348 lines
10 KiB
Markdown
348 lines
10 KiB
Markdown
# Queries
|
|
|
|
## QuerySet
|
|
|
|
Each Model is auto registered with a QuerySet that represents the underlaying query and it's options.
|
|
|
|
Most of the methods are also available through many to many relation interface.
|
|
|
|
Given the Models like this
|
|
|
|
```Python
|
|
--8<-- "../docs_src/queries/docs001.py"
|
|
```
|
|
|
|
we can demonstrate available methods to fetch and save the data into the database.
|
|
|
|
|
|
### create
|
|
|
|
`create(**kwargs): -> Model`
|
|
|
|
Creates the model instance, saves it in a database and returns the updates model
|
|
(with pk populated if not passed and autoincrement is set).
|
|
|
|
The allowed kwargs are `Model` fields names and proper value types.
|
|
|
|
```python
|
|
malibu = await Album.objects.create(name="Malibu")
|
|
await Track.objects.create(album=malibu, title="The Bird", position=1)
|
|
```
|
|
|
|
The alternative is a split creation and persistence of the `Model`.
|
|
```python
|
|
malibu = Album(name="Malibu")
|
|
await malibu.save()
|
|
```
|
|
|
|
!!!tip
|
|
Check other `Model` methods in [models][models]
|
|
|
|
### get
|
|
|
|
`get(**kwargs): -> Model`
|
|
|
|
Get's the first row from the db meeting the criteria set by kwargs.
|
|
|
|
If no criteria set it will return the first row in db.
|
|
|
|
Passing a criteria is actually calling filter(**kwargs) method described below.
|
|
|
|
```python
|
|
track = await Track.objects.get(name='The Bird')
|
|
# note that above is equivalent to await Track.objects.filter(name='The Bird').get()
|
|
track2 = track = await Track.objects.get()
|
|
track == track2 # True since it's the only row in db in our example
|
|
```
|
|
|
|
!!!warning
|
|
If no row meets the criteria `NoMatch` exception is raised.
|
|
|
|
If there are multiple rows meeting the criteria the `MultipleMatches` exception is raised.
|
|
|
|
### get_or_create
|
|
|
|
`get_or_create(**kwargs) -> Model`
|
|
|
|
Combination of create and get methods.
|
|
|
|
Tries to get a row meeting the criteria and if `NoMatch` exception is raised it creates a new one with given kwargs.
|
|
|
|
```python
|
|
album = await Album.objects.get_or_create(name='The Cat')
|
|
# object is created as it does not exist
|
|
album2 = await Album.objects.get_or_create(name='The Cat')
|
|
assert album == album2
|
|
# return True as the same db row is returned
|
|
```
|
|
|
|
!!!warning
|
|
Despite being a equivalent row from database the `album` and `album2` in example above are 2 different python objects!
|
|
Updating one of them will not refresh the second one until you excplicitly load() the fresh data from db.
|
|
|
|
!!!note
|
|
Note that if you want to create a new object you either have to pass pk column value or pk column has to be set as autoincrement
|
|
|
|
### update
|
|
|
|
`update(each: bool = False, **kwargs) -> int`
|
|
|
|
QuerySet level update is used to update multiple records with the same value at once.
|
|
|
|
You either have to filter the QuerySet first or provide a `each=True` flag to update whole table.
|
|
|
|
If you do not provide this flag or a filter a `QueryDefinitionError` will be raised.
|
|
|
|
Return number of rows updated.
|
|
|
|
```python hl_lines="24-28"
|
|
import databases
|
|
import ormar
|
|
import sqlalchemy
|
|
|
|
database = databases.Database("sqlite:///db.sqlite")
|
|
metadata = sqlalchemy.MetaData()
|
|
|
|
class Book(ormar.Model):
|
|
class Meta:
|
|
tablename = "books"
|
|
metadata = metadata
|
|
database = database
|
|
|
|
id: ormar.Integer(primary_key=True)
|
|
title: ormar.String(max_length=200)
|
|
author: ormar.String(max_length=100)
|
|
genre: ormar.String(max_length=100, default='Fiction', choices=['Fiction', 'Adventure', 'Historic', 'Fantasy'])
|
|
|
|
await Book.objects.create(title='Tom Sawyer', author="Twain, Mark", genre='Adventure')
|
|
await Book.objects.create(title='War and Peace', author="Tolstoy, Leo", genre='Fiction')
|
|
await Book.objects.create(title='Anna Karenina', author="Tolstoy, Leo", genre='Fiction')
|
|
|
|
|
|
# queryset needs to be filtered before deleting to prevent accidental overwrite
|
|
# to update whole database table each=True needs to be provided as a safety switch
|
|
await Book.objects.update(each=True, genre='Fiction')
|
|
all_books = await Book.objects.filter(genre='Fiction').all()
|
|
assert len(all_books) == 3
|
|
```
|
|
|
|
### update_or_create
|
|
|
|
`update_or_create(**kwargs) -> Model`
|
|
|
|
### bulk_create
|
|
|
|
`bulk_create(objects: List["Model"]) -> None`
|
|
|
|
Allows you to create multiple objects at once.
