There is a Model1. In Model 2, I need to make two fields:
some_list = models.ManyToManyField (Model1)
some_field = models.ForeignKey (Model1)
I see error:
Reverse accessor for 'Model2.some_field' clashes with reverse accessor for 'Model2.some_list'.
P.S. I do not want to manually create a table "through" and and use only the list.
I think you can use two different related names, like this:
lead_researcher = models.ForeignKey(related_name='lead_researcher')
participating_researcher = models.ManyToManyField(related_name='participating_researcher')
Related
I am trying to initiate a relationship between two columns in Neo4j. my dataset is a CSV file with two-column refers to Co-Authorship and I want to Construct a Network of it. I already load the data, return them and match them.
Loading
load csv from 'file:///conet1.csv' as rec
return the data
create (:Guys {source: rec[0], target: rec[1]})
now I need to Construct the Collaboration Network of data by making a relationship between source and target columns. What do you propose for the purpose?
I was able to make a relationship between mentioned columns in NetworkX graph libray in python like this:
import pandas as pd
import networkx as nx
g = nx.Graph()
df = pd.read_excel('Colab.csv', columns= ['source', 'target'])
g = nx.from_pandas_edgelist(df,'source','target', 'weight')
If I understand your use case, I do not believe you should be creating Guys nodes just to store relationship info. Instead, the graph-oriented approach would be to create an Author node for each author and a relationship (say, of type COLLABORATED_WITH) between the co-authors.
This might work for you, or at least give you a clue:
LOAD CSV FROM 'file:///conet1.csv' AS rec
MERGE (source:Author {id: rec[0]})
MERGE (target:Author {id: rec[1]})
CREATE (source)-[:COLLABORATED_WITH]->(target)
If it is possible that the same relationship could be re-created, you should replace the CREATE with a more expensive MERGE. Also, a work can have any number of co-authors, so having a relationship between every pair may be sub-optimal depending on what you are trying to do; but that is a separate issue.
i have a model attribute having the following
class ph_no(models.Model):
phone_no = models.CharField(max_length = 20)
phone_no_assigned_to = models.CharField(max_length = 50)
actually the value for the field phone_no_assigned_to should come from many tables in db like
personal_usage
bussiness_usage etc..
Each of the willl have assigned to field
Also this phone_no_assigned_to can have mutiple values
Can anyone help me how to define it
You might want to define relationships, i.e. have a model phone_usage with usage types and link it to model's ph_no field phone_no_assigned_to. Or if "usage" is a small list of possible values use choices.
Have a look at:
https://docs.djangoproject.com/en/1.9/topics/db/models/#relationships
https://docs.djangoproject.com/en/1.9/topics/db/examples/
https://docs.djangoproject.com/en/1.9/ref/models/fields/#choices
I think nested data loading in ExtJS 4 is impossible in real world. For example, I have some models for trainings, for users, and some model which describes how trainings assigned to users, which user assigned training, etc. I think it's wrong to get join in PHP Model (I use ZF 1.x) to get users first names and last names instead their identifiers, and it's wrong to merge data from two selects (select join with traings and trainings-to-users table and select from users where identifier in (list of identifiers from join above)) in Controller. Good practise to do it in View, isn't it?
But ExtJS 4 nested data loading tells me: make hierarchial structure (with a lot of duplicates of nested data!) and pass it me. Why I need to do this work? I'll better merge data in Controller!
My final question is: if I have JSON like this:
{
trainings: [{"id":"1", "user_id":278,"assigner_id":30, ...}, {...}],
users: ["278": {"firstname":"Guy", "lastname":"Fawkes"}, "300":{....}, ...]
}
Can I to create another nested data loading from this data?
Thanks.
Yes you can ... sort of. One way to do it is to define separate stores for users and trainings and then use loadData(JSON.users) to load data that was prefetched.
I'm developping a web application using google appengine and django, but I think my problem is more general.
The users have the possibility to create tables, look: tables are not represented as TABLES in the database. I give you an example:
First form:
Name of the the table: __________
First column name: __________
Second column name: _________
...
The number of columns is not fixed, but there is a maximum (100 for example). The type in every columns is the same.
Second form (after choosing a particular table the user can fill the table):
column_name1: _____________
column_name2: _____________
....
