MongoDB : Sort exceeded memory limit of 104857600 bytes

Performs a large sort operation (Aggregation) in a collection, and hits the following error message :

> db.bigdata.aggregate(
	{$group : {_id : "$range", total : { $sum : 1 }}},
	{$sort : {total : -1}}
);
#...
 aggregate failed
    at Error (<anonymous>)
    at doassert (src/mongo/shell/assert.js:11:14)
    #...
    Error: command failed: {
        "errmsg" : "exception: Sort exceeded memory limit of 104857600 bytes, 
		  but did not opt in to external sorting. Aborting operation. Pass allowDiskUse:true to opt in.",
        "code" : 16819,
        "ok" : 0

P.S Tested with MongoDB 3.0.6

Solution

To fix it, enable the allowDiskUse option in your query :

db.bigdata.aggregate(
	{$group : {_id : "$range", total : { $sum : 1 }}},
	{$sort : {total : -1}}
],
	{allowDiskUse: true}
);

References

1. Perform Large Sort Operation with External Sort
2. Aggregation Pipeline Limits
3. MongoDB – Aggregate and Group example