CODEWITHSUNDEEP
mongodb
Jany
Jany

Reputation: 73

Mongo DB : Impact of object schema changes on document design

How do you handle schema changes in Mongo db e.g. say after refactoring you change your object schema design and that impacts the document schema. Is there a way to update the document schema?

Upvotes: 1

Views: 1376

Answers (1)

Eve Freeman
Eve Freeman

Reputation: 33145

You can run an update on the entire schema, removing fields, or adding fields and setting them to calculated values, if that's what you're getting at.

Say you had an x field, and you want to add a y field that should be set to x/2, you could do something like this:

PRIMARY> db.test.insert({x:15});
PRIMARY> db.test.insert({x:30});
PRIMARY> db.test.insert({x:50}); 
PRIMARY> db.test.find();
{ "_id" : ObjectId("4f9df1ebed2b924eedb8cad9"), "x" : 15 }
{ "_id" : ObjectId("4f9df1eeed2b924eedb8cada"), "x" : 30 }
{ "_id" : ObjectId("4f9df1f1ed2b924eedb8cadb"), "x" : 50 }
PRIMARY> db.test.find().forEach(function(doc) { 
            doc.y = doc.x/2; 
            db.test.save(doc); 
         });
PRIMARY> db.test.find();
{ "_id" : ObjectId("4f9df1ebed2b924eedb8cad9"), "x" : 15, "y" : 7.5 }
{ "_id" : ObjectId("4f9df1eeed2b924eedb8cada"), "x" : 30, "y" : 15 }
{ "_id" : ObjectId("4f9df1f1ed2b924eedb8cadb"), "x" : 50, "y" : 25 }

Upvotes: 3

Related Questions