AW: [gentle-devel] Updating Records

[<Gr...@mi...>]

You should follow OO guidelines.
=20
In my case, I have a table "Contact", which has several rows with =
contact information, like first name, last name, etc., and a field which =
contains the last modified date, which gets updated by a SQL trigger and =
is very important, because I need to set the HTTP-headers properly so =
the caching subsystem works right.
=20
I also have fields with password, last login date and failed login =
count. Now the problem was, that a login shouldnt trigger the last =
modified date to be updated, because the "real" contact information =
didnt change. So I've rewritten the trigger to only update if changes =
occured on the contact information, but not on the login information. =
However, Gentle updated all rows, no matter if they were changed or if =
they are null. The easiest way was using a nested class approach:
=20
[TableName("Contacts"), XmlInclude(typeof(Contact))]
public class Contact
{
[TableColumn("FirstName", NotNull=3Dfalse), XmlAttribute]
public string FirstName;
=20
[TableColumn("LastName", NotNull=3Dfalse), XmlAttribute]
public string LastName;
=20
[TableColumn("LastModified", NotNull=3Dfalse, IsReadOnly=3Dtrue, =
IsUpdateAfterWrite=3Dtrue), XmlAttribute]
public DateTime LastModified;
=20
[TableName("Contacts")]
private class ContactLogin
{
[TableColumn("LastLogin", NotNull=3Dfalse)]
public DateTime LastLogin;
=20
[TableColumn("Logins", NotNull=3Dtrue)]
public int Logins;
=20
[TableColumn("FailedCount", NotNull=3Dtrue)]
public int FailedCount;
}
=20
private ContactLogin _contactLogin;
=20
public void PersistLogin()
{
if (_contactLogin!=3Dnull)
{
_contactLogin.IsPersisted=3Dtrue;
_contactLogin.UUID=3Dthis.UUID;
_contactLogin.Persist();
}
}
=20
  [XmlAttribute, XmlIgnore]
  public int Logins
  {
   get
   {
    if (_contactLogin =3D=3D null)
     _contactLogin=3DContactLogin.Retrieve(UUID);
=20
    if (_contactLogin !=3D null)
     return _contactLogin.Logins;
    else
     return 0;
   }
   set
   {
    if (_contactLogin =3D=3D null)
     _contactLogin=3DContactLogin.Retrieve(UUID);
=20
    if (_contactLogin =3D=3D null)
     _contactLogin=3Dnew ContactLogin(UUID, null, null, =
DateTime.MinValue, value,  0);
    else
     _contactLogin.Logins=3Dvalue;
   }
  }
  ...
=20
}
=20
Seems a little bit complicated in the inside, but from the outside, you =
can simply do this:
=20
Contact contact=3DContact.Retrieve("te...@te...");
contact.Logins=3D3;
contact.PersistLogin(); // This tells the object to only update the =
login-part
=20
You can also go one step further and implement the cols as properties =
instead of fields, update two seperate dirty-flags, and simply override =
the Persist()-method, where the object will then decide itself if it =
needs to update all fields, or only the login-subpart. You shouldnt =
think of the objects as interfaces to your table rows, but instead see =
the objects as if they were your table rows. Wouldnt it be nice if your =
table rows decide for their selves which columns they need to update?
=20
One thing: *Never* use inheritance. This will confuse the Gentle caching =
subsystem, because two different objects can reference the same table =
row. And without the caching, the perfomance doesnt scale very well with =
the number of users.
=20
Regards, Alex


________________________________

	Von: gop...@li... =
[mailto:gop...@li...] Im Auftrag von David =
Cumps
	Gesendet: Montag, 19. September 2005 13:33
	An: gop...@li...
	Betreff: RE: [gentle-devel] Updating Records
=09
=09
	Ouch, that's an ugly solution imho :/
	=20
	If there was only a way to simply discard the parameters which have a =
null value from the query, everything would be solved :p
	=20
	Anything planned to make this easier Morton?
	=20
	Greets
	=20
	David

________________________________

	Van: gop...@li... =
[mailto:gop...@li...] Namens Birgir =
Kristmannsson
	Verzonden: maandag 19 september 2005 13:20
	Aan: gop...@li...
	Onderwerp: RE: [gentle-devel] Updating Records
=09
=09

	For this you need to have two (or more) classes.

	=20

	class BaseClass : Persistent

	{

	    // Define the properties that you want to update

	}

	=20

	class FullClass : BaseClass

	{

	   // Define the rest of the properties

	}

	=20

	And for your update scenario, you would work exclusively with BaseClass

	=20

	AFAIK that is the only way to do it in Gentle.NET - but it works like a =
charm

	=20

	Biggi

=09
________________________________


	From: gop...@li... =
[mailto:gop...@li...] On Behalf Of David Cumps
	Sent: 19. september 2005 07:11
	To: gop...@li...
	Subject: [gentle-devel] Updating Records

	=20

	Hello,

	=20

	I have been working with Gentle for some time now, and starting to help =
myself just enough to make everything work, until now :(

	=20

	I'm looking for a way to create an update query, which does *not* set =
all the fields.

	=20

	I know how to insert, update, delete, select a single record. But for =
multiple updates, I can't get it to work.

	=20

	I'm looking to create something like: "UPDATE *table* SET =
*a_field_i_want*=3D*value*, *maybe another field* WHERE =
*yet_another_field*=3D*value*"

	=20

	The problems I encountered are that it wants to put every column in the =
SET clause.

	=20

	Any suggestions?

	=20

	Thanks

	=20

	Best Regards,

	=20

	David