Struct DataChunk 

pub struct DataChunk { /* private fields */ }

A non-owning wrapper around a duckdb_data_chunk.

This wrapper does not destroy the chunk on drop — DuckDB owns the chunk and manages its lifetime. DataChunk simply provides ergonomic methods for accessing vectors and metadata within callback functions.

Implementations

impl DataChunk

pub const unsafe fn from_raw(raw: duckdb_data_chunk) -> Self

Wraps a raw duckdb_data_chunk handle.

Safety

raw must be a valid duckdb_data_chunk obtained from a DuckDB callback (e.g., a scan callback’s output parameter or an aggregate update callback’s input chunk). The chunk must remain valid for the lifetime of this wrapper.

pub fn size(&self) -> usize

Returns the number of rows in this data chunk.

pub unsafe fn set_size(&self, size: usize)

Sets the number of rows in this data chunk.

Call this in scan callbacks after writing output rows. Set to 0 to signal end of stream.

Safety

size must not exceed the chunk’s capacity (typically 2048).

pub fn column_count(&self) -> usize

Returns the number of columns in this data chunk.

pub unsafe fn vector(&self, col_idx: usize) -> duckdb_vector

Returns the raw duckdb_vector handle for the given column index.

Safety

col_idx must be less than column_count.

pub unsafe fn writer(&self, col_idx: usize) -> VectorWriter

Creates a VectorWriter for the given column index.

Safety

• col_idx must be less than column_count.
• The chunk must be a writable output chunk (not a read-only input chunk).

pub unsafe fn reader(&self, col_idx: usize) -> VectorReader

Creates a VectorReader for the given column index.

The reader’s row count is set to this chunk’s current size.

Safety

col_idx must be less than column_count.

pub unsafe fn struct_reader( &self, col_idx: usize, field_count: usize, ) -> StructReader

Creates a StructReader for a STRUCT column at the given index.

This is a convenience method that combines vector with StructReader::new.

Safety

• col_idx must be less than column_count.
• The column at col_idx must have a STRUCT type with field_count fields.

pub unsafe fn struct_field_reader( &self, col_idx: usize, field_idx: usize, ) -> VectorReader

Creates a VectorReader for a field of a STRUCT column.

Convenience for accessing a specific field in a STRUCT input column.

Safety

• col_idx must be less than column_count.
• The column at col_idx must have a STRUCT type.
• field_idx must be a valid field index within the STRUCT.

pub unsafe fn struct_writer( &self, col_idx: usize, field_count: usize, ) -> StructWriter

Creates a StructWriter for a STRUCT column at the given index.

This is a convenience method that combines vector with StructWriter::new.

Safety

• col_idx must be less than column_count.
• The column at col_idx must have a STRUCT type with field_count fields.
• The chunk must be a writable output chunk.

pub const unsafe fn into_chunk_writer(self) -> ChunkWriter

Creates a ChunkWriter for this output data chunk.

The ChunkWriter tracks rows via next_row() and automatically calls set_size on drop.

Safety

This chunk must be a valid, writable output chunk from a table function scan callback.

pub const fn as_raw(&self) -> duckdb_data_chunk

Returns the raw duckdb_data_chunk handle.