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Release Notes for MongoDB 1.2.x![](/docs/v5.2/assets/link.svg)
New Features![](/docs/v5.2/assets/link.svg)
More indexes per collection
Faster index creation
Map/Reduce
Stored JavaScript functions
Configurable fsync time
Several small features and fixes
DB Upgrade Required![](/docs/v5.2/assets/link.svg)
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
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![](/docs/v5.2/assets/link.svg)
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.
mongoimport![](/docs/v5.2/assets/link.svg)
mongoimportjson
has been removed and is replaced withmongoimport
that can do json/csv/tsv
field filter changing![](/docs/v5.2/assets/link.svg)
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