[WFS provider] Do not issue full layer download when requesting featu…

…res by fids... and when they are already in the local cache. Fixes #42049
qgis · May 31, 2021 · 647b0f0 · 647b0f0
1 parent c060b3b
commit 647b0f0
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Showing 2 changed files with 84 additions and 26 deletions.
diff --git a/src/providers/wfs/qgsbackgroundcachedfeatureiterator.cpp b/src/providers/wfs/qgsbackgroundcachedfeatureiterator.cpp
@@ -271,6 +271,7 @@ QgsBackgroundCachedFeatureIterator::QgsBackgroundCachedFeatureIterator(
   const QgsFeatureRequest &request )
   : QgsAbstractFeatureIteratorFromSource<QgsBackgroundCachedFeatureSource>( source, ownSource, request )
   , mShared( shared )
+  , mCachedFeaturesIter( mCachedFeatures.begin() )
 {
   if ( !shared->clientSideFilterExpression().isEmpty() )
   {
@@ -305,19 +306,41 @@ QgsBackgroundCachedFeatureIterator::QgsBackgroundCachedFeatureIterator(
   if ( !threshold.isEmpty() )
     mWriteTransferThreshold = threshold.toInt();
 
-  // Particular case: if a single feature is requested by Fid and we already
-  // have it in cache, no need to interrupt any download
+  // Particular case: if a single feature or a reasonable set of features
+  // are requested by Fid and we already have them in cache, no need to
+  // download anything.
   auto cacheDataProvider = mShared->cacheDataProvider();
   if ( cacheDataProvider &&
-       mRequest.filterType() == QgsFeatureRequest::FilterFid )
+       ( mRequest.filterType() == QgsFeatureRequest::FilterFid ||
+         ( mRequest.filterType() == QgsFeatureRequest::FilterFids && mRequest.filterFids().size() < 100000 ) ) )
   {
-    QgsFeatureRequest requestCache = buildRequestCache( -1 );
-    QgsFeature f;
-    if ( cacheDataProvider->getFeatures( requestCache ).nextFeature( f ) )
+    QgsFeatureRequest requestCache;
+    QgsFeatureIds qgisIds;
+    if ( mRequest.filterType() == QgsFeatureRequest::FilterFid )
+      qgisIds.insert( mRequest.filterFid() );
+    else
+      qgisIds = mRequest.filterFids();
+    QgsFeatureIds dbIds = mShared->dbIdsFromQgisIds( qgisIds );
+    // Do all requested fids have been known at some point by the provider ?
+    if ( dbIds.size() == qgisIds.size() )
     {
-      mCacheIterator = cacheDataProvider->getFeatures( requestCache );
-      mDownloadFinished = true;
-      return;
+      requestCache.setFilterFids( dbIds );
+      fillRequestCache( requestCache );
+      QgsFeatureIterator cacheIterator = cacheDataProvider->getFeatures( requestCache );
+      QgsFeature f;
+      while ( cacheIterator.nextFeature( f ) )
+      {
+        mCachedFeatures << f;
+      }
+      // Are are the requested fids actually in the cache ?
+      if ( mCachedFeatures.size() == dbIds.size() )
+      {
+        // Yes, no need to download anything.
+        mCachedFeaturesIter = mCachedFeatures.begin();
+        mDownloadFinished = true;
+        return;
+      }
+      mCachedFeatures.clear();
     }
   }
 
@@ -332,10 +355,12 @@ QgsBackgroundCachedFeatureIterator::QgsBackgroundCachedFeatureIterator(
 
   QgsDebugMsgLevel( QStringLiteral( "QgsBackgroundCachedFeatureIterator::constructor(): genCounter=%1 " ).arg( genCounter ), 4 );
 
-  mCacheIterator = cacheDataProvider->getFeatures( buildRequestCache( genCounter ) );
+  QgsFeatureRequest requestCache = initRequestCache( genCounter ) ;
+  fillRequestCache( requestCache );
+  mCacheIterator = cacheDataProvider->getFeatures( requestCache );
 }
 
-QgsFeatureRequest QgsBackgroundCachedFeatureIterator::buildRequestCache( int genCounter )
+QgsFeatureRequest QgsBackgroundCachedFeatureIterator::initRequestCache( int genCounter )
 {
   QgsFeatureRequest requestCache;
 
@@ -392,6 +417,11 @@ QgsFeatureRequest QgsBackgroundCachedFeatureIterator::buildRequestCache( int gen
     }
   }
 
