Avoid installing QgsCPLHTTPFetchOverrider for every ogr feature

fetched if we can avoid it

This is a relatively expensive operation to do (specifically
the calls to QgsCPLHTTPFetchOverrider::setAttribute) compared
with the actual costs of fetching features from GDAL

Avoid creating a new override for every feature, if we detect
that its safe to use an override created in the OGR feature
iterator constructor.

src/core/providers/ogr/qgsogrfeatureiterator.cpp

@@ -18,9 +18,8 @@
 #include "qgsogrexpressioncompiler.h"
 #include "qgssqliteexpressioncompiler.h"
 
-#include "qgscplhttpfetchoverrider.h"
 #include "qgsogrutils.h"
-#include "qgsapplication.h"
+#include "qgscplhttpfetchoverrider.h"
 #include "qgsgeometry.h"
 #include "qgsexception.h"
 #include "qgswkbtypes.h"
@@ -60,8 +59,8 @@ QgsOgrFeatureIterator::QgsOgrFeatureIterator( QgsOgrFeatureSource *source, bool
                        ( mRequest.filterType() != QgsFeatureRequest::FilterType::FilterFid
                          && mRequest.filterType() != QgsFeatureRequest::FilterType::FilterFids );
 
-  QgsCPLHTTPFetchOverrider oCPLHTTPFetcher( mAuthCfg );
-  QgsSetCPLHTTPFetchOverriderInitiatorClass( oCPLHTTPFetcher, QStringLiteral( "QgsOgrFeatureIterator" ) )
+  mCplHttpFetchOverrider = std::make_unique< QgsCPLHTTPFetchOverrider >( mAuthCfg );
+  QgsSetCPLHTTPFetchOverriderInitiatorClass( *mCplHttpFetchOverrider, QStringLiteral( "QgsOgrFeatureIterator" ) )
 
   for ( const auto &id :  mRequest.filterFids() )
   {
@@ -401,14 +400,24 @@ bool QgsOgrFeatureIterator::checkFeature( gdal::ogr_feature_unique_ptr &fet, Qgs
 void QgsOgrFeatureIterator::setInterruptionChecker( QgsFeedback *interruptionChecker )
 {
   mInterruptionChecker = interruptionChecker;
+  if ( mCplHttpFetchOverrider && QThread::currentThread() == mCplHttpFetchOverrider->thread() )
+  {
+    mCplHttpFetchOverrider->setFeedback( interruptionChecker );
+  }
 }
 
 bool QgsOgrFeatureIterator::fetchFeature( QgsFeature &feature )
 {
   QMutexLocker locker( mSharedDS ? &mSharedDS->mutex() : nullptr );
 
-  QgsCPLHTTPFetchOverrider oCPLHTTPFetcher( mAuthCfg, mInterruptionChecker );
-  QgsSetCPLHTTPFetchOverriderInitiatorClass( oCPLHTTPFetcher, QStringLiteral( "QgsOgrFeatureIterator" ) )
+  // if we are on the same thread as the iterator was created in, we don't need to initializer another
+  // QgsCPLHTTPFetchOverrider (which is expensive)
+  std::unique_ptr< QgsCPLHTTPFetchOverrider > localHttpFetchOverride;
+  if ( QThread::currentThread() != mCplHttpFetchOverrider->thread() )
+  {
+    localHttpFetchOverride = std::make_unique< QgsCPLHTTPFetchOverrider >( mAuthCfg, mInterruptionChecker );
+    QgsSetCPLHTTPFetchOverriderInitiatorClass( *localHttpFetchOverride, QStringLiteral( "QgsOgrFeatureIterator" ) )
+  }
 
   feature.setValid( false );
 

src/core/providers/ogr/qgsogrfeatureiterator.h

@@ -27,12 +27,15 @@
 #include <set>
 #include "qgis_sip.h"
 
