I want to rename foo.one to foo.two.

Mongodb has a way to rename fields with update $rename:

db.foo.update({}, { $rename: { 'one': 'two' } }, { multi: true })

However, the app will be running during migration, so there could be some new records created with some two before migration finishes, and if I understand correctly, they'd get overwritten by migration.

Is there any way to migrate without such risks?

CodePudding user response：

Use the filter part of the update call to exclude documents that already have a 'two' field:

db.foo.update({two:{$exists:false}}, { $rename: { 'one': 'two' } }, { multi: true })