HTTP interface for indexes

The result is an object describing the index. It has at least the following attributes:

• id: the identifier of the index

• type: the index type

All other attributes are type-dependent. For example, some indexes provide unique or sparse flags, whereas others don’t. Some indexes also provide a selectivity estimate in the selectivityEstimate attribute of the result.

Creates a new index in the collection collection. Expects an object containing the index details.

The type of the index to be created must specified in the type attribute of the index details. Depending on the index type, additional other attributes may need to specified in the request in order to create the index.

Indexes require the to be indexed attribute(s) in the fields attribute of the index details. Depending on the index type, a single attribute or multiple attributes can be indexed. In the latter case, an array of strings is expected.

The . character denotes sub-attributes in attribute paths. Attributes with literal . in their name cannot be indexed. Attributes with the name _id cannot be indexed either, neither as a top-level attribute nor as a sub-attribute.

Optionally, an index name may be specified as a string in the name attribute. Index names have the same restrictions as collection names. If no value is specified, one will be auto-generated.

Persistent indexes (including vertex-centric indexes) can be created as unique or non-unique variants. Uniqueness can be controlled by specifying the unique option for the index definition. Setting it to true creates a unique index. Setting it to false or omitting the unique attribute creates a non-unique index.

Persistent indexes can optionally be created in a sparse variant. A sparse index will be created if the sparse attribute in the index details is set to true. Sparse indexes do not index documents for which any of the index attributes is either not set or is null.

The optional deduplicate attribute is supported by persistent array indexes. It controls whether inserting duplicate index values from the same document into a unique array index will lead to a unique constraint error or not. The default value is true, so only a single instance of each non-unique index value will be inserted into the index per document. Trying to insert a value into the index that already exists in the index always fails, regardless of the value of this attribute.

The optional estimates attribute is supported by persistent indexes. This attribute controls whether index selectivity estimates are maintained for the index. Not maintaining index selectivity estimates can have a slightly positive impact on write performance. The downside of turning off index selectivity estimates will be that the query optimizer will not be able to determine the usefulness of different competing indexes in AQL queries when there are multiple candidate indexes to choose from. The estimates attribute is optional and defaults to true if not set. It will have no effect on indexes other than persistent indexes.

The optional attribute cacheEnabled is supported by indexes of type persistent. This attribute controls whether an extra in-memory hash cache is created for the index. The hash cache can be used to speed up index lookups. The cache can only be used for queries that look up all index attributes via an equality lookup (==). The hash cache cannot be used for range scans, partial lookups or sorting. The cache will be populated lazily upon reading data from the index. Writing data into the collection or updating existing data will invalidate entries in the cache. The cache may have a negative effect on performance in case index values are updated more often than they are read. The maximum size of cache entries that can be stored is currently 4 MB, i.e. the cumulated size of all index entries for any index lookup value must be less than 4 MB. This limitation is there to avoid storing the index entries of “super nodes” in the cache. cacheEnabled defaults to false and should only be used for indexes that are known to benefit from an extra layer of caching.

The optional attribute inBackground can be set to true to create the index in the background, which will not write-lock the underlying collection for as long as if the index is built in the foreground.