Puede probar debajo de la canalización de agregación.
Nota mergeObjects
el operador de agregación está disponible en 3.5.6 + versión de desarrollo que se incluirá en el próximo 3.6 liberar.
db.collection.find();
{
"data" : [
[
{
"movie" : "starwars",
"showday" : "monday"
},
{
"movie" : "batman",
"showday" : "thursday"
},
{
"movie" : "sleepless",
"showday" : "tuesday"
}
],
[
{
"actor" : "angelina",
"location" : "new york"
},
{
"actor" : "jamie",
"location" : "california"
},
{
"actor" : "mcavoy",
"location" : "arizona"
}
]
]
}
Agregación mediante expresión condicional.
aggregate({
$project: {
cp: {
$reduce: {
input: "$data",
initialValue: {
$arrayElemAt: ["$data", 0] // Set the initial value to the first element of the arrays.
},
in: {
$let: {
vars: {
currentr: "$$this", // Current processing element
currenta: "$$value" // Current accumulated value
},
in: {
$cond: [{ // Conditional expression to return the accumulated value as initial value for first element
$eq: ["$$currentr", "$$currenta"]
},
"$$currenta",
{ // From second element onwards prepare the cartesian product
$reduce: {
input: {
$map: {
input: "$$currenta",
as: a"a",
in: {
$map: {
input: "$$currentr",
as: r"r",
in: {
$mergeObjects: ["$$a", "$$r"] // Merge accumulated value with the current processing element
}
}
}
}
},
initialValue: [],
in: {
$concatArrays: ["$$value", "$$this"] // Reduce the merged values which will be used as accumulator for next element
}
}
}]
}
}
}
}
}
}
});
Agregación (usando $setUnion ).
Esta solución solo se agregó para suprimir la expresión condicional para brindar una canalización más legible.
aggregate({
$project: {
cp: {
$reduce: {
input: "$data",
initialValue: {
$arrayElemAt: ["$data", 0] // Set the initial value to the first element of the arrays.
},
in: {
$let: {
vars: {
currentr: "$$this", // Current processing element
currenta: "$$value" // Current accumulated value
},
in:{
$reduce: {
input: {
$map: {
input: "$$currenta",
as: "a",
in: {
$map: {
input: "$$currentr",
as: "r",
in: {
$mergeObjects: ["$$a", "$$r"] // Merge accumulated value with the current processing element
}
}
}
}
},
initialValue: [],
in: {
$setUnion: ["$$value", "$$this"] // Reduce the merged values which will be used as accumulator for next element
}
}
}
}
}
}
}
}
});
Actualizar
Las dos soluciones anteriores no funcionarán con valores repetidos en matrices como se indica en los comentarios de Asya Kamsky a continuación debido al $cond incorrecto en la primera solución y $setUnion en segunda solución.
La solución correcta es
comienza con initialValue de [ { } ]
O
cambiar input para excluir el primer elemento como input: {$slice:["$data", 1, {$subtract:[{$size:"$data"},1]}]},
Tubería de agregación completa
aggregate({
$project: {
cp: {
$reduce: {
input: {$slice:["$data", 1, {$subtract:[{$size:"$data"},1]}]},
initialValue: {$arrayElemAt:["$data",0]},
in: {
$let: {
vars: {
currentr: "$$this",
currenta: "$$value"
},
in:{
$reduce: {
input: {
$map: {
input: "$$currenta",
as: "a",
in: {
$map: {
input: "$$currentr",
as: "r",
in: {
$mergeObjects: ["$$a", "$$r"]
}
}
}
}
},
initialValue: [],
in: {
$concatArrays: ["$$value", "$$this"]
}
}
}
}
}
}
}
}
});
Referencia:Producto cartesiano de múltiples matrices en JavaScript
