fix for motherduck to use multiple schema

[NamanMahor]

Closes PLAT-428: Support multiple databases/schemas for Motherduck

Checklist:

• Covered by tests
• Ran it and it works as intended
• Reviewed the diff before requesting a review
• Checked for unhandled edge cases
• Linked the issues it closes
• Checked if the docs need to be updated. If so, create a separate Linear DOCS issue
• Intend to cherry-pick into the release branch
• I'm proud of this work!

[k-anshul]

Is it guaranteed that motherduck can't have a db named main_db otherwise there is a chance of an edge case here ?

[NamanMahor]

@k-anshul we cannot attach main_db because our local duckdb name is also main_db we need to attach using as.

[k-anshul]

The local db is called main<UUID> in case of motherduck:

rill/runtime/pkg/rduckdb/generic.go

Line 101 in 4576c64

localFileName := filepath.Join(opts.LocalDataDir, "main"+uuid.NewString()[:8]+".db")

[NamanMahor]

@begelundmuller Me and Anshul had the discussion. There are few options here we can have

1. DialectGenericDuckDB
2. type Dialect struct {
   Name string
   SingleSchema bool
   }
3. type OLAPDialect struct {
   Dialect Dialect
   SingleSchema bool
   }

Any thought on this?

[begelundmuller]

Sharing some thoughts in a DM

[NamanMahor]

@k-anshul is it okay to merge this. and will raise the separate pr for Dialect refactorying .

[k-anshul]

Shouldn't we revisit this after Dialect refactoring ? I think we should close this and open a new one after refactoring instead.