[processing] Port 'Add unique value index field' to c++

And implement some fixes/improvements (refs discussion on the dev mailing list):
- allow user to specify created field name
- allow optional creation of a summary table showing new class value vs original
value

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

@@ -58,7 +58,6 @@
 from .DensifyGeometriesInterval import DensifyGeometriesInterval
 from .Difference import Difference
 from .EliminateSelection import EliminateSelection
-from .EquivalentNumField import EquivalentNumField
 from .ExecuteSQL import ExecuteSQL
 from .Explode import Explode
 from .ExportGeometryInfo import ExportGeometryInfo
@@ -180,7 +179,6 @@ def getAlgs(self):
                 DensifyGeometriesInterval(),
                 Difference(),
                 EliminateSelection(),
-                EquivalentNumField(),
                 ExecuteSQL(),
                 Explode(),
                 ExportGeometryInfo(),

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

@@ -2,7 +2,7 @@
 
 """
 ***************************************************************************
-    EquivalentNumField.py
+    VectorLayerHistogram.py
     ---------------------
     Date                 : January 2013
     Copyright            : (C) 2013 by Victor Olaya

python/plugins/processing/tests/testdata/expected/add_unique_field_summary.gml

@@ -0,0 +1,27 @@
+<?xml version="1.0" encoding="utf-8" ?>
+<ogr:FeatureCollection
+     xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
+     xsi:schemaLocation="http://ogr.maptools.org/ add_unique_field_summary.xsd"
+     xmlns:ogr="http://ogr.maptools.org/"
+     xmlns:gml="http://www.opengis.net/gml">
+  <gml:boundedBy><gml:null>missing</gml:null></gml:boundedBy>
+
+  <gml:featureMember>
+    <ogr:add_unique_field_summary fid="add_unique_field_summary.0">
+      <ogr:classes>0</ogr:classes>
+      <ogr:id2>2</ogr:id2>
+    </ogr:add_unique_field_summary>
+  </gml:featureMember>
+  <gml:featureMember>
+    <ogr:add_unique_field_summary fid="add_unique_field_summary.1">
+      <ogr:classes>1</ogr:classes>
+      <ogr:id2>1</ogr:id2>
+    </ogr:add_unique_field_summary>
+  </gml:featureMember>
+  <gml:featureMember>
+    <ogr:add_unique_field_summary fid="add_unique_field_summary.2">
+      <ogr:classes>2</ogr:classes>
+      <ogr:id2>0</ogr:id2>
+    </ogr:add_unique_field_summary>
+  </gml:featureMember>
+</ogr:FeatureCollection>

python/plugins/processing/tests/testdata/expected/add_unique_field_summary.xsd

@@ -0,0 +1,36 @@
+<?xml version="1.0" encoding="UTF-8"?>
+<xs:schema targetNamespace="http://ogr.maptools.org/" xmlns:ogr="http://ogr.maptools.org/" xmlns:xs="http://www.w3.org/2001/XMLSchema" xmlns:gml="http://www.opengis.net/gml" elementFormDefault="qualified" version="1.0">
+<xs:import namespace="http://www.opengis.net/gml" schemaLocation="http://schemas.opengis.net/gml/2.1.2/feature.xsd"/>
+<xs:element name="FeatureCollection" type="ogr:FeatureCollectionType" substitutionGroup="gml:_FeatureCollection"/>
+<xs:complexType name="FeatureCollectionType">
+  <xs:complexContent>
+    <xs:extension base="gml:AbstractFeatureCollectionType">
+      <xs:attribute name="lockId" type="xs:string" use="optional"/>
+      <xs:attribute name="scope" type="xs:string" use="optional"/>
+    </xs:extension>
+  </xs:complexContent>
+</xs:complexType>
+<xs:element name="add_unique_field_summary" type="ogr:add_unique_field_summary_Type" substitutionGroup="gml:_Feature"/>
+<xs:complexType name="add_unique_field_summary_Type">
+  <xs:complexContent>
+    <xs:extension base="gml:AbstractFeatureType">
+      <xs:sequence>
+        <xs:element name="classes" nillable="true" minOccurs="0" maxOccurs="1">
+          <xs:simpleType>
+            <xs:restriction base="xs:integer">
+              <xs:totalDigits value="10"/>
+            </xs:restriction>
+          </xs:simpleType>
+        </xs:element>
+        <xs:element name="id2" nillable="true" minOccurs="0" maxOccurs="1">
+          <xs:simpleType>
+            <xs:restriction base="xs:integer">
+              <xs:totalDigits value="10"/>
+            </xs:restriction>
+          </xs:simpleType>
+        </xs:element>
+      </xs:sequence>
+    </xs:extension>
+  </xs:complexContent>
+</xs:complexType>
+</xs:schema>

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

@@ -2534,7 +2534,7 @@ tests:
             fid: skip
 
 
-  - algorithm: qgis:adduniquevalueindexfield
+  - algorithm: native:adduniquevalueindexfield
     name: add unique field based on another field
     params:
       FIELD: id2
@@ -2546,6 +2546,24 @@ tests:
         name: expected/add_unique_field.gml
         type: vector
 
+  - algorithm: native:adduniquevalueindexfield
+    name: Add unique field summary
+    params:
+      FIELD: id2
+      FIELD_NAME: classes
+      INPUT:
+        name: points.gml
+        type: vector
+    results:
+      SUMMARY_OUTPUT:
+        name: expected/add_unique_field_summary.gml
+        type: vector
+        compare:
+          fields:
+            fid: skip
+        pk:
+        - id2
+
   - algorithm: qgis:linestopolygons
     name: convert lines to polygon
     params:

src/analysis/CMakeLists.txt

@@ -65,6 +65,7 @@ SET(QGIS_ANALYSIS_SRCS
   processing/qgsalgorithmtransect.cpp
   processing/qgsalgorithmtransform.cpp
   processing/qgsalgorithmtranslate.cpp
+  processing/qgsalgorithmuniquevalueindex.cpp
 
   processing/qgsnativealgorithms.cpp