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How do I clone a Django model instance object and save it to the database?
...imary key of your object and run save().
obj = Foo.objects.get(pk=<some_existing_pk>)
obj.pk = None
obj.save()
If you want auto-generated key, set the new key to None.
More on UPDATE/INSERT here.
Official docs on copying model instances: https://docs.djangoproject.com/en/2.2/topics/db/que...
Redis cache vs using memory directly
... storing the data in local memory (since it involves socket roundtrips to fetch/store the data). However, it also brings some interesting properties:
Redis can be accessed by all the processes of your applications, possibly running on several nodes (something local memory cannot achieve).
Redis me...
What happens when there's insufficient memory to throw an OutOfMemoryError?
...
The JVM never really runs out of memory. It does memory computation of the heap stack in advance.
The Structure of the JVM, Chapter 3, section 3.5.2 states:
If Java virtual machine stacks can be dynamically expanded, and expansion is...
How to rollback a specific migration?
...nt to go back.
For example:
rake db:rollback STEP=5
Will also rollback all the migration that happened later (4, 3, 2 and also 1).
To roll back all migrations back to (and including) a target migration, use: (This corrected command was added AFTER all the comments pointing out the error in the ...
Rails: Missing host to link to! Please provide :host parameter or set default_url_options[:host]
...s.
In each of your environment files (e.g. development.rb, production.rb, etc.) you can specify the default_url_options to use for action_mailer:
config.action_mailer.default_url_options = { host: 'lvh.me', port: '3000' }
However, these are not set for MyApp:Application.default_url_options:
$ M...
SQL Server - stop or break execution of a SQL script
...e multiple blocks within Begin..End? Meaning STATEMENT; GO; STATEMENT; GO; etc etc? I'm getting errors and I guess that might be the reason.
– Joel Peltonen
May 6 '14 at 12:48
3
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How do I run a Ruby file in a Rails environment?
...------
#!/usr/bin/env /Users/me/rails_project/script/rails runner
Product.all.each { |p| p.price *= 2 ; p.save! }
-------------------------------------------------------------
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Sorting Python list based on the length of the string
...
def lensort(list_1):
list_2=[];list_3=[]
for i in list_1:
list_2.append([i,len(i)])
list_2.sort(key = lambda x : x[1])
for i in list_2:
list_3.append(i[0])
return list_3
This works for me!
...
Why do we need fibers
...ed param: #{param}"
Fiber.yield #nothing sent, nothing received
puts 'etc'
end
puts f.resume
f.resume 'param'
f.resume
prints this:
some code
return
received param: param
etc
Implementation of this logic with other ruby features will be less readable.
With this feature, good fibers usage...
Backbone.View “el” confusion
...
A views el is where all the event binding takes place. You don't have to use it but if you want backbone to fire events you need to do your rendering work on the el. A views el is a DOM element but it does not have to be a pre-existing element. ...