data creation using createTestData("test", 8000, 20, 4, 20); -->

olivers-mbp-4:Duplicate Oliver$ mongo localhost:27017/local BugRep.js
MongoDB shell version: 2.6.5
connecting to: localhost:27017/local
createTestData...
createCollection...
base size: 198172
aggregation...
agg size: 7317

Log:
2014-12-09T16:28:21.568+0100 [initandlisten] connection accepted from 127.0.0.1:51851 #13 (10 connections now open)
2014-12-09T16:28:24.277+0100 [conn13] remove local.base ndeleted:41831 keyUpdates:0 numYields:2 locks(micros) w:449278 264ms
2014-12-09T16:28:24.277+0100 [conn13] command local.$cmd command: delete { delete: "base", deletes: [ { q: {}, limit: 0.0 } ], ordered: true } keyUpdates:0 numYields:0  reslen:40 264ms
2014-12-09T16:28:28.069+0100 [initandlisten] connection accepted from 127.0.0.1:51852 #14 (11 connections now open)
2014-12-09T16:28:31.069+0100 [clientcursormon] mem (MB) res:126 virt:2685
2014-12-09T16:28:31.069+0100 [clientcursormon]  mapped (incl journal view):160
2014-12-09T16:28:31.069+0100 [clientcursormon]  connections:11
2014-12-09T16:28:31.335+0100 [FileAllocator] allocating new datafile pdb/local.1, filling with zeroes...
2014-12-09T16:28:31.632+0100 [FileAllocator] done allocating datafile pdb/local.1, size: 128MB,  took 0.297 secs
2014-12-09T16:28:31.657+0100 [conn13] insert local.base query: { _id: ObjectId('5487151f135b690f42388fb7'), name: "jcgg", ref: ObjectId('54871516135b690f4235d311') } ninserted:1 keyUpdates:0 numYields:0 locks(micros) w:322755 322ms
2014-12-09T16:28:31.665+0100 [conn13] command local.$cmd command: insert { $msg: "query not recording (too large)" } keyUpdates:0 numYields:0 locks(micros) w:95 reslen:40 338ms
2014-12-09T16:28:34.432+0100 [conn13] build index on: local.tmp.agg_out.4 properties: { v: 1, key: { _id: 1 }, name: "_id_", ns: "local.tmp.agg_out.4" }
2014-12-09T16:28:34.432+0100 [conn13] 	 added index to empty collection
2014-12-09T16:28:35.760+0100 [conn13] warning: DR102 too much data written uncommitted 314.577MB
2014-12-09T16:28:37.737+0100 [conn13] insert local.tmp.agg_out.4 ninserted:247680 keyUpdates:0 numYields:0 locks(micros) w:2128864 2129ms
2014-12-09T16:28:38.154+0100 [conn13] command local.$cmd command: aggregate { aggregate: "base", pipeline: [ { $group: { _id: "$name", refs: { $addToSet: "$ref" } } }, { $out: "agg" } ], allowDiskUse: true } keyUpdates:0 numYields:13 locks(micros) R:372822 r:186122 reslen:50 3722ms
2014-12-09T16:28:41.086+0100 [conn13] remove local.agg query: { refs.1: { $exists: 0.0 } } ndeleted:234279 keyUpdates:0 numYields:28 locks(micros) R:23848 w:4815184 2931ms
2014-12-09T16:28:41.086+0100 [conn13] command local.$cmd command: delete { delete: "agg", deletes: [ { q: { refs.1: { $exists: 0.0 } }, limit: 0.0 } ], ordered: true } keyUpdates:0 numYields:0  reslen:40 2931ms
2014-12-09T16:28:41.097+0100 [conn13] end connection 127.0.0.1:51851 (10 connections now open)