SOLR schema - storing of document Id field. Maximum number of documents in Lucene index

Question

I have a couple of questions about Lucene/SOLR index schema

1. Here's my document Id field (UniqueKey) as defined in SOLR schema:

   <field name="Id" type="long" indexed="true" stored="true" required="true" />

I will never perform search by the Id field so does it need to be indexed="true"? And BTW, does it need to be stored="true" (I assume it will be stored anyway so it doesn't matter).

And 2: what is the maximum number of documents that can be stored in single SOLR index? Or, to be more precise: can it hold 5 billion of small documents?

Third question: I need to perform search on a combination of 2 fields: one of type long and one integer. What is the most efficient way of storing and indexing such fields - store and index them separately or pre-compute some hash value based on both of them and search by the hash only? Since I want to have few billions of such documents I need to minimize storage needs while keeping the search efficient.

Thanks RG

Answer 1

1. http://wiki.apache.org/solr/SchemaXml#The_Unique_Key_Field

   It is not mandatory for a schema to have a uniqueKey field

2. Solr can hold a maximum of ~274 billion Documents. Handling and Search response will depend on the memory. However, if your index size grows and is not maintainable, you can use Distributed Search .

3. You can combine the fields into a single field as hash and not mark it as stored to reduce the index size. This would speed up the initial searches. Caching should take care of similar searches.