Struct Connection 

pub struct Connection {
    pub cache: RefCell<CacheManager>,
    /* private fields */
}

Wraps a DuckDB connection and registers parquet files as views.

Uses schema introspection to adapt views dynamically:

• CSV VARCHAR columns are auto-detected and converted to arrays
• Wide-format legalities are auto-UNPIVOTed to (uuid, format, status) rows

Fields

cache: RefCell<CacheManager>

The cache manager used to download/locate data files.

Implementations

impl Connection

pub fn new(cache: CacheManager) -> Result<Self>

Create a connection backed by the given cache.

Opens an in-memory DuckDB database.

pub fn ensure_views(&self, views: &[&str]) -> Result<()>

Ensure one or more views are registered, downloading data if needed.

pub fn execute( &self, sql: &str, params: &[String], ) -> Result<Vec<HashMap<String, Value>>>

Execute SQL and return results as a Vec of HashMaps.

Each row is represented as a HashMap<String, serde_json::Value>. Automatically converts DuckDB types to serde_json::Value.

pub fn execute_into<T: DeserializeOwned>( &self, sql: &str, params: &[String], ) -> Result<Vec<T>>

Execute SQL and deserialize each row into type T.

First executes the query as HashMap rows, then deserializes each row using serde_json.

pub fn execute_scalar( &self, sql: &str, params: &[String], ) -> Result<Option<Value>>

Execute SQL and return the first column of the first row.

Returns None if the result set is empty.

pub fn register_table_from_ndjson( &self, table_name: &str, ndjson_path: &str, ) -> Result<()>

Create a DuckDB table from a newline-delimited JSON file.

More memory-efficient than loading data into a Rust structure first, since data is streamed from disk by DuckDB.

pub fn has_view(&self, name: &str) -> bool

Check whether a view has been registered.

pub fn views(&self) -> Vec<String>

Return a list of all registered view names.

pub fn reset_views(&self)

Clear all registered views so they will be re-created on next access.

pub fn raw(&self) -> &DuckDbConnection

Access the underlying DuckDB connection for advanced usage.

pub fn export_db(&self, path: &Path) -> Result<PathBuf>

Export the in-memory DuckDB database to a directory on disk.

Uses DuckDB’s EXPORT DATABASE command.