PHPORM-106 Implement pagination for groupBy queries

Author: GromNaN

src/Query/Builder.php

@@ -910,6 +910,28 @@ public function newQuery()
         return new static($this->connection, $this->grammar, $this->processor);
     }
 
+    public function runPaginationCountQuery($columns = ['*'])
+    {
+        if ($this->distinct) {
+            throw new BadMethodCallException('Distinct queries cannot be used for pagination. Use GroupBy instead');
+        }
+
+        if ($this->groups || $this->havings) {
+            $without = $this->unions ? ['orders', 'limit', 'offset'] : ['columns', 'orders', 'limit', 'offset'];
+
+            $mql = $this->cloneWithout($without)
+                ->cloneWithoutBindings($this->unions ? ['order'] : ['select', 'order'])
+                ->toMql();
+
+            // Adds the $count stage to the pipeline
+            $mql['aggregate'][0][] = ['$count' => 'aggregate'];
+
+            return $this->collection->aggregate($mql['aggregate'][0], $mql['aggregate'][1])->toArray();
+        }
+
+        return parent::runPaginationCountQuery($columns);
+    }
+
     /**
      * Perform an update query.
      *

tests/QueryTest.php

@@ -4,6 +4,7 @@
 
 namespace MongoDB\Laravel\Tests;
 
+use BadMethodCallException;
 use DateTimeImmutable;
 use LogicException;
 use MongoDB\BSON\Regex;
@@ -534,6 +535,33 @@ public function testCursorPaginate(): void
         $this->assertNull($results->first()->title);
     }
 
+    public function testPaginateGroup(): void
+    {
+        $results = User::groupBy('age')->paginate(2);
+        $this->assertEquals(2, $results->count());
+        $this->assertEquals(6, $results->total());
+        $this->assertEquals(3, $results->lastPage());
+        $this->assertEquals(1, $results->currentPage());
+        $this->assertCount(2, $results->items());
+        $this->assertNotNull($results->first()->age);
+
+        $results = User::groupBy('age')->paginate(4, page: 2);
+        $this->assertEquals(2, $results->count());
+        $this->assertEquals(6, $results->total());
+        $this->assertEquals(2, $results->lastPage());
+        $this->assertEquals(2, $results->currentPage());
+        $this->assertCount(2, $results->items());
+        $this->assertNotNull($results->first()->age);
+    }
+
+    public function testPaginateDistinct(): void
+    {
+        $this->expectException(BadMethodCallException::class);
+        $this->expectExceptionMessage('Distinct queries cannot be used for pagination. Use GroupBy instead');
+
+        User::distinct('age')->paginate(2);
+    }
+
     public function testUpdate(): void
     {
         $this->assertEquals(1, User::where(['name' => 'John Doe'])->update(['name' => 'Jim Morrison']));