This is the sample of my mongodb document( try to use jsonformatter.com to analyse it):
{"_id":"6278686","playerName":"Rohit Lal","tournamentId":"197831","score":[{"_id":"1611380","runsScored":0,"ballFaced":0,"fours":0,"sixes":0,"strikeRate":0,"oversBowled":0,"runsConceded":0,"economyRate":0,"wickets":0,"maiden":0,"howToOut":"-","catches":["Mohit Mishra"],"stumping":[],"runout":[],"participatedRunout":[]},{"_id":"1602732","runsScored":0,"ballFaced":0,"fours":0,"sixes":0,"strikeRate":0,"oversBowled":0,"runsConceded":0,"economyRate":0,"wickets":0,"maiden":0,"howToOut":"-","catches":[],"stumping":[],"runout":[],"participatedRunout":[]},{"_id":"1536514","runsScored":1,"ballFaced":3,"fours":0,"sixes":0,"strikeRate":33.33,"oversBowled":0,"runsConceded":0,"economyRate":0,"wickets":0,"maiden":0,"howToOut":"run out Sameer Baveja","catches":[],"stumping":[],"runout":[],"participatedRunout":[]},{"_id":"1536474","runsScored":2,"ballFaced":7,"fours":0,"sixes":0,"strikeRate":28.57,"oversBowled":0,"runsConceded":0,"economyRate":0,"wickets":0,"maiden":0,"howToOut":"c Rajesh b Prasad Naik","catches":[],"stumping":[],"runout":[],"participatedRunout":[]},{"_id":"1536467","runsScored":0,"ballFaced":0,"fours":0,"sixes":0,"strikeRate":0,"oversBowled":0,"runsConceded":0,"economyRate":0,"wickets":0,"maiden":0,"howToOut":"-","catches":[],"stumping":[],"runout":[],"participatedRunout":[]},{"_id":"1500825","runsScored":0,"ballFaced":0,"fours":0,"sixes":0,"strikeRate":0,"oversBowled":0,"runsConceded":0,"economyRate":0,"wickets":0,"maiden":0,"howToOut":"-","catches":[],"stumping":[],"runout":[],"participatedRunout":[]},{"_id":"1461428","runsScored":18,"ballFaced":6,"fours":1,"sixes":2,"strikeRate":300,"oversBowled":0,"runsConceded":0,"economyRate":0,"wickets":0,"maiden":0,"howToOut":"not out","catches":[],"stumping":[],"runout":[],"participatedRunout":[]},{"_id":"1461408","runsScored":0,"ballFaced":1,"fours":0,"sixes":0,"strikeRate":0,"oversBowled":0,"runsConceded":0,"economyRate":0,"wickets":0,"maiden":0,"howToOut":"c Sudhir b Vinay Kasat *vk*","catches":[],"stumping":[],"runout":[],"participatedRunout":[]},{"_id":"1451175","runsScored":0,"ballFaced":0,"fours":0,"sixes":0,"strikeRate":0,"oversBowled":0,"runsConceded":0,"economyRate":0,"wickets":0,"maiden":0,"howToOut":"-","catches":[],"stumping":[],"runout":[],"participatedRunout":[]},{"_id":"1451146","runsScored":0,"ballFaced":0,"fours":0,"sixes":0,"strikeRate":0,"oversBowled":0,"runsConceded":0,"economyRate":0,"wickets":0,"maiden":0,"howToOut":"-","catches":[],"stumping":[],"runout":[],"participatedRunout":[]},{"_id":"1392796","runsScored":0,"ballFaced":1,"fours":0,"sixes":0,"strikeRate":0,"oversBowled":0,"runsConceded":0,"economyRate":0,"wickets":0,"maiden":0,"howToOut":"c †Vinay Kedia b Lalit","catches":[],"stumping":[],"runout":[],"participatedRunout":[]}],"__v":0}
I want to sum the length of catches array field of all objects inside score array. I know, I can achieve it using aggregation framework, but I am begineer in mongodb and does not have knowledge of many aggregation operators. Here is the aggregation pipeline I have tried but it returns the number of existence of this field, not the sum of length of this array:
[
"totalCatches": {
$size: "$score.catches"
}
]
$unwind - Descontruct score array field to multiple documents.$group - Group by null (for all objects), next $sum for the $size of score.catches.db.collection.aggregate([
{
$unwind: "$score"
},
{
$group: {
_id: null,
"totalCatches": {
$sum: {
$size: "$score.catches"
}
}
}
}
])
Note: If you want the result to be based on each document (not combine all documents), then you need to change the $group's _id as:
{
$group: {
_id: "$_id",
...
}
}