I am building an application using MongoDB 4 / Mongoose 5.
I have a collection 'records' with an array of subdocuments 'Items'.
{
RecordID: 1,
Items: [
{
Title: 'Example Title 1',
Description: 'Example Description 1',
},
{
Title: 'Example Title 2',
Description: 'Example Description 2',
}
]
}
I am building a dynamic query generator that creates MongoDB expression operators based on a UI query builder. The dynamic query builder is building the MongoDB expressions correctly. However, the expressions are not working as expected when querying an array of subdocuments.
Question: Why is this expression not working for the nested array of subdocuments 'Items'?
This query works correctly.
db.records.find({ 'Items.Title': { $eq: 'Example title 1'} })
This same query as an expression is not returning any results.
db.records.find({ '$expr': { '$and': [ { '$eq': [ 'Items.Title', 'Example title 1' ] } ] }})
Also tried this:
db.records.find({ '$expr': { '$and': [ { '$eq': [ '$Items.Title', 'Example title 1' ] } ] }})
UPDATE: The query will work if updated to use $elemMatch
instead. However, I need to use $expr
because I am building nested queries using multiple and/or conditions which are constructed using the $expr
operator. Is there any way to get this to work using $expr
?
Use $elemMatch
instead:
db.records.find({
"Items" : {"$elemMatch" : {"Title" : "Example title 1"}}
})
Hope this helps.
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