Esta fue complicada para alguien nuevo en MongoDb aggregate de 's . Desglosaré mi respuesta en pasos para demostrar a otros que intentan agregar una matriz con referencias a varias colecciones.
Paso 1:$coincidencia para filtrar en la colección
El $match acepta las mismas consultas que db.collection.find({}) y devuelve una matriz de resultados coincidentes en el caso a continuación, selecciono 4 registros específicos aquí
{ '$match':
{ _id:
{ '$in':
[
ObjectId('5f7bdb3eea134b5a5c976285'),
ObjectId('5f7bdb3eea134b5a5c976283'),
ObjectId('5f7bdb3eea134b5a5c976284'),
ObjectId('5f7bdb3eea134b5a5c976289')
]
}
}
}
[
{ _id: ObjectId('5f7be0b37e2bdf5b19e4724d'),
name: 'CAPTAIN_SAIL',
classes: [ 'sail' ],
license: 'WC-1',
watercraftContexts:
[ { _id: ObjectId('5f7be0b37e2bdf5b19e47241'),
watercraftType: 'Sailboat',
ref: 'sailboats' } ],
__v: 0 },
{ _id: ObjectId('5f7be0b37e2bdf5b19e4724e'),
name: 'CAPTAIN_YATCH',
classes: [ 'yatch' ],
license: 'WC-2',
watercraftContexts:
[ { _id: ObjectId('5f7be0b37e2bdf5b19e47242'),
watercraftType: 'Yatch',
ref: 'yatches' } ],
__v: 0 },
{ _id: ObjectId('5f7be0b37e2bdf5b19e4724f'),
name: 'CAPTAIN_SHIP',
classes: [ 'ship' ],
license: 'WC-3',
watercraftContexts:
[ { _id: ObjectId('5f7be0b37e2bdf5b19e47243'),
watercraftType: 'Ship',
ref: 'ships' } ],
__v: 0 },
{ _id: ObjectId('5f7be0b37e2bdf5b19e47253'),
name: 'CAPTAIN_SAIL_YATCH_SHIP',
classes: [ 'sail', 'yatch', 'ship' ],
license: 'WC-7',
watercraftContexts:
[ { _id: ObjectId('5f7be0b37e2bdf5b19e4724a'),
watercraftType: 'Sailboat',
ref: 'sailboats' },
{ _id: ObjectId('5f7be0b37e2bdf5b19e4724b'),
watercraftType: 'Yatch',
ref: 'yatches' },
{ _id: ObjectId('5f7be0b37e2bdf5b19e4724c'),
watercraftType: 'Ship',
ref: 'ships' } ],
__v: 0 }
]
Paso 2:$relájate para que podamos iterar con $loopup
En este conjunto de resultados hay una matriz de objetos con { _id: <ObjectId>, watercraftType: <ModelName> } para recorrer la matriz y unir cada uno de estos objetos con su respectivo registro de colección, tenemos que dividir la matriz en registros independientes individuales. El $unwind la característica creará un nuevo conjunto de datos para la siguiente etapa agregada
{ '$unwind': '$watercraftContexts' },
Como puedes ver $unwind ahora crea un registro con un solo watercraftContext ahora estamos configurados para usar $lookup
[ { _id: ObjectId('5f7be2231da37c5b5915bf9b'),
name: 'CAPTAIN_SAIL',
classes: [ 'sail' ],
license: 'WC-1',
watercraftContexts:
{ _id: ObjectId('5f7be2231da37c5b5915bf8f'),
watercraftType: 'Sailboat',
ref: 'sailboats' },
__v: 0 },
{ _id: ObjectId('5f7be2231da37c5b5915bf9c'),
name: 'CAPTAIN_YATCH',
classes: [ 'yatch' ],
license: 'WC-2',
watercraftContexts:
{ _id: ObjectId('5f7be2231da37c5b5915bf90'),
watercraftType: 'Yatch',
ref: 'yatches' },
