laravel cursor的底层实现
更新:HHH   时间:2023-1-7


foreach (BillInfo::where('id', '>', 0)->orderBy('id', 'desc')->limit(10000)->cursor() as $value) {
   print_r($value);
}


Illuminate\Database\Query\Builder.php;
/**
* Get a generator for the given query.
*
* @return \Generator
*/
public function cursor()
{
   if (is_null($this->columns)) {
       $this->columns = ['*'];
   }

   return $this->connection->cursor(
       $this->toSql(), $this->getBindings(), ! $this->useWritePdo
   );
}


Illuminate\Database\Connection.php;
/**
* Run a select statement against the database and returns a generator.
*
* @param  string  $query
* @param  array  $bindings
* @param  bool  $useReadPdo
* @return \Generator
*/
public function cursor($query, $bindings = [], $useReadPdo = true)
{
   $statement = $this->run($query, $bindings, function ($query, $bindings) use ($useReadPdo) {
       if ($this->pretending()) {
           return [];
       }

       // First we will create a statement for the query. Then, we will set the fetch
       // mode and prepare the bindings for the query. Once that's done we will be
       // ready to execute the query against the database and return the cursor.
       $statement = $this->prepared($this->getPdoForSelect($useReadPdo)
                         ->prepare($query));

       $this->bindValues(
           $statement, $this->prepareBindings($bindings)
       );

       // Next, we'll execute the query against the database and return the statement
       // so we can return the cursor. The cursor will use a PHP generator to give
       // back one row at a time without using a bunch of memory to render them.
       $statement->execute();

       return $statement;
   });

   while ($record = $statement->fetch()) {
       yield $record;
   }
}
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