RFC: UUID 2.0 data types about clickhouse

[UnamedRus]

There is also problem with "awful" hash function, for UUID in uniq aggregate function #34425 (comment)

[den-crane]

The only concern is that Clickhouse is a DWH database and users may want to store uuids from different sources in the same column and also users may not know what their uuids are.
Of course in this case they can use the old UUID.
But I would consider the implementation of one new UUID type and name it nUUID or xUUID or ...

[UnamedRus]

I think, for new ClickHouse installations we need to use "new" variant.
For older, users need to explicitly enable this setting.

[alexey-milovidov]

Original proposal:

Often we store UUIDs from external systems, and they could be both v4 and v7. There is already a problem that sorting is not as expected. I think the only way will be to introduce data types UUID1, UUID2 (or with better names) and when a user writes UUID in the table definition or while casting, it will be persisted as either UUID1 or UUID2, depending on a setting, and then we will enable UUID2 by default.

@rschu1ze for some reason your proposal is entirely different from the original.

Closing this because it does not make sense to have different data types for UUIDv4 and UUIDv7.
It should be a single data type for UUID, but without these abominations.