Struct Appender

pub struct Appender<'conn> { /* private fields */ }

Appender for fast import data

Thread Safety

Appender is neither Send nor Sync:

• Not Send because it holds a reference to Connection, which is !Sync
• Not Sync because DuckDB appenders don’t support concurrent access

To use an appender in another thread, move the Connection to that thread and create the appender there.

If you need to share an Appender across threads, wrap it in a Mutex.

See DuckDB concurrency documentation for more details.

Wide Tables (Many Columns)

Array literals [value; N] are supported for tables with up to 32 columns.

appender.append_row([0; 32])?;
appender.append_row([1, 2, 3, 4, 5])?;

For tables with more than 32 columns, use one of these alternatives:

1. Slice approach - convert values to &dyn ToSql

let values: Vec<i32> = vec![0; 100];
let params: Vec<&dyn ToSql> = values.iter().map(|v| v as &dyn ToSql).collect();
appender.append_row(params.as_slice())?;

2. params! macro - write values explicitly

appender.append_row(params![v1, v2, v3, ..., v50])?;

3. appender_params_from_iter - pass an iterator directly

use duckdb::appender_params_from_iter;
let values: Vec<i32> = vec![0; 100];
appender.append_row(appender_params_from_iter(values))?;

All three methods can be used interchangeably and mixed in the same appender.

Implementations

impl Appender<'_>

pub fn append_rows<P, I>(&mut self, rows: I) -> Result<()>

where I: IntoIterator<Item = P>, P: AppenderParams,

Append multiple rows from Iterator

Example

fn insert_rows(conn: &Connection) -> Result<()> {
    let mut app = conn.appender("foo")?;
    app.append_rows([[1, 2], [3, 4], [5, 6], [7, 8], [9, 10]])?;
    Ok(())
}

Failure

Will return Err if append column count not the same with the table schema

pub fn append_row<P: AppenderParams>(&mut self, params: P) -> Result<()>

Append one row

Example

fn insert_row(conn: &Connection) -> Result<()> {
    let mut app = conn.appender("foo")?;
    app.append_row([1, 2])?;
    Ok(())
}

Failure

Will return Err if append column count not the same with the table schema

pub fn flush(&mut self) -> Result<()>

Flush data into DB

pub fn add_column(&mut self, name: &str) -> Result<()>

Add a column to the appender’s active column list.

When columns are added, only those columns need values during append. Other columns will use their DEFAULT value (or NULL if no default).

This flushes any pending data before modifying the column list.

pub fn clear_columns(&mut self) -> Result<()>

Clear the appender’s active column list.

After clearing, all columns become active again and values must be provided for every column during append.

This flushes any pending data before clearing.

Trait Implementations

impl Debug for Appender<'_>

fn fmt(&self, f: &mut Formatter<'_>) -> Result

Formats the value using the given formatter.

impl Drop for Appender<'_>

fn drop(&mut self)

Executes the destructor for this type.