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How to add an auto-incrementing primary key to an existing table, in PostgreSQL?
...SEQUENCE test_id_seq OWNED BY test1.id;
ALTER TABLE test ALTER COLUMN id SET DEFAULT nextval('test_id_seq');
UPDATE test1 SET id = nextval('test_id_seq');
Again, in recent versions of Postgres this is roughly equivalent to the single command above.
...
Why can't I use a list as a dict key in python?
...
Because lists are mutable, dict keys (and set members) need to be hashable, and hashing mutable objects is a bad idea because hash values should be computed on the basis of instance attributes.
In this answer, I will give some concrete examples, hopefully adding val...
What's the difference between an object initializer and a constructor?
...h used to create the new MyObject in memory. The created object (which is setup using those parameters) gets returned, and set to myObjectInstance.
In general, it's considered good practice to have a constructor require the parameters needed in order to completely setup an object, so that it's imp...
C#: Assign same value to multiple variables in single statement
...ow that the get accessor of the intermediate value is not called. Only the set accessor is invoked for all property accessed in the assignation sequence.
Take for example a class that write to the console everytime the get and set accessor are invoked.
static void Main(string[] args)
{
var acc...
How to use sessions in an ASP.NET MVC 4 application?
...izable]
public class UserProfileSessionData
{
public int UserId { get; set; }
public string EmailAddress { get; set; }
public string FullName { get; set; }
}
Use case:
public class LoginController : Controller {
[HttpPost]
public ActionResult Login(LoginModel model)
{
...
What's the difference between Html.Label, Html.LabelFor and Html.LabelForModel
...perty matching the string expression):
// Model
public string Test { get; set; }
// View
@Html.Label("Test")
// Output
<label for="Test">Test</label>
Html.LabelFor gives you a label for the property represented by the provided expression (typically a model property):
// Model
publi...
Adding a user to a group in django
...sing Group model with the name of the group, then add the user to the user_set
from django.contrib.auth.models import Group
my_group = Group.objects.get(name='my_group_name')
my_group.user_set.add(your_user)
share
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What does |= (single pipe equal) and &=(single ampersand equal) mean
...utes &= ~FileAttributes.System;
~ is bitwise negation. You will thus set all bits to 1 except the System bit. and-ing it with the mask will set System to 0 and leave all other bits intact because 0 & x = 0 and 1 & x = x for any x
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When to use AtomicReference in Java?
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Atomic reference should be used in a setting where you need to do simple atomic (i.e. thread-safe, non-trivial) operations on a reference, for which monitor-based synchronization is not appropriate. Suppose you want to check to see if a specific field only if th...
In Vim, how do I apply a macro to a set of lines?
... editor after snippets, if snippets enabled
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