[sgarland]

Not AFAIK. In MySQL, the only time “cluster” is used is to refer to NDB Cluster, which is a distributed DB product. Schema means a logical grouping of tables, the same (more or less) as Postgres.

As to schema itself, yes, it’s heavily overloaded, and you just to grok it from context. I can talk about a table’s schema or a DB’s schema, or as you mentioned, JSON schema. Although the latter is helped by simply not using JSON in a relational DB.

You must remember that SQL is an ancient language, and the relational model is even older. There are going to be oddities.