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What's new in MongoDB v1.8
 

What's new in MongoDB v1.8

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    What's new in MongoDB v1.8 What's new in MongoDB v1.8 Presentation Transcript

    • What’s New in MongoDB 1.8 — Webinar Richard M Kreuter 10gen Inc. richard@10gen.com March 17, 2011What’s New in MongoDB 1.8 — Webinar
    • What is new Write-ahead Journaling Covered and sparse indexes New map/reduce interface Spherical geospatial search Many new features for replica sets What’s New in MongoDB 1.8 — Webinar
    • Write-ahead Journaling MongoDB now supports a journaling mode, enabled with --journal, that commits to an append-only write-ahead log before making changes to database files. On a clean system shutdown, database files are closed and journal files are removed. In case of an unclean shutdown, journal sections are automatically replayed to bring database files into a coherent state. What’s New in MongoDB 1.8 — Webinar
    • Journaling, continued In MongoDB 1.8.0, journaling is not enabled by default; this default may change in future. At the moment, journaling slows down writes more than we expect it will in the long term, and so for now you should consider enable journaling on a case-by-case basis. The principle purpose of the journaling feature is to speed up recovery after a node crashes; you can think of it as a better solution than our existing “dbrepair” command. What’s New in MongoDB 1.8 — Webinar
    • Journaling, continued continued At present, the journal is committed to the file system every 100ms, or every 100MB, whichever is smaller. (Adaptive automagic tuning of this parameter is something we’re thinking about.) So on an unclean shutdown and restart, journal replay will bring the database up to the most recent completed journal section, i.e., the last 100ms or so of writes can be lost. Client applications can use getLastError with the fsync option to wait for their last write to have been written to the journal. (An interface for triggering, rather than waiting for, a journal write is forthcoming in the next weeks.) What’s New in MongoDB 1.8 — Webinar
    • Sparse Indexes Sparse indexes are a new flavor of index that may be useful when you want to index on a field that is present in only a smallish subset of a collection. A sparse index is created by specifying { sparse : true } to the index constructor, and it only create entries for documents that contain the field. What’s New in MongoDB 1.8 — Webinar
    • Covered Indexes A covered index is an index from which a query’s results can be produced without needing to access full document records. So, for example, if you have an index on attributes foo and bar and you execute find({ bar : { $gt : 10 } }, { foo : 1 , id : 0 }), the results can be computed just by examining the index. Note that the id attribute is not present in indexes by default, and so in order to take advantage of covered indexes, you’ll need to exclude it from a query’s projection argument or include it in the index explicitly. What’s New in MongoDB 1.8 — Webinar
    • New map/reduce interface The mapreduce command no longer creates “temporary collections”, and now requires an out argument specifying where the map/reduce job’s output goes. The out parameter must be one of: a collection name (a string), which will replace an collection { merge : collectionName } , which will merge the Map/Reduce job’s output into an existing collection by replacing any existing keys’ values in the collection with the M/R output for those keys, and adding key/value pairs for any new keys in the M/R output. { reduce : collectionName } , which uses the collection’s key/value pairs as the initial state for a new reduce job. { inline : 1 } , which returns the Map/Reduce output as a single document. What’s New in MongoDB 1.8 — Webinar
    • Spherical geoSpatial search MongoDB 1.8 includes support for “spherical” geoSpatial searches in addition to our existing Cartesian search. Two new geoSpatial query operators, $nearSphere and $centerSphere can be used to produce result sets that take the curvature of the earth into account when computing distances. db.places.find({a : {$nearSphere : [50, 50]}}) db.places.find({ a: {$within: {$centerSphere: [[50, 50], 10]}}}}) db.runCommand( { geoNear : "places" , near : [50,50], num : 10, spherical : true } ) What’s New in MongoDB 1.8 — Webinar
    • Many new features for replica sets Replica Sets have got some new features: hidden – don’t advertize this member to client initialSync – specify another node to perform an initial sync getLastErrorDefaults – specify default parameters (e.g., w and wtimeout) for getLastError calls with no arguments. Additionally, in sharded deployments, the mongos query router now knows how to route queries to Replica Set secondaries when slaveOk is enabled. What’s New in MongoDB 1.8 — Webinar
    • New features in tools mongostat now supports a --discover mode that automatically discovers all nodes in a cluster and queries each for statistics. mongodump now supports a “point in time” feature that dumps out the replication oplog after dumping all collections (enable with --oplog). mongorestore supports replaying an oplog dump as generated by the new mongodump option (enable with --oplogReplay). What’s New in MongoDB 1.8 — Webinar
    • Odds and Ends Maximum BSON document size has been increased to 16MB. A new update modifier for changing attribute names, $rename, has been added. Naturally, many bug fixes and other improvements have been committed. What’s New in MongoDB 1.8 — Webinar
    • So try MongoDB 1.8 today! http://www.mongodb.org/downloads http://www.mongodb.org/display/DOCS/1.8+Release+Notes 10gen, Inc. offers support, training, and advising services for mongodb. What’s New in MongoDB 1.8 — Webinar