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The following page has been changed by NoblePaul:
http://wiki.apache.org/solr/DataImportHandler

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  As the name suggests, this is implemented as a SolrRequestHandler. The 
configuration is provided in two places:
   * solrconfig.xml (data source information is read from here e.g. JDBC 
Driver, JDBC URL, Username, Password etc.)
   * data-config.xml (DB Table/column to SOLR document mapping comes here)
- inline:DataImportHandlerOverview.png
+ 
  
  = Usage =
  In order to use this handler, the following steps are required.
@@ -362, +362 @@

         </lst>
  }}}
  
+ = Architecture =
+ The following diagram describes the logical flow for a sample configuration.
+ 
+ inline:DataImportHandlerOverview.png
+ 
+ The use case is as follows:
+ There are 3 datasources two RDBMS (jdbc1,jdbc2) and one xml/http (B)
+ 
+  * The root entity starts with a table called 'A' in the 'jdbc1' . The entity 
is conveniently named as the table itself
+  * Each row that emitted by the 'query' in entity 'A' is fed into its sub 
entities B, C
+  * The queries in B and C use a column in 'A' to construct their queries 
using placeholders like `${A.a}`
+    * B has a url  (B is an xml/http datasource) 
+    * C has a query
+  * C has two transformers ('f' and 'g' )   
+  * Each row that comes out of C is fed into 'f' and 'g' sequentially 
(transformers are chained) . Each transformer produces changes the input. Note 
that the transformer 'g' produces 2 output rows for an input row `f(C.1))
+  * The end output of each entity is combined together to construct a document
+    * Note that the intermediate rows from C i.e `C.1, C.2, f(C.1) , f(C1)` 
are ignored
+ 
+ 
  = Where to find it? =
  DataImportHandler is not in SOLR right now. You can either:
   * Download the patch in [http://issues.apache.org/jira/browse/SOLR-469 
SOLR-469] in the SOLR JIRA, or

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