How to write a complex query using `expr` in mongodb? - mongodb

Question

I'm trying to write a bit complicated query to the MongoDB and I honestly don't know how to write it correctly. In SQL pseudocode it's something like:
SELECT *
FROM Something
WHERE
(IF Item.NestedItem THEN NULL ELSE Item.NestedItem.Id) == 'f4421f9e-5962-4c68-8049-a45600f36f4b'
OR (IF Item.NestedItem THEN NULL ELSE Item.NestedItem.OtherId) == 'd6b799dc-f464-4919-8435-a7b600cc408a'
I succeeded in writing IF as
{ "$cond" : [{ "$eq" : ["$Item.NestedItem", null] }, null, "$Item.NestedItem.Id"] }
{ "$cond" : [{ "$eq" : ["$Item.NestedItem", null] }, null, "$Item.NestedItem.OtherId"] }
But now I'm not sure how to compare them to constants and then join. I'm trying to write a translator from SQL-like language to MongoDb and this is example of query I cannot translate. I want something like
{ "$and" :
{ "$eq" : { "$cond" : [{ "$eq" : ["$Item.NestedItem", null] }, null, "$Item.NestedItem.Id"] }, "f4421f9e-5962-4c68-8049-a45600f36f4b" },
{ "$eq" : { "$cond" : [{ "$eq" : ["$Item.NestedItem", null] }, null, "$Item.NestedItem.OtherId"] }, "d6b799dc-f464-4919-8435-a7b600cc408a" } }
But it's an invalid query as I get it

Answer 1

The $cond is a aggregation expression, you need to use $expr before $and operation, in your SQL query you have user OR so just updating in query $and to $or
corrected $eq syntax after $or
db.collection.aggregate([
{
$match: {
$expr: {
$or: [
{
$eq: [
{
$cond: [
{ $eq: ["$Item.NestedItem", null] },
null,
"$Item.NestedItem.Id"
]
},
"f4421f9e-5962-4c68-8049-a45600f36f4b"
]
},
{
$eq: [
{
$cond: [
{ $eq: ["$Item.NestedItem", null] },
null,
"$Item.NestedItem.OtherId"
]
},
"d6b799dc-f464-4919-8435-a7b600cc408a"
]
}
]
}
}
}
])
Playground