[ghc]

My point was that the current relational features of Kdb didn't exist originally (they were grafted on later) so it's not "marketed" as a TSDB, but it is in fact a TSDB marketed as a relational DB.

The definition of relational is very precise, whether you use the domain calculus, relational calculus or relational algebra. Wiki has a good summary of what must be natively supported by a database system to be relational: https://en.wikipedia.org/wiki/Relational_algebra

If you don't implement this at the transaction log level, but implement it via emulation at the output level, you can't make full relational guarantees, so these operations are fundamental to database design.

[manigandham]

Why does it matter what it was originally? We're talking about what the product is today, not 20 years ago.

kdb+ supports a superset of SQL and relational algebra, so it's a relational database. How it's implemented doesn't matter if it provide the functionality, which it can.