Mapping one-to-many entities in SOLR - lucene

Question

I'm trying to map a few entities from an existing database to SOLR.
The tables are:
Hotel:
hotel_id
hotel_name
HotelToCategory:
hotel_id
category_id
rate
Category:
category_id
name
value
How can I use DataImportHandler to produce documents like this:
{
hotel_name: 'name',
hotel_id: 1,
categories: [
{ category_name: 'cname',
value: 'val',
rate: 3,
}
]
}
Any help will be greatly appreciated!

Answer 1

Relationships are indexed using stacked entities in DIH. Have a look in the DIH page in the Solr wiki.
There's also a few basic examples of this included in Solr distributions, have a look in examples/example-DIH.
There is a limitation here though, solr does not (currently) support relationships between index documents, so you will have to find a workaround for indexing this. For instance by just storing display data in a non-indexed field (which might require very frequent reindexing):
<document>
<entity name="hotel" query="select * from hotel">
<field column="id" name="hotel_id" />
<field column="hotel_name" name="hotel_name" />
<entity name="hotel_category_display"
query="SELECT STATEMENT THAT RETURNS JSON REPRESENTATION">
<field column="category" name="category" />
</entity>
</document>
Or by storing just category ID and do lookups (either against the database, or index categories separately and lookup against Solr) at search time:
<entity name="hotel_category_display"
query="SELECT STATEMENT THAT RETURNS JSON REPRESENTATION">
<field column="category" name="category" />
</entity>