Here a simple example:
class Example(model.RedisModel): database = main_database foo = field.StringField() bar = field.StringField()
To create an instance, it’s as easy as:
>>> example = Example(foo='FOO', bar='BAR')
By just doing this, the fields are created, and a PKField is set with a value that you can use:
>>> print("New example object with pk #%s" % example.pk.get()) New example object with pk #1
Then later to get an instance from Redis with it’s pk, it’s as simple as:
>>> example = Example(1)
So, to create an object, pass fields and their values as named arguments, and to retrieve it, pass its pk as the only argument. To retrieve instances via other fields than the pk, check the Collections section in this documentation.
If you don’t pass any argument to the
RedisModel, default one from fields are taken and are saved. But if no arguments and no default values, you get an empty instance, with no filled fields and no pk set.
The pk will be created with the first field. It’s important to know that we do not store any concept of “model”, each field is totally independent, though the keys to save them in Redis are based on the object’s pk. So you can have 50 fields in a model and save only one of them.
Another really important thing to know is that when you create/retrieve an object, there is absolutely no data stored in it. Each time you access data via a field, the data is fetched from Redis.
When defining a model, you will add fields, but there is also some other attributes that are mandatory or may be useful.
You can’t have two models with the same name on the same database. Except if you use namespacing.
Each model has a
namespace, default to an empty string.
namespace can be used to regroup models. All models about registration could have the
namespace “registration”, ones about the payment could have “payment”, and so on.
With this you can have models with the same name in different
namespaces, because the Redis keys created to store your data is computed with the
namespace, the model name, and the pk of objects.
If you have many models sharing some field names, and/or within the same database and/or the same namespace, it could be useful to regroup all common stuff into a “base model”, without using it to really store data in Redis.
For this you have the
False by default:
class Content(model.RedisModel): database = main_database namespace = "content" abstract = True title = fields.InstanceHashField() pub_date = field.InstanceHashField() class Article(Content): content = fields.StringField() class Image(Content): path = fields.InstanceHashField()
In this example, only
Image are real models, both using the
main_database database, the
namespace “content”, and having
pub_date fields, in addition to their own.
By default, when updating am
indexable field, update of the same field for all other instances of the model are locked while the update is not finished, to ensure consistency.
If you prefer speed, or are sure that you don’t have more than one thread/process/server that write to the same database, you can set this
lockable attribute to False to disable it for all the model’s fields.
Note that you can also disable it at the field’s level.
Model class methods¶
Return an instance of the model given a pk, or some fields to filter on. See the Collections section in this documentation.
It will raises a
DoesNotExist exception if no instance was found with the given arguments, and
ValueError if more than one instance is found.
article = Article.get(12) article = Article.get(pk=12) article = Article.get(title='foo', content='bar')
Try to get an instance from the database, or create it if it does not exists. Uses the same arguments as
article = Article.get_or_connect(title='foo') same_article = Article.get_or_connect(title='foo')
Check if an instance with the given pk or filters exists in the database. Uses the same arguments as
if not Article.exists(title='foo'): article = Article(title='foo', content='bar')
This is an advanced feature. It takes a PK and create an object with this PK without checking for its existence in the database until an operation is done with the instance.
existing = Article.lazy_connect(10) existing.title.get() # connects only now to the database non_existing = Article.lazy_connect(11) non_existing.title.get() # will raise ``DoesNotExist``
Also an advanced/debug feature, allows to retrieve (as a generator, or can be casted to a set, for example) all the keys related to this model: collection, max pk used, indexes and all instances fields.
print('Keys used for model Article:') for key in Article.scan_model_keys(): print(' - ' + key)
Model instance methods¶
Will delete the instance and remove its content from the indexes if any.
article = Article(title='foo') article.delete()
Also an advanced/debug feature, allows to retrieve (as a generator, or can be casted to a set, for example) all the keys related to this instance (ie keys holding all defined fields or the ones with a default values):
print('Keys used for Article #%s:' % article.pk.get()) for key in article.scan_keys(): print(' - ' + key)