MongoDB group and compute results from multiple fields within same document - mongodb

Question

Can I have your help regarding MongoDB aggregation framework. I trying to build a Premier League Table from following collection of games:
{
"_id" : ObjectId("5b39fec4b5f8df161d259f36"),
"gameWeek" : 1,
"homeTeam" : "Arsenal",
"awayTeam" : "Leicester",
"homeGoals" : 2,
"awayGoals" : 1
}, {
"_id" : ObjectId("5b39ffc2b5f8df161d259f6d"),
"gameWeek" : 2,
"homeTeam" : "Arsenal",
"awayTeam" : "Sunderland",
"homeGoals" : 1,
"awayGoals" : 1
}, {
"_id" : ObjectId("5b39ffe8b5f8df161d259f7f"),
"gameWeek" : 2,
"homeTeam" : "Sunderland",
"awayTeam" : "Manchester United",
"homeGoals" : 1,
"awayGoals" : 1
}, {
"_id" : ObjectId("5b492cbea5aef964f0911cce"),
"gameWeek" : 1,
"homeTeam" : "Manchester United",
"awayTeam" : "Leicester",
"homeGoals" : 0,
"awayGoals" : 1
}
I wish to get following results:
{
"_id" : "Arsenal",
"team" : "Arsenal",
"gamesPlayed" : 2,
"goalsFor" : 3,
"goalsAgainst" : 2,
"goalsDifference" : 1,
"gamesWon" : 1,
"gamesDraw" : 1,
"gamesLost" : 0,
"points" : 4
}, {
"_id" : "Leicester",
"team" : "Leicester",
"gamesPlayed" : 2,
"goalsFor" : 2,
"goalsAgainst" : 2,
"goalsDifference" : 0,
"gamesWon" : 1,
"gamesDraw" : 0,
"gamesLost" : 1,
"points" : 3
}, {
"_id" : "Sunderland",
"team" : "Sunderland",
"gamesPlayed" : 2,
"goalsFor" : 2,
"goalsAgainst" : 2,
"goalsDifference" : 0,
"gamesWon" : 0,
"gamesDraw" : 2,
"gamesLost" : 0,
"points" : 2
}, {
"_id" : "Manchester United",
"team" : "Manchester United",
"gamesPlayed" : 2,
"goalsFor" : 1,
"goalsAgainst" : 2,
"goalsDifference" : -1,
"gamesWon" : 0,
"gamesDraw" : 1,
"gamesLost" : 1,
"points" : 1
}
where:
gamesPlayed - total number of the games played,
goalsFor - total goals made by team,
goalsAgainst - total let in goals,
goalsDifference - 'goalsFor' subtracting 'goalsAgainst'
points - gets calculated scoring 3 points for each won game and 1 point for every draw game.
So far I have following query for building team standing by homeTeam results:
db.football_matches.aggregate([
{
$group: {
_id: "$homeTeam",
gamesPlayed : { $sum: NumberInt(1) },
goalsFor: { $sum: "$homeGoals" },
goalsAgainst: { $sum: "$awayGoals" },
gamesWon: { $sum: { $cond: { if: { $gt: [ "$homeGoals", "$awayGoals" ]}, then: NumberInt(1), else: NumberInt(0) } }},
gamesDraw: { $sum: { $cond: { if: { $eq: [ "$homeGoals", "$awayGoals" ]}, then: NumberInt(1), else: NumberInt(0) } }},
gamesLost: { $sum: { $cond: { if: { $lt: [ "$homeGoals", "$awayGoals" ]}, then: NumberInt(1), else: NumberInt(0) } }}
}
}, {
$project: {
team: "$_id" ,
gamesPlayed: "$gamesPlayed",
goalsFor: "$goalsFor",
goalsAgainst: "$goalsAgainst",
goalsDifference: { $subtract: [ "$goalsFor", "$goalsAgainst"] },
gamesWon: "$gamesWon",
gamesDraw: "$gamesDraw",
gamesLost: "$gamesLost",
points: { $add: [ {$multiply: [ "$gamesWon", NumberInt(3)]}, {$multiply: [ "$gamesDraw", NumberInt(1)]} ]}
}
}, {
$sort: { points: -1, goalsDifference: -1 }
}
])
Theoretically I need to combine following grouping results with another similar group statement where similar action will be perform against awayTeam fields:
{
$group: {
_id: "$awayTeam",
gamesPlayed : { $sum: NumberInt(1) },
goalsFor: { $sum: "$awayGoals" },
goalsAgainst: { $sum: "$homeGoals" },
gamesWon: { $sum: { $cond: { if: { $gt: [ "$awayGoals", "$homeGoals" ]}, then: NumberInt(1), else: NumberInt(0) } }},
gamesDraw: { $sum: { $cond: { if: { $eq: [ "$awayGoals", "$homeGoals" ]}, then: NumberInt(1), else: NumberInt(0) } }},
gamesLost: { $sum: { $cond: { if: { $lt: [ "$awayGoals", "$homeGoals" ]}, then: NumberInt(1), else: NumberInt(0) } }}
}
}
How can I do that? Thank you very much. Please accept my apologies if similar question was asked before.

