Function duckdb_get_or_create_from_cache 

pub unsafe extern "C" fn duckdb_get_or_create_from_cache(
    instance_cache: duckdb_instance_cache,
    path: *const c_char,
    out_database: *mut duckdb_database,
    config: duckdb_config,
    out_error: *mut *mut c_char,
) -> duckdb_state

Creates a new database instance in the instance cache, or retrieves an existing database instance. Must be closed with ‘duckdb_close’.

@param instance_cache The instance cache in which to create the database, or from which to take the database. @param path Path to the database file on disk. Both nullptr and :memory: open or retrieve an in-memory database. @param out_database The resulting cached database. @param config (Optional) configuration used to create the database. @param out_error If set and the function returns DuckDBError, this contains the error message. Note that the error message must be freed using duckdb_free. @return DuckDBSuccess on success or DuckDBError on failure.