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qgsfeatureiterator.cpp
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qgsfeatureiterator.cpp
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/***************************************************************************
qgsfeatureiterator.cpp
---------------------
begin : Juli 2012
copyright : (C) 2012 by Martin Dobias
email : wonder dot sk at gmail dot com
***************************************************************************
* *
* This program is free software; you can redistribute it and/or modify *
* it under the terms of the GNU General Public License as published by *
* the Free Software Foundation; either version 2 of the License, or *
* (at your option) any later version. *
* *
***************************************************************************/
#include "qgsfeatureiterator.h"
#include "qgslogger.h"
#include "qgssimplifymethod.h"
#include "qgsexception.h"
#include "qgsexpressionsorter.h"
#include "qgsfeedback.h"
QgsAbstractFeatureIterator::QgsAbstractFeatureIterator( const QgsFeatureRequest &request )
: mRequest( request )
{
}
bool QgsAbstractFeatureIterator::nextFeature( QgsFeature &f )
{
bool dataOk = false;
if ( mRequest.limit() >= 0 && mFetchedCount >= mRequest.limit() )
{
return false;
}
if ( mRequest.feedback() && mRequest.feedback()->isCanceled() )
return false;
if ( mUseCachedFeatures )
{
if ( mFeatureIterator != mCachedFeatures.constEnd() )
{
f = mFeatureIterator->mFeature;
++mFeatureIterator;
dataOk = true;
}
else
{
dataOk = false;
// even the zombie dies at this point...
mZombie = false;
}
}
else
{
switch ( mRequest.filterType() )
{
case QgsFeatureRequest::FilterExpression:
dataOk = nextFeatureFilterExpression( f );
break;
case QgsFeatureRequest::FilterFids:
dataOk = nextFeatureFilterFids( f );
break;
default:
dataOk = fetchFeature( f );
break;
}
}
if ( dataOk )
mFetchedCount++;
return dataOk;
}
bool QgsAbstractFeatureIterator::nextFeatureFilterExpression( QgsFeature &f )
{
while ( fetchFeature( f ) )
{
mRequest.expressionContext()->setFeature( f );
if ( mRequest.filterExpression()->evaluate( mRequest.expressionContext() ).toBool() )
return true;
}
return false;
}
bool QgsAbstractFeatureIterator::nextFeatureFilterFids( QgsFeature &f )
{
while ( fetchFeature( f ) )
{
if ( mRequest.filterFids().contains( f.id() ) )
return true;
}
return false;
}
void QgsAbstractFeatureIterator::geometryToDestinationCrs( QgsFeature &feature, const QgsCoordinateTransform &transform ) const
{
if ( transform.isValid() && feature.hasGeometry() )
{
try
{
QgsGeometry g = feature.geometry();
g.transform( transform );
feature.setGeometry( g );
}
catch ( QgsCsException & )
{
// transform error
if ( mRequest.transformErrorCallback() )
{
mRequest.transformErrorCallback()( feature );
}
// remove geometry - we can't reproject so better not return a geometry in a different crs
feature.clearGeometry();
}
}
}
QgsRectangle QgsAbstractFeatureIterator::filterRectToSourceCrs( const QgsCoordinateTransform &transform ) const
{
if ( mRequest.filterRect().isNull() )
return QgsRectangle();
return transform.transformBoundingBox( mRequest.filterRect(), QgsCoordinateTransform::ReverseTransform );
}
void QgsAbstractFeatureIterator::ref()
{
// Prepare if required the simplification of geometries to fetch:
// This code runs here because of 'prepareSimplification()' is virtual and it can be overridden
// in inherited iterators who change the default behavior.
// It would be better to call this method in the constructor enabling virtual-calls as it is described by example at:
// http://www.parashift.com/c%2B%2B-faq-lite/calling-virtuals-from-ctor-idiom.html
if ( refs == 0 )
{
prepareSimplification( mRequest.simplifyMethod() );
// Should be called as last preparation step since it possibly will already fetch all features
setupOrderBy( mRequest.orderBy() );
}
refs++;
}
void QgsAbstractFeatureIterator::deref()
{
refs--;
if ( !refs )
delete this;
}
bool QgsAbstractFeatureIterator::compileFailed() const
{
return mCompileFailed;
}
bool QgsAbstractFeatureIterator::prepareSimplification( const QgsSimplifyMethod &simplifyMethod )
{
Q_UNUSED( simplifyMethod )
return false;
}
void QgsAbstractFeatureIterator::setupOrderBy( const QList<QgsFeatureRequest::OrderByClause> &orderBys )
{
// Let the provider try using an efficient order by strategy first
if ( !orderBys.isEmpty() && !prepareOrderBy( orderBys ) )
{
// No success from the provider
// Prepare the expressions
QList<QgsFeatureRequest::OrderByClause> preparedOrderBys( orderBys );
QList<QgsFeatureRequest::OrderByClause>::iterator orderByIt( preparedOrderBys.begin() );
QgsExpressionContext *expressionContext( mRequest.expressionContext() );
do
{
orderByIt->prepare( expressionContext );
}
while ( ++orderByIt != preparedOrderBys.end() );
// Fetch all features
QgsIndexedFeature indexedFeature;
indexedFeature.mIndexes.resize( preparedOrderBys.size() );
while ( nextFeature( indexedFeature.mFeature ) )
{
expressionContext->setFeature( indexedFeature.mFeature );
int i = 0;
const auto constPreparedOrderBys = preparedOrderBys;
for ( const QgsFeatureRequest::OrderByClause &orderBy : constPreparedOrderBys )
{
indexedFeature.mIndexes.replace( i++, orderBy.expression().evaluate( expressionContext ) );
}
// We need all features, to ignore the limit for this pre-fetch
// keep the fetched count at 0.
mFetchedCount = 0;
mCachedFeatures.append( indexedFeature );
}
std::sort( mCachedFeatures.begin(), mCachedFeatures.end(), QgsExpressionSorter( preparedOrderBys ) );
mFeatureIterator = mCachedFeatures.constBegin();
mUseCachedFeatures = true;
// The real iterator is closed, we are only serving cached features
mZombie = true;
}
}
bool QgsAbstractFeatureIterator::providerCanSimplify( QgsSimplifyMethod::MethodType methodType ) const
{
Q_UNUSED( methodType )
return false;
}
bool QgsAbstractFeatureIterator::prepareOrderBy( const QList<QgsFeatureRequest::OrderByClause> &orderBys )
{
Q_UNUSED( orderBys )
return false;
}
void QgsAbstractFeatureIterator::setInterruptionChecker( QgsFeedback * )
{
}
///////
QgsFeatureIterator &QgsFeatureIterator::operator=( const QgsFeatureIterator &other )
{
if ( this != &other )
{
if ( mIter )
mIter->deref();
mIter = other.mIter;
if ( mIter )
mIter->ref();
}
return *this;
}
bool QgsFeatureIterator::isValid() const
{
return mIter && mIter->isValid();
}