Implement chunkById in descending order

Author: cristiancalara

src/Illuminate/Database/Concerns/BuildsQueries.php

@@ -112,6 +112,35 @@ public function each(callable $callback, $count = 1000)
      * @return bool
      */
     public function chunkById($count, callable $callback, $column = null, $alias = null)
+    {
+        return $this->orderedChunkById($count, $callback, $column, $alias);
+    }
+
+    /**
+     * Chunk the results of a query by comparing IDs in descending order.
+     *
+     * @param  int  $count
+     * @param  callable  $callback
+     * @param  string|null  $column
+     * @param  string|null  $alias
+     * @return bool
+     */
+    public function chunkByIdDesc($count, callable $callback, $column = null, $alias = null)
+    {
+        return $this->orderedChunkById($count, $callback, $column, $alias, true);
+    }
+
+    /**
+     * Chunk the results of a query by comparing IDs in a given order.
+     *
+     * @param  int  $count
+     * @param  callable  $callback
+     * @param  string|null  $column
+     * @param  string|null  $alias
+     * @param  bool $descending
+     * @return bool
+     */
+    public function orderedChunkById($count, callable $callback, $column = null, $alias = null, $descending = false)
     {
         $column ??= $this->defaultKeyName();
 
@@ -127,7 +156,11 @@ public function chunkById($count, callable $callback, $column = null, $alias = n
             // We'll execute the query for the given page and get the results. If there are
             // no results we can just break and return from here. When there are results
             // we will call the callback with the current chunk of these results here.
-            $results = $clone->forPageAfterId($count, $lastId, $column)->get();
+            if($descending){
+                $results = $clone->forPageBeforeId($count, $lastId, $column)->get();
+            } else {
+                $results = $clone->forPageAfterId($count, $lastId, $column)->get();
+            }
 
             $countResults = $results->count();
 

tests/Database/DatabaseQueryBuilderTest.php

@@ -4421,6 +4421,26 @@ public function testChunkPaginatesUsingIdWithAlias()
         }, 'table.id', 'table_id');
     }
 
+    public function testChunkPaginatesUsingIdDesc()
+    {
+        $builder = $this->getMockQueryBuilder();
+        $builder->orders[] = ['column' => 'foobar', 'direction' => 'desc'];
+
+        $chunk1 = collect([(object) ['someIdField' => 10], (object) ['someIdField' => 1]]);
+        $chunk2 = collect([]);
+        $builder->shouldReceive('forPageBeforeId')->once()->with(2, 0, 'someIdField')->andReturnSelf();
+        $builder->shouldReceive('forPageBeforeId')->once()->with(2, 1, 'someIdField')->andReturnSelf();
+        $builder->shouldReceive('get')->times(2)->andReturn($chunk1, $chunk2);
+
+        $callbackAssertor = m::mock(stdClass::class);
+        $callbackAssertor->shouldReceive('doSomething')->once()->with($chunk1);
+        $callbackAssertor->shouldReceive('doSomething')->never()->with($chunk2);
+
+        $builder->chunkByIdDesc(2, function ($results) use ($callbackAssertor) {
+            $callbackAssertor->doSomething($results);
+        }, 'someIdField');
+    }
+
     public function testPaginate()
     {
         $perPage = 16;