[Solr Wiki] Update of "Atomic_Updates" by TadhgMulkern

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The "Atomic_Updates" page has been changed by TadhgMulkern:
http://wiki.apache.org/solr/Atomic_Updates

New page:
<!> [[Solr4.0]]

= Atomic Updates =
 
<<TableOfContents(2)>>
== Introduction ==

Atomic Updates is a new feature in Solr 4.0 that allows you to update on a field level rather than on a document level (In previous versions). This means that you can update individual fields without having to send the document to Solr with the update fields values. Internally Solr re-adds the document to the index with the updated fields.

== Available Modifiers ==

 * {{{set}}} – sets or replaces a particular value, or remove the value if {{{null}}} is specified as the new value. <!> Note: In the case of multi-valued fields if {{{null}}} is specified on {{{set}}} all the values in the field are removed. See [[https://issues.apache.org/jira/browse/SOLR-3862|SOLR-3862]]
 * {{{add}}} – adds an additional value to a multi-valued field 
 * {{{inc}}} – increments a numeric value by a specific amount

[[http://wiki.apache.org/solr/UpdateJSON#Solr_4.0_Example | Update JSON Example]] <<BR>>
[[http://wiki.apache.org/solr/UpdateXmlMessages#Optional_attributes_for_.22field.22 | Update XML Example]]


= References =

https://issues.apache.org/jira/browse/SOLR-139 <<BR>>
http://yonik.com/solr/atomic-updates/