[FEATURE] Add expression function array_agg

Author: arnaud-morvan

python/core/qgsaggregatecalculator.sip

@@ -47,7 +47,8 @@ class QgsAggregateCalculator
       StringMinimumLength,
       StringMaximumLength,
       StringConcatenate,
-      GeometryCollect
+      GeometryCollect,
+      ArrayAggregate
     };
 
     struct AggregateParameters

resources/function_help/json/array_agg

@@ -0,0 +1,13 @@
+{
+  "name": "array_agg",
+  "type": "function",
+  "description": "Returns an array of aggregated values from a field or expression.",
+  "arguments": [
+    {"arg": "expression", "description": "sub expression of field to aggregate"},
+    {"arg": "group_by", "optional": true, "description": "optional expression to use to group aggregate calculations"},
+    {"arg": "filter", "optional": true, "description": "optional expression to use to filter features used to calculate aggregate"}
+  ],
+  "examples": [
+    { "expression": "array_agg(\"name\",group_by:=\"state\")", "returns":"list of name values, grouped by state field"}
+  ]
+}

src/core/expression/qgsexpressionfunction.cpp

@@ -830,6 +830,11 @@ static QVariant fcnAggregateStringConcat( const QVariantList &values, const QgsE
   return fcnAggregateGeneric( QgsAggregateCalculator::StringConcatenate, values, parameters, context, parent );
 }
 
+static QVariant fcnAggregateArray( const QVariantList &values, const QgsExpressionContext *context, QgsExpression *parent )
+{
+  return fcnAggregateGeneric( QgsAggregateCalculator::ArrayAggregate, values, QgsAggregateCalculator::AggregateParameters(), context, parent );
+}
+
 static QVariant fcnClamp( const QVariantList &values, const QgsExpressionContext *, QgsExpression *parent )
 {
   double minValue = QgsExpressionUtils::getDoubleValue( values.at( 0 ), parent );
@@ -3918,6 +3923,7 @@ const QList<QgsExpressionFunction *> &QgsExpression::Functions()
         << new QgsStaticExpressionFunction( QStringLiteral( "max_length" ), aggParams, fcnAggregateMaxLength, QStringLiteral( "Aggregates" ), QString(), false, QSet<QString>(), true )
         << new QgsStaticExpressionFunction( QStringLiteral( "collect" ), aggParams, fcnAggregateCollectGeometry, QStringLiteral( "Aggregates" ), QString(), false, QSet<QString>(), true )
         << new QgsStaticExpressionFunction( QStringLiteral( "concatenate" ), aggParams << QgsExpressionFunction::Parameter( QStringLiteral( "concatenator" ), true ), fcnAggregateStringConcat, QStringLiteral( "Aggregates" ), QString(), false, QSet<QString>(), true )
+        << new QgsStaticExpressionFunction( QStringLiteral( "array_agg" ), aggParams, fcnAggregateArray, QStringLiteral( "Aggregates" ), QString(), false, QSet<QString>(), true )
 
         << new QgsStaticExpressionFunction( QStringLiteral( "regexp_match" ), QgsExpressionFunction::ParameterList() << QgsExpressionFunction::Parameter( QStringLiteral( "string" ) ) << QgsExpressionFunction::Parameter( QStringLiteral( "regex" ) ), fcnRegexpMatch, QStringList() << QStringLiteral( "Conditionals" ) << QStringLiteral( "String" ) )
         << new QgsStaticExpressionFunction( QStringLiteral( "regexp_matches" ), QgsExpressionFunction::ParameterList() << QgsExpressionFunction::Parameter( QStringLiteral( "string" ) ) << QgsExpressionFunction::Parameter( QStringLiteral( "regex" ) ) << QgsExpressionFunction::Parameter( QStringLiteral( "emptyvalue" ), true, "" ), fcnRegexpMatches, QStringLiteral( "Arrays" ) )

src/core/qgsaggregatecalculator.cpp

@@ -165,6 +165,8 @@ QgsAggregateCalculator::Aggregate QgsAggregateCalculator::stringToAggregate( con
     return StringConcatenate;
   else if ( normalized == QLatin1String( "collect" ) )
     return GeometryCollect;
+  else if ( normalized == QLatin1String( "array_agg" ) )
+    return ArrayAggregate;
 
   if ( ok )
     *ok = false;
@@ -178,6 +180,13 @@ QVariant QgsAggregateCalculator::calculate( QgsAggregateCalculator::Aggregate ag
   if ( ok )
     *ok = false;
 
