How can I search two columns (one of which only appears in a few records)? - mongodb

Question

I am performing a search on the following 2 columns of a document: name and displayName. However, only a few records have displayName column. When a record has both, I want to search both fields (name and displayName) for the possible match. Otherwise, if the record doesn't have the column displayName, I just want to search name instead. So I thought I'd do an OR. This however will only search fields that have both columns - although I want to search all records.
How can I update the query to achieve the above? Here's what I tried:
function search(search) {
return this.find({ $or: [
{"displayName" : {"$regex" : ".*"+ search +".*", "$options": "-i"}},
{"name" : {"$regex" : ".*"+ search +".*", "$options": "-i"}}
]}).exec();
}
So on the query above, the logic tells me that if displayName column doesn't exist, the first check will return false so it will then search name which will return true/false based on the match. I am obviously missing something here because even if the second check would be true, the overall result comes out false (which is more like AND behavior instead of OR).
Data Example:
{ id: 3, name: "John Steinbeck", displayName: "Steinbeck" }
{ id: 4, name: "John Lennon" }
{ id: 5, name: "Doe", displayName: "John" }
{ id: 5, name: "Harry Potter", displayName: "Harry" }
Search word:
john
Expected Result:
{ id: 3, name: "John Steinbeck", displayName: "Steinbeck" }
{ id: 4, name: "John Lennon" }
{ id: 5, name: "Doe", displayName: "John" }
Later Edit
This query does seem to work after all, the problem turned out to be the data and not the query. Human error. My apologies :)

Answer 1

change your query:
db.getCollection('user').find({ $or: [
{"name" : {$regex: "john", $options: "$i"}},
{"displayName" : {$regex: "john", $options: "$i"}}]})

Answer 2

You've to different conditions:
Both field exist and have the correct value
Only name exist and have the correct value
use $exist and $or!
for example:
db.col.find({ $or: [ { name: {$regex : ".*John.*"}}, displayName: {$regex : ".*Steinbeck.*"}}, { name: "john", { displayName: { $exists: false } } } ] } )