mongodb lookup using multiple fields not working - mongodb

Question

I am trying to get some other information from titleInfo collection using siteId of regCodes collection
I have two collections
regCodes
{
"siteId" : "123A",
"registration_code" : "ABC",
"used_flag" : true,
"Allowed_Use" : 1,
"Remaining_Use" : 0,
"BatchId" : "SNGL",
"CodeDuration" : 180
}
titleInfo
{
"title" : "Principles of Microeconomics",
"product_form_detail" : "EPUB",
"final_binding_description" : "Ebook",
"vitalsource_enabled" : false,
"reading_line" : "with InQuizitive and Smartwork5",
"volume" : "",
"protected_content" : {
"ebookSiteIds" : [
"123A"
],
"studySpaceSiteIds" : [],
"iqSiteIds" : []
}
}
below query not working, getting 'regcodeData' as empty array.
using mongodb version 3.6.18
db.getCollection('regCodes').aggregate([
{
$match: {
registration_code: 'ABC'
}
},
{
$lookup: {
from: "titleInfo",
let: {
regcode_siteId: "$siteId"
},
pipeline: [
{
$match: {
$expr: {
$or: [
{
$eq: [
"$protected_content.ebookSiteIds",
"$$regcode_siteId"
]
},
{
$eq: [
"$protected_content.studySpaceSiteIds",
"$$regcode_siteId"
]
},
{
$eq: [
"$protected_content.iqSiteIds",
"$$regcode_siteId"
]
}
]
}
}
}
],
as: "regcodeData"
}
}
])
below query is working as expected
db.getCollection('titleInfo').find({
$or: [
{
"protected_content.ebookSiteIds": "123A"
},
{
"protected_content.studySpaceSiteIds": "123A"
},
{
"protected_content.iqSiteIds": "123A"
}
]
})

Answer 1

You just need to unwind the arrays, by using $unwind operator with preserveNullAndEmptyArrays option set to true.
Updated Query:
db.regCodes.aggregate([
{
$match: {
registration_code: "ABC"
}
},
{
$lookup: {
from: "titleInfo",
let: {
regcode_siteId: "$siteId"
},
pipeline: [
{
$unwind: {
path: "$protected_content.ebookSiteIds",
preserveNullAndEmptyArrays: true
}
},
{
$unwind: {
path: "$protected_content.studySpaceSiteIds",
preserveNullAndEmptyArrays: true
}
},
{
$unwind: {
path: "$protected_content.iqSiteIds",
preserveNullAndEmptyArrays: true
}
},
{
$match: {
$expr: {
$or: [
{
$eq: [
"$protected_content.ebookSiteIds",
"$$regcode_siteId"
]
},
{
$eq: [
"$protected_content.studySpaceSiteIds",
"$$regcode_siteId"
]
},
{
$eq: [
"$protected_content.iqSiteIds",
"$$regcode_siteId"
]
}
]
}
}
}
],
as: "regcodeData"
}
}
])
MongoPlayGroundLink

Answer 2

My bad trying to match array with string
Answer is as below
db.getCollection('regCodes').aggregate([
{
$match: {
registration_code: 'ABC'
}
},
{
$lookup: {
from: "titleInfo",
let: {
regcode_siteId: "$siteId"
},
pipeline: [
{
$match: {
$expr: {
$or: [
{
$in: [
"$$regcode_siteId",
"$protected_content.ebookSiteIds"
]
},
{
$in: [
"$$regcode_siteId",
"$protected_content.studySpaceSiteIds"
]
},
{
$in: [
"$$regcode_siteId",
"$protected_content.iqSiteIds"
]
}
]
}
}
}
],
as: "regcodeData"
}
}
])