mongoexport not working if you add query of selection

Question

If you want to export any collections of any of your mongodb database, you can use mongoexport command. For example:

mongoexport --db dbname --collection collectionName --query '{"fields":1}' --out output.json

However, if you add any of selection criteria to the query, mongoexport command doesn't work. For example, if you run the following command:

mongoexport --db dbname --collection collectionName --query '{},{"fields":0}' --out output.json

the resultant JSON file includes data of every field, despite me excluding a filed named fields.

So why does this such strange behavior occur? And how can I fix it?

For your information, db.colName.find({},{"fields":0}) in mongoDB shell works as usual.

I'm on MongoDB 2.4.3 and OS X 10.9.

Thanks.

Answer 1

That's because --query argument takes only query and there is no option to pass projection. See mongoexport --query in official documentation. If you want to use a projection you have to add --fields option