A simple query looks like this
User.query.filter(User.name == 'admin')
In my code, I need to check the parameters that are being passed and then filter the results from the database based on the parameter.
For example, if the User table contains columns like username, location and email, the request parameter can contain either one of them or can have combination of columns. Instead of checking each parameter as shown below and chaining the filter, I'd like to create one dynamic query string which can be passed to one filter and can get the results back. I'd like to create a separate function which will evaluate all parameters and will generate a query string. Once the query string is generated, I can pass that query string object and get the desired result. I want to avoid using RAW SQL query as it defeats the purpose of using ORM.
if location:
User.query.filter(User.name == 'admin', User.location == location)
elif email:
User.query.filter(User.email == email)
You can apply filter to the query repeatedly:
query = User.query
if location:
query = query.filter(User.location == location)
if email:
query = query.filter(User.email == email)
If you only need exact matches, there’s also filter_by:
criteria = {}
# If you already have a dict, there are easier ways to get a subset of its keys
if location: criteria['location'] = location
if email: criteria['email'] = email
query = User.query.filter_by(**criteria)
If you don’t like those for some reason, the best I can offer is this:
from sqlalchemy.sql.expression import and_
def get_query(table, lookups, form_data):
conditions = [
getattr(table, field_name) == form_data[field_name]
for field_name in lookups if form_data[field_name]
]
return table.query.filter(and_(*conditions))
get_query(User, ['location', 'email', ...], form_data)
Late to write an answer but if anyone is looking for the answer then sqlalchemy-json-querybuilder can be useful. It can be installed as -
pip install sqlalchemy-json-querybuilder
e.g.
filter_by = [{
"field_name": "SomeModel.field1",
"field_value": "somevalue",
"operator": "contains"
}]
order_by = ['-SomeModel.field2']
results = Search(session, "pkg.models", (SomeModel,), filter_by=filter_by,order_by=order_by, page=1, per_page=5).results
https://github.com/kolypto/py-mongosql/
MongoSQL is a query builder that uses JSON as the input.
Capable of:
Choosing which columns to load
Loading relationships
Filtering using complex conditions
Ordering
Pagination
Example:
{
project: ['id', 'name'], // Only fetch these columns
sort: ['age+'], // Sort by age, ascending
filter: {
// Filter condition
sex: 'female', // Girls
age: { $gte: 18 }, // Age >= 18
},
join: ['user_profile'], // Load the 'user_profile' relationship
limit: 100, // Display 100 per page
skip: 10, // Skip first 10 rows
}
Related
Using Graphene in Django to create Gql schema, now trying to filter Foreign Keys with list of strings. It kinda works, but not exactly.
schema.py
class CharInFilter(BaseInFilter, CharFilter):
pass
class ProductFilter(FilterSet):
softwares__name = CharInFilter(field_name="softwares__name", lookup_expr="in")
class Meta:
model = Product
fields = {"name": ["exact", "icontains"]}
class ProductType(DjangoObjectType):
class Meta:
model = Product
filterset_class = ProductFilter
interfaces = (graphene.relay.Node,)
query
query authorPageProducts {
user(slug: "john") {
productSet(softwares_Name: "Blender") {
edges {
node {
name
softwares {
name
}
}
}
}
}
}
Here is what works and what not:
softwares_Name: "Blender" -> correct
softwares_Name: "Houdini" -> correct
softwares_Name: "Blender,Houdini" -> empty result, not correct
I am passing string separated with comma. Can/should I pass list of strings in Gql query? Im not sure if its possible/necessary.
I do have Products that have both Foreign Keys with values "Houdini" and "Blender", so query with "Blender,Houdini" shouldn't be empty.
I tried this query in shell, and its correct. Here I used list of strings.
u = User.objects.get(id=2)
p = u.product_set.filter(softwares__name__in=["Blender", "Houdini"])
Here is some info from Django Debug Toolbar, to see SQL expression for third case.
SELECT COUNT(*) AS "__count"
FROM "shop_product"
INNER JOIN "shop_product_softwares"
ON ("shop_product"."id" = "shop_product_softwares"."product_id")
INNER JOIN "shop_software"
ON ("shop_product_softwares"."software_id" = "shop_software"."id")
WHERE ("shop_product"."author_id" = 2 AND "shop_software"."name" IN ('Blender,Houdini'))
I cannot figure out where is the issue, while querying with comma separated string, as docs suggest.
Thank you
I am asking for a suggestion abount how to detect which filters are being used by the user, a filtering system can have different options to get the data, but using if statements to check if a value comes in a POST and then add it to a filters set is not really a good option specially when there a lot of them.
# Some if statements detecting if a filter is used (if it is not null in the POST)
# Adding the filter to filters
filters = {
# filters after being added
'{}__{}'.format('categories', 'exact'): request.POST['category'],
'{}__{}'.format('price', 'gte'): request.POST['price'], # Only an example
}
products = Product.objects.filter(**filters)
This works, but i just want to know what would you recommend.
If I understood your question correctly, I would chain filters instead:
queryset = Product.objects.all()
if 'category' in request.POST:
queryset.filter(categories__exact=request.POST['category'])
if 'price' in request.POST:
queryset.filter(price__gte=request.POST['price'])
To expand on Gasanov's suggestion:
possible_filters = {
'category': 'exact',
'price': 'gte',
# etc. Not sure if this can be done any smarter
# maybe if you pass `cateogry__exact` in the POST data instead of just `category`?
}
queryset = Product.objects.all()
for key, val in request.POST.items():
if key in possible_filters:
filter_kwargs = {
f'{key}__{possible_filters[key]}': val,
}
queryset = queryset.filter(**filter_kwargs)
Or you can build up the kwargs and have a single call to filter. Unless you are filtering over reverse FK relationships or M2M relationships, the two are pretty much the same (docs for when they are not the same are here)
filter_kwargs = {}
for key, val in request.POST.items():
if key in possible_filters:
filter_key = f'{key}__{possible_filters[key]}'
filter_kwargs[filter_key] = val
queryset = queryset.filter(**filter_kwargs)
I am trying to use map/reduce to find the duplication of the data in couchDB
the map function is like this:
function(doc) {
if(doc.coordinates) {
emit({
twitter_id: doc.id_str,
text: doc.text,
coordinates: doc.coordinates
},1)};
}
}
and the reduce function is:
function(keys,values,rereduce){return sum(values)}
I want to find the sum of the data in the same key, but it just add everything together and I get the result:
<Row key=None, value=1035>
Is that a problem of group? How can I set it to true?
Assuming you're using the couchdb package from pypi, you'll need to pass a dictionary with all of the options you require to the view.
for example:
import couchdb
# the design doc and view name of the view you want to use
ddoc = "my_design_document"
view_name = "my_view"
#your server
server = couchdb.server("http://localhost:5984")
db = server["aCouchDatabase"]
#naming convention when passing a ddoc and view to the view method
view_string = ddoc +"/" + view_name
#query options
view_options = {"reduce": True,
"group" : True,
"group_level" : 2}
#call the view
results = db.view(view_string, view_options)
for row in results:
#do something
pass
I'm trying to implement dynamic filtering using SQLAlchemy ORM.
I was looking through StackOverflow and found very similar question:SQLALchemy dynamic filter_by
It's useful for me, but not enough.
So, here is some example of code, I'm trying to write:
# engine - MySQL engine
session_maker = sessionmaker(bind=engine)
session = session_maker()
# my custom model
model = User
def get_query(session, filters):
if type(filters) == tuple:
query = session.query(model).filter(*filters)
elif type(filters) == dict:
query = session.query(model).filter(**filters)
return query
then I'm trying to reuse it with something very similar:
filters = (User.name == 'Johny')
get_query(s, filters) # it works just fine
filters = {'name': 'Johny'}
get_query(s, filters)
After the second run, there are some issues:
TypeError: filter() got an unexpected keyword argument 'name'
When I'm trying to change my filters to:
filters = {User.name: 'Johny'}
it returns:
TypeError: filter() keywords must be strings
But it works fine for manual querying:
s.query(User).filter(User.name == 'Johny')
What is wrong with my filters?
BTW, it looks like it works fine for case:
filters = {'name':'Johny'}
s.query(User).filter_by(**filters)
But following the recommendations from mentioned post I'm trying to use just filter.
If it's just one possible to use filter_by instead of filter, is there any differences between these two methods?
Your problem is that filter_by takes keyword arguments, but filter takes expressions. So expanding a dict for filter_by **mydict will work. With filter, you normally pass it one argument, which happens to be an expression. So when you expand your **filters dict to filter, you pass filter a bunch of keyword arguments that it doesn't understand.
If you want to build up a set of filters from a dict of stored filter args, you can use the generative nature of the query to keep applying filters. For example:
# assuming a model class, User, with attributes, name_last, name_first
my_filters = {'name_last':'Duncan', 'name_first':'Iain'}
query = session.query(User)
for attr,value in my_filters.iteritems():
query = query.filter( getattr(User,attr)==value )
# now we can run the query
results = query.all()
The great thing about the above pattern is you can use it across multiple joined columns, you can construct 'ands' and 'ors' with and_ and or_, you can do <= or date comparisons, whatever. It's much more flexible than using filter_by with keywords. The only caveat is that for joins you have to be a bit careful you don't accidentally try to join a table twice, and you might have to specify the join condition for complex filtering. I use this in some very complex filtering over a pretty involved domain model and it works like a charm, I just keep a dict going of entities_joined to keep track of the joins.
I have a similar issue, tried to filter from a dictionary:
filters = {"field": "value"}
Wrong:
...query(MyModel).filter(**filters).all()
Good:
...query(MyModel).filter_by(**filters).all()
FWIW, There's a Python library designed to solve this exact problem: sqlalchemy-filters
It allows to dynamically filter using all operators, not only ==.
from sqlalchemy_filters import apply_filters
# `query` should be a SQLAlchemy query object
filter_spec = [{'field': 'name', 'op': '==', 'value': 'name_1'}]
filtered_query = apply_filters(query, filter_spec)
more_filters = [{'field': 'foo_id', 'op': 'is_not_null'}]
filtered_query = apply_filters(filtered_query, more_filters)
result = filtered_query.all()
For the people using FastAPI and SQLAlchemy, here is a example of dynamic filtering:
api/app/app/crud/order.py
from typing import Optional
from pydantic import UUID4
from sqlalchemy.orm import Session
from app.crud.base import CRUDBase
from app.models.order import Order
from app.schemas.order import OrderCreate, OrderUpdate
class CRUDOrder(CRUDBase[Order, OrderCreate, OrderUpdate]):
def get_orders(
self,
db: Session,
owner_id: UUID4,
status: str,
trading_type: str,
pair: str,
skip: int = 0,
limit: int = 100,
) -> Optional[Order]:
filters = {
arg: value
for arg, value in locals().items()
if arg != "self" and arg != "db" and arg != "skip" and arg != "limit" and value is not None
}
query = db.query(self.model)
for attr, value in filters.items():
query = query.filter(getattr(self.model, attr) == value)
return (
query
.offset(skip)
.limit(limit)
.all()
)
order = CRUDOrder(Order)
class Place(db.Model):
id = db.Column(db.Integer, primary_key=True)
search_id = db.Column(db.Integer, db.ForeignKey('search.id'), nullable=False)
#classmethod
def dynamic_filter(model_class, filter_condition):
'''
Return filtered queryset based on condition.
:param query: takes query
:param filter_condition: Its a list, ie: [(key,operator,value)]
operator list:
eq for ==
lt for <
ge for >=
in for in_
like for like
value could be list or a string
:return: queryset
'''
__query = db.session.query(model_class)
for raw in filter_condition:
try:
key, op, value = raw
except ValueError:
raise Exception('Invalid filter: %s' % raw)
column = getattr(model_class, key, None)
if not column:
raise Exception('Invalid filter column: %s' % key)
if op == 'in':
if isinstance(value, list):
filt = column.in_(value)
else:
filt = column.in_(value.split(','))
else:
try:
attr = list(filter(lambda e: hasattr(column, e % op), ['%s', '%s_', '__%s__']))[0] % op
except IndexError:
raise Exception('Invalid filter operator: %s' % op)
if value == 'null':
value = None
filt = getattr(column, attr)(value)
__query = __query.filter(filt)
return __query
Execute like:
places = Place.dynamic_filter([('search_id', 'eq', 1)]).all()
For Example.. In Mongodb..
> db.test.findOne({}, {'mapField.FREE':1})
{
"_id" : ObjectId("4fb7b248c450190a2000006a"),
"mapField" : {
"BOXFLUX" : {
"a" : "f",
}
}
}
The 'mapField' field is made of MapField of Mongoengine.
and 'mapField' field has a log of key and data.. but I just retrieved only 'BOXFLUX'..
this query is not working in MongoEngine....
for example..
BoxfluxDocument.objects( ~~ querying ~~ ).only('mapField.BOXFLUX')
AS you can see..
only('mapField.BOXFLUX') or only only('mapField__BOXFLUX') does not work.
it retrieves all 'mapField' data, including 'BOXFLUX' one..
How can I retrieve only a field of MapField???
I see there is a ticket for this: https://github.com/hmarr/mongoengine/issues/508
Works for me heres an example test case:
def test_only_with_mapfields(self):
class BlogPost(Document):
content = StringField()
author = MapField(field=StringField())
BlogPost.drop_collection()
post = BlogPost(content='Had a good coffee today...',
author={'name': "Ross", "age": "20"}).save()
obj = BlogPost.objects.only('author__name',).get()
self.assertEquals(obj.author['name'], "Ross")
self.assertEquals(obj.author.get("age", None), None)
Try this:
query = BlogPost.objects({your: query})
if name:
query = query.only('author__'+name)
else:
query = query.only('author')
I found my fault! I used only twice.
For example:
BlogPost.objects.only('author').only('author__name')
I spent a whole day finding out what is wrong with Mongoengine.
So my wrong conclusion was:
BlogPost.objects()._collection.find_one(~~ filtering query ~~, {'author.'+ name:1})
But as you know it's a just raw data not a mongoengine query.
After this code, I cannot run any mongoengine methods.
In my case, I should have to query depending on some conditions.
so it will be great that 'only' method overwrites 'only' methods written before.. In my humble opinion.
I hope this feature would be integrated with next version. Right now, I have to code duplicate code:
not this code:
query = BlogPost.objects()
query( query~~).only('author')
if name:
query = query.only('author__'+name)
This code:
query = BlogPost.objects()
query( query~~).only('author')
if name:
query = BlogPost.objects().only('author__'+name)
So I think the second one looks dirtier than first one.
of course, the first code shows you all the data
using only('author') not only('author__name')