问题
I am currently dealing with a set of in-game-events for various matches. In the game it is possible to kill enemies and purchase items in a shop.
What I have been trying to do right now, is to count the number of kills that have occured in a single match up until every purchasing event.
{
"_id" : ObjectId("5988f89ae5873exxxxxxx"),
"gameId" : NumberLong(2910126xxx)
"participantId" : 3,
"type" : "ITEM_PURCHASED",
"timestamp" : 656664 },
{
"_id" : ObjectId("5988f89ae5873exxxxxxx"),
"gameId" : NumberLong(2910126xxx)
"participantId" : 3,
"victimId" : 9,
"type" : "ENEMY_KILLED",
"timestamp" : 745245 },
{
"_id" : ObjectId("5988f89ae5873exxxxxxx"),
"gameId" : NumberLong(2910126xxx)
"participantId" : 3,
"victimId" : 7,
"type" : "ENEMY_KILLED",
"timestamp" : 746223 },
{
"_id" : ObjectId("5988f89ae5873exxxxxxx"),
"gameId" : NumberLong(2910126xxx)
"participantId" : 3,
"type" : "ITEM_PURCHASED",
"timestamp" : 840245 },
In which this is a desired outcome for me:
{
"_id" : ObjectId("5988f89ae5873exxxxxxx"),
"gameId" : NumberLong(2910126xxx)
"participantId" : 3,
"type" : "ITEM_PURCHASED",
"timestamp" : 656664,
"kills": 0 },
{
"_id" : ObjectId("5988f89ae5873exxxxxxx"),
"gameId" : NumberLong(2910126xxx)
"participantId" : 3,
"type" : "ITEM_PURCHASED",
"timestamp" : 840245 ,
"kills": 2 }
Although I am inclined to think that this is quite impossible, I am not yet that experienced with all the capabilities mongo offers.
Is there a way to count occurrances of certain values up until the appearance of an purchasing event?
回答1:
try this aggregation
$match
- filter by gameId$sort
- order documents by timestamp$group
- accumulate all matched to an array$addFields
-$reduce
to calculate kills, filter and map kills to document$unwind
- flat array to get original document structure$replaceRoot
- move data to top level as in original structure
pipeline
db.games.aggregate([
{$match : {gameId : 1}},
{$sort : {timestamp : 1}},
{$group : {_id : "$gameId", data : {$push : "$$ROOT"}}},
{$addFields : {data : {
$reduce : {
input : "$data",
initialValue : {kills : [], data : [], count : 0},
in : {
count : {$sum : ["$$value.count", {$cond : [{$eq : ["$$this.type", "ENEMY_KILLED"]}, 1, 0]}]},
data : { $concatArrays : [
"$$value.data",
{$cond : [
{$ne : ["$$this.type", "ENEMY_KILLED"]},
[
{
_id : "$$this._id",
gameId : "$$this.gameId",
participantId : "$$this.participantId",
type : "$$this.type",
timestamp : "$$this.timestamp",
kills : {$sum : ["$$value.count", {$cond : [{$eq : ["$$this.type", "ENEMY_KILLED"]}, 1, 0]}]}
}
],
[]
]}
]}
}
}}
}},
{$unwind : "$data.data"},
{$replaceRoot : {newRoot : "$data.data"}}
]).pretty()
collection
> db.games.find()
{ "_id" : 1, "gameId" : 1, "participantId" : 3, "type" : "ITEM_PURCHASED", "timestamp" : 656664 }
{ "_id" : 2, "gameId" : 1, "participantId" : 3, "victimId" : 9, "type" : "ENEMY_KILLED", "timestamp" : 745245 }
{ "_id" : 3, "gameId" : 1, "participantId" : 3, "victimId" : 7, "type" : "ENEMY_KILLED", "timestamp" : 746223 }
{ "_id" : 4, "gameId" : 1, "participantId" : 3, "type" : "ITEM_PURCHASED", "timestamp" : 840245 }
result
{
"_id" : 1,
"gameId" : 1,
"participantId" : 3,
"type" : "ITEM_PURCHASED",
"timestamp" : 656664,
"kills" : 0
}
{
"_id" : 4,
"gameId" : 1,
"participantId" : 3,
"type" : "ITEM_PURCHASED",
"timestamp" : 840245,
"kills" : 2
}
>
来源:https://stackoverflow.com/questions/48956526/mongodb-running-total-like-aggregation-of-previous-records-up-until-occurrance-o