- added warning and chance to cancel Natural break classification for

  dataset >50k records
- modified test script to generate gowing sizes tables (for timing)

Author: vmora

src/gui/symbology-ng/qgsgraduatedsymbolrendererv2widget.cpp

@@ -482,6 +482,15 @@ void QgsGraduatedSymbolRendererV2Widget::classifyGraduated()
   else // default should be quantile for now
     mode = QgsGraduatedSymbolRendererV2::Quantile;
 
+
+  // Jenks is n^2 complexity, warn for big dataset (more than 50k records)
+  // and give the user the chance to cancel
+  if ( QgsGraduatedSymbolRendererV2::Jenks == mode
+       && mLayer->featureCount() > 50000 )
+  {
+    if ( QMessageBox::Cancel == QMessageBox::question( this, tr( "Warning" ), tr( "Natural break classification (Jenks) is O(n2) complexity, your classification may take a long time." ), QMessageBox::Cancel, QMessageBox::Ok ) ) return;
+  }
+
   // create and set new renderer
   QApplication::setOverrideCursor( Qt::WaitCursor );
   QgsGraduatedSymbolRendererV2* r = QgsGraduatedSymbolRendererV2::createRenderer(

tests/src/python/test_qgsissue6483.py

@@ -14,6 +14,7 @@
 
 import os
 import random
+import math
 
 from qgis.core import *
 from qgis.gui import *
@@ -45,23 +46,29 @@ def setUpClass(cls):
         sql = "SELECT InitSpatialMetadata()"
         cur.execute(sql)
 
-        # simple table with primary key
-        sql = "CREATE TABLE test_mpg (id SERIAL PRIMARY KEY, height DOUBLE)"
-        cur.execute(sql)
-        sql = "SELECT AddGeometryColumn('test_mpg', 'geometry', 4326, 'MULTIPOLYGON', 'XY')"
-        cur.execute(sql)
-        for i in range(0,253):
-            for j in range (0,253):
-                sql = "INSERT INTO test_mpg (height, geometry) "
-                sql +=    "VALUES ("+str(random.random())+", GeomFromText('MULTIPOLYGON((("
-                sql += str(i)   + " " + str(j)   + ","
-                sql += str(i+1) + " " + str(j)   + ","
-                sql += str(i+1) + " " + str(j+1) + ","
-                sql += str(i)   + " " + str(j+1) + ","
-                sql += str(i)   + " " + str(j) + ")))', 4326))"
-                cur.execute(sql)
-
-        con.commit()
+        # growing size tables
+        nbOrders = 7
+        for order in range(0,nbOrders):
+            size = 10000*pow(2,order);
+            tab = "test_mpg_" + str(size) + "_rows"
+            print "creating table " + tab + " " + str(order) + "/" + str(nbOrders)
+            sql = "CREATE TABLE " + tab + " (id SERIAL PRIMARY KEY, height DOUBLE)"
+            cur.execute(sql)
+            sql = "SELECT AddGeometryColumn('" + tab + "', 'geometry', 4326, 'MULTIPOLYGON', 'XY')"
+            cur.execute(sql)
+            r = int(math.sqrt(size))
+            for i in range(0,r):
+                for j in range (0,r):
+                    sql = "INSERT INTO " + tab + " (height, geometry) "
+                    sql +=    "VALUES ("+str(random.random())+", GeomFromText('MULTIPOLYGON((("
+                    sql += str(i)   + " " + str(j)   + ","
+                    sql += str(i+1) + " " + str(j)   + ","
+                    sql += str(i+1) + " " + str(j+1) + ","
+                    sql += str(i)   + " " + str(j+1) + ","
+                    sql += str(i)   + " " + str(j) + ")))', 4326))"
+                    cur.execute(sql)
+                con.commit()
+
         con.close()
 
     @classmethod
@@ -81,10 +88,7 @@ def tearDown(self):
         pass
 
     def test_Nothing(self):
-        """Create spatialite database"""
-        layer = QgsVectorLayer("dbname=test.sqlite table=test_mpg (geometry)", "test_mpg", "spatialite")
-        assert(layer.isValid())
-        assert(layer.hasGeometryType())
+        """do nothing"""