[Solr Wiki] Update of "DataImportHandler" by ShalinMangar

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

New page:
= Overview =

== Motivation ==
Most applications store data in relational databases and searching over such data is a common use-case. However, there is no standard way to import this data into SOLR index requiring custom tools external to SOLR.

== Goals ==
 * Read data residing in relational databases
 * Build SOLR documents by aggregating data from multiple columns and tables according to configuration
 * Update SOLR with such documents
 * Provide ability to do full imports according to configuration
 * Detect inserts/update deltas (changes) and do delta imports (we assume a last-modified timestamp column for this to work)
 * Schedule full imports and delta imports

= Design Overview =
As the name suggests, this is implemented as a SolrRequestHandler. The configuration is provided in two places:
 * solrconfig.xml (DataSource 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)

= Usage =
TODO

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CategorySolrRequestHandler