I've been trying to debug why the last_updated field in several of my models wasn't being updated when doing eg model.objects.filter(**lookups).update(**defaults) with eg:
class PaymentMethod(models.Model):
MONTHLY_DIRECT_DEBIT = 'MDD'
QUARTERLY_DIRECT_DEBIT = 'QDD'
CASH_OR_CHEQUE = 'CAC'
PAY_IN_ADVANCE = 'PYM'
PAYMENT_CHOICES = (
(MONTHLY_DIRECT_DEBIT, 'Monthly Direct Debit'),
(QUARTERLY_DIRECT_DEBIT, 'Quarterly Direct Debit'),
(CASH_OR_CHEQUE, 'Cash or Cheque'),
(PAY_IN_ADVANCE, 'Pay Monthly in Advance'),
)
unique_id = models.CharField(max_length=3, choices=PAYMENT_CHOICES)
last_updated = models.DateTimeField(auto_now=True)
def __str__(self):
Here I am just trying to update a single entry and don't need to load the instance into memory. This seems to be a won't fix 'bug' explained in docshttps://code.djangoproject.com/ticket/15566 (for some reason I can't see it in the docs).
However, what is the best way to update a single row including the last_updated field (without needing to load into memory)?
It doesn't work as posted in this issue (declared as won't fix) https://code.djangoproject.com/ticket/22981
.update() will only update the fields explicitly passed to it, so datetimefields with auto_now =True aren't updated.
I know the documented behavior is that .update() will ignore updating auto_now[_add] fields as is also confirmed by Yunti's answer. However, for those who wish to force the desired effect - for example, having an auto_now field updated as part of an .update() invocation, the following approach seems to work...
update(field1=val1, field2=val2,..., last_update=datetime.now())
Where last_update is a models.DateTime type field with (or without) auto_now=True. However, note that if you pass some other value to this field other than now() - the current timestamp that is, the ORM doesn't help in correcting this to the current timestamp (which is what the auto_now flag semantics imply). So, for example, in the following snippet, the last_update field does get overridden with the specified timestamp, irrespective of whether it's past, present or future...
update(field1=val1, field2=val2,..., last_update=datetime.strptime('Jun 1 2005 1:33PM', '%b %d %Y %I:%M%p'))
So, if you wish to enforce the standard semantics of auto_now when making your calls to update(), ensure to correctly pass the current timestamp as the update value to these fields. You are doing it manually (due to a flaw/deficiency in the Django ORM implementation), but you are doing it correctly thus.
Related
I am trying to query if a certain date belongs to a specific range of dates. Source code example:
billing_period_found = BillingPeriod.query(
ndb.AND(
transaction.date > BillingPeriod.start_date,
transaction.date < BillingPeriod.end_date)
).get()
Data definition:
class Transaction(ndb.Model):
date = ndb.DateProperty(required=False)
class BillingPeriod(ndb.Model):
start_date = ndb.DateProperty(required=False)
end_date = ndb.DateProperty(required=False)
Getting the following error:
TypeError: can't compare datetime.date to DateProperty
The message error does make sense because datetime is different from DateProperty. However, as you can see, the definition for transaction.date is not datetime, so I am not getting where this attempt to convert datetime to date is coming from. Anyways - If I figure out how to convert datetime to DateProperty, I guess it would fix the problem.
Any ideas on how to solve this?
Thanks!
The App Engine datastore does not allow queries with inequalities on multiple properties (not a limitation of ndb, but of the underlying datastore). Selecting date-range entities that contain a certain date is a typical example of tasks that this makes it impossible to achieve in a single query.
Check out Optimizing a inequality query in ndb over two properties for an example of this question, and, in the answer, one suggestion that might work: query for (in your case) all BillingPeriod entities with end_date greater than the desired date, perhaps with a projection to just get their key and start_date; then, select out of those only those with start_date less than the desired date, in your own application (if you only want one of them, then a next over the iterator will stop as soon as it finds one).
