From 29207a1617678eb3a3922ff3dd74c3b6b6b193a5 Mon Sep 17 00:00:00 2001
From: Alexander Bruy <alexander.bruy@gmail.com>
Date: Wed, 4 Jul 2018 18:30:30 +0300
Subject: [PATCH 1/2] [processing] fix Random extract/select within subset when
 subset is smaller than number of requested features (fix #19322)

---
 .../algs/qgis/RandomExtractWithinSubsets.py      |  2 +-
 .../algs/qgis/RandomSelectionWithinSubsets.py    |  2 +-
 .../tests/testdata/qgis_algorithm_tests.yaml     | 16 ++++++++++++++++
 3 files changed, 18 insertions(+), 2 deletions(-)

diff --git a/python/plugins/processing/algs/qgis/RandomExtractWithinSubsets.py b/python/plugins/processing/algs/qgis/RandomExtractWithinSubsets.py
index 7ba41634ec7d..10826a165b16 100644
--- a/python/plugins/processing/algs/qgis/RandomExtractWithinSubsets.py
+++ b/python/plugins/processing/algs/qgis/RandomExtractWithinSubsets.py
@@ -127,7 +127,7 @@ def processAlgorithm(self, parameters, context, feedback):
 
         for subset in classes.values():
             selValue = value if method != 1 else int(round(value * len(subset), 0))
-            selran.extend(random.sample(subset, selValue))
+            selran.extend(random.sample(subset, min(selValue, len(subset))))
 
         total = 100.0 / featureCount if featureCount else 1
         for (i, feat) in enumerate(selran):
diff --git a/python/plugins/processing/algs/qgis/RandomSelectionWithinSubsets.py b/python/plugins/processing/algs/qgis/RandomSelectionWithinSubsets.py
index 9281da0545b3..98ce833d9951 100644
--- a/python/plugins/processing/algs/qgis/RandomSelectionWithinSubsets.py
+++ b/python/plugins/processing/algs/qgis/RandomSelectionWithinSubsets.py
@@ -138,7 +138,7 @@ def processAlgorithm(self, parameters, context, feedback):
                     break
 
                 selValue = value if method != 1 else int(round(value * len(subset), 0))
-                selran.extend(random.sample(subset, selValue))
+                selran.extend(random.sample(subset, min(selValue, len(subset))))
 
             layer.selectByIds(selran)
         else:
diff --git a/python/plugins/processing/tests/testdata/qgis_algorithm_tests.yaml b/python/plugins/processing/tests/testdata/qgis_algorithm_tests.yaml
index 6db7255abd07..239e17459576 100644
--- a/python/plugins/processing/tests/testdata/qgis_algorithm_tests.yaml
+++ b/python/plugins/processing/tests/testdata/qgis_algorithm_tests.yaml
@@ -3923,6 +3923,21 @@ tests:
         name: points_weighted.gml
         compare: false
 
+  - algorithm: qgis:randomextractwithinsubsets
+    name: Random extract within subset (subset smaller than number)
+    params:
+      FIELD: id2
+      INPUT:
+        name: points.gml
+        type: vector
+      METHOD: 0
+      NUMBER: 3
+    results:
+      OUTPUT:
+        type: vector
+        name: points.gml
+        compare: false
+
   - algorithm: qgis:heatmapkerneldensityestimation
     name: Heatmap (Kernel density estimation)
     params:
@@ -5355,6 +5370,7 @@ tests:
         compare:
           fields:
             fid: skip
+
   - algorithm: native:difference
     name: Test Difference B - A (basic)
     params:

From b72f5d1a5387377cde1e63562456ef81ca14e0ff Mon Sep 17 00:00:00 2001
From: Alexander Bruy <alexander.bruy@gmail.com>
Date: Wed, 4 Jul 2018 19:15:29 +0300
Subject: [PATCH 2/2] [processing] log cases when subset is smaller than
 requested number of features

---
 .../processing/algs/qgis/RandomExtractWithinSubsets.py     | 7 +++++--
 .../processing/algs/qgis/RandomSelectionWithinSubsets.py   | 7 +++++--
 2 files changed, 10 insertions(+), 4 deletions(-)

diff --git a/python/plugins/processing/algs/qgis/RandomExtractWithinSubsets.py b/python/plugins/processing/algs/qgis/RandomExtractWithinSubsets.py
index 10826a165b16..7afffe0411bf 100644
--- a/python/plugins/processing/algs/qgis/RandomExtractWithinSubsets.py
+++ b/python/plugins/processing/algs/qgis/RandomExtractWithinSubsets.py
@@ -125,9 +125,12 @@ def processAlgorithm(self, parameters, context, feedback):
             classes[attrs[index]].append(feature)
             feedback.setProgress(int(i * total))
 
-        for subset in classes.values():
+        for k, subset in classes.items():
             selValue = value if method != 1 else int(round(value * len(subset), 0))
-            selran.extend(random.sample(subset, min(selValue, len(subset))))
+            if selValue > len(subset):
+                selValue = len(subset)
+                feedback.reportError(self.tr('Subset "{}" is smaller than requested number of features.'.format(k)))
+            selran.extend(random.sample(subset, selValue))
 
         total = 100.0 / featureCount if featureCount else 1
         for (i, feat) in enumerate(selran):
diff --git a/python/plugins/processing/algs/qgis/RandomSelectionWithinSubsets.py b/python/plugins/processing/algs/qgis/RandomSelectionWithinSubsets.py
index 98ce833d9951..4321f1d586db 100644
--- a/python/plugins/processing/algs/qgis/RandomSelectionWithinSubsets.py
+++ b/python/plugins/processing/algs/qgis/RandomSelectionWithinSubsets.py
@@ -133,12 +133,15 @@ def processAlgorithm(self, parameters, context, feedback):
                 feedback.setProgress(int(i * total))
 
             selran = []
-            for subset in classes.values():
+            for k, subset in classes.items():
                 if feedback.isCanceled():
                     break
 
                 selValue = value if method != 1 else int(round(value * len(subset), 0))
-                selran.extend(random.sample(subset, min(selValue, len(subset))))
+                if selValue > len(subset):
+                    selValue = len(subset)
+                    feedback.reportError(self.tr('Subset "{}" is smaller than requested number of features.'.format(k)))
+                selran.extend(random.sample(subset, selValue))
 
             layer.selectByIds(selran)
         else: