Removed GroupedDataFrame::toDF()

UPGRADE.md

@@ -23,6 +23,11 @@ Above changes were introduced in all 3 types of joins:
 - `DataFrame::joinEach()`
 - `DataFrame::crossJoin()`
 
+### 2) GroupBy
+
+From now on, DataFrame::groupBy() method will return GroupedDataFrame object, which is nothing more than a GroupBy
+statement Builder. In order to get the results you first need to define the aggregation functions or optionally pivot the data.
+
 ## Upgrading from 0.6.x to 0.7.x
 
 ### 1) DataFrame::appendSafe() method was removed

src/core/etl/src/Flow/ETL/DataFrame/GroupedDataFrame.php

@@ -18,18 +18,6 @@ public function aggregate(AggregatingFunction ...$aggregations) : DataFrame
     {
         $this->groupBy->aggregate(...$aggregations);
 
-        return $this->toDataFrame();
-    }
-
-    public function pivot(Reference $ref) : self
-    {
-        $this->groupBy->pivot($ref);
-
-        return $this;
-    }
-
-    public function toDataFrame() : DataFrame
-    {
         return $this->df->rebuild(function (Pipeline $pipeline, FlowContext $context) : DataFrame {
             return new DataFrame(
                 new Pipeline\LinkedPipeline(new Pipeline\GroupByPipeline($this->groupBy, $pipeline)),
@@ -38,8 +26,10 @@ public function toDataFrame() : DataFrame
         });
     }
 
-    public function toDF() : DataFrame
+    public function pivot(Reference $ref) : self
     {
-        return $this->toDataFrame();
+        $this->groupBy->pivot($ref);
+
+        return $this;
     }
 }

src/core/etl/src/Flow/ETL/Pipeline/HashJoinPipeline.php

@@ -114,13 +114,6 @@ public function process(FlowContext $context) : \Generator
         }
     }
 
-    public function setSource(Extractor $extractor) : Pipeline
-    {
-        $this->extractor = $extractor;
-
-        return $this;
-    }
-
     public function source() : Extractor
     {
         return $this->extractor;

src/core/etl/src/Flow/ETL/Pipeline/SynchronousPipeline.php

@@ -82,13 +82,6 @@ public function process(FlowContext $context) : \Generator
         }
     }
 
-    public function setSource(Extractor $extractor) : self
-    {
-        $this->extractor = $extractor;
-
-        return $this;
-    }
-
     public function source() : Extractor
     {
         return $this->extractor;

src/core/etl/src/Flow/ETL/Pipeline/VoidPipeline.php

@@ -36,11 +36,6 @@ public function process(FlowContext $context) : \Generator
         yield new Rows();
     }
 
-    public function setSource(Extractor $extractor) : self
-    {
-        return $this;
-    }
-
     public function source() : Extractor
     {
         return $this->pipeline->source();

src/core/etl/tests/Flow/ETL/Tests/Integration/DataFrame/GroupByTest.php

@@ -4,7 +4,23 @@
 
 namespace Flow\ETL\Tests\Integration\DataFrame;
 
-use function Flow\ETL\DSL\{average, count, df, float_entry, from_all, from_array, from_memory, from_rows, int_entry, integer_entry, lit, max, rank, ref, str_entry, sum, window};
+use function Flow\ETL\DSL\{average,
+    count,
+    df,
+    float_entry,
+    from_all,
+    from_array,
+    from_memory,
+    from_rows,
+    int_entry,
+    integer_entry,
+    lit,
+    max,
+    rank,
+    ref,
+    str_entry,
+    sum,
+    window};
 use Flow\ETL\Memory\ArrayMemory;
 use Flow\ETL\Tests\Integration\IntegrationTestCase;
 use Flow\ETL\{Loader, Row, Rows};
@@ -32,19 +48,20 @@ public function test_group_by_multiple_columns_and_batch_size() : void
                 )
             ))
             ->groupBy('country', 'gender')
-            ->toDF()
+            ->aggregate(average(ref('age')))
+            ->withEntry('age_avg', ref('age_avg')->round(lit(2)))
             ->batchSize(1)
             ->write($loader)
             ->fetch();
 
         self::assertEquals(
-            new Rows(
-                Row::create(str_entry('country', 'PL'), str_entry('gender', 'male')),
-                Row::create(str_entry('country', 'PL'), str_entry('gender', 'female')),
-                Row::create(str_entry('country', 'US'), str_entry('gender', 'female')),
-                Row::create(str_entry('country', 'US'), str_entry('gender', 'male')),
-            ),
-            $rows
+            [
+                ['country' => 'PL', 'gender' => 'male', 'age_avg' => 21.67],
+                ['country' => 'PL', 'gender' => 'female', 'age_avg' => 30.0],
+                ['country' => 'US', 'gender' => 'female', 'age_avg' => 42.5],
+                ['country' => 'US', 'gender' => 'male', 'age_avg' => 45],
+            ],
+            $rows->toArray()
         );
     }
 
@@ -125,15 +142,15 @@ public function test_group_by_single_column() : void
                 )
             ))
             ->groupBy('country')
-            ->toDF()
+            ->aggregate(sum(ref('age')))
             ->fetch();
 
         self::assertEquals(
-            new Rows(
-                Row::create(str_entry('country', 'PL')),
-                Row::create(str_entry('country', 'US')),
-            ),
-            $rows
+            [
+                ['country' => 'PL', 'age_sum' => 95],
+                ['country' => 'US', 'age_sum' => 175],
+            ],
+            $rows->toArray()
         );
     }
 

src/core/etl/tests/Flow/ETL/Tests/Integration/DataFrame/PartitioningTest.php

@@ -5,7 +5,8 @@
 namespace Flow\ETL\Tests\Integration\DataFrame;
 
 use function Flow\ETL\Adapter\Text\{from_text, to_text};
-use function Flow\ETL\DSL\{df,
+use function Flow\ETL\DSL\{collect,
+    df,
     from_array,
     from_rows,
     int_entry,
@@ -195,7 +196,7 @@ public function test_pruning_single_partition() : void
             ->select('year')
             ->withEntry('year', ref('year')->cast('int'))
             ->groupBy(ref('year'))
-            ->toDF()
+            ->aggregate(collect(ref('year')))
             ->fetch();
 
         self::assertCount(1, $rows);