This data connector was historically used to produce both the "eduPersonTargetedID" SAML Attribute and to generate SAML 2.0 "persistent" NameID values. The original Attribute use case is essentially deprecated because SAML 1 itself is a legacy standard and because the use of the Attribute in SAML 2 is both redundant, and overly complex. The NameID use case has been replaced by an equivalent NameID "generator" (see the NameIDGenerationConfiguration topic).
The connector remains supported for use with the new SAML SubjectID specification's "pairwise-id" replacement for all these legacy approaches.
That said, we strongly suggest considering use of the ComputedId DataConnector, which is much less troublesome. When you inevitably find that the database approach lacks reliability, there won't be a lot you can do about it if you have services relying on the values. Start with the hashing approach and only then really consider whether you need anything else.