Could not find anything on this-- seems like it should be straight forward though.
So the example the Doctrine2 docs give for type conversion on bound parameters looks like this:
$date = new \DateTime("2011-03-05 14:00:21");
$stmt = $conn->prepare("SELECT * FROM articles WHERE publish_date > ?");
$stmt->bindValue(1, $date, "datetime");
$stmt->execute();
What I want to do is specify the type conversion for one of the columns, but there is nothing in the documents or on StackOverflow that I could find. A pseudo-example of what this might look like:
$stmt = $conn -> prepare("SELECT datetime FROM articles WHERE id = 1");
$stmt -> setType(0, "date_type"); // 0 being the column position, "date_type" being the PHP type to convert to
If anybody knows how to do this, (this is SQL not DQL), I would greatly appreciate. Thank you.
This is not something that works at DBAL level. If you are using NativeSQL Queries in ORM, you can get that kind of conversion through hydration (see the NativeSQL section in the Doctrine ORM documentation) by using the HYDRATE_ARRAY mode and mapping some of the fetched fields to an entity. The fastest solution (if you don't intend to use ORM) is to iterate over the results and applying the type conversion manually by accessing Doctrine\DBAL\Types\Type::getType($someType)->convertToPhpValue($fetchedValue). It could be a valuable addition to ORM to be able to specify a third parameter stating the fetched type in Doctrine\ORM\Query\ResultSetMapping#addScalarResult.
Related
To optimize a lot my database I would like to make as less as possible any query.
I'm trying to get an object, increment the field "count_limit" and make an If statement after on the Customer instance.
To achieve it I've made this query who worked well.
Customer.objects.filter(user=user).update(count_limit=F('count_limit') + 1)
So after this query, count_limit has been incremented by 1 as I wanted.
When I'm trying to get the Customer instance as a result of this query, it returns "1".
Is it possible to make both, update the instance and get it as a return object ?
Thanks a lot
The update() method will return the number of updated rows. If you are using Postgres, then you can use the returning clause with the raw query.
query = 'UPDATE customer SET count_limit=(customer.count_limit + 1) WHERE customer.user_id=%s returning *'
updated_obj = Customer.objects.raw(query, [user.id])
I don't know if this can be achieved by ORM, but suggestions will be appreciated.
Make sure that the table name in raw query is correct. If you haven't definer db_table in the meta class of your model, then by default it will be myapp_model.
And to prevent SQL injection, from the Docs:
Do not use string formatting on raw queries or quote placeholders in
your SQL strings!
Follow Docs on raw()
You are looking for F functions: https://docs.djangoproject.com/en/3.0/ref/models/expressions/#f-expressions
Example from their documentation how to increase a counter
from django.db.models import F
reporter = Reporters.objects.get(name='Tintin')
reporter.stories_filed = F('stories_filed') + 1
reporter.save()
I have a rather complex query that's generating a Django RawQuerySet. This specific query returns some fields that aren't part of the model that the RawQuerySet is based on, so I'm using .annotate(field_name=models.Value('field_name')) to attach it as an attribute to individual records in the RawQuerySet. The most important custom field is actually a uuid, which I use to compose URLs using Django's {% url %} functionality.
Here's the problem: I'm not using standard uuids inside my app, I'm using SmallUUIDs (compressed UUIDs.) These are stored in the database as native uuidfields then converted to shorter strings in python. So I need to somehow convert the uuid returned as part of the RawQuerySet to a SmallUUID for use inside a template to generate a URL.
My code looks somewhat like this:
query = "SELECT othertable.uuid_field as my_uuid FROM myapp_mymodel
JOIN othertable o ON myapp_mymodel.x = othertable.x"
MyModel.objects.annotate(
my_uuid=models.Value('my_uuid'),
).raw(query)
Now there is a logical solution here, there's an optional kwarg for models.Value called output_field, making the code look like this:
MyModel.objects.annotate(
my_uuid=models.Value('my_uuid', output_field=SmallUUIDField()),
).raw(query)
But it doesn't work! That kwarg is completely ignored and the type of the attribute is based on the type returned from the database and not what's in output_field. In my case, I'm getting a uuid output because Postgres is returning a UUID type, but if I were to change the query to SELECT cast othertable.uuid_field as text) as my_uuid I'd get the attribute in the format of a string. It appears that Django (at least version 1.11.12) doesn't actually care what is in that kwarg in this instance.
So here's what I'm thinking are my potential solutions, in no particular order:
Change the way the query is formatted somehow (either in Django or in the SQL)
Change the resulting RawQuerySet in some way before it's passed to the view
Change something inside the templates to convert the UUID to a smalluuid for use in the URL reverse process.
What's my best next steps here?
A couple of issues with your current approach:
Value() isn't doing what you think it is - your annotation is literally just annotating each row with the value "my_uuid" because that is what you have passed to it. It isn't looking up the field of that name (to do that you need to use F expressions).
Point 1 above doesn't matter anyway because as soon as you use raw() then the annotation is ignored - which is why you see no effect coming from it.
Bottom line is that trying to annotate a RawQuerySet isn't going to be easy. There is a translations argument that it accepts, but I can't think of a way to get that to work with the type of join you are using.