|
|
|
|
A valid list of `Model` objects needs to be passed.
|
|
|
|
```python hl_lines="20-26"
|
|
import databases
|
|
import ormar
|
|
import sqlalchemy
|
|
|
|
database = databases.Database("sqlite:///db.sqlite")
|
|
metadata = sqlalchemy.MetaData()
|
|
|
|
|
|
class ToDo(ormar.Model):
|
|
class Meta:
|
|
tablename = "todos"
|
|
metadata = metadata
|
|
database = database
|
|
|
|
id: ormar.Integer(primary_key=True)
|
|
text: ormar.String(max_length=500)
|
|
completed: ormar.Boolean(default=False)
|
|
|
|
# create multiple instances at once with bulk_create
|
|
await ToDo.objects.bulk_create(
|
|
[
|
|
ToDo(text="Buy the groceries."),
|
|
ToDo(text="Call Mum.", completed=True),
|
|
ToDo(text="Send invoices.", completed=True),
|
|
]
|
|
)
|
|
|
|
todoes = await ToDo.objects.all()
|
|
assert len(todoes) == 3
|
|
```
|
|
|
|
### bulk_update
|
|
|
|
`bulk_update(objects: List["Model"], columns: List[str] = None) -> None`
|
|
|
|
Allows to update multiple instance at once.
|
|
|
|
All `Models` passed need to have primary key column populated.
|
|
|
|
You can also select which fields to update by passing `columns` list as a list of string names.
|
|
|
|
```python hl_lines="8"
|
|
# continuing the example from bulk_create
|
|
# update objects
|
|
for todo in todoes:
|
|
todo.completed = False
|
|
|
|
# perform update of all objects at once
|
|
# objects need to have pk column set, otherwise exception is raised
|
|
await ToDo.objects.bulk_update(todoes)
|
|
|
|
completed = await ToDo.objects.filter(completed=False).all()
|
|
assert len(completed) == 3
|
|
```
|
|
|
|
### delete
|
|
|
|
`delete(each: bool = False, **kwargs) -> int`
|
|
|
|
QuerySet level delete is used to delete multiple records at once.
|
|
|
|
You either have to filter the QuerySet first or provide a `each=True` flag to delete whole table.
|
|
|
|
If you do not provide this flag or a filter a `QueryDefinitionError` will be raised.
|
|
|
|
Return number of rows deleted.
|
|
|
|
```python hl_lines="23-27"
|
|
import databases
|
|
import ormar
|
|
import sqlalchemy
|
|
|
|
database = databases.Database("sqlite:///db.sqlite")
|
|
metadata = sqlalchemy.MetaData()
|
|
|
|
class Book(ormar.Model):
|
|
class Meta:
|
|
tablename = "books"
|
|
metadata = metadata
|
|
database = database
|
|
|
|
id: ormar.Integer(primary_key=True)
|
|
title: ormar.String(max_length=200)
|
|
author: ormar.String(max_length=100)
|
|
genre: ormar.String(max_length=100, default='Fiction', choices=['Fiction', 'Adventure', 'Historic', 'Fantasy'])
|
|
|
|
await Book.objects.create(title='Tom Sawyer', author="Twain, Mark", genre='Adventure')
|
|
await Book.objects.create(title='War and Peace in Space', author="Tolstoy, Leo", genre='Fantasy')
|
|
await Book.objects.create(title='Anna Karenina', author="Tolstoy, Leo", genre='Fiction')
|
|
|
|
# delete accepts kwargs that will be used in filter
|
|
# acting in same way as queryset.filter(**kwargs).delete()
|
|
await Book.objects.delete(genre='Fantasy') # delete all fantasy books
|
|
all_books = await Book.objects.all()
|
|
assert len(all_books) == 2
|
|
```
|
|
|
|
### all
|
|
|
|
Returns all rows from a database for given model
|
|
|
|
```python
|
|
tracks = await Track.objects.select_related("album").all()
|
|
# will return a list of all Tracks
|
|
```
|
|
|
|
### filter
|
|
|
|
Allows you to filter by any `Model` attribute/field
|
|
as well as to fetch instances, with a filter across an FK relationship.