I'm using this solution, but it's wrong:
class Table(db.Model):
name = db.StringProperty(required = True)
class Column(db.Model):
name = db.StringProperty(required = True)
number = db.IntegerProperty()
table = db.ReferenceProperty(table, collection_name="columns")
class Value(db.Model):
time = db.TimeProperty()
column = db.ReferenceProperty(Column, collection_name="values")
when I want to list a table I take its columns and from every columns I take their values:
data = []
for column in data.columns:
column_data = []
for value in column.values:
column_data.append(value.time)
data.append(column_data)
data = zip(*data)
I think that the problem is the order of the values, because it is not true that the order for one column is the same for the others. I'm waiting for this bug (but until now I never seen it):
Table as I want: as I will got:
a z c a e c
d e f d h f
g h i g z i
Better solutions? Maybe using ListProperty?
Here's a data model that might do the trick for you:
class Table(db.Model):
name = db.StringProperty(required=True)
owner = db.UserProperty()
column_names = db.StringListProperty()
class Row(db.Model):
values = db.ListProperty(yourtype)
table = db.ReferenceProperty(Table, collection_name='rows')
My reasoning:
You don't really need a separate entity to store column names. Since all columns are of the same data type, you only need to store the name, and the fact that they are stored in a list gives you an implicit order number.
By storing the values in a list in the Row entity, you can use an index into the column_names property to find the matching value in the values property.
By storing all of the values for a row together in a single entity, there is no possibility of values appearing out of their correct order.
Caveat emptor:
This model will not work well if the table can have columns added to it after it has been populated with data. To make that possible, every time that a column is added, every existing row belonging to that table would have to have a value appended to its values list. If it were possible to efficiently store dictionaries in the datastore, this would not be a problem, but list can really only be appended to.
Alternatively, you could use Expando...
Another possibility is that you could define the Row model as an Expando, which allows you to dynamically create properties on an entity. You could set column values only for the columns that have values in them, and that you could also add columns to the table after it has data in it and not break anything:
class Row(db.Expando):
table = db.ReferenceProperty(Table, collection_name='rows')
#staticmethod
def __name_for_column_index(index):
return "column_%d" % index
def __getitem__(self, key):
# Allows one to get at the columns of Row entities with
# subscript syntax:
# first_row = Row.get()
# col1 = first_row[1]
# col12 = first_row[12]
value = None
try:
value = self.__dict__[Row.__name_for_column_index]
catch KeyError:
# The given column is not defined for this Row
pass
return value
def __setitem__(self, key, value):
# Allows one to set the columns of Row entities with
# subscript syntax:
# first_row = Row.get()
# first_row[5] = "New values for column 5"
self.__dict__[Row.__name_for_column_index] = value
# In order to allow efficient multiple column changes,
# the put() can go somewhere else.
self.put()
Why don't you add an IntegerProperty to Value for rowNumber and increment it every time you add a new row of values and then you can reconstruct the table by sorting by rowNumber.
You're going to make life very hard for yourself unless your user's 'tables' are actually stored as real tables in a relational database. Find some way of actually creating tables and use the power of an RDBMS, or you're reinventing a very complex and sophisticated wheel.
This is the conceptual idea I would use:
I would create two classes for the data-store:
table this would serve as a
dictionary, storing the structure of
the pseudo-tables your app would
create. it would have two fields :
table_name, column_name,
column_order . where column_order
would give the position of the
column within the table
data
this would store the actual data in
the pseudo-tables. it would have
four fields : row_id, table_name,
column_name , column_data. row_id
would be the same for data
pertaining to the same row and would
be unique for data across the
various pseudo-tables.
Put the data in a LongBlob.
The power of a database is to be able to search and organise data so that you are able to get only the part you want for performances and simplicity issues : you don't want the whole database, you just want a part of it and want it fast. But from what I understand, when you retrieve a user's data, you retrieve it all and display it. So you don't need to sotre the data in a normal "database" way.
What I would suggest is to simply format and store the whole data from a single user in a single column with a suitable type (LongBlob for example). The format would be an object with a list of columns and rows of type. And you define the object in whatever language you use to communicate with the database.
