Cast INTERVAL and UUID to VARCHAR

[guenp]

Fixes MotherDuck-Open-Source/duckdb-power-query-connector#7.

Power Query/Power BI currently does not support INTERVAL and loading data with this type results in an error:

ODBC: ERROR [22007] ODBC_DuckDB->GetDataStmtResult Not implemented Error: Unimplemented type for cast (INTERVAL -> TIME)

Similarly, implementing a cast to TIME also won't work because in Power Query, valid values for TIME hours are 0-23.

UUID has a similar problem that it throws an "Unimplemented type for cast (UUID -> DOUBLE)` error.

This PR casts INTERVAL and UUID to VARCHAR by default. The INTERVAL value can be parsed separately in Power Query, for instance by using Duration.FromText (see docs).

[Mytherin]

Thanks for the PR! I wonder what the Postgres ODBC clients' behavior is, as they have the same interval type that we do. Do they just cast to VARCHAR as well or do something different? We should likely do what they do here.

[Mytherin]

Looks like they have an ifdef and likely turn it into varchar in regular releases as some applications don't handle the interval type correctly.

[guenp]

thanks @Mytherin for taking a look!
Indeed, it looks like Postgres doesn't offer interval support for the ODBC driver either:
https://github.com/hiinoue/psqlodbc/blob/f28b1dcc197c8775d6a34a419d73a0cfa97fa643/pgtypes.h#L82

/*
 *	SQL_INTERVAL support is disabled because I found
 *	some applications which are unhappy with it.
 *
#define	PG_INTERVAL_AS_SQL_INTERVAL
 */

I can't find anywhere in the code that they convert INTERVAL to VARCHAR so I wonder if it's simply not supported.

[maiadegraaf]

Hi Guen, thanks for your PR, could you reopen it on the new ODBC repo?
Thanks!

[guenp]

@maiadegraaf yes of course! PR is open here