Working with indexes

IBM® Cloudant® for IBM Cloud® endpoints can be used to create, list, update, and delete indexes in a database, and to query data by using these indexes.

Table 1. Available methods and endpoints
Methods	Path	Description
`DELETE`	`/$DATABASE/_index`	Delete an index.
`GET`	`/$DATABASE/_index`	List all IBM Cloudant Query indexes.
`POST`	`/$DATABASE/_find`	Find documents by using a global index.
`POST`	`/$DATABASE/_partition/$PARTITION_KEY/_find`	Find documents by using a partitioned index.
`POST`	`/$DATABASE/_index`	Create an index.

Creating a partial index

IBM Cloudant Query supports partial indexes by using the partial_filter_selector field. For more information, see the CouchDB documentation and the original example.

The partial_filter_selector field replaces the selector field, previously only valid in text indexes. The selector field is still compatible with an earlier version for text indexes only.

See the following example query:

{
  "selector": {
    "status": {
      "$ne": "archived"
    },
    "type": "user"
  }
}

Without a partial index, this query requires a full index scan to find all the documents of type:user that don't have a status of archived. This situation occurs because a normal index can be used to match contiguous rows, and the $ne operator can't guarantee that.

To improve response time, you can create an index that excludes documents with status: { $ne: archived } at index time by using the partial_filter_selector field that is shown in the following example:

POST /db/_index HTTP/1.1
Content-Type: application/json
Content-Length: 144
Host: localhost:5984

{
  "index": {
    "partial_filter_selector": {
      "status": {
        "$ne": "archived"
      }
    },
    "fields": ["type"]
  },
  "ddoc" : "type-not-archived",
  "type" : "json"
}

Partial indexes aren't currently used by the query planner unless specified by a use_index field, so you must modify the original query:

{
  "selector": {
    "status": {
      "$ne": "archived"
    },
    "type": "user"
  },
  "use_index": "type-not-archived"
}

Technically, you don't need to include the filter on the status field in the query selector. The partial index ensures that this value is always true. However, if you include the filter, it makes the intent of the selector clearer. It also makes it easier to take advantage of future improvements to query planning (for example, automatic selection of partial indexes).