when i update my serverdata by using session db,
db_post = deb.query(models.Post).filter(models.Post.id === post.id).first()
db_post.likes.append(email)
setattr(db_post,"likes",db_post_likes)
db.add(db_post)
db.commit()
db.refresh(db_post)
return db_post
then it is not updated db_post_likes,
but when i use below code it works with out append
db_post = deb.query(models.Post).filter(models.Post.id === post.id).first()
setattr(db_post,"likes",db_post_likes + [email])
db.add(db_post)
db.commit()
db.refresh(db_post)
return db_post
the problem is append can be skipped upper code, but remove is also problem
how can i fix this?
now i know.
list.append or list.remove not return event.
so sqlalchemy session can not detect changed
so sqlalchemy recommned to use MutableList
and now it works
Related
I have a SQLAlchemy query that I build, such as :
query_one = User.query.filter(User.id == 1) # Note that I don't call .first() or .all() as I want the "select" instance.
I want to store this Select query in such a way that I can retrieve it by having the same query :
stored_queries = {}
stored_queries[hash(query_one)] = query_one
# ... later on:
query_two = User.query.filter(User.id == 1)
if hash(query_two) in stored_queries:
# Execute custom code because it's the same query
Of course, hash in that case does not work, but is there a SQLAlchemy method that works in the same way?
I thought of str(query_one), but that query only consider the request, without the value. I need both.
Thank you in advance.
You can compile the query to get access to the parameters, and use those as part of your key:
def query_key(query):
statement = query_one.statement.compile()
return str(statement), str(statement.params)
query_key(query_one)
('SELECT user.id, ... FROM user WHERE user.id = :id_1', "{'id_1': 1}")
See https://docs.sqlalchemy.org/en/14/core/selectable.html#sqlalchemy.sql.expression.TableClause.compile
I am working on a discord bot written in nodejs, the bot utilises a mysql database server to store information. The problem I have run into is that I cannot seem to retrieve the data from the database in a neat way, every single thing I try seems to run into some issue or another.
The select query returns an object called RowDataPacket. When googling every single result will reference this solution: Object.values(JSON.parse(JSON.stringify(rows)))
It postulates that I should get the values back, but I dont I get an array back that is as hard to work with as the rowdatapacket object.
This is a snippet of my code:
const kenneledMemberRolesTableName = 'kenneled_member_roles'
const kenneledMemberKey = 'kenneled_member'
const kenneledMemberRoleKey = 'kenneled_member_role_id'
const kenneledStaffMemberKey = 'kenneled_staff_member'
const kenneledDateKey = 'kenneled_date'
const kenneledReturnableRoleKey = 'kenneled_role_can_be_returned'
async function findKenneledMemberRoles(kenneledMemberId) {
let sql = `SELECT CAST(${kenneledMemberRoleKey} AS Char) FROM ${kenneledMemberRolesTableName} WHERE ${kenneledMemberKey} = ${kenneledMemberId}`
let rows = await databaseAccessor.runQuery(sql)
let result = JSON.parse(JSON.stringify(rows)).map(row => {
return row.kenneled_member_role_id
})
return result
}
This seemed to work, until I had to do a type conversion on the value, now the dot notations requires me to reference row.CAST(kenneled_member_role_id AS Char), this cannot work, and I have found no other way to retrieve the data than through dot notation. I swear there must be a better way to work with mysql rowdatapackets but the solution eludes me
I figured out something that works, however I still feel like this is an inelegant solution, I would love to hear from others if I am misunderstanding how to work with mysql code in nodejs, or if this is just a consequence of the library:
let result = JSON.parse(JSON.stringify(rows)).map(row => {
return row[`CAST(${kenneledMemberRoleKey} AS CHAR)`];
})
So what I did is I access the value through brackets instead of dot notation, this seems to work, and at least makes me able to store part of or the whole expression in a constant variable, hiding the ugliness.
I have a model that saves reports in binary fields for archiving. To do that I use the pdf_get().
document = self.env['report'].sudo().get_pdf(ids, report_name)
The problem is when I want to create a report that doesn't use the models fields but has to compute values from related models with the model that is pass with ids.
My report model
class ReportHistory(models.AbstractModel):
_name = 'report.hr.report_history'
def _get_report(self, ids[0]):
record = self.env['hr.history'].search([('id', '=', ids[0])])
return record
def _get_company(self, ids):
rec = self._get_report(ids)
if len(rec) > 0:
return rec[0].company_name
My biggest problem is that I can't debug so I can't what data is passed. The print or logger or raise ValidationError won't work. Probably due to running odoo on windows pc.
Every answer that I found it was said to pass values to report like this but it doesn't work.
#api.model
def render_html(self, docids, data=None):
docargs =
'doc_ids': self.ids,
'doc_model': self.model,
'data': data,
'company': self._get_company,
}
return self.env['report'].render()
So how to correctly pass values from methods to report? Or did I only do a dumb mistake?
Try this:
return self.env['report'].render(report_name, docargs)
I'd like to update a table with Django - something like this in raw SQL:
update tbl_name set name = 'foo' where name = 'bar'
My first result is something like this - but that's nasty, isn't it?
list = ModelClass.objects.filter(name = 'bar')
for obj in list:
obj.name = 'foo'
obj.save()
Is there a more elegant way?
Update:
Django 2.2 version now has a bulk_update.
