Function openBaseDB

server/server.go:839–866

openBaseDB creates and configures a DuckDB connection with threads, memory limit, temp directory, extensions, and cache_httpfs settings. This shared setup is used by both regular and passthrough connections. When DataDir is set, the database is file-backed at / .duckdb. DuckDB mem

(cfg Config, username string)

		entry.refs++
		return entry.db, nil
	}

	var db *sql.DB
	var err error
	if passthrough {
		db, err = CreatePassthroughDBConnection(s.cfg, s.duckLakeSem, username, processStartTime, processVersion)
	} else {
		db, err = CreateDBConnection(s.cfg, s.duckLakeSem, username, processStartTime, processVersion)
	}
	if err != nil {
		return nil, err
	}

	// openBaseDB sets MaxOpenConns(1) for single-session use; override for shared pool.
	db.SetMaxOpenConns(0) // unlimited
	db.SetMaxIdleConns(4)

	stopRefresh := StartCredentialRefresh(db, s.cfg.DuckLake)

	s.fileDBs[username] = &fileDBEntry{
		db:          db,
		refs:        1,
		stopRefresh: stopRefresh,
	}
	return db, nil
}

// releaseFileDB decrements the ref count for a user's shared DB.
// When the last reference is released, the DB is closed and removed from the pool.
func (s *Server) releaseFileDB(username string) {
	s.fileDBsMu.Lock()