The OrderByClause class represents an order by clause for a QgsFeatureRequest. More...

#include <qgsfeaturerequest.h>

Public Member Functions
	OrderByClause (const QString &expression, bool ascending=true)
	Creates a new OrderByClause for a QgsFeatureRequest. More...

	OrderByClause (const QString &expression, bool ascending, bool nullsfirst)
	Creates a new OrderByClause for a QgsFeatureRequest. More...

bool	ascending () const
	Order ascending. More...

QString	dump () const
	Dumps the content to an SQL equivalent. More...

QgsExpression	expression () const
	The expression. More...

bool	nullsFirst () const
	Set if NULLS should be returned first. More...

void	setAscending (bool ascending)
	Set if ascending order is requested. More...

void	setNullsFirst (bool nullsFirst)
	Set if NULLS should be returned first. More...

Detailed Description

The OrderByClause class represents an order by clause for a QgsFeatureRequest.

It can be a simple field or an expression. Multiple order by clauses can be added to a QgsFeatureRequest to fine tune the behavior if a single field or expression is not enough to completely specify the required behavior.

If expression compilation is activated in the settings and the expression can be translated for the provider in question, it will be evaluated on provider side. If one of these two premises does not apply, the ordering will take place locally which results in increased memory and CPU usage.

If the ordering is done on strings, the order depends on the system's locale if the local fallback implementation is used. The order depends on the server system's locale and implementation if ordering is done on the server.

In case the fallback code needs to be used, a limit set on the request will be respected for the features returned by the iterator but internally all features will be requested from the provider.

Note: added in QGIS 2.14

Definition at line 109 of file qgsfeaturerequest.h.

Constructor & Destructor Documentation

◆ OrderByClause() [1/2]

QgsFeatureRequest::OrderByClause::OrderByClause	(	const QString &	expression,
		bool	ascending = `true`
	)

Creates a new OrderByClause for a QgsFeatureRequest.

Parameters

expression	The expression to use for ordering
ascending	If the order should be ascending (1,2,3) or descending (3,2,1) If the order is ascending, by default nulls are last If the order is descending, by default nulls are first

Definition at line 276 of file qgsfeaturerequest.cpp.

◆ OrderByClause() [2/2]

QgsFeatureRequest::OrderByClause::OrderByClause	(	const QString &	expression,
		bool	ascending,
		bool	nullsfirst
	)

Creates a new OrderByClause for a QgsFeatureRequest.

Parameters

expression	The expression to use for ordering
ascending	If the order should be ascending (1,2,3) or descending (3,2,1)
nullsfirst	If true, NULLS are at the beginning, if false, NULLS are at the end

Definition at line 284 of file qgsfeaturerequest.cpp.

Member Function Documentation

◆ ascending()

bool QgsFeatureRequest::OrderByClause::ascending ( ) const

Order ascending.

Returns: If ascending order is requested

Definition at line 291 of file qgsfeaturerequest.cpp.

◆ dump()

QString QgsFeatureRequest::OrderByClause::dump ( ) const

Dumps the content to an SQL equivalent.

Definition at line 311 of file qgsfeaturerequest.cpp.

◆ expression()

QgsExpression QgsFeatureRequest::OrderByClause::expression ( ) const

The expression.

Returns: the expression

Definition at line 319 of file qgsfeaturerequest.cpp.

◆ nullsFirst()

bool QgsFeatureRequest::OrderByClause::nullsFirst ( ) const

Set if NULLS should be returned first.

Returns: if NULLS should be returned first

Definition at line 301 of file qgsfeaturerequest.cpp.

◆ setAscending()

void QgsFeatureRequest::OrderByClause::setAscending ( bool ascending )

Set if ascending order is requested.

Definition at line 296 of file qgsfeaturerequest.cpp.

◆ setNullsFirst()

void QgsFeatureRequest::OrderByClause::setNullsFirst ( bool nullsFirst )