+  if ( aggregate == QgsAggregateCalculator::ArrayAggregate )
+  {
+    if ( ok )
+      *ok = true;
+    return calculateArrayAggregate( fit, attr, expression, context );
+  }
+
   switch ( resultType )
   {
     case QVariant::Int:
@@ -293,6 +302,7 @@ QgsStatisticalSummary::Statistic QgsAggregateCalculator::numericStatFromAggregat
     case StringMaximumLength:
     case StringConcatenate:
     case GeometryCollect:
+    case ArrayAggregate:
     {
       if ( ok )
         *ok = false;
@@ -340,6 +350,7 @@ QgsStringStatisticalSummary::Statistic QgsAggregateCalculator::stringStatFromAgg
     case InterQuartileRange:
     case StringConcatenate:
     case GeometryCollect:
+    case ArrayAggregate:
     {
       if ( ok )
         *ok = false;
@@ -386,6 +397,7 @@ QgsDateTimeStatisticalSummary::Statistic QgsAggregateCalculator::dateTimeStatFro
     case StringMaximumLength:
     case StringConcatenate:
     case GeometryCollect:
+    case ArrayAggregate:
     {
       if ( ok )
         *ok = false;
@@ -512,6 +524,9 @@ QVariant QgsAggregateCalculator::defaultValue( QgsAggregateCalculator::Aggregate
     case StringConcatenate:
       return ""; // zero length string - not null!
 
+    case ArrayAggregate:
+      return QVariantList(); // empty list
+
     // undefined - nothing makes sense here
     case Sum:
     case Min:
@@ -559,3 +574,29 @@ QVariant QgsAggregateCalculator::calculateDateTimeAggregate( QgsFeatureIterator
   s.finalize();
   return s.statistic( stat );
 }
+
+QVariant QgsAggregateCalculator::calculateArrayAggregate( QgsFeatureIterator &fit, int attr, QgsExpression *expression,
+    QgsExpressionContext *context )
+{
+  Q_ASSERT( expression || attr >= 0 );
+
+  QgsFeature f;
+
+  QVariantList array;
+
+  while ( fit.nextFeature( f ) )
+  {
+    if ( expression )
+    {
+      Q_ASSERT( context );
+      context->setFeature( f );
+      QVariant v = expression->evaluate( context );
+      array.append( v );
+    }
+    else
+    {
+      array.append( f.attribute( attr ) );
+    }
+  }
+  return array;
+}

src/core/qgsaggregatecalculator.h

@@ -65,7 +65,8 @@ class CORE_EXPORT QgsAggregateCalculator
       StringMinimumLength, //!< Minimum length of string (string fields only)
       StringMaximumLength, //!< Maximum length of string (string fields only)
       StringConcatenate, //! Concatenate values with a joining string (string fields only). Specify the delimiter using setDelimiter().
-      GeometryCollect //! Create a multipart geometry from aggregated geometries
+      GeometryCollect, //! Create a multipart geometry from aggregated geometries
+      ArrayAggregate //! Create an array of values
     };
 
     //! A bundle of parameters controlling aggregate calculation
@@ -165,6 +166,9 @@ class CORE_EXPORT QgsAggregateCalculator
         QgsExpressionContext *context, QgsDateTimeStatisticalSummary::Statistic stat );
     static QVariant calculateGeometryAggregate( QgsFeatureIterator &fit, QgsExpression *expression, QgsExpressionContext *context );
 