__v: 0 },
{ _id: ObjectId('5f7be2231da37c5b5915bf9d'),
name: 'CAPTAIN_SHIP',
classes: [ 'ship' ],
license: 'WC-3',
watercraftContexts:
{ _id: ObjectId('5f7be2231da37c5b5915bf91'),
watercraftType: 'Ship',
ref: 'ships' },
__v: 0 },
{ _id: ObjectId('5f7be2231da37c5b5915bfa1'),
name: 'CAPTAIN_SAIL_YATCH_SHIP',
classes: [ 'sail', 'yatch', 'ship' ],
license: 'WC-7',
watercraftContexts:
{ _id: ObjectId('5f7be2231da37c5b5915bf98'),
watercraftType: 'Sailboat',
ref: 'sailboats' },
__v: 0 },
{ _id: ObjectId('5f7be2231da37c5b5915bfa1'),
name: 'CAPTAIN_SAIL_YATCH_SHIP',
classes: [ 'sail', 'yatch', 'ship' ],
license: 'WC-7',
watercraftContexts:
{ _id: ObjectId('5f7be2231da37c5b5915bf99'),
watercraftType: 'Yatch',
ref: 'yatches' },
__v: 0 },
{ _id: ObjectId('5f7be2231da37c5b5915bfa1'),
name: 'CAPTAIN_SAIL_YATCH_SHIP',
classes: [ 'sail', 'yatch', 'ship' ],
license: 'WC-7',
watercraftContexts:
{ _id: ObjectId('5f7be2231da37c5b5915bf9a'),
watercraftType: 'Ship',
ref: 'ships' },
__v: 0 } ]
Es importante tener en cuenta que debemos $unwind antes de llamar a $lookup para cada colección diferente que necesitamos unir. Dado que queremos unir varias colecciones, debemos almacenar el resultado en un objeto con clave de la colección para su posterior agregación.
// Only performs $lookup on 'ships' collection
{ '$lookup':
{ from: 'ships', // Collection Name - Note: repeat for each collection
localField: 'watercraftContexts._id', // The field with id to link
foreignField: '_id', // The field on the foreign collection to match
as: 'watercrafts.ships' // The path where to store the lookup result
}
}
Paso 5:repita $unwind y $busque las otras uniones
Repita los pasos anteriores para las uniones adicionales y escriba el nombre de la colección. He combinado las etapas agregadas para demostrar la repetición.
{ '$unwind': '$watercraftContexts' },
{ '$lookup':
{ from: 'yatches',
localField: 'watercraftContexts._id',
foreignField: '_id',
as: 'watercrafts.yatches' } },
{ '$unwind': '$watercraftContexts' },
{ '$lookup':
{ from: 'sailboats',
localField: 'watercraftContexts._id',
foreignField: '_id',
as: 'watercrafts.sailboats' } }
Si miras detenidamente, notas que uno de los Captain los registros existen 3 veces con un watercraftType diferente . $lookup solo devolverá registros que coincidan con un nombre de colección específico. Es por eso que almacenarlos en un Object clave por collectionName
[
{ _id: ObjectId('5f7be7145320a65b942bb450'),
name: 'CAPTAIN_SAIL',
classes: [ 'sail' ],
license: 'WC-1',
watercraftContexts:
{ _id: ObjectId('5f7be7145320a65b942bb444'),
watercraftType: 'Sailboat',
ref: 'sailboats' },
__v: 0,
watercrafts:
{ ships: [],
yatches: [],
sailboats:
[ { _id: ObjectId('5f7be7145320a65b942bb444'),
class: 'sail',
name: 'Gone with the Wind',
