Moped::Errors::QueryFailure: The operation: #<Moped::Protocol::Query @length=210 @request_id=88981 @response_to=0 @op_code=2004 @flags=[] @full_collection_name="comments-loadtest.contents" @skip=24800 @limit=100 @selector={"$query"=>{"_type"=>"CommentThread", "course_id"=>"BerkeleyX/ColWri2.2x/1T2014", "context"=>:course}, "$orderby"=>{"pinned"=>-1, "last_activity_at"=>-1}} @fields=nil>failed with error 17144: "Runner error: Overflow sort stage buffered data usage of 33556783 bytes exceeds internal limit of 33554432 bytes"See https://github.com/mongodb/mongo/blob/master/docs/errors.mdfor details about this error.
Hitting the 32MB limit for in-memory sort. Commonly suggested causes were missing indexes.
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{"$query"=>{"_type"=>"CommentThread", "course_id"=>"BerkeleyX/ColWri2.2x/1T2014", "context"=>:course}, "$orderby"=>{"pinned"=>-1, "last_activity_at"=>-1}}
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There exists a query for "_type", "course_id", "pinned" but none for "_type", "course_id", "pinned", "last_activity_at"
Equivalent query in mongo shell:
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Will also return the memory error.
Note: Sorting by "asc" can lead to similar errors as that is not indexed specifically.
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Suggested solution:
Add the index for because the default query for GET Thread_list uses last_activity_at as a filter.
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db.contents.ensureIndex({"_type" : 1, "course_id" : 1, "context" : 1, "pinned" : -1, "last_activity_at" : -1 }, {"background":true}); |
Production and browser discussion api:
There is a possibility that this may be an issue on production.
