate shell helper
+(function() {
+    "use strict";
+    var t = db.server18198;
+    t.drop();
+
+    var mongo = db.getMongo();
+
+    try {
+        var commandsRan = [];
+        // hook in our patched mongo
+        var mockMongo = {
+            getSlaveOk: function() { return true; },
+            runCommand: function(db, cmd, opts) {
+              commandsRan.push({db: db, cmd: cmd, opts: opts});
+              return {ok: 1.0};
+            },
+            getReadPref: function() { return {mode: "secondaryPreferred"}; },
+            getReadPrefMode: function() { return "secondaryPreferred"; }
+        };
+
+        db._mongo = mockMongo;
+
+        // this query should not get a read pref
+        t.aggregate([{$sort: {"x" : 1}}, {$out: "foo"}]);
+        assert.eq(commandsRan.length, 1);
+        // check that it doesn't have a read preference
+        assert(!commandsRan[0].cmd.hasOwnProperty("$readPreference"));
+
+        commandsRan = [];
+
+        t.aggregate([{$sort: {"x" : 1}}]);
+        // check another command was run
+        assert.eq(commandsRan.length, 1);
+        // check that it has a read preference
+        assert(commandsRan[0].cmd.hasOwnProperty("$readPreference"));
+    }
+    finally {
+        db._mongo = mongo;
+    }
+})();