What startSetup() and endSetup() methods actually does?

The startSetup() and endSetup() methods are used in setup scripts. They are often at the beginning and the end of an upgrade/install method, like in “upgrade()” method of Magento/Catalog/Setup/UpgradeData.php

The question is “do you really need them?” Or does it just “look necessary”? This blog post explores what these functions do and then explains when you do and do not need to use these methods.

Let’s see what these methods are doing.

First, startSetup():

public function startSetup() { 

 $this->rawQuery("SET SQL_MODE=''"); 

$this->rawQuery("SET @OLD_FOREIGN_KEY_CHECKS=@@FOREIGN_KEY_CHECKS, FOREIGN_KEY_CHECKS=0"); 

 $this->rawQuery("SET @OLD_SQL_MODE=@@SQL_MODE, SQL_MODE='NO_AUTO_VALUE_ON_ZERO'"); 

 return $this; 

}

1. Disable foreign keys check. It may be necessary in some rare cases (for example, in a case of cyclic references between tables), but it’s not needed in common situations. It even may lead to hiding real problems with the upgrade script, like if inserted values really break the integrity of the database.

2. Disable generation of auto-increment values when ‘0’ is inserted. It may also be useful in some cases, such as when you are certain that you’re going to insert ‘0’ values and you want them to be treated as ‘0’s, instead of defaulting to auto-incrementing. This type of scenario is not necessary for common install/upgrade scripts.

Then, endSetup() just rolls back both foreign keys check and auto-increment behavior to the previous state:

 public function endSetup() { 

    $this->rawQuery("SET SQL_MODE=IFNULL(@OLD_SQL_MODE,'')"); 

     $this->rawQuery("SET FOREIGN_KEY_CHECKS=IF(@OLD_FOREIGN_KEY_CHECKS=0, 0,     1)"); 

  return $this; 

 }

 Do you really need this for every install/upgrade? Probably not. Use startSetup() and endSetup() selectively, only for the cases where you really have some data or schema changes that are impossible without modifying default MySQL behavior.

I would recommend using these methods only when you really need such functionality during your upgrade. It would keep the foreign keys validation in place, as it may help discover potential data corruption issues.

conclusion:

==============

1:By default, don’t use startSetup() and endSetup() combination in your setup scripts. Most likely, you don’t need them.

2:The startSetup() and endSetup() may be helpful and you should use them if you want to:

   1:disable foreign key checks, or

   2:disable auto-increment for ‘0’ values.