Ensure stability of QGIS FeatureId when reloading layer [WFS provider]

src/core/qgssqliteutils.cpp

@@ -91,6 +91,21 @@ sqlite3_statement_unique_ptr sqlite3_database_unique_ptr::prepare( const QString
   return s;
 }
 
+int sqlite3_database_unique_ptr::exec( const QString &sql, QString &errorMessage ) const
+{
+  char *errMsg;
+
+  int ret = sqlite3_exec( get(), sql.toUtf8(), nullptr, nullptr, &errMsg );
+
+  if ( errMsg )
+  {
+    errorMessage = QString::fromUtf8( errMsg );
+    sqlite3_free( errMsg );
+  }
+
+  return ret;
+}
+
 QString QgsSqliteUtils::quotedString( const QString &value )
 {
   if ( value.isNull() )

src/core/qgssqliteutils.h

@@ -21,6 +21,8 @@
 #define SIP_NO_FILE
 
 #include "qgis_core.h"
+#include "qgis_sip.h"
+
 #include <memory>
 #include <QString>
 
@@ -134,8 +136,17 @@ class CORE_EXPORT sqlite3_database_unique_ptr : public std::unique_ptr< sqlite3,
      * Prepares a \a sql statement, returning the result. The \a resultCode
      * argument will be filled with the sqlite3 result code.
      */
-    sqlite3_statement_unique_ptr prepare( const QString &sql, int &resultCode ) const;
+    sqlite3_statement_unique_ptr prepare( const QString &sql, int &resultCode SIP_OUT ) const;
 
+    /**
+     * Executes the \a sql command in the database. Multiple sql queries can be run within
+     * one single command.
+     * Errors are reported to \a errorMessage.
+     * Returns SQLITE_OK in case of success or an sqlite error code.
+     *
+     * \since QGIS 3.4.5
+     */
+    int exec( const QString &sql, QString &errorMessage SIP_OUT ) const;
 };
 
 /**

src/providers/wfs/qgswfsfeatureiterator.cpp

@@ -32,13 +32,16 @@
 #include "qgssettings.h"
 #include "qgsexception.h"
 #include "qgsfeedback.h"
+#include "qgssqliteutils.h"
 
 #include <algorithm>
 #include <QDir>
 #include <QProgressDialog>
 #include <QTimer>
 #include <QStyle>
 
+#include <sqlite3.h>
+
 QgsWFSFeatureHitsAsyncRequest::QgsWFSFeatureHitsAsyncRequest( QgsWFSDataSourceURI &uri )
   : QgsWfsRequest( uri )
   , mNumberMatched( -1 )
@@ -986,7 +989,15 @@ QgsFeatureRequest QgsWFSFeatureIterator::buildRequestCache( int genCounter )
   QgsFeatureRequest requestCache;
   if ( mRequest.filterType() == QgsFeatureRequest::FilterFid ||
        mRequest.filterType() == QgsFeatureRequest::FilterFids )
-    requestCache = mRequest;
+  {
+    QgsFeatureIds qgisIds;
+    if ( mRequest.filterType() == QgsFeatureRequest::FilterFid )
+      qgisIds.insert( mRequest.filterFid() );
+    else
+      qgisIds = mRequest.filterFids();
+
+    requestCache.setFilterFids( mShared->dbIdsFromQgisIds( qgisIds ) );
+  }
   else
   {
     if ( mRequest.filterType() == QgsFeatureRequest::FilterExpression )
@@ -1238,6 +1249,19 @@ bool QgsWFSFeatureIterator::fetchFeature( QgsFeature &f )
 
     copyFeature( cachedFeature, f );
     geometryToDestinationCrs( f, mTransform );
+
+    // Retrieve the user-visible id from the Spatialite cache database Id
+    if ( mShared->mCacheIdDb.get() )
+    {
+      auto sql = QgsSqlite3Mprintf( "SELECT qgisId FROM id_cache WHERE dbId = %lld", cachedFeature.id() );
+      int resultCode;
+      auto stmt = mShared->mCacheIdDb.prepare( sql, resultCode );
+      if ( stmt.step() == SQLITE_ROW )
+      {
+        f.setId( stmt.columnAsInt64( 0 ) );
+      }
+    }
+
     return true;
   }