[CathodeAnode]

Summary

Add native SQL collection support for std::vector fields in PostgreSQL and DuckDB.

PostgreSQL maps vectors to native arrays, while DuckDB maps them to native lists. Nested vectors and nullable collections or elements are supported.

Backends without native collection support reject models containing vectors at compile time when used through the typed API.

Tests

Added PostgreSQL and DuckDB tests covering:

• Native collection schema generation.
• Collection serialization and database round trips.
• Nested collections.
• Nullable collections and nullable elements.
• Values requiring escaping, empty collections, and NULL elements.

[liuzicheng1987]

@CathodeAnode this looks like a pretty cool feature. Could you also update the documentation?

[liuzicheng1987]

@CathodeAnode something is up with the build pipeline. I will take a look at this tonight.

[CathodeAnode]

I updated the documentation.

[liuzicheng1987]

@CathodeAnode could you just quickly merge the main branch? That should fix the test pipelines.

[CathodeAnode]

I merged main into the branch.

[liuzicheng1987]

@CathodeAnode thanks for your contribution. I am merging.