Defining key Solr terms
Solr terms include several names for an index of documents and configuration on a single node.
- A Solr core
- A collection
- One shard of a collection
Each document in a Solr core/collection is considered unique and contains a set of fields that adhere to a user-defined schema. The schema lists the field types and how they should be indexed. DSE Search maps Solr cores/collections to Cassandra tables. Each table has a separate Solr core/collection on a particular node. Solr documents are mapped to Cassandra rows, and document fields to columns. The shard is analogous to a partition of the table. The Cassandra keyspace is a prefix for the name of the Solr core/collection and has no counterpart in Solr.
This table shows the relationship between Cassandra and Solr concepts:
| Cassandra | Solr--single node environment | Solr--distributed environment |
|---|---|---|
| Table | Solr core or collection | Collection |
| Row | Document | Document |
| Primary key | Unique key | Unique key |
| Column | Field | Field |
| Node | N/A | Node |
| Partition | N/A | Shard |
| Keyspace | N/A | N/A |
With Cassandra replication, a Cassandra node or Solr core contains more than one partition (shard) of table (collection) data. Unless the replication factor equals the number of cluster nodes, the Cassandra node or Solr core contains only a portion of the data of the table or collection.