Answer 1

You can try below aggregation using $facet, $replaceRoot, $unwind, $concatArrays and finally with one more $group stage
db.collection.aggregate([
{ "$facet": {
"first": [
{ "$group": {
"_id": "$homeTeam",
"gamesPlayed": { "$sum": 1 },
"goalsFor": { "$sum": "$homeGoals" },
"goalsAgainst": { "$sum": "$awayGoals" },
"gamesWon": {
"$sum": { "$cond": { "if": { "$gt": [ "$homeGoals", "$awayGoals" ] }, "then": 1, "else": 0 } }
},
"gamesDraw": {
"$sum": { "$cond": { "if": { "$eq": [ "$homeGoals", "$awayGoals" ] }, "then": 1, "else": 0 } }
},
"gamesLost": {
"$sum": { "$cond": { "if": { "$lt": [ "$homeGoals", "$awayGoals" ] }, "then": 1, "else": 0 } }
}
}},
{ "$project": {
"team": "$_id",
"gamesPlayed": "$gamesPlayed",
"goalsFor": "$goalsFor",
"goalsAgainst": "$goalsAgainst",
"goalsDifference": { "$subtract": [ "$goalsFor", "$goalsAgainst" ] },
"gamesWon": "$gamesWon",
"gamesDraw": "$gamesDraw",
"gamesLost": "$gamesLost",
"points": { "$add": [{ "$multiply": [ "$gamesWon", 3 ] }, { "$multiply": [ "$gamesDraw", 1 ] }] }
}},
{ "$sort": { "points": -1, "goalsDifference": -1 } }
],
"second": [
{ "$group": {
"_id": "$awayTeam",
"gamesPlayed": { "$sum": 1 },
"goalsFor": { "$sum": "$awayGoals" },
"goalsAgainst": { "$sum": "$homeGoals" },
"gamesWon": {
"$sum": { "$cond": { "if": { "$gt": [ "$awayGoals", "$homeGoals" ] }, "then": 1, "else": 0 } }
},
"gamesDraw": {
"$sum": { "$cond": { "if": { "$eq": [ "$awayGoals", "$homeGoals" ] }, "then": 1, "else": 0 } }
},
"gamesLost": {
"$sum": { "$cond": { "if": { "$lt": [ "$awayGoals", "$homeGoals" ] }, "then": 1, "else": 0 } }
}
}},
{ "$project": {
"team": "$_id",
"gamesPlayed": "$gamesPlayed",
"goalsFor": "$goalsFor",
"goalsAgainst": "$goalsAgainst",
"goalsDifference": { "$subtract": [ "$goalsFor", "$goalsAgainst" ] },
"gamesWon": "$gamesWon",
"gamesDraw": "$gamesDraw",
"gamesLost": "$gamesLost",
"points": { "$add": [{ "$multiply": [ "$gamesWon",3 ] }, { "$multiply": [ "$gamesDraw",1 ] } ] }
}},
{ "$sort": { "points": -1, "goalsDifference": -1 } }
]
}},
{ "$project": {
"data": {
"$concatArrays": [ "$first", "$second" ]
}
}},
{ "$unwind": "$data" },
{ "$replaceRoot": { "newRoot": "$data" } },
{ "$group": {
"_id": "$_id",
"gamesPlayed": { "$sum": "$gamesPlayed" },
"goalsFor": { "$sum": "$goalsFor" },
"goalsAgainst": { "$sum": "$goalsAgainst" },
"gamesWon": { "$sum": "$gamesWon" },
"gamesDraw": { "$sum": "$gamesDraw" },
"gamesLost": { "$sum": "$gamesLost" }
}}
])