Indexes and Indexing


      Description — Couchbase mobile database indexing concepts
      Related Content — Databases | Documents | Indexing |


      Querying documents using a pre-existing database index is much faster because an index narrows down the set of documents to examine — see: the Query Troubleshooting topic.

      When planning the indexes you need for your database, remember that while indexes make queries faster, they may also:

      • Make writes slightly slower, because each index must be updated whenever a document is updated

      • Make your Couchbase Lite database slightly larger.

      Too many indexes may hurt performance. Optimal performance depends on designing and creating the right indexes to go along with your queries.

      Couchbase Lite for ios does not currently support partial value indexes; indexes with non-property expressions. You should only index with properties that you plan to use in the query.

      Creating a new index

      You can use SQL++ or QueryBuilder syntaxes to create an index

      Example 2 creates a new index for the type and name properties, shown in this data model:

      Example 1. Data Model
          "_id": "hotel123",
          "type": "hotel",
          "name": "The Michigander",
          "overview": "Ideally situated for exploration of the Motor City and the wider state of Michigan. Tripadvisor rated the hotel ...",
          "state": "Michigan"


      The code to create the index will look something like this:

      Example 2. Create index
      CBLValueIndexConfiguration* config = [[CBLValueIndexConfiguration alloc]
                                            initWithExpression: @[@"type", @"name"]];
      [collection createIndexWithName:@"TypeNameIndex" config:config error: &error];


      See the QueryBuilder topic to learn more about QueryBuilder.

      The code to create the index will look something like this:

      Example 3. Create index with QueryBuilder
      CBLValueIndexItem *type = [CBLValueIndexItem property:@"type"];
      CBLValueIndexItem *name = [CBLValueIndexItem property:@"name"];
      CBLIndex *index = [CBLIndexBuilder valueIndexWithItems:@[type, name]];
      [collection createIndex:index name:@"TypeNameIndex" error:&error];