Merge pull request #4209 from nyalldawson/postgres_queue_size2

nyalldawson · web-flow · commit 5a543e44de77 · 2017-03-05T14:01:35.000+10:00
Dynamically adjust postgres feature queue size
diff --git a/src/providers/postgres/qgspostgresfeatureiterator.cpp b/src/providers/postgres/qgspostgresfeatureiterator.cpp
@@ -22,15 +22,12 @@
 #include "qgsmessagelog.h"
 #include "qgssettings.h"
 
+#include <QElapsedTimer>
 #include <QObject>
 
-
-const int QgsPostgresFeatureIterator::FEATURE_QUEUE_SIZE = 2000;
-
-
 QgsPostgresFeatureIterator::QgsPostgresFeatureIterator( QgsPostgresFeatureSource *source, bool ownSource, const QgsFeatureRequest &request )
   : QgsAbstractFeatureIteratorFromSource<QgsPostgresFeatureSource>( source, ownSource, request )
-  , mFeatureQueueSize( FEATURE_QUEUE_SIZE )
+  , mFeatureQueueSize( 1 )
   , mFetched( 0 )
   , mFetchGeometry( false )
   , mExpressionCompiled( false )
@@ -223,6 +220,9 @@ bool QgsPostgresFeatureIterator::fetchFeature( QgsFeature &feature )
 
   if ( mFeatureQueue.empty() && !mLastFetch )
   {
+    QElapsedTimer timer;
+    timer.start();
+
     QString fetch = QStringLiteral( "FETCH FORWARD %1 FROM %2" ).arg( mFeatureQueueSize ).arg( mCursorName );
     QgsDebugMsgLevel( QString( "fetching %1 features." ).arg( mFeatureQueueSize ), 4 );
 
@@ -258,6 +258,15 @@ 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
@@ -110,8 +110,6 @@ class QgsPostgresFeatureIterator : public QgsAbstractFeatureIteratorFromSource<Q
 
     bool mIsTransactionConnection;
 
-    static const int FEATURE_QUEUE_SIZE;
-
   private:
     virtual bool providerCanSimplify( QgsSimplifyMethod::MethodType methodType ) const override;
 
