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Bob Grabar
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DOCS-391 migrate 1.8 release notes - draft 3
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source/release-notes/1.8.txt

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@@ -19,12 +19,13 @@ a drop-in replacement for MongoDB 1.6, except:
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- :term:`Replica set <replica set>` members should be upgraded in a
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particular order, as described in :ref:`1.8-upgrade-replica-set`.
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- The options for the :wiki:`MapReduce` operation have changed in 1.8,
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causing incompatibility with previous releases. If you use MapReduce,
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see the MapReduce
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:wiki:`Output Options <MapReduce#MapReduce-Outputoptions>`
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page. If you use MapReduce, this also likely means you need a recent
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version of your client driver.
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- The :dbcommand:`mapReduce` command has changed in 1.8, causing
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incompatibility with previous releases. :dbcommand:`mapReduce` no
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longer generates temporary collections (thus, ``keepTemp`` has been
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removed). Now, you must always supply a value for ``out``. See the
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``out`` field options in the :dbcommand:`mapReduce` document. If you
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use MapReduce, this also likely means you need a recent version of
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your client driver.
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Preparation
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~~~~~~~~~~~
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Sparse and Covered Indexes
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~~~~~~~~~~~~~~~~~~~~~~~~~~
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:wiki:`Sparse Indexes <Indexes#Indexes-sparse%3Atrue>` are indexes that
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only include documents that contain the fields specified in the index.
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Documents missing the field will not appear in the index at all. This
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can significantly reduce index size for attributes that are contained in
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a subset of documents within a :term:`collection`.
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:ref:`Sparse Indexes <sparse-index>` are indexes that only include
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documents that contain the fields specified in the index. Documents
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missing the field will not appear in the index at all. This can
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significantly reduce index size for attributes that are contained in a
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subset of documents within a :term:`collection`.
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:wiki:`Covered Indexes <Retrieving+a+Subset+of+Fields#RetrievingaSubsetofFields-CoveredIndexes>`
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enable queries to be answered entirely from the index when the query
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only requests fields that are contained in the index.
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:ref:`Covered Indexes <use-covered-queries>` enable queries to be
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answered entirely from the index when the query only requests fields
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that are contained in the index.
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Incremental MapReduce Support
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~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
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MapReduce supports new :wiki:`MapReduce Output Options<MapReduce#MapReduce-Outputoptions>`
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that enable incrementally updating existing :term:`collections
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<collection>`. Previously, a MapReduce job could output either to a
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temporary collection or to a named permanent collection, which it would
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overwrite with new data.
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The :dbcommand:`mapReduce` command supports new options that enable
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incrementally updating existing :term:`collections <collection>`.
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Previously, a MapReduce job could output either to a temporary
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collection or to a named permanent collection, which it would overwrite
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with new data.
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You now have several options for the output of your MapReduce jobs:
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@@ -276,6 +277,9 @@ You now have several options for the output of your MapReduce jobs:
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temporary collections generated in previous releases, except results
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are limited to 8MB.
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For more information, see the ``out`` field options in the
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:dbcommand:`mapReduce` document.
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Additional Changes and Enhancements
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~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
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@@ -314,18 +318,18 @@ Additional Changes and Enhancements
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- :program:`mongos` routes ``slaveOk`` queries to :term:`secondaries
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<secondary>` in :term:`replica sets <replica set>`.
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- New :wiki:`MapReduce output options<MapReduce#MapReduce-Outputoptions>`.
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- New :dbcommand:`mapReduce` output options
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- :wiki:`Sparse indexes <Indexes#Indexes-sparse%3Atrue>`.
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- :ref:`sparse-index`.
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1.7.3
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`````
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- :wiki:`Initial covered index support </Retrieving+a+Subset+of+Fields#RetrievingaSubsetofFields-CoveredIndexes>`.
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- Initial :ref:`covered index <use-covered-queries>` support
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- Distinct can use data from indexes when possible.
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- :wiki:`MapReduce can merge or reduce results into an existing collection </MapReduce#MapReduce-Outputoptions>`.
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- :dbcommand:`mapReduce` can merge or reduce results into an existing collection.
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- :program:`mongod` tracks and :program:`mongostat` displays network usage. See :ref:`mongostat`.
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- :operator:`$rename` operator allows renaming of attributes in a document.
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- :wiki:`Option to db.eval not to block </Server-side+Code+Execution>`.
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- :method:`db.eval()` not to block.
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- Geo queries with sharding.
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