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## New Features in Release 21.2

Unnesting of Arrays and Maps in Queries

The UNNEST clause has been introduced, which converts an array or map into a series of rows. The syntax of the FROM clause has also been extended to allow specifying a list of expressions after the table or tables used by the query, which can influence which indexes the query runtime selects for queries that have UNNEST clauses.

Erasing User Data

Added support for erasing obsolete user data within a specified time period after becoming obsolete, without adding significant performance impact to the application. This new feature, data erasure, runs in the background to zero out obsolete data. All data that is obsolete from the database point of view is removed: i.e. deleted data, older versions of updated records, and expired data. Data erasure also removes corresponding obsolete index records.

Two new Rep Node parameters control erasure: "enableErasure" is used to enable erasure, which is disabled by default, and "erasurePeriod" specifies the time required to complete an erasure cycle.

Note:

Snapshot-based backups create hard links to original files. Until these backups are copied to their target location and the corresponding hard links are removed, erasure will not process obsolete data in those files. Erasure ignores files with hard links to them.

Deprecating Property Graph Package

Starting with release 21.2, the RDF Property Graph package is deprecated and is no longer certified with Oracle NoSQL Database.

Disabling DSA (ssh-dss) SSH Keys in the Diagnostics Utility

The diagnostics utility no longer supports DSA (ssh-dss) SSH keys due to security weaknesses with that algorithm. Attempting to use the diagnostics utility with a DSA (ssh-dss) SSH key will produce an error message similar to:

    DefaultAuthFuture[ssh-connection]: Failed (IllegalArgumentException) to
    execute: No signer could be located for key type=ssh-dss

In a future version, RSA (ssh-rsa) SSH key support may also be removed for similar reasons. It's recommended to migrate to other SSH key algorithms, for example ECDSA or ED25519.