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QGIS API Documentation
3.4.15-Madeira (e83d02e274)
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QGIS API Documentation
3.4.15-Madeira (e83d02e274)
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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... | |
| OrderByClause (const QgsExpression &expression, bool ascending=true) | |
| Creates a new OrderByClause for a QgsFeatureRequest. More... | |
| OrderByClause (const QgsExpression &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... | |
| bool | prepare (QgsExpressionContext *context) |
| Prepare the expression with the given context. More... | |
| void | setAscending (bool ascending) |
| Set if ascending order is requested. More... | |
| void | setNullsFirst (bool nullsFirst) |
| Set if NULLS should be returned first. More... | |
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.
Definition at line 126 of file qgsfeaturerequest.h.
| QgsFeatureRequest::OrderByClause::OrderByClause | ( | const QString & | expression, |
| bool | ascending = true |
||
| ) |
Creates a new OrderByClause for a QgsFeatureRequest.
| 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 356 of file qgsfeaturerequest.cpp.
| QgsFeatureRequest::OrderByClause::OrderByClause | ( | const QString & | expression, |
| bool | ascending, | ||
| bool | nullsfirst | ||
| ) |
Creates a new OrderByClause for a QgsFeatureRequest.
| 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 364 of file qgsfeaturerequest.cpp.
| QgsFeatureRequest::OrderByClause::OrderByClause | ( | const QgsExpression & | expression, |
| bool | ascending = true |
||
| ) |
Creates a new OrderByClause for a QgsFeatureRequest.
| 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 371 of file qgsfeaturerequest.cpp.
| QgsFeatureRequest::OrderByClause::OrderByClause | ( | const QgsExpression & | expression, |
| bool | ascending, | ||
| bool | nullsfirst | ||
| ) |
Creates a new OrderByClause for a QgsFeatureRequest.
| 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 379 of file qgsfeaturerequest.cpp.
| bool QgsFeatureRequest::OrderByClause::ascending | ( | ) | const |
Order ascending.
Definition at line 387 of file qgsfeaturerequest.cpp.
| QString QgsFeatureRequest::OrderByClause::dump | ( | ) | const |
Dumps the content to an SQL equivalent.
Definition at line 407 of file qgsfeaturerequest.cpp.
| QgsExpression QgsFeatureRequest::OrderByClause::expression | ( | ) | const |
| bool QgsFeatureRequest::OrderByClause::nullsFirst | ( | ) | const |
Set if NULLS should be returned first.
Definition at line 397 of file qgsfeaturerequest.cpp.
| bool QgsFeatureRequest::OrderByClause::prepare | ( | QgsExpressionContext * | context | ) |
Prepare the expression with the given context.
Definition at line 420 of file qgsfeaturerequest.cpp.
| void QgsFeatureRequest::OrderByClause::setAscending | ( | bool | ascending | ) |
Set if ascending order is requested.
Definition at line 392 of file qgsfeaturerequest.cpp.
| void QgsFeatureRequest::OrderByClause::setNullsFirst | ( | bool | nullsFirst | ) |
Set if NULLS should be returned first.
Definition at line 402 of file qgsfeaturerequest.cpp.
1.8.11
