如何从闭包中终止 Eloquent 分块

Question

使用 Eloquent，如何根据chunk函数闭包内的条件终止分块？我试过返回，但这似乎只终止当前块而不是所有块。此时，我想停止从数据库中检索记录。

$query->chunk(self::CHUNK_SIZE, function ($objects) {
    if (someCondition) {
        // terminate chunking here
        return;
    }
});

Answer 1

如果你return false它会打破。如果您处于do while循环中并且return任何事情都将退出循环。在下面的源代码中，您可以看到：

        if ($callback($results) === false) {
            return false;
        }

这让您有机会退出。

 /**
     * Chunk the results of the query.
     *
     * @param  int  $count
     * @param  callable  $callback
     * @return bool
     */
    public function chunk($count, callable $callback)
    {
        $this->enforceOrderBy();
        $page = 1;
        do {
            // 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 = $this->forPage($page, $count)->get();
            $countResults = $results->count();
            if ($countResults == 0) {
                break;
            }
            // On each chunk result set, we will pass them to the callback and then let the
            // developer take care of everything within the callback, which allows us to
            // keep the memory low for spinning through large result sets for working.
            if ($callback($results) === false) {
                return false;
            }
            $page++;
        } while ($countResults == $count);
        return true;
    }

https://github.com/laravel/framework/blob/5.4/src/Illuminate/Database/Concerns/BuildsQueries.php#L18