[DDC-280] UnitOfWork changeSet population should take advantage of Comparable technique Created: 27/Jan/10  Updated: 04/Feb/11

Status: Open
Project: Doctrine 2 - ORM
Component/s: ORM
Affects Version/s: None
Fix Version/s: None
Security Level: All

Type: Improvement Priority: Minor
Reporter: Guilherme Blanco Assignee: Roman S. Borschel
Resolution: Unresolved Votes: 1
Labels: None


 Description   

Currently our UnitOfWork computes the changeset by checking actual instances of Objects.

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// UnitOfWork, lines 501-507 

            foreach ($actualData as $propName => $actualValue) { 
                $orgValue = isset($originalData[$propName]) ? $originalData[$propName] : null; 
                if (is_object($orgValue) && $orgValue !== $actualValue) { 
                    $changeSet[$propName] = array($orgValue, $actualValue); 
                } else if ($orgValue != $actualValue || ($orgValue === null ^ $actualValue === null))  
	                    $changeSet[$propName] = array($orgValue, $actualValue);
                } 

While this is ok when you do new object assignments, it just bypass same instances of same object, since the hash is the same.
A user on IRC (post-o-matic) has a quite complex object logic that he would like to avoid clone and even instantiate another class.
I agree with him that cloning is not the ideal technique, mainly because the changeset would always compute the object (since then hashs would be different).

He implemented this datatype:

Unable to find source-code formatter for language: php. Available languages are: actionscript, html, java, javascript, none, sql, xhtml, xml
class EffortGraphType extends Type 
{ 
    public function getSqlDeclaration(array $fieldDeclaration, AbstractPlatform $platform) 
    { 
        return $platform->getClobTypeDeclarationSql($fieldDeclaration); 
    } 

    public function convertToPHPValue($value, AbstractPlatform $platform) 
    { 
        return new EffortGraph(unserialize($value)); 
    } 

    public function convertToDatabaseValue($value, AbstractPlatform $platform) 
    { 
        return serialize($value->getGraphPoints()); 
    } 

    public function getName() 
    { 
        return 'effort_graph'; 
    } 
}

I was thinking in a possible alternative and it came up to me the same basic idea we have with operators overloading OR Comparable interface of Java. I know in Java it supports way more things, but at least for this situation (as a start point) it would make developer's life easier.

Basic idea is to have an interface in Doctrine\Common:

Unable to find source-code formatter for language: php. Available languages are: actionscript, html, java, javascript, none, sql, xhtml, xml
namespace Doctrine\Common;

interface Comparable
{
    public function compareTo($value);
}

And update our UnitOfWork to take advantage of it:

Unable to find source-code formatter for language: php. Available languages are: actionscript, html, java, javascript, none, sql, xhtml, xml
// UnitOfWork, lines 501-507 

            foreach ($actualData as $propName => $actualValue) { 
                $orgValue = isset($originalData[$propName]) ? $originalData[$propName] : null; 

                if (is_object($orgValue)) { 
                    $isDiff = ($orgValue instanceof Doctrine\Common\Comparable) 
                        ? $orgValue->compareTo($actualValue) :  ($orgValue !== $actualValue);

                    if ($isDiff) {
                        $changeSet[$propName] = array($orgValue, $actualValue); 
                    }
                } else if ($orgValue != $actualValue || ($orgValue === null ^ $actualValue === null))  
	                    $changeSet[$propName] = array($orgValue, $actualValue);
                } 

In this user's usecase, it'd require him to update the EffortGraph class and implement Comparable interface.
For his specific situation, he'd need to store original value and updated value, just like we do internally in UnitOfWork for Entities.



 Comments   
Comment by Guilherme Blanco [ 19/May/10 ]

What's the final status of this?

IMHO this should be incorporated, since it adds a powerful support that users can take advantage in our Types.

Cheers,

Comment by Guilherme Blanco [ 19/May/10 ]

You're the main guy that can give a final word in this subject.

I'm +1 for this

Comment by Robert [ 04/Feb/11 ]

+1 for this...

if you have datetimes in a table and are using the DateTime object, you end up with useless update queries, if you persist an unchanged object...

Comment by Benjamin Eberlei [ 04/Feb/11 ]

That is not true.

Comment by Robert [ 04/Feb/11 ]

Sorry, I wasn't clear.

It does not happen in all cases.

I have a simple object, that I save to the session. After merging it and flushing the entitiy manager, an update query is generated, which sets all the datetime fields of the object to their current value:

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$item = $_SESSION['item'];
$item = $this->_em->merge($item);
$this->_em->persist($item);
$this->_em->flush();

This code results in the expected SELECT query, which refreshes the item from DB, but it also results in an update query which sets the datetime of the object to the same value.
This query could be omitted, if I could use a comparable interface and a custom type for datetimes, which implement it.

Comment by Benjamin Eberlei [ 04/Feb/11 ]

This rather seems like a bug with the merging. Can you open up a new ticket describing this? Thank you

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