Do arrays stored in MongoDB keep their order?

Solution 1:

yep MongoDB keeps the order of the array.. just like Javascript engines..

Solution 2:

Yes, in fact from a quick google search on the subject, it seems that it's rather difficult to re-order them: http://groups.google.com/group/mongodb-user/browse_thread/thread/1df1654889e664c1

Solution 3:

I realise this is an old question, but the Mongo docs do now specify that all document properties retain their order as they are inserted. This naturally extends to arrays, too.

Document Field Order

MongoDB preserves the order of the document fields following write operations except for the following cases:

• The _id field is always the first field in the document.
• Updates that include renaming of field names may result in the reordering of fields in the document.

Changed in version 2.6: Starting in version 2.6, MongoDB actively attempts to preserve the field order in a document. Before version 2.6, MongoDB did not actively preserve the order of the fields in a document.