__v: 0 } ] } },
{ _id: ObjectId('5f7be7145320a65b942bb451'),
name: 'CAPTAIN_YATCH',
classes: [ 'yatch' ],
license: 'WC-2',
watercraftContexts:
{ _id: ObjectId('5f7be7145320a65b942bb445'),
watercraftType: 'Yatch',
ref: 'yatches' },
__v: 0,
watercrafts:
{ ships: [],
yatches:
[ { _id: ObjectId('5f7be7145320a65b942bb445'),
class: 'yatch',
name: 'Liquid Gold',
__v: 0 } ],
sailboats: [] } },
{ _id: ObjectId('5f7be7145320a65b942bb452'),
name: 'CAPTAIN_SHIP',
classes: [ 'ship' ],
license: 'WC-3',
watercraftContexts:
{ _id: ObjectId('5f7be7145320a65b942bb446'),
watercraftType: 'Ship',
ref: 'ships' },
__v: 0,
watercrafts:
{ ships:
[ { _id: ObjectId('5f7be7145320a65b942bb446'),
class: 'ship',
name: 'Jenny',
__v: 0 } ],
yatches: [],
sailboats: [] } },
{ _id: ObjectId('5f7be7145320a65b942bb456'),
name: 'CAPTAIN_SAIL_YATCH_SHIP',
classes: [ 'sail', 'yatch', 'ship' ],
license: 'WC-7',
watercraftContexts:
{ _id: ObjectId('5f7be7145320a65b942bb44d'),
watercraftType: 'Sailboat',
ref: 'sailboats' },
__v: 0,
watercrafts:
{ ships: [],
yatches: [],
sailboats:
[ { _id: ObjectId('5f7be7145320a65b942bb44d'),
class: 'sail',
name: 'Swell Shredder',
__v: 0 } ] } },
{ _id: ObjectId('5f7be7145320a65b942bb456'),
name: 'CAPTAIN_SAIL_YATCH_SHIP',
classes: [ 'sail', 'yatch', 'ship' ],
license: 'WC-7',
watercraftContexts:
{ _id: ObjectId('5f7be7145320a65b942bb44e'),
watercraftType: 'Yatch',
ref: 'yatches' },
__v: 0,
watercrafts:
{ ships: [],
yatches:
[ { _id: ObjectId('5f7be7145320a65b942bb44e'),
class: 'yatch',
name: 'Audrey',
__v: 0 } ],
sailboats: [] } },
{ _id: ObjectId('5f7be7145320a65b942bb456'),
name: 'CAPTAIN_SAIL_YATCH_SHIP',
classes: [ 'sail', 'yatch', 'ship' ],
license: 'WC-7',
watercraftContexts:
{ _id: ObjectId('5f7be7145320a65b942bb44f'),
watercraftType: 'Ship',
ref: 'ships' },
__v: 0,
watercrafts:
{ ships:
[ { _id: ObjectId('5f7be7145320a65b942bb44f'),
class: 'ship',
name: 'Jenny IV',
__v: 0 } ],
yatches: [],
sailboats: [] } } ]
Paso 6 $proyecto:utilice el proyecto para aplanar el mapa de objetos de las uniones
Podemos usar el proyecto para seleccionar todos los datos existentes y aplanar el Mapa de objetos de los resultados de unión en una sola matriz.
{ '$project':
// keys with the value 'true' will be included
{ name: true,
license: true,
classes: true,
_id: true,
watercraftContexts: true,
__v: true,
watercrafts: // Re-assigns value of watercrafts
{ '$setUnion': // Accepts an array of arrays to flatten
[
'$watercrafts.ships',
'$watercrafts.yatches',
'$watercrafts.sailboats'
]
}
}
}
Los resultados del $project anterior reemplazará a las watercrafts objeto con una matriz aplanada de watercrafts , pero es importante tener en cuenta que todavía hay registros duplicados de Captain donde coinciden muchas búsquedas diferentes. Los volveremos a unir en el siguiente paso.
