For a database of games, where one game is called different names by different users, I have two tables, set up as one-to-many:
class Game(db.Entity):
name = Set('Name')
...
class Name(db.Entity):
game = Required(Game)
name = Required(str)
...
How can I access the names for a specific game? They come back as "Multiset", which (I think) is a special Counter object, when I do this:
games = Game.select()
for g in games:
names = g.name.name
print(names)
>>> Multiset({'Sticks And Stones': 1, 'May Break Your Bones': 1 })
This also seems pretty ugly to me, I suppose there must be a better way?
It turns out the to_dict() method, well documented in PonyORM's API Reference, helps greatly with to-many relationships.
for g in games:
this_game = g.to_dict(
with_collections=True,
related_objects=True,
exclude=['game_meta', 'statistics']
)
And then access the dict() entries like this: this_game['name']
Related
So... I've inherited this rather large project based on Zend Framework 1.12 and a feature that I'm trying to add involves a more complex database operation than what I'm used to doing with the project. I'm extremely new to Zend Framework, or MVC for that matter. I found an answer for Zend Framework 3 which would have been perfect but I have to make do with this version.
The function basically builds a Zend_Db_Select based on various parameters and the feature I'm trying to add will involve joining two different tables and checking if a specific combination exists in one or the other.
Here's what I have so far:
//SQL that I'm trying to do. Assume table1 and table2 are already joined.
//Ignore the imperfect syntax. I'm trying to get the concept across.
//SELECT * FROM (table1 joined to table2 by a common key)
//WHERE ( (table1.column1 = myParam1) AND (table1.column2 = myParam2) )
//OR WHERE ( (table2.column1 = myParam1) AND (table2.column2 = myParam2) )
public function buildSelect($params){
//Zend code starts here
//This one starts the Zend_Db_Select
$select = $this->select();
$table1Name = get_table_name_from_object($table1);
//lots of preexisting code here
//my code starts here.
$table2Name = get_table_name_from_object($table2);
$select->join($table2Name, "$table1Name.key = $table2Name.key", array('column1', 'column2', 'key');
//After I wrote this, I instantly realized why it won't work the way I intended it but putting it here to show what I tried at which point I got stuck.
$select->where("($table1Name.column1 = ?) OR ($table2Name.column1 = ?)",$params[1]);
$select->where( "($table1Name.column2 = ?) OR ($table2Name.column2 = ?)", $params[2]);
//more preexisting code below.
return $select
}
Obviously, if I tried this as is, the program will happily return results that include a combination of, say, an entry where param1 is in table1.column1 and param2 is in table2.column2.
I received some feedback from a friend and posting here for posterity.
They noticed my code already contains parentheses and recommended that I simply take advantage of orWhere() then write it like this:
$select->where("($tableName1.column1 = ?", $params[param1])
->where("$tableName1.column2 = ?)", $params[param2]);
$select->orWhere("($tableName1.column1 = ?",$params[param1])
->where("$tableName2.column2 = ?)",$params[param2]);
Using the (modified) examples in the Realm Swift documentation:
class Dog: Object {
dynamic var name = ""
dynamic var age = 0
let puppies = List<Puppies>()
}
class Person: Object {
dynamic var name = ""
dynamic var picture: NSData? = nil // optionals supported
let dogs = List<Dog>()
}
class Puppies: Object {
dynamic var name = ""
}
Let's assume that the Person.name = Bob, and that Bob has several dogs added to his dogs List. I have added another model class called Puppies, which would represent puppies that belong to Bob's dogs. (Apparently Bob owns a kennel.)
How would I get the values to display the names of Bob's dogs and the number of puppies belonging to each dog in a UITableview?
More specifically, what is the code to extract the property values of the List of dogs that belong to Bob. I assume that once I get those values it won't be difficult to list them in the tableview cells.
I decide to use the slightly modified example from the documentation instead of my own code so that those who read this won't have to try and interpret my code, and be able to focus on the solution.
I have been able to save my data and believe I have made the relationships between the objects link properly, but don't know how to get the values of the List objects, based on the primary key I have in my top level model. The problem I have is that (using the example above): the puppies know what dog they belong to, and the dog knows the person it belongs to, but the inverse relationships don't seem to work.
(By the way; I used the LinkingObject examples in the documentation in a playground and it throws and error. I'm not sure if the examples are incomplete in some way.)
In the Realm Browser (displaying the Person object) I can see the data as entered but the link that shows [Dog] has a 0 next to it and when I click on the link, the table that shows is blank. Maybe solving that issues will be the answer to make everything else work.
Please excuse my ignorance. I'm still learning.
Thanks to Ahmad F. for pointing me in the right direction.
Here is the answer:
I did not know how to append to the list property in each of the object classes. Following the example above, it is done by creating a variable that holds the Person object. Then the realm.write function would look something like this.
newDog = Dog()
newDog.name = "Phydeaux"
.....
try! realm.write {
currentPerson?.dogs.append(newDog)
I have an issue with defining model in spyne to generate several levels "in" SOAP11.
I used example at first, but my task is to generate service for tables already existing, so I got stuck and try to understand wheter to seek in Spyne properties or Sqlalchemy.
To be precise, i'll take example from site and show what i'm trying to reach:
class Permission(TableModel):
__tablename__ = 'permission'
id = UnsignedInteger32(pk=True)
application = Unicode(values=('usermgr', 'accountmgr'))
operation = Unicode(values=('read', 'modify', 'delete'))
perm_user_id = integer
last field is the FK for user table, but its name is different from user_id
class User(TableModel):
__tablename__ = 'user'
id = UnsignedInteger32(pk=True)
user_name = Unicode(32, min_len=4, pattern='[a-z0-9.]+', unique=True)
full_name = Unicode(64, pattern='\w+( \w+)+')
email = Unicode(64, pattern=r'[a-z0-9._%+-]+#[a-z0-9.-]+\.[A-Z]{2,4}')
last_pos = Point(2, index='gist')
permissions = Array(Permission).store_as('table')
--- SQL generated tries to add "WHEN user.id = permission.user_id" but I need another field (perm_user_id) to be filtered
Help me to define class to get correct inner tags.. actually it'll be about 3 more classes deep.
Thanx in Advance, Yury
Your answer is correct. Just as an alternative for simple tables, you can omit column definitions and let sqlalchemy's reflection engine figure it out.
meta = TableModel.Attributes.sqla_metadata
meta.reflect()
class User(TableModel):
__table__ = meta.tables['user']
The User class will be reconstructed using as much information as possible from the table columns and their types.
Found it myself, sorry to disturb anyone,
from spyne.model.complex import table
Permissions= Array(permission).customize(store_as=table(right='perm_user_id'))
This seems a silly, simple question. I'm going round in circles trying to get this work, but I can't see the wood for the trees.
Given a simple model such as (I've skipped the imports):
class Location(models.Model):
description = model.CharField(max_length=40)
address1 = model.CharField(max_length=40)
# ..... (and so on)
tel = model.CharField(max_length=12)
and another with a relationship to it:
class InformationRequest(models.Model):
source = models.ForeignKey(Location)
request_date = Models.DateField(default=datetime.now())
# ..... (and so on)
How do I add a field that references the 'tel' field from the Location model in such a way that it can be populated automatically or from a select list in Django admin.
OK, if I get this right than you are, nomen est omen, thoroughly confusing the way that relational databases work :] One of key principles is to eliminate redundancy. There shouldn't be the very same piece of data stored in two tables that are related to one another.
I think that your current models are correct. Given these instances (I'm ignoring the fact that you have other, non-nullable fields)...
>>> loc = Location()
>>> loc.tel = "123"
>>> loc.save()
>>> info = InformationRequest()
>>> info.source = loc
>>> info.save()
...you can access tel from InformationRequest instance just like this:
>>> info.source.tel
'123'
You can also create a method...
class InformationRequest(models.Model):
source = models.ForeignKey(Location, related_name="information_requests")
request_date = Models.DateField(default=datetime.now())
# ..... (and so on)
def contact_tel(self):
return self.source.tel
... and get it like this:
>>> info.contact_tel()
'123'
You can even trick it into being an attribute...
class InformationRequest(models.Model):
source = models.ForeignKey(Location, related_name="information_requests")
request_date = Models.DateField(default=datetime.now())
# ..... (and so on)
#property
def contact_tel(self):
return self.source.tel
... and get it without parentheses:
>>> info.contact_tel
'123'
Anyway, you should work your way around it programatically. Hope that helps.
I have an entity A with a simple navigation property B. For any given instance of A, we expect several related thousand instances of B.
There is no case where I call something like:
foreach(var x in A.B) { ... }
Instead, I'm only interested in doing aggregate operations such as
var statY = A.B.Where(o => o.Property == "Y");
var statZ = A.B.Where(o => o.CreateDate > DateTime.Now.AddDays(-1));
As far as I can tell, EF instantiates thousands of references to B and does these operations in memory. This is because navigation properties use EntityCollection. Instead, I'd like it to perform these queries at the SQL level if possible.
My current hunch is that Navigation Properties may not be the right way to go. I'm not attached to EF, so I am open to other approaches. But I'd be very interested to know the right way to do this under EF if possible.
(I'm using EF4.)
CreateSourceQuery seems to do the trick.
So my examples would now be:
var statY = A.B.CreateSourceQuery().Where(o => o.Property == "Y");
var statZ = A.B.CreateSourceQuery().Where(o => o.CreateDate > DateTime.Now.AddDays(-1));
There's one thing you should know. Members that derives from IQueryable<> are executed on the server, not in memory. Members which are derived from IEnumerable<> is executed in memory.
for example
var someEntities = db.SomeEntities; <-- returns an IQueryable<> object. no data fetched. SomeEntities table may contain thousands of rows, but we are not fetching it yet, we are just building a query.
someEntities = someEntities.Where(s => s.Id > 100 && s.Id < 200); <-- creates expression tree with where statement. The query is not executed yet and data is not fetched on the client. We just tell EF to perform a where filter when query will execute. This statement too returns an IQueryable<> object.
var entities = someEntities.AsEnumerable(); <-- here we tell EF to execute query. now entities will be fetched and any additional linq query will be performed in memory.
you can also fetch the data using foreach, calling ToArray() or ToList<>.
Hope you understand what I mean, and sorry for my english :)