+  return requestCache;
+}
+
+void QgsBackgroundCachedFeatureIterator::fillRequestCache( QgsFeatureRequest requestCache )
+{
   requestCache.setFilterRect( mFilterRect );
 
   if ( !( mRequest.flags() & QgsFeatureRequest::NoGeometry ) ||
@@ -402,6 +432,8 @@ QgsFeatureRequest QgsBackgroundCachedFeatureIterator::buildRequestCache( int gen
 
   if ( mRequest.flags() & QgsFeatureRequest::SubsetOfAttributes )
   {
+    const QgsFields fields = mShared->fields();
+    auto cacheDataProvider = mShared->cacheDataProvider();
     QgsFields dataProviderFields = cacheDataProvider->fields();
     QgsAttributeList cacheSubSet;
     const auto subsetOfAttributes = mRequest.subsetOfAttributes();
@@ -460,8 +492,6 @@ QgsFeatureRequest QgsBackgroundCachedFeatureIterator::buildRequestCache( int gen
     }
     requestCache.setSubsetOfAttributes( cacheSubSet );
   }
-
-  return requestCache;
 }
 
 QgsBackgroundCachedFeatureIterator::~QgsBackgroundCachedFeatureIterator()
@@ -572,8 +602,21 @@ bool QgsBackgroundCachedFeatureIterator::fetchFeature( QgsFeature &f )
 
   // First step is to iterate over the on-disk cache
   QgsFeature cachedFeature;
-  while ( mCacheIterator.nextFeature( cachedFeature ) )
+  while ( true )
   {
+    if ( !mCachedFeatures.empty() )
+    {
+      if ( mCachedFeaturesIter == mCachedFeatures.end() )
+        return false;
+      cachedFeature = *mCachedFeaturesIter;
+      ++mCachedFeaturesIter;
+    }
+    else
+    {
+      if ( !mCacheIterator.nextFeature( cachedFeature ) )
+        break;
+    }
+
     if ( mInterruptionChecker && mInterruptionChecker->isCanceled() )
       return false;
 
@@ -803,17 +846,25 @@ bool QgsBackgroundCachedFeatureIterator::rewind()
   if ( mClosed )
     return false;
 
-  cleanupReaderStreamAndFile();
-
-  QgsFeatureRequest requestCache;
-  int genCounter = mShared->getUpdatedCounter();
-  if ( genCounter >= 0 )
-    requestCache.setFilterExpression( QString( QgsBackgroundCachedFeatureIteratorConstants::FIELD_GEN_COUNTER + " <= %1" ).arg( genCounter ) );
+  if ( !mCachedFeatures.empty() )
+  {
+    mCachedFeaturesIter = mCachedFeatures.begin();
+  }
   else
-    mDownloadFinished = true;
-  auto cacheDataProvider = mShared->cacheDataProvider();
-  if ( cacheDataProvider )
-    mCacheIterator = cacheDataProvider->getFeatures( requestCache );
+  {
+    cleanupReaderStreamAndFile();
+
+    QgsFeatureRequest requestCache;
+    int genCounter = mShared->getUpdatedCounter();
+    if ( genCounter >= 0 )
+      requestCache.setFilterExpression( QString( QgsBackgroundCachedFeatureIteratorConstants::FIELD_GEN_COUNTER + " <= %1" ).arg( genCounter ) );
+    else
+      mDownloadFinished = true;
+    auto cacheDataProvider = mShared->cacheDataProvider();
+    if ( cacheDataProvider )
+      mCacheIterator = cacheDataProvider->getFeatures( requestCache );
+  }
+
   return true;
 }
 

diff --git a/src/providers/wfs/qgsbackgroundcachedfeatureiterator.h b/src/providers/wfs/qgsbackgroundcachedfeatureiterator.h
@@ -352,6 +352,10 @@ class QgsBackgroundCachedFeatureIterator final: public QObject,
     QgsFeedback *mInterruptionChecker = nullptr;
     bool mTimeoutOrInterruptionOccurred = false;
 
+    //! Cached features for request by fid
+    QVector<QgsFeature> mCachedFeatures;
+    QVector<QgsFeature>::iterator mCachedFeaturesIter;
+
     //! this mutex synchronizes the mWriterXXXX variables between featureReceivedSynchronous() and fetchFeature()
     QMutex mMutex;
     QWaitCondition mWaitCond;
@@ -378,8 +382,11 @@ class QgsBackgroundCachedFeatureIterator final: public QObject,
 
     ///////////////// METHODS
 
-    //! Translate mRequest to a request compatible of the Spatialite cache
-    QgsFeatureRequest buildRequestCache( int gencounter );
+    //! Translate mRequest to a request compatible of the Spatialite cache (first part)
+    QgsFeatureRequest initRequestCache( int gencounter );
+
+    //! Finishes to fill the request to the cache (second part)
+    void fillRequestCache( QgsFeatureRequest );
 
     bool fetchFeature( QgsFeature &f ) override;