[ { _id: ObjectId('5f7bea8d79dfe25bf3cb9695'),
name: 'CAPTAIN_SAIL',
classes: [ 'sail' ],
license: 'WC-1',
watercraftContexts:
{ _id: ObjectId('5f7bea8d79dfe25bf3cb9689'),
watercraftType: 'Sailboat',
ref: 'sailboats' },
__v: 0,
watercrafts:
[ { _id: ObjectId('5f7bea8d79dfe25bf3cb9689'),
class: 'sail',
name: 'Gone with the Wind',
__v: 0 } ] },
{ _id: ObjectId('5f7bea8d79dfe25bf3cb9696'),
name: 'CAPTAIN_YATCH',
classes: [ 'yatch' ],
license: 'WC-2',
watercraftContexts:
{ _id: ObjectId('5f7bea8d79dfe25bf3cb968a'),
watercraftType: 'Yatch',
ref: 'yatches' },
__v: 0,
watercrafts:
[ { _id: ObjectId('5f7bea8d79dfe25bf3cb968a'),
class: 'yatch',
name: 'Liquid Gold',
__v: 0 } ] },
{ _id: ObjectId('5f7bea8d79dfe25bf3cb9697'),
name: 'CAPTAIN_SHIP',
classes: [ 'ship' ],
license: 'WC-3',
watercraftContexts:
{ _id: ObjectId('5f7bea8d79dfe25bf3cb968b'),
watercraftType: 'Ship',
ref: 'ships' },
__v: 0,
watercrafts:
[ { _id: ObjectId('5f7bea8d79dfe25bf3cb968b'),
class: 'ship',
name: 'Jenny',
__v: 0 } ] },
{ _id: ObjectId('5f7bea8d79dfe25bf3cb969b'),
name: 'CAPTAIN_SAIL_YATCH_SHIP',
classes: [ 'sail', 'yatch', 'ship' ],
license: 'WC-7',
watercraftContexts:
{ _id: ObjectId('5f7bea8d79dfe25bf3cb9692'),
watercraftType: 'Sailboat',
ref: 'sailboats' },
__v: 0,
watercrafts:
[ { _id: ObjectId('5f7bea8d79dfe25bf3cb9692'),
class: 'sail',
name: 'Swell Shredder',
__v: 0 } ] },
{ _id: ObjectId('5f7bea8d79dfe25bf3cb969b'),
name: 'CAPTAIN_SAIL_YATCH_SHIP',
classes: [ 'sail', 'yatch', 'ship' ],
license: 'WC-7',
watercraftContexts:
{ _id: ObjectId('5f7bea8d79dfe25bf3cb9693'),
watercraftType: 'Yatch',
ref: 'yatches' },
__v: 0,
watercrafts:
[ { _id: ObjectId('5f7bea8d79dfe25bf3cb9693'),
class: 'yatch',
name: 'Audrey',
__v: 0 } ] },
{ _id: ObjectId('5f7bea8d79dfe25bf3cb969b'),
name: 'CAPTAIN_SAIL_YATCH_SHIP',
classes: [ 'sail', 'yatch', 'ship' ],
license: 'WC-7',
watercraftContexts:
{ _id: ObjectId('5f7bea8d79dfe25bf3cb9694'),
watercraftType: 'Ship',
ref: 'ships' },
__v: 0,
watercrafts:
[ { _id: ObjectId('5f7bea8d79dfe25bf3cb9694'),
class: 'ship',
name: 'Jenny IV',
__v: 0 } ] } ]
Paso 7 $relajarse y $agruparse
Nosotros $unwind para que ahora podamos agrupar todas las watercrafts perteneciente al mismo Captain . También tenemos que usar $mergeObjects para almacenar temporalmente los datos adicionales del Captain colección bajo una nueva variable temporal para prepararse para las etapas finales.
{ '$unwind': '$watercrafts' },
{ '$group':
{ _id: '$_id',
data:
{ '$mergeObjects':
{ name: '$name',
license: '$license',
classes: '$classes',
watercraftContexts: '$watercraftContexts',
__v: '$__v' } },
watercrafts: { '$push': '$watercrafts' } } }
$unwind y $group Resultado
Ahora realmente estamos llegando a alguna parte. Hemos reducido nuestra transformación a nuestros 4 Captain iniciales s y aplanamos nuestras uniones en una sola matriz.