+    static QVariant calculateArrayAggregate( QgsFeatureIterator &fit, int attr, QgsExpression *expression,
+        QgsExpressionContext *context );
+
     static QVariant calculate( Aggregate aggregate, QgsFeatureIterator &fit, QVariant::Type resultType,
                                int attr, QgsExpression *expression,
                                const QString &delimiter,

tests/src/core/testqgsexpression.cpp

@@ -1375,6 +1375,10 @@ class TestQgsExpression: public QObject
 
       QTest::newRow( "geometry collect" ) << "geom_to_wkt(aggregate('aggregate_layer','collect',$geometry))" << false << QVariant( QStringLiteral( "MultiPoint ((0 0),(1 0),(2 0),(3 0),(5 0))" ) );
 
+      QVariantList array;
+      array << "test" << QVariant( QVariant::String ) << "test333" << "test4" << QVariant( QVariant::String ) << "test4";
+      QTest::newRow( "array aggregate" ) << "aggregate('aggregate_layer','array_agg',\"col2\")" << false << QVariant( array );
+
       QTest::newRow( "sub expression" ) << "aggregate('test','sum',\"col1\" * 2)" << false << QVariant( 65 * 2 );
       QTest::newRow( "bad sub expression" ) << "aggregate('test','sum',\"xcvxcv\" * 2)" << true << QVariant();
 

tests/src/python/test_qgsaggregatecalculator.py

@@ -130,13 +130,15 @@ def testNumeric(self):
                  [QgsAggregateCalculator.ThirdQuartile, 'flddbl', 7.5],
                  [QgsAggregateCalculator.InterQuartileRange, 'fldint', 3.0],
                  [QgsAggregateCalculator.InterQuartileRange, 'flddbl', 2.5],
+                 [QgsAggregateCalculator.ArrayAggregate, 'fldint', int_values],
+                 [QgsAggregateCalculator.ArrayAggregate, 'flddbl', dbl_values],
                  ]
 
         agg = QgsAggregateCalculator(layer)
         for t in tests:
             val, ok = agg.calculate(t[0], t[1])
             self.assertTrue(ok)
-            if isinstance(t[2], int):
+            if isinstance(t[2], (int, list)):
                 self.assertEqual(val, t[2])
             else:
                 self.assertAlmostEqual(val, t[2], 3)
@@ -171,6 +173,7 @@ def testString(self):
                  [QgsAggregateCalculator.Max, 'fldstring', 'eeee'],
                  [QgsAggregateCalculator.StringMinimumLength, 'fldstring', 0],
                  [QgsAggregateCalculator.StringMaximumLength, 'fldstring', 8],
+                 [QgsAggregateCalculator.ArrayAggregate, 'fldstring', values],
                  ]
 
         agg = QgsAggregateCalculator(layer)
@@ -251,6 +254,8 @@ def testDateTime(self):
                  [QgsAggregateCalculator.Range, 'flddatetime', QgsInterval(693871147)],
                  [QgsAggregateCalculator.Range, 'flddate', QgsInterval(693792000)],
 
+                 [QgsAggregateCalculator.ArrayAggregate, 'flddatetime', [None if v.isNull() else v for v in datetime_values]],
+                 [QgsAggregateCalculator.ArrayAggregate, 'flddate', [None if v.isNull() else v for v in date_values]],
                  ]
 
         agg = QgsAggregateCalculator(layer)
@@ -425,6 +430,12 @@ def testExpressionNoMatch(self):
         self.assertTrue(ok)
         self.assertEqual(val, None)
 
+        # array_agg
+        agg = QgsAggregateCalculator(layer)
+        val, ok = agg.calculate(QgsAggregateCalculator.ArrayAggregate, 'fldint * 2')
+        self.assertTrue(ok)
+        self.assertEqual(val, [])
+
     def testStringToAggregate(self):
         """ test converting strings to aggregate types """