+
 ///@cond PRIVATE
 #define SIP_NO_FILE
 
 class QgsOgrFeatureIterator;
 class QgsOgrProvider;
 class QgsOgrDataset;
+class QgsCPLHTTPFetchOverrider;
+
 using QgsOgrDatasetSharedPtr = std::shared_ptr< QgsOgrDataset>;
 
 class QgsOgrFeatureSource final: public QgsAbstractFeatureSource
@@ -121,6 +124,8 @@ class QgsOgrFeatureIterator final: public QgsAbstractFeatureIteratorFromSource<Q
     QgsGeometry mDistanceWithinGeom;
     std::unique_ptr< QgsGeometryEngine > mDistanceWithinEngine;
 
+    std::unique_ptr< QgsCPLHTTPFetchOverrider > mCplHttpFetchOverrider;
+
     QVector< int > mRequestAttributes;
 
     bool fetchFeatureWithId( QgsFeatureId id, QgsFeature &feature ) const;

src/core/qgscplhttpfetchoverrider.cpp

@@ -20,9 +20,10 @@
 #include "cpl_http.h"
 #include "gdal.h"
 
-QgsCPLHTTPFetchOverrider::QgsCPLHTTPFetchOverrider( const QString &authCfg, QgsFeedback *feedback ):
-  mAuthCfg( authCfg ),
-  mFeedback( feedback )
+QgsCPLHTTPFetchOverrider::QgsCPLHTTPFetchOverrider( const QString &authCfg, QgsFeedback *feedback )
+  : mAuthCfg( authCfg )
+  , mFeedback( feedback )
+  , mThread( QThread::currentThread() )
 {
   CPLHTTPPushFetchCallback( QgsCPLHTTPFetchOverrider::callback, this );
 }
@@ -188,3 +189,13 @@ void QgsCPLHTTPFetchOverrider::setAttribute( QNetworkRequest::Attribute code, co
 {
   mAttributes[code] = value;
 }
+
+void QgsCPLHTTPFetchOverrider::setFeedback( QgsFeedback *feedback )
+{
+  mFeedback = feedback;
+}
+
+QThread *QgsCPLHTTPFetchOverrider::thread() const
+{
+  return mThread;
+}

src/core/qgscplhttpfetchoverrider.h

@@ -20,6 +20,7 @@
 
 #include <QNetworkRequest>
 #include <QString>
+#include <QPointer>
 #include "qgsnetworkaccessmanager.h" // for QgsSetRequestInitiatorClass
 
 #include "cpl_http.h"
@@ -28,7 +29,7 @@
 class QgsFeedback;
 
 #ifndef SIP_RUN
-#define QgsSetCPLHTTPFetchOverriderInitiatorClass(overrider, _class) QgsSetRequestInitiatorClass(overrider, _class)
+#define QgsSetCPLHTTPFetchOverriderInitiatorClass(overrider, _class) QgsSetRequestInitiatorClass((overrider), _class)
 #endif
 
 /**
@@ -53,6 +54,20 @@ class QgsCPLHTTPFetchOverrider
     //! Define attribute that must be forwarded to the actual QNetworkRequest
     void setAttribute( QNetworkRequest::Attribute code, const QVariant &value );
 
+    /**
+     * Sets the \a feedback cancellation object for the redirection.
+     *
+     * \since QGIS 3.32
+     */
+    void setFeedback( QgsFeedback *feedback );
+
+    /**
+     * Returns the thread associated with the overrider.
+     *
+     * \since QGIS 3.32
+     */
+    QThread *thread() const;
+
   private:
 
 #if GDAL_VERSION_NUM >= GDAL_COMPUTE_VERSION(3,2,0)
@@ -69,6 +84,8 @@ class QgsCPLHTTPFetchOverrider
 
     QgsFeedback *mFeedback = nullptr;
 
+    QPointer< QThread > mThread;
+
     std::map<QNetworkRequest::Attribute, QVariant> mAttributes;
 };