The next best suggestion that I can think of is that you just manually convert the field into a SmallUUID object when you need it - something like this:
from smalluuid import SmallUUID
objects = MyModel.objects.raw(query)
for o in objects:
# Take the hex string obtained from the database and convert it to a SmallUUID object.
# If your database has a built-in UUID type you will need to do
# SmallUUID(small=o.my_uuid) instead.
my_uuid = SmallUUID(hex=o.my_uuid)
(I'm doing this in a loop just to illustrate - depending on where you need this you can do it in a template tag or view).
I want to retrieve all records with shelfId=1 and between two dates. I wrote a query like this in my webservice Its not working. can anyone please correct this one.
#NamedQuery(name = "BinEnvironment.BinEnvironmentByStartDateEndDate", query = "SELECT b FROM BinEnvironment b where shelfId ='?1' and dateTime between '1?' and '?2'")
Reply as soon as possible
Regards
Hema
There is a problem with your parameter declaration: you are trying to use the same param for shelfId and dateTime.
The declaration of parameters for the between case shoudl probably be between '?2' and '?3.
Please note the correct syntax (use ?1 instead of 1?):
Input parameters are designated by the question mark (?) prefix followed by an integer. For example: ?1.
I have a class Image with the following GenericRelation:
properties = models.GenericRelation(Property)
I'm trying to get all Images with certain properties, so I do this:
Image.objects.filter(properties__type = "foo", properties__user = request.user)
But this results in the following error:
DatabaseError: operator does not exist: integer = text
LINE 1: ...perties_property" ON ("myapp_image"."id" = "propert...
^
HINT: No operator matches the given name and argument type(s). You might need to add explicit type casts.
Is it not possible to query that way? What can I do as an alternative?
If you need to do very complex queries over generic relations, then i would rather suggest you write the sql yourself and use raw queries rather. So i guess i would say raw query is an alternative.
I have a simple query on django's built in comments model and getting the error below with heroku's postgreSQL database:
DatabaseError: operator does not exist: integer = text LINE 1:
... INNER JOIN "django_comments" ON ("pi ns_pin"."id" = "django_...
^
HINT: No operator matches the given name and argument type(s).
You might need to add explicit type casts.
After googling around it seems this error has been addressed many times before in django, but I'm still getting it (all related issues were closed 3-5 years ago) . I am using django version 1.4 and the latest build of tastypie.
The query is made under orm filters and works perfectly with my development database (sqlite3):
class MyResource(ModelResource):
comments = fields.ToManyField('my.api.api.CmntResource', 'comments', full=True, null=True)
def build_filters(self, filters=None):
if filters is None:
filters = {}
orm_filters = super(MyResource, self).build_filters(filters)
if 'cmnts' in filters:
orm_filters['comments__user__id__exact'] = filters['cmnts']
class CmntResource(ModelResource):
user = fields.ToOneField('my.api.api.UserResource', 'user', full=True)
site_id = fields.CharField(attribute = 'site_id')
content_object = GenericForeignKeyField({
My: MyResource,
}, 'content_object')
username = fields.CharField(attribute = 'user__username', null=True)
user_id = fields.CharField(attribute = 'user__id', null=True)
Anybody have any experience with getting around this error without writing raw SQL?
PostgreSQL is "strongly typed" - that is, every value in every query has a particular type, either defined explicitly (e.g. the type of a column in a table) or implicitly (e.g. the values input into a WHERE clause). All functions and operators, including =, have to be defined as accepting specific types - so, for instance there is an operator for VarChar = VarChar, and a different one for int = int.
In your case, you have a column which is explicitly defined as type int, but you are comparing it against a value which PostgreSQL has interpreted as type text.
SQLite, on the other hand, is "weakly typed" - values are freely treated as being of whatever type best suits the action being performed. So in your dev SQLite database the operation '42' = 42 can be computed just fine, where PostgreSQL would need a specific definition of VarChar = int (or text = int, text being the type for unbounded strings in PostgreSQL).
Now, PostgreSQL will sometimes be helpful and automatically "cast" your values to make the types match a known operator, but more often, as the hint says, you need to do it explicitly. If you were writing the SQL yourself, an explicit type case could look like WHERE id = CAST('42' AS INT) (or WHERE CAST(id AS text) = '42').
Since you're not, you need to ensure that the input you give to the query generator is an actual integer, not just a string which happens to consist of digits. I suspect this is as simple as using fields.IntegerField rather than fields.CharField, but I don't actually know Django, or even Python, so I thought I'd give you the background in the hope you can take it from there.
Building on IMSoP's answer: This is a limitation of django's ORM layer when a Generic foreign key uses a text field for the object_id and the object's id field is not a text field. Django does not want to make any assumptions or cast the object's id as something it's not. I found an excellent article on this http://charlesleifer.com/blog/working-around-django-s-orm-to-do-interesting-things-with-gfks/.
The author of the article, Charles Leifer came up with a very cool solution for query's that are affected by this and will be very useful in dealing with this issue moving forward.
Alternatively, i managed to get my query to work as follows:
if 'cmnts' in filters:
comments = Comment.objects.filter(user__id=filters['cmnts'], content_type__name = 'my', site_id=settings.SITE_ID ).values_list('object_pk', flat=True)
comments = [int(c) for c in comments]
orm_filters['pk__in'] = comments
Originally i was searching for a way to modify the SQL similar to what Charles has done, but it turns out all i had to do was break the query out into two parts and convert the str(id)'s to int(id)'s.
To do not hack you ORM and external software postgres allow you register your own casts and compare operations. Please look example in similar question.