Release Notes for MongoDB 1.2.x

New Features

  • More indexes per collection
  • Faster index creation
  • Map/Reduce
  • Stored JavaScript functions
  • Configurable fsync time
  • Several small features and fixes

DB Upgrade Required

There are some changes that will require doing an upgrade if your previous version is <= 1.0.x. If you’re already using a version >= 1.1.x then these changes aren’t required. There are 2 ways to do it:

  • --upgrade
    • stop your mongod process
    • run ./mongod --upgrade
    • start mongod again
  • use a slave
    • start a slave on a different port and data directory
    • when its synced, shut down the master, and start the new slave on the regular port.

Ask in the forums or IRC for more help.

Replication Changes

  • There have been minor changes in replication. If you are upgrading a master/slave setup from <= 1.1.2 you have to update the slave first.


  • mongoimportjson has been removed and is replaced with mongoimport that can do json/csv/tsv

field filter changing

  • We’ve changed the semantics of the field filter a little bit. Previously only objects with those fields would be returned. Now the field filter only changes the output, not which objects are returned. If you need that behavior, you can use $exists