[ { _id: ObjectId('5f7bed5e271dd95c306c25a4'),
data:
{ name: 'CAPTAIN_SHIP',
license: 'WC-3',
classes: [ 'ship' ],
watercraftContexts:
{ _id: ObjectId('5f7bed5e271dd95c306c2598'),
watercraftType: 'Ship',
ref: 'ships' },
__v: 0 },
watercrafts:
[ { _id: ObjectId('5f7bed5e271dd95c306c2598'),
class: 'ship',
name: 'Jenny',
__v: 0 } ] },
{ _id: ObjectId('5f7bed5e271dd95c306c25a8'),
data:
{ name: 'CAPTAIN_SAIL_YATCH_SHIP',
license: 'WC-7',
classes: [ 'sail', 'yatch', 'ship' ],
watercraftContexts:
{ _id: ObjectId('5f7bed5e271dd95c306c25a1'),
watercraftType: 'Ship',
ref: 'ships' },
__v: 0 },
watercrafts:
[ { _id: ObjectId('5f7bed5e271dd95c306c259f'),
class: 'sail',
name: 'Swell Shredder',
__v: 0 },
{ _id: ObjectId('5f7bed5e271dd95c306c25a0'),
class: 'yatch',
name: 'Audrey',
__v: 0 },
{ _id: ObjectId('5f7bed5e271dd95c306c25a1'),
class: 'ship',
name: 'Jenny IV',
__v: 0 } ] },
{ _id: ObjectId('5f7bed5e271dd95c306c25a2'),
data:
{ name: 'CAPTAIN_SAIL',
license: 'WC-1',
classes: [ 'sail' ],
watercraftContexts:
{ _id: Object('5f7bed5e271dd95c306c2596'),
watercraftType: 'Sailboat',
ref: 'sailboats' },
__v: 0 },
watercrafts:
[ { _id: ObjectId('5f7bed5e271dd95c306c2596'),
class: 'sail',
name: 'Gone with the Wind',
__v: 0 } ] },
{ _id: ObjectId('5f7bed5e271dd95c306c25a3'),
data:
{ name: 'CAPTAIN_YATCH',
license: 'WC-2',
classes: [ 'yatch' ],
watercraftContexts:
{ _id: ObjectId('5f7bed5e271dd95c306c2597'),
watercraftType: 'Yatch',
ref: 'yatches' },
__v: 0 },
watercrafts:
[ { _id: ObjectId('5f7bed5e271dd95c306c2597'),
class: 'yatch',
name: 'Liquid Gold',
__v: 0 } ] } ]
Paso 8 $replaceRoot y $proyecto
Todo lo que nos queda es fusionar nuestros data en la raíz de cada registro y elimine la variable temporal data
// Merges 'data' into the root of each record
{ '$replaceRoot': { newRoot: { '$mergeObjects': [ '$data', '$$ROOT' ] } } },
// Use $project to remove data (include only the fields we want)
{ '$project':
{ name: true,
license: true,
classes: true,
_id: true,
watercraftContexts: true,
__v: true,
watercrafts: true }
}
Ahora tenemos el resultado que nos propusimos... Un Captain con una variedad de tipos mixtos asociados watercrafts
[
{ name: 'CAPTAIN_SAIL_YATCH_SHIP',
license: 'WC-7',
classes: [ 'sail', 'yatch', 'ship' ],
watercraftContexts:
{ _id: ObjectId('5f7bf3b3680b375ca1755ea6'),
watercraftType: 'Ship',
ref: 'ships' },
__v: 0,
_id: ObjectId('5f7bf3b3680b375ca1755ead'),
watercrafts:
[ { _id: ObjectId('5f7bf3b3680b375ca1755ea4'),
class: 'sail',
name: 'Swell Shredder',
__v: 0 },
{ _id: ObjectId('5f7bf3b3680b375ca1755ea5'),
class: 'yatch',
name: 'Audrey',
