Delegate DuckDbChunkReadingFunc<TState, TReturn>

Encapsulates user-defined code that accesses DuckDbChunkReader and its columns/vectors.

Namespace: Mallard

Assembly: Mallard.dll

Syntax

public delegate TReturn DuckDbChunkReadingFunc<in TState, out TReturn>(in DuckDbChunkReader chunk, TState state) where TState : allows ref struct

Parameters

Type	Name	Description
DuckDbChunkReader	chunk	Gives (temporary) access to the current chunk.
TState	state	Arbitrary state that the user-defined code can take.

Returns

Type	Description
TReturn	Whatever is desired. Typically the return value would be the result of some transformation in the chunk's data.

Type Parameters

Name	Description
TState	Type of arbitrary state that the user-defined code can take. The state may be represented by a "ref struct", although it is always passed in by value so that it is impossible for the user-defined code to leak out dangling pointers to inside the current chunk (unless unsafe code is used).
TReturn	Arbitrary return type from the user-defined function. This type may not be a "ref struct", to prevent dangling pointers to inside the current chunk from being returned. (The presence of the return value is for convenience; even if this delegate has been defined to return void, user-defined code can still propagate results out of the function by assigning to "ref" members suitably defined inside TState.)