Old answer:
Refer to the following django documentation section
Updating multiple objects at once
In short you should be able to use:
ModelClass.objects.filter(name='bar').update(name="foo")
You can also use F objects to do things like incrementing rows:
from django.db.models import F
Entry.objects.all().update(n_pingbacks=F('n_pingbacks') + 1)
See the documentation.
However, note that:
This won't use ModelClass.save method (so if you have some logic inside it won't be triggered).
No django signals will be emitted.
You can't perform an .update() on a sliced QuerySet, it must be on an original QuerySet so you'll need to lean on the .filter() and .exclude() methods.
Consider using django-bulk-update found here on GitHub.
Install: pip install django-bulk-update
Implement: (code taken directly from projects ReadMe file)
from bulk_update.helper import bulk_update
random_names = ['Walter', 'The Dude', 'Donny', 'Jesus']
people = Person.objects.all()
for person in people:
r = random.randrange(4)
person.name = random_names[r]
bulk_update(people) # updates all columns using the default db
Update: As Marc points out in the comments this is not suitable for updating thousands of rows at once. Though it is suitable for smaller batches 10's to 100's. The size of the batch that is right for you depends on your CPU and query complexity. This tool is more like a wheel barrow than a dump truck.
Django 2.2 version now has a bulk_update method (release notes).
https://docs.djangoproject.com/en/stable/ref/models/querysets/#bulk-update
Example:
# get a pk: record dictionary of existing records
updates = YourModel.objects.filter(...).in_bulk()
....
# do something with the updates dict
....
if hasattr(YourModel.objects, 'bulk_update') and updates:
# Use the new method
YourModel.objects.bulk_update(updates.values(), [list the fields to update], batch_size=100)
else:
# The old & slow way
with transaction.atomic():
for obj in updates.values():
obj.save(update_fields=[list the fields to update])
If you want to set the same value on a collection of rows, you can use the update() method combined with any query term to update all rows in one query:
some_list = ModelClass.objects.filter(some condition).values('id')
ModelClass.objects.filter(pk__in=some_list).update(foo=bar)
If you want to update a collection of rows with different values depending on some condition, you can in best case batch the updates according to values. Let's say you have 1000 rows where you want to set a column to one of X values, then you could prepare the batches beforehand and then only run X update-queries (each essentially having the form of the first example above) + the initial SELECT-query.
If every row requires a unique value there is no way to avoid one query per update. Perhaps look into other architectures like CQRS/Event sourcing if you need performance in this latter case.
Here is a useful content which i found in internet regarding the above question
https://www.sankalpjonna.com/learn-django/running-a-bulk-update-with-django
The inefficient way
model_qs= ModelClass.objects.filter(name = 'bar')
for obj in model_qs:
obj.name = 'foo'
obj.save()
The efficient way
ModelClass.objects.filter(name = 'bar').update(name="foo") # for single value 'foo' or add loop
Using bulk_update
update_list = []
model_qs= ModelClass.objects.filter(name = 'bar')
for model_obj in model_qs:
model_obj.name = "foo" # Or what ever the value is for simplicty im providing foo only
update_list.append(model_obj)
ModelClass.objects.bulk_update(update_list,['name'])
Using an atomic transaction
from django.db import transaction
with transaction.atomic():
model_qs = ModelClass.objects.filter(name = 'bar')
for obj in model_qs:
ModelClass.objects.filter(name = 'bar').update(name="foo")
Any Up Votes ? Thanks in advance : Thank you for keep an attention ;)
To update with same value we can simply use this
ModelClass.objects.filter(name = 'bar').update(name='foo')
To update with different values
ob_list = ModelClass.objects.filter(name = 'bar')
obj_to_be_update = []
for obj in obj_list:
obj.name = "Dear "+obj.name
obj_to_be_update.append(obj)
ModelClass.objects.bulk_update(obj_to_be_update, ['name'], batch_size=1000)
It won't trigger save signal every time instead we keep all the objects to be updated on the list and trigger update signal at once.
IT returns number of objects are updated in table.
update_counts = ModelClass.objects.filter(name='bar').update(name="foo")
You can refer this link to get more information on bulk update and create.
Bulk update and Create
I have in MySQL database table containing "tasks". Each task have flag (if it's taken or not).
And now for example 3 threads do:
query_base = session.query(PredykcjaRow).filter(
PredykcjaRow.predyktor == predictor,
PredykcjaRow.czy_wziete == False
)
query_disprot = query_base.join(NieustrRow, NieustrRow.fastaId == PredykcjaRow.fastaId)
query_pdb = query_base.join(RawBialkoRow, RawBialkoRow.fasta_id == PredykcjaRow.fastaId)
response = query_pdb.union(query_disprot)
response = response.with_for_update()
response = response.first()
if response is None:
return None
response.czy_wziete = True
try:
session.commit()
return response
except:
return None
each thread have own session (ScopedSession) but all 3 threads get the same object.
In configuration
tx_isolation..... REPEATABLE-READ
Assuming the scoped session is created like this:
Session = scoped_session(sessionmaker(bind=engine))
Make sure you aren't doing this
session = Session()
give_to_thread1(session)
give_to_thread2(session)
With a scoped session, you can use it directly, e.g.
Session.query(...)
So your threads should do this:
def runs_in_thread():
Session.add(...)
# or
session = Session()
session.add(...)
The problem is union statement. MySQL does not provide accumulative SELECTS with FOR UPDATE - it execute without warning, but row is not locked.
I found this information in official documentation but now I can't. If anyone can, please post comment.