The root entity is the central table whose columns can be used to join this table with other child entities.
To run it, do the following steps: Here, the root entity is a table called "item" whose primary key is a column "id".
Data can be read from this table with the query "select * from item".
Each item can have multiple "features" which are in the table In the above example, there are mappings of fields to Solr fields.
Most applications store data in relational databases or XML files and searching over such data is a common use-case.
The Data Import Handler is a Solr contrib that provides a configuration driven way to import this data into Solr in both "full builds" and using incremental delta imports.
It is possible to have more than one datasources for a configuration.
To configure an extra datasource , just keep an another 'data Source' tag .
There is an implicit attribute "name" for a datasource.
If there are more than one, each extra datasource must be identified by a unique name represents one kind of document. A root entity can contain multiple sub-entities which in turn can contain other entities.