__v: 0 },
{ _id: ObjectId('5f7bf3b3680b375ca1755ea6'),
class: 'ship',
name: 'Jenny IV',
__v: 0 } ] },
{ name: 'CAPTAIN_SAIL',
license: 'WC-1',
classes: [ 'sail' ],
watercraftContexts:
{ _id: ObjectId('5f7bf3b3680b375ca1755e9b'),
watercraftType: 'Sailboat',
ref: 'sailboats' },
__v: 0,
_id: ObjectId('5f7bf3b3680b375ca1755ea7'),
watercrafts:
[ { _id: ObjectId('5f7bf3b3680b375ca1755e9b'),
class: 'sail',
name: 'Gone with the Wind',
__v: 0 } ] },
{ name: 'CAPTAIN_YATCH',
license: 'WC-2',
classes: [ 'yatch' ],
watercraftContexts:
{ _id: ObjectId('5f7bf3b3680b375ca1755e9c'),
watercraftType: 'Yatch',
ref: 'yatches' },
__v: 0,
_id: ObjectId('5f7bf3b3680b375ca1755ea8'),
watercrafts:
[ { _id: ObjectId('5f7bf3b3680b375ca1755e9c'),
class: 'yatch',
name: 'Liquid Gold',
__v: 0 } ] },
{ name: 'CAPTAIN_SHIP',
license: 'WC-3',
classes: [ 'ship' ],
watercraftContexts:
{ _id: ObjectId('5f7bf3b3680b375ca1755e9d'),
watercraftType: 'Ship',
ref: 'ships' },
__v: 0,
_id: ObjectId('5f7bf3b3680b375ca1755ea9'),
watercrafts:
[ { _id: ObjectId('5f7bf3b3680b375ca1755e9d'),
class: 'ship',
name: 'Jenny',
__v: 0 } ] } ]
Y ahí lo tienes... sólo tomó 2 días para resolver esto. Espero que le ahorre algo de tiempo si está intentando una asociación agregada similar. ¡Feliz codificación!
Canalización final
[
{ '$match':
{ _id:
{ '$in':
[ ObjectId('5f7bf3b3680b375ca1755ea9'),
ObjectId('5f7bf3b3680b375ca1755ea7'),
ObjectId('5f7bf3b3680b375ca1755ea8'),
ObjectId('5f7bf3b3680b375ca1755ead')
]
}
}
},
{ '$unwind': '$watercraftContexts' },
{ '$lookup':
{ from: 'ships',
localField: 'watercraftContexts._id',
foreignField: '_id',
as: 'watercrafts.ships' } },
{ '$unwind': '$watercraftContexts' },
{ '$lookup':
{ from: 'yatches',
localField: 'watercraftContexts._id',
foreignField: '_id',
as: 'watercrafts.yatches' } },
{ '$unwind': '$watercraftContexts' },
{ '$lookup':
{ from: 'sailboats',
localField: 'watercraftContexts._id',
foreignField: '_id',
as: 'watercrafts.sailboats' } },
{ '$project':
{ name: true,
license: true,
classes: true,
_id: true,
watercraftContexts: true,
__v: true,
watercrafts:
{ '$setUnion':
[ '$watercrafts.ships',
'$watercrafts.yatches',
'$watercrafts.sailboats' ] } } },
{ '$unwind': '$watercrafts' },
{ '$group':
{ _id: '$_id',
data:
{ '$mergeObjects':
{ name: '$name',
license: '$license',
classes: '$classes',
watercraftContexts: '$watercraftContexts',
__v: '$__v' } },
watercrafts: { '$push': '$watercrafts' } } },
{ '$replaceRoot': { newRoot: { '$mergeObjects': [ '$data', '$$ROOT' ] } } },
{ '$project':
{ name: true,
license: true,
classes: true,
_id: true,
watercraftContexts: true,
__v: true,
watercrafts: true } }
]
