Added DataFrame::dropPartitions() transformation (#922)

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

@@ -34,6 +34,7 @@
 use Flow\ETL\Transformer\CallbackRowTransformer;
 use Flow\ETL\Transformer\CrossJoinRowsTransformer;
 use Flow\ETL\Transformer\DropDuplicatesTransformer;
+use Flow\ETL\Transformer\DropPartitionsTransformer;
 use Flow\ETL\Transformer\EntryNameStyleConverterTransformer;
 use Flow\ETL\Transformer\JoinEachRowsTransformer;
 use Flow\ETL\Transformer\JoinRowsTransformer;
@@ -300,6 +301,13 @@ public function dropDuplicates(string|Reference ...$entries) : self
         return $this;
     }
 
+    public function dropPartitions() : self
+    {
+        $this->pipeline->add(new DropPartitionsTransformer());
+
+        return $this;
+    }
+
     /**
      * Be aware that fetch is not memory safe and will load all rows into memory.
      * If you want to safely iterate over Rows use oe of the following methods:.

src/core/etl/src/Flow/ETL/Rows.php

@@ -142,6 +142,11 @@ public function drop(int $size) : self
         return self::partitioned(\array_slice($this->rows, $size), $this->partitions);
     }
 
+    public function dropPartitions() : self
+    {
+        return new self(...$this->rows);
+    }
+
     public function dropRight(int $size) : self
     {
         if ($size === 0) {

src/core/etl/src/Flow/ETL/Transformer/DropPartitionsTransformer.php

@@ -0,0 +1,21 @@
+<?php
+
+declare(strict_types=1);
+
+namespace Flow\ETL\Transformer;
+
+use Flow\ETL\FlowContext;
+use Flow\ETL\Rows;
+use Flow\ETL\Transformer;
+
+final class DropPartitionsTransformer implements Transformer
+{
+    public function transform(Rows $rows, FlowContext $context) : Rows
+    {
+        if ($rows->isPartitioned()) {
+            return $rows->dropPartitions();
+        }
+
+        return $rows;
+    }
+}

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

@@ -20,6 +20,28 @@
 
 final class PartitioningTest extends IntegrationTestCase
 {
+    public function test_dropping_partitions() : void
+    {
+        $rows = df()
+            ->read(from_rows(
+                rows_partitioned(
+                    [
+                        row(int_entry('id', 1), str_entry('country', 'PL'), int_entry('age', 20)),
+                        row(int_entry('id', 2), str_entry('country', 'PL'), int_entry('age', 20)),
+                        row(int_entry('id', 3), str_entry('country', 'PL'), int_entry('age', 25)),
+                        row(int_entry('id', 4), str_entry('country', 'PL'), int_entry('age', 30)),
+                    ],
+                    [
+                        partition('country', 'PL'),
+                    ]
+                )
+            ))
+            ->dropPartitions()
+            ->fetch();
+
+        $this->assertFalse($rows->isPartitioned());
+    }
+
     public function test_partition_by() : void
     {
         $rows = df()

src/core/etl/tests/Flow/ETL/Tests/Unit/Transformer/DropPartitionsTransformerTest.php

@@ -0,0 +1,59 @@
+<?php
+
+declare(strict_types=1);
+
+namespace Flow\ETL\Tests\Unit\Transformer;
+
+use function Flow\ETL\DSL\array_to_rows;
+use function Flow\ETL\DSL\flow_context;
+use function Flow\ETL\DSL\ref;
+use Flow\ETL\Transformer\DropPartitionsTransformer;
+use PHPUnit\Framework\TestCase;
+
+final class DropPartitionsTransformerTest extends TestCase
+{
+    public function test_dropping_partitions() : void
+    {
+        $partitioned = array_to_rows([
+            ['id' => 1, 'name' => 'one', 'category' => 'a'],
+            ['id' => 2, 'name' => 'two', 'category' => 'a'],
+            ['id' => 3, 'name' => 'three', 'category' => 'a'],
+            ['id' => 4, 'name' => 'four', 'category' => 'a'],
+            ['id' => 5, 'name' => 'five', 'category' => 'a'],
+            ['id' => 6, 'name' => 'six', 'category' => 'b'],
+            ['id' => 7, 'name' => 'seven', 'category' => 'b'],
+            ['id' => 8, 'name' => 'eight', 'category' => 'b'],
+            ['id' => 9, 'name' => 'nine', 'category' => 'b'],
+            ['id' => 10, 'name' => 'ten', 'category' => 'b'],
+        ])->partitionBy(ref('category'));
+
+        foreach ($partitioned as $rows) {
+            $this->assertTrue($rows->isPartitioned());
+
+            $notPartitioned = (new DropPartitionsTransformer())->transform($rows, flow_context());
+
+            $this->assertFalse($notPartitioned->isPartitioned());
+        }
+    }
+
+    public function test_transforming_not_partitioned_rows() : void
+    {
+        $rows = array_to_rows([
+            ['id' => 1, 'name' => 'one', 'category' => 'a'],
+            ['id' => 2, 'name' => 'two', 'category' => 'a'],
+            ['id' => 3, 'name' => 'three', 'category' => 'a'],
+            ['id' => 4, 'name' => 'four', 'category' => 'a'],
+            ['id' => 5, 'name' => 'five', 'category' => 'a'],
+            ['id' => 6, 'name' => 'six', 'category' => 'b'],
+            ['id' => 7, 'name' => 'seven', 'category' => 'b'],
+            ['id' => 8, 'name' => 'eight', 'category' => 'b'],
+            ['id' => 9, 'name' => 'nine', 'category' => 'b'],
+            ['id' => 10, 'name' => 'ten', 'category' => 'b'],
+        ]);
+
+        $this->assertSame(
+            $rows,
+            (new DropPartitionsTransformer())->transform($rows, flow_context())
+        );
+    }
+}