fix #2036

git-svn-id: http://svn.osgeo.org/qgis/trunk/qgis@11861 c8812cc2-4d05-0410-92ff-de0c093fc19c

python/core/qgsdataprovider.sip

@@ -66,6 +66,11 @@ class QgsDataProvider : QObject
       */
       virtual bool setSubsetString(QString subset);
 
+      /**
+       * provider supports setting of subset strings
+       * @note added in 1.4
+       */
+      virtual bool supportsSubsetString();
 
       /**
        * Returns the subset definition string (typically sql) currently in

src/app/qgsvectorlayerproperties.cpp

@@ -438,7 +438,7 @@ void QgsVectorLayerProperties::reset( void )
   // on the builder. If the ability to enter a query directly into the box is required,
   // a mechanism to check it must be implemented.
   txtSubsetSQL->setEnabled( false );
-  pbnQueryBuilder->setEnabled( true );
+  pbnQueryBuilder->setEnabled( layer && layer->dataProvider() && layer->dataProvider()->supportsSubsetString() );
 
   //get field list for display field combo
   const QgsFieldMap& myFields = layer->pendingFields();

src/core/qgsdataprovider.h

@@ -121,6 +121,12 @@ class CORE_EXPORT QgsDataProvider : public QObject
     }
 
 
+    /**
+     * provider supports setting of subset strings
+     * @note added in 1.4
+     */
+    virtual bool supportsSubsetString() { return false; }
+
     /**
      * Returns the subset definition string (typically sql) currently in
      * use by the layer and used by the provider to limit the feature set.

src/providers/ogr/qgsogrprovider.h

@@ -95,6 +95,8 @@ class QgsOgrProvider : public QgsVectorDataProvider
     /** Accessor for sql where clause used to limit dataset */
     virtual QString subsetString();
 
+    virtual bool supportsSubsetString() { return true; }
+
     /** mutator for sql where clause used to limit dataset size */
     virtual bool setSubsetString( QString theSQL );
 

src/providers/postgres/qgspostgresprovider.h

@@ -255,6 +255,8 @@ class QgsPostgresProvider : public QgsVectorDataProvider
     /** mutator for sql where clause used to limit dataset size */
     bool setSubsetString( QString theSQL );
 
+    virtual bool supportsSubsetString() { return true; }
+
     /**Returns a bitmask containing the supported capabilities*/
     int capabilities() const;
 

src/providers/spatialite/qgsspatialiteprovider.h

@@ -81,6 +81,8 @@ class QgsSpatiaLiteProvider: public QgsVectorDataProvider
     /** mutator for sql where clause used to limit dataset size */
     virtual bool setSubsetString( QString theSQL );
 
+    virtual bool supportsSubsetString() { return true; }
+
     /** Select features based on a bounding rectangle. Features can be retrieved with calls to nextFeature.
      *  @param fetchAttributes list of attributes which should be fetched
      *  @param rect spatial filter