The columns in your (real) database would be : User int, TableNo int, Table Longblob.
If user8 has 3 tables, you will have the following rows :
8, 1, objectcontaintingtable1;
8, 2, objectcontaintingtable2;
8, 3, objectcontaintingtable3;
I have a n...n structure for two tables, makes and models. So far no problem.
In a third table (products) like:
id
make_id
model_id
...
My problem is creating a view for products of one specifi make inside my ProductsController containing just that's make models:
I thought this could work:
var $uses = array('Make', 'Model');
$this->Make->id = 5; // My Make
$this->Make->find(); // Returns only the make I want with it's Models (HABTM)
$this->Model->find('list'); // Returns ALL models
$this->Make->Model->find('list'); // Returns ALL models
So, If I want to use the list to pass to my view to create radio buttons I will have to do a foreach() in my make array to find all models titles and create a new array and send to the view via $this->set().
$makeArray = $this->Make->find();
foreach ($makeArray['Model'] as $model) {
$modelList[] = $model['title'];
}
$this->set('models', $models)
Is there any easier way to get that list without stressing the make Array. It will be a commom task to develops such scenarios in my application(s).
Thanks in advance for any hint!
Here's my hint: Try getting your query written in regular SQL before trying to reconstruct using the Cake library. In essence you're doing a lot of extra work that the DB can do for you.
Your approach (just for show - not good SQL):
SELECT * FROM makes, models, products WHERE make_id = 5
You're not taking into consideration the relationships (unless Cake auto-magically understands the relationships of the tables)
You're probably looking for something that joins these things together:
SELECT models.title FROM models
INNER JOIN products
ON products.model_id = models.model_id
AND products.make_id = 5
Hopefully this is a nudge in the right direction?
Judging from your comment, what you're asking for is how to get results from a certain model, where the condition is in a HABTM related model. I.e. something you'd usually do with a JOIN statement in raw SQL.
Currently that's one of the few weak points of Cake. There are different strategies to deal with that.
Have the related model B return all ids of possible candidates for Model A, then do a second query on Model A. I.e.:
$this->ModelB->find('first', array('conditions' => array('field' => $condition)));
array(
['ModelB'] => array( ... ),
['ModelA'] => array(
[0] => array(
'id' => 1
)
)
Now you have an array of all ids of ModelA that belong to ModelB that matches your conditions, which you can easily extract using Set::extract(). Basically the equivalent of SELECT model_a.id FROM model_b JOIN model_a WHERE model_b.field = xxx. Next you look for ModelA:
$this->ModelA->find('all', array('conditions' => array('id' => $model_a_ids)));
That will produce SELECT model_a.* FROM model_a WHERE id IN (1, 2, 3), which is a roundabout way of doing the JOIN statement. If you need conditions on more than one related model, repeat until you have all the ids for ModelA, SQL will use the intersection of all ids (WHERE id IN (1, 2, 3) AND id IN (3, 4, 5)).
If you only need one condition on ModelB but want to retrieve ModelA, just search for ModelB. Cake will automatically retrieve related ModelAs for you (see above). You might need to Set::extract() them again, but that might already be sufficient.
You can use the above method and combine it with the Containable behaviour to get more control over the results.
If all else fails or the above methods simply produce too much overhead, you can still write your own raw SQL with $this->Model->query(). If you stick to the Cake SQL standards (naming tables correctly with FROM model_as AS ModelA) Cake will still post-process your results correctly.
Hope this sends you in the right direction.
All your different Make->find() and Model->find() calls are completely independent of each other. Even Make->Model->find() is the same as Model->find(), Cake does not in any way remember or take into account what you have already found in other models. What you're looking for is something like:
$this->Product->find('all', array('conditions' => array('make_id' => 5)));
Check out the Set::extract() method for getting a list of model titles from the results of $this->Make->find()
The solution can be achieved with the use of the with operation in habtm array on the model.
Using with you can define the "middle" table like:
$habtm = " ...
'with' => 'MakeModel',
... ";
And internally, in the Model or Controller, you can issue conditions to the find method.
See: http://www.cricava.com/blogs/index.php?blog=6&title=modelizing_habtm_join_tables_in_cakephp_&more=1&c=1&tb=1&pb=1