Revert "Dynamically adjust postgres feature queue size"

nyalldawson · nyalldawson · commit 2a6bcebd5edb · 2017-03-06T06:02:15.000+10:00
This reverts commit 37a7a22. Leads to performance regressions in some tests
diff --git a/src/providers/postgres/qgspostgresfeatureiterator.cpp b/src/providers/postgres/qgspostgresfeatureiterator.cpp
@@ -22,13 +22,16 @@
 #include "qgslogger.h"
 #include "qgsmessagelog.h"
 
-#include <QElapsedTimer>
 #include <QObject>
 #include <QSettings>
 
+
+const int QgsPostgresFeatureIterator::sFeatureQueueSize = 2000;
+
+
 QgsPostgresFeatureIterator::QgsPostgresFeatureIterator( QgsPostgresFeatureSource* source, bool ownSource, const QgsFeatureRequest& request )
     : QgsAbstractFeatureIteratorFromSource<QgsPostgresFeatureSource>( source, ownSource, request )
-    , mFeatureQueueSize( 1 )
+    , mFeatureQueueSize( sFeatureQueueSize )
     , mFetched( 0 )
     , mFetchGeometry( false )
     , mExpressionCompiled( false )
@@ -224,9 +227,6 @@ bool QgsPostgresFeatureIterator::fetchFeature( QgsFeature& feature )
 
   if ( mFeatureQueue.empty() && !mLastFetch )
   {
-    QElapsedTimer timer;
-    timer.start();
-
     QString fetch = QString( "FETCH FORWARD %1 FROM %2" ).arg( mFeatureQueueSize ).arg( mCursorName );
     QgsDebugMsgLevel( QString( "fetching %1 features." ).arg( mFeatureQueueSize ), 4 );
 
@@ -262,15 +262,6 @@ bool QgsPostgresFeatureIterator::fetchFeature( QgsFeature& feature )
       } // for each row in queue
     }
     unlock();
-
-    if ( timer.elapsed() > 500 && mFeatureQueueSize > 1 )
-    {
-      mFeatureQueueSize /= 2;
-    }
-    else if ( timer.elapsed() < 50 && mFeatureQueueSize < 10000 )
-    {
-      mFeatureQueueSize *= 2;
-    }
   }
 
   if ( mFeatureQueue.empty() )
diff --git a/src/providers/postgres/qgspostgresfeatureiterator.h b/src/providers/postgres/qgspostgresfeatureiterator.h
@@ -118,6 +118,8 @@ class QgsPostgresFeatureIterator : public QgsAbstractFeatureIteratorFromSource<Q
 
     bool mIsTransactionConnection;
 
+    static const int sFeatureQueueSize;
+
   private:
     //! returns whether the iterator supports simplify geometries on provider side
     virtual bool providerCanSimplify( QgsSimplifyMethod::MethodType methodType ) const override;
