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Type:
Bug
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Resolution: Fixed
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Priority:
Major - P3
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Affects Version/s: 4.4.0-rc2
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Component/s: Aggregation Framework
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Fully Compatible
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ALL
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v4.4
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Query 2020-08-24
I'm not sure how $accumulator contributes to tracking group size but it appears to be way overcounting when passed documents (unless it's allocating a huge amount to JS in general?)
db.scores.aggregate([{$match:{game:/^G[123]/}},{$count:"c"}])
{ "c" : 368061 }
db.scores.aggregate([{$match:{game:/^G[123]/}},{$group:{_id:0, size:{$sum:{$bsonSize:"$$ROOT"}}}}])
{ "_id" : 0, "size" : 30215379 } /* 28GBs */
db.scores.aggregate([{$match:{game:/^G[123]/}}, {$group:{_id:"$game", top2: { $accumulator: { init: function() { return null; }, accumulateArgs: [ [1,2,3,4,5,"$player","$score"] ], accumulate: function(state, val) { return state; }, merge: function(state1, state2) { return state1; }, finalize: function(state) { return state; } } } } },{$count:"c"}])
{ "c" : 33 }
/* as soon as I pass a document as args */
db.scores.aggregate([{$match:{game:/^G[123]/}}, {$group:{_id:"$game", top2: { $accumulator: { init: function() { return null; }, accumulateArgs: [ {score:"$score"} ], accumulate: function(state, val) { return state; }, merge: function(state1, state2) { return state1; }, finalize: function(state) { return state; } } } } },{$count:"c"}])
Error: command failed: {
"ok" : 0,
"errmsg" : "Exceeded memory limit for $group, but didn't allow external sort. Pass allowDiskUse:true to opt in.",
"code" : 292,
"codeName" : "QueryExceededMemoryLimitNoDiskUseAllowed"
} : aggregate failed :
_getErrorWithCode@src/mongo/shell/utils.js:25:13
doassert@src/mongo/shell/assert.js:18:14
_assertCommandWorked@src/mongo/shell/assert.js:618:17
assert.commandWorked@src/mongo/shell/assert.js:708:16
DB.prototype._runAggregate@src/mongo/shell/db.js:266:5
DBCollection.prototype.aggregate@src/mongo/shell/collection.js:1012:12
@(shell):1:1
/* with limit */
db.scores.aggregate([{$match:{game:/^G[123]/}},{$limit:335000}, {$group:{_id:"$game", top2: { $accumulator: { init: function() { return null; }, accumulateArgs: [ {score:"$score"} ], accumulate: function(state, val) { return state; }, merge: function(state1, state2) { return state1; }, finalize: function(state) { return state; } } } } },{$count:"c"}])
{ "c" : 30 }
db.scores.aggregate([{$match:{game:/^G[123]/}},{$limit:340000}, {$group:{_id:"$game", top2: { $accumulator: { init: function() { return null; }, accumulateArgs: [ {score:"$score"} ], accumulate: function(state, val) { return state; }, merge: function(state1, state2) { return state1; }, finalize: function(state) { return state; } } } } },{$count:"c"}])
Error: command failed: {
"ok" : 0,
"errmsg" : "Exceeded memory limit for $group, but didn't allow external sort. Pass allowDiskUse:true to opt in.", ...
Collection stats:
db.scores.aggregate({$collStats:{storageStats:{scale:1024*1024}}},{$project:{"storageStats.wiredTiger":0,"storageStats.indexDetails":0}}).pretty()
{
"ns" : "agg.scores",
"host" : "asyas-mbp-4.lan:27017",
"localTime" : ISODate("2020-05-23T18:44:17.107Z"),
"storageStats" : {
"size" : 95,
"count" : 1130151,
"avgObjSize" : 88,
"storageSize" : 31,
"freeStorageSize" : 0,
"capped" : false,
"nindexes" : 2,
"indexBuilds" : [ ],
"totalIndexSize" : 51,
"totalSize" : 82,
"indexSizes" : {
"_id_" : 19,
"game_1_score_-1" : 32
},
"scaleFactor" : 1048576
}
}