Class DuckDbResultChunk

A chunk that has been retrieved (and captured) from the results of a query to DuckDB.

Inheritance

object

DuckDbResultChunk

Implements

IDisposable

Inherited Members

object.Equals(object)

object.Equals(object, object)

object.GetHashCode()

object.GetType()

object.ReferenceEquals(object, object)

object.ToString()

Namespace: Mallard

Assembly: Mallard.dll

Syntax

public sealed class DuckDbResultChunk : IDisposable

Remarks

This class allows the same chunk to be processed or read over and over again. Such functionality helps to implement row-oriented readers (whereas DuckDB is naturally column-oriented), that implement methods returning individual rows.

For more efficient column-oriented, streaming processing, use methods like ProcessNextChunk<TState, TReturn>(TState, DuckDbChunkReadingFunc<TState, TReturn>, out TReturn) instead.

The data in the chunk is held by the native DuckDB library. Instances of this class should be disposed after the user is finished with a chunk, to avoid unpredictable memory usage (before garbage collection kicks in).

Properties

ColumnCount

Declaration

public int ColumnCount { get; }

Property Value

Type	Description
int

Length

The number of rows present in this chunk.

Declaration

public int Length { get; }

Property Value

Type	Description
int

Methods

Dispose()

Disposes this object along with resources allocated in the native DuckDB library for it.

Declaration

public void Dispose()

~DuckDbResultChunk()

Destructor which will dispose this object if it has yet been already.

Declaration

protected ~DuckDbResultChunk()

GetColumnIndex(string)

Declaration

public int GetColumnIndex(string columnName)

Parameters

Type	Name	Description
string	columnName

Returns

Type	Description
int

GetColumnInfo(int)

Declaration

public DuckDbColumnInfo GetColumnInfo(int columnIndex)

Parameters

Type	Name	Description
int	columnIndex

Returns

Type	Description
DuckDbColumnInfo

GetColumnName(int)

Declaration

public string GetColumnName(int columnIndex)

Parameters

Type	Name	Description
int	columnIndex

Returns

Type	Description
string

ProcessContents<TState, TResult>(TState, DuckDbChunkReadingFunc<TState, TResult>)

Access the contents of this chunk of results in a direct, column-oriented manner.

Declaration

public TResult ProcessContents<TState, TResult>(TState state, DuckDbChunkReadingFunc<TState, TResult> func) where TState : allows ref struct

Parameters

Type	Name	Description
TState	state	The state object or structure to pass into func.
DuckDbChunkReadingFunc<TState, TResult>	func	The caller-specified function that receives the results from the next chunk and may do any processing on it.

Returns

Type	Description
TResult	Whatever func returns.

Type Parameters

Name	Description
TState	Type of arbitrary state to pass into the caller-specified function.
TResult	The type of value returned by the caller-specified function.

Remarks

This method offers fast, direct access to the native memory backing the DuckDB vectors (columns) of the results. However, to make these operations safe (allowing no dangling pointers), this library must be able to bound the scope of access. Thus, the code to consume the vectors' data must be encapsulated in a function that this method invokes.

This method can be called over and over again, and the same data will be seen by the caller-specified function on each invocation.

Implements

IDisposable