MongoDB query that looks for documents with lowercase values-CodePudding

Is it possible to make a MongoDB query that searches a field for completely lowercase string values?

Something like this pseudo query perhaps?

{ address: { $eq: { $toLower: "$address" } } }

...that would return docs with data like: { "address": "123 main st" }, but won't return docs like { "address": "123 Main St" }, or is such a query not possible with MongoDB?

CodePudding user response：

Based on the clarification, yes what you want is possible and you were pretty close with the original syntax. Try something like the following:

db.collection.find({
  $expr: {
    $eq: [
      {
        $toLower: "$address"
      },
      "$address"
    ]
  }
})

Playground link is here.

There may be some extra considerations depending on language, collation, etc. But this should serve as a good starting point.

CodePudding user response：

Are you asking to search for string with lowercase or you want to return its value in lowercase

CodePudding user response：

Yes, you can use aggregation pipeline that makes specific fields lowercase and than does matching against them, for examples look at https://www.mongodb.com/docs/manual/reference/operator/aggregation/toLower/#example and https://www.mongodb.com/docs/manual/reference/operator/aggregation/match/#examples

On large datasets this way of querying would not be efficient, but for one time queries may be useful.