|
|
|
|
```python
|
|
track = Track.objects.filter(name="The Bird").get()
|
|
# will return a track with name equal to 'The Bird'
|
|
|
|
tracks = Track.objects.filter(album__name="Fantasies").all()
|
|
# will return all tracks where the columns album name = 'Fantasies'
|
|
```
|
|
|
|
You can use special filter suffix to change the filter operands:
|
|
|
|
* exact - like `album__name__exact='Malibu'` (exact match)
|
|
* iexact - like `album__name__iexact='malibu'` (exact match case insensitive)
|
|
* contains - like `album__name__conatins='Mal'` (sql like)
|
|
* icontains - like `album__name__icontains='mal'` (sql like case insensitive)
|
|
* in - like `album__name__in=['Malibu', 'Barclay']` (sql in)
|
|
* gt - like `position__gt=3` (sql >)
|
|
* gte - like `position__gte=3` (sql >=)
|
|
* lt - like `position__lt=3` (sql <)
|
|
* lte - like `position__lte=3` (sql <=)
|
|
|
|
!!!note
|
|
`filter()`, `select_related()`, `limit()` and `offset()` returns a QueySet instance so you can chain them together.
|
|
|
|
Something like `Track.object.select_related("album").filter(album__name="Malibu").offset(1).limit(1).all()`
|
|
|
|
### exclude
|
|
|
|
### select_related
|
|
|
|
Allows to prefetch related models.
|
|
|
|
To fetch related model use `ForeignKey` names.
|
|
|
|
To chain related `Models` relation use double underscore.
|
|
|
|
```python
|
|
album = await Album.objects.select_related("tracks").all()
|
|
# will return album will all columns tracks
|
|
```
|
|
|
|
You can provide a string or a list of strings
|
|
|
|
```python
|
|
classes = await SchoolClass.objects.select_related(
|
|
["teachers__category", "students"]).all()
|
|
# will return classes with teachers and teachers categories
|
|
# as well as classes students
|
|
```
|
|
|
|
!!!warning
|
|
If you set `ForeignKey` field as not nullable (so required) during
|
|
all queries the not nullable `Models` will be auto prefetched, even if you do not include them in select_related.
|
|
|
|
!!!note
|
|
`filter()`, `select_related()`, `limit()` and `offset()` returns a QueySet instance so you can chain them together.
|
|
|
|
Something like `Track.object.select_related("album").filter(album__name="Malibu").offset(1).limit(1).all()`
|
|
|
|
### limit
|
|
|
|
You can limit the results to desired number of rows.
|
|
|
|
```python
|
|
tracks = await Track.objects.limit(1).all()
|
|
# will return just one Track
|
|
```
|
|
|
|
!!!note
|
|
`filter()`, `select_related()`, `limit()` and `offset()` returns a QueySet instance so you can chain them together.
|
|
|
|
Something like `Track.object.select_related("album").filter(album__name="Malibu").offset(1).limit(1).all()`
|
|
|
|
### offset
|
|
|
|
You can also offset the results by desired number of rows.
|
|
|
|
```python
|
|
tracks = await Track.objects.offset(1).limit(1).all()
|
|
# will return just one Track, but this time the second one
|
|
```
|
|
|
|
### count
|
|
|
|
|
|
### exists
|
|
|
|
### fields
|
|
|
|
|
|
|
|
!!!note
|
|
`filter()`, `select_related()`, `limit()` and `offset()` returns a QueySet instance so you can chain them together.
|
|
|
|
Something like `Track.object.select_related("album").filter(album__name="Malibu").offset(1).limit(1).all()`
|
|
|
|
[models]: ./models.md |