you can't add a second '$or' expression specified as '$or : [Document{{priority=1}}]'. Criteria already contains '$or : [Document{{title=xuqiu1}}]'.

The error message you're seeing suggests that you're trying to use two `$or` operators in the same MongoDB query, which is not allowed. The `$or` operator in MongoDB is used to specify multiple conditions, where at least one of the conditions must be true for a document to match the query.

Here's an example of a valid query that uses the `$or` operator:

db.collection.find({
  $or: [
    { priority: 1 },
    { title: "xuqiu1" }
  ]
})

In this query, we're searching for documents where either the `priority` field is equal to 1 or the `title` field is equal to "xuqiu1". This is achieved by using the `$or` operator to group the two conditions together.

If you want to add another condition to the query, you can use another operator like `$and` or `$nor`. For example, if you also want to include documents where the `status` field is "open", you could modify the query like this:

db.collection.find({
  $or: [
    { priority: 1 },
    { title: "xuqiu1" }
  ],
  status: "open"
})

This query will return documents where either the `priority` field is equal to 1 or the `title` field is equal to "xuqiu1", and the `status` field is equal to "open".