@@ -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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~~~~~~~~~~~
@@ -237,24 +238,24 @@ aggregation
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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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+
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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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@@ -336,7 +340,7 @@ Additional Changes and Enhancements
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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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