[FEATURE][processing] New 'drop geometries' algorithm

Simply removes any geometries from an input layer and returns
the features with attributes only

python/plugins/processing/algs/help/qgis.yaml

@@ -144,12 +144,14 @@ qgis:dissolve: >
 qgis:distancematrix: >
   This algorithms creates a table containing a distance matrix, with distances between all the points in a points layer.
 
-
 qgis:distancetonearesthub: >
   Given a layer with source point and another one representing destination points, this algorithm computes the distance between each source point and the closest detination one.
 
   The resulting layer can contain only source points with an additional field indicating the distance to the nearest point and the name of the destination point, or lines linking each source point with its nearest destination point.
 
+qgis:dropgeometries: >
+  This algorithm removes any geometries from an input layer and returns a layer containing only the feature attributes.
+
 qgis:eliminatesliverpolygons: >
   This algorithm combines selected polygons of the input layer with certain adjacent polygons by erasing their common boundary. Eliminate can either use an existing selection or a logical query based on one of the layer's fields to make the selection itself. The adjacent polygon can be either the one with the largest or smallest area or the one sharing the largest common boundary with the polygon to be eliminated. Eliminate is normally used to get rid of sliver polygons, i.e. tiny polygons that are a result of polygon intersection processes where boundaries of the inputs are similar but not identical.
 

python/plugins/processing/algs/qgis/DropGeometry.py

@@ -0,0 +1,68 @@
+# -*- coding: utf-8 -*-
+
+"""
+***************************************************************************
+    DropGeometry.py
+    --------------
+    Date                 : November 2016
+    Copyright            : (C) 2016 by Nyall Dawson
+    Email                : nyall dot dawson at gmail dot com
+***************************************************************************
+*                                                                         *
+*   This program is free software; you can redistribute it and/or modify  *
+*   it under the terms of the GNU General Public License as published by  *
+*   the Free Software Foundation; either version 2 of the License, or     *
+*   (at your option) any later version.                                   *
+*                                                                         *
+***************************************************************************
+"""
+
+__author__ = 'Nyall Dawson'
+__date__ = 'November 2016'
+__copyright__ = '(C) 2016, Nyall Dawson'
+
+# This will get replaced with a git SHA1 when you do a git archive323
+
+__revision__ = '$Format:%H$'
+
+from qgis.core import QgsFeatureRequest, QgsWkbTypes, QgsCoordinateReferenceSystem
+from processing.core.GeoAlgorithm import GeoAlgorithm
+from processing.core.parameters import ParameterVector
+from processing.core.outputs import OutputVector
+from processing.tools import dataobjects, vector
+
+
+class DropGeometry(GeoAlgorithm):
+
+    INPUT_LAYER = 'INPUT_LAYER'
+    OUTPUT_TABLE = 'OUTPUT_TABLE'
+
+    def defineCharacteristics(self):
+        self.name, self.i18n_name = self.trAlgorithm('Drop geometries')
+        self.group, self.i18n_group = self.trAlgorithm('Vector general tools')
+        self.tags = self.tr('remove,drop,delete,geometry,objects')
+
+        self.addParameter(ParameterVector(self.INPUT_LAYER,
+                                          self.tr('Input layer'), [dataobjects.TYPE_VECTOR_POINT,
+                                                                   dataobjects.TYPE_VECTOR_LINE,
+                                                                   dataobjects.TYPE_VECTOR_POLYGON]))
+        self.addOutput(OutputVector(self.OUTPUT_TABLE, self.tr('Dropped geometry')))
+
+    def processAlgorithm(self, progress):
+        layer = dataobjects.getObjectFromUri(
+            self.getParameterValue(self.INPUT_LAYER))
+        writer = self.getOutputFromName(
+            self.OUTPUT_TABLE).getVectorWriter(
+                layer.fields(),
+                QgsWkbTypes.NoGeometry,
+                QgsCoordinateReferenceSystem())
+
+        request = QgsFeatureRequest().setFlags(QgsFeatureRequest.NoGeometry)
+        features = vector.features(layer, request)
+        total = 100.0 / len(features)
+
+        for current, input_feature in enumerate(features):
+            writer.addFeature(input_feature)
+            progress.setPercentage(int(current * total))
+
+        del writer

python/plugins/processing/algs/qgis/QGISAlgorithmProvider.py

@@ -179,6 +179,7 @@
 from .SnapGeometries import SnapGeometriesToLayer
 from .PoleOfInaccessibility import PoleOfInaccessibility
 from .CreateAttributeIndex import CreateAttributeIndex
+from .DropGeometry import DropGeometry
 
 pluginPath = os.path.normpath(os.path.join(
     os.path.split(os.path.dirname(__file__))[0], os.pardir))
@@ -227,7 +228,7 @@ def __init__(self):
                         PostGISExecuteSQL(), ImportIntoPostGIS(),
                         SetVectorStyle(), SetRasterStyle(),
                         SelectByExpression(), HypsometricCurves(),
-                        SplitWithLines(), SplitLinesWithLines(),  CreateConstantRaster(),
+                        SplitWithLines(), SplitLinesWithLines(), CreateConstantRaster(),
                         FieldsMapper(), SelectByAttributeSum(), Datasources2Vrt(),
                         CheckValidity(), OrientedMinimumBoundingBox(), Smooth(),
                         ReverseLineDirection(), SpatialIndex(), DefineProjection(),
@@ -242,7 +243,7 @@ def __init__(self):
                         TinInterpolationZValue(), TinInterpolationAttribute(),
                         RemoveNullGeometry(), ExtractByExpression(), ExtendLines(),
                         ExtractSpecificNodes(), GeometryByExpression(), SnapGeometriesToLayer(),
-                        PoleOfInaccessibility(), CreateAttributeIndex()
+                        PoleOfInaccessibility(), CreateAttributeIndex(), DropGeometry()
                         ]
 
         if hasMatplotlib:

python/plugins/processing/algs/qgis/RemoveNullGeometry.py

@@ -39,6 +39,7 @@ class RemoveNullGeometry(GeoAlgorithm):
     def defineCharacteristics(self):
         self.name, self.i18n_name = self.trAlgorithm('Remove null geometries')
         self.group, self.i18n_group = self.trAlgorithm('Vector selection tools')
+        self.tags = self.tr('remove,drop,delete,empty,geometry')
 
         self.addParameter(ParameterVector(self.INPUT_LAYER,
                                           self.tr('Input layer'), [dataobjects.TYPE_VECTOR_ANY]))

python/plugins/processing/tests/testdata/expected/dropped_geometry.csv

@@ -0,0 +1,7 @@
+fid,name,intval,floatval
+polys.0,aaaaa,33,44.123456
+polys.1,Aaaaa,-33,0
+polys.2,bbaaa,,0.123
+polys.3,ASDF,0,
+polys.4,,120,-100291.43213
+polys.5,elim,2,3.33

python/plugins/processing/tests/testdata/qgis_algorithm_tests.yaml

@@ -1637,3 +1637,14 @@ tests:
       OUTPUT:
         name: expected/split_lines_with_lines_same.gml
         type: vector
+
+  - algorithm: qgis:dropgeometries
+    name: Drop geometries
+    params:
+      INPUT_LAYER:
+        name: polys.gml
+        type: vector
+    results:
+      OUTPUT_TABLE:
+        name: expected/dropped_geometry.csv
+        type: vector