ECS 3.6.2 Data Access Guide

Metadata Search

The ECS S3-compatible API provides a metadata search extension. The search enables objects within a bucket to be indexed based on their metadata, and for the metadata index to be queried to find objects and their associated data.

Metadata can be associated with objects using the ECS S3 API. If you know the identity of an object, you can read an object's metadata. Without the ECS metadata search feature, it is not possible to find an object using its metadata without iterating through the set of object in a bucket.

Metadata can be either user metadata or system metadata. System metadata is defined and automatically written to objects by ECS, clients write the user metadata with reference to the user requirements. Both system and user metadata can be indexed and used as the basis for metadata searches. The number of metadata values that can be indexed is limited to 30 and must be defined when the bucket is created.

When querying objects based on their indexed metadata, the objects that match the query and the values of their indexed metadata are returned. You can also choose to return all of the system and/or user metadata that is associated with the returned objects. In addition to system metadata, objects also have attributes which can be returned as part of metadata search results. The system metadata values that are available and can be indexed, and the metadata values that can optionally be returned with search query results, are listed ECS system metadata and optional attributes.

The following topics cover the steps involves in setting up and using the metadata search feature:

• Assign metadata index values to a bucket
• Assign metatdata to objects using S3 protocol
• Use metadata search queries