Edit: the issue above is problem #1 with this code; once solved, problem #2 arises -- as clearly listed at https://cloud.google.com/appengine/docs/python/ndb/queries, the property is ndb queries is always on the left of the comparison operator. So, one can't do date < BillingPeriod.end_date, as that would have the property on the right; rather, one does BillingPeriod.end_date > date.
I am working currently on telecom analytics project and newbie in query optimisation. To show result in browser it takes a full minute while just 45,000 records are to be accessed. Could you please suggest on ways to reduce time for showing results.
I wrote following query to find call-duration of a person of age-group:
sigma=0
popn=len(Demo.objects.filter(age_group=age))
card_list=[Demo.objects.filter(age_group=age)[i].card_no
for i in range(popn)]
for card in card_list:
dic=Fact_table.objects.filter(card_no=card.aggregate(Sum('duration'))
sigma+=dic['duration__sum']
avgDur=sigma/popn
Above code is within for loop to iterate over age-groups.
Model is as follows:
class Demo(models.Model):
card_no=models.CharField(max_length=20,primary_key=True)
gender=models.IntegerField()
age=models.IntegerField()
age_group=models.IntegerField()
class Fact_table(models.Model):
pri_key=models.BigIntegerField(primary_key=True)
card_no=models.CharField(max_length=20)
duration=models.IntegerField()
time_8bit=models.CharField(max_length=8)
time_of_day=models.IntegerField()
isBusinessHr=models.IntegerField()
Day_of_week=models.IntegerField()
Day=models.IntegerField()
Thanks
Try that:
sigma=0
demo_by_age = Demo.objects.filter(age_group=age);
popn=demo_by_age.count() #One
card_list = demo_by_age.values_list('card_no', flat=True) # Two
dic = Fact_table.objects.filter(card_no__in=card_list).aggregate(Sum('duration') #Three
sigma = dic['duration__sum']
avgDur=sigma/popn
A statement like card_list=[Demo.objects.filter(age_group=age)[i].card_no for i in range(popn)] will generate popn seperate queries and database hits. The query in the for-loop will also hit the database popn times. As a general rule, you should try to minimize the amount of queries you use, and you should only select the records you need.
With a few adjustments to your code this can be done in just one query.
There's generally no need to manually specify a primary_key, and in all but some very specific cases it's even better not to define any. Django automatically adds an indexed, auto-incremental primary key field. If you need the card_no field as a unique field, and you need to find rows based on this field, use this:
class Demo(models.Model):
card_no = models.SlugField(max_length=20, unique=True)
...
SlugField automatically adds a database index to the column, essentially making selections by this field as fast as when it is a primary key. This still allows other ways to access the table, e.g. foreign keys (as I'll explain in my next point), to use the (slightly) faster integer field specified by Django, and will ease the use of the model in Django.
If you need to relate an object to an object in another table, use models.ForeignKey. Django gives you a whole set of new functionality that not only makes it easier to use the models, it also makes a lot of queries faster by using JOIN clauses in the SQL query. So for you example:
class Fact_table(models.Model):
card = models.ForeignKey(Demo, related_name='facts')
...
The related_name fields allows you to access all Fact_table objects related to a Demo instance by using instance.facts in Django. (See https://docs.djangoproject.com/en/dev/ref/models/fields/#module-django.db.models.fields.related)
With these two changes, your query (including the loop over the different age_groups) can be changed into a blazing-fast one-hit query giving you the average duration of calls made by each age_group:
age_groups = Demo.objects.values('age_group').annotate(duration_avg=Avg('facts__duration'))
for group in age_groups:
print "Age group: %s - Average duration: %s" % group['age_group'], group['duration_avg']
.values('age_group') selects just the age_group field from the Demo's database table. .annotate(duration_avg=Avg('facts__duration')) takes every unique result from values (thus each unique age_group), and for each unique result will fetch all Fact_table objects related to any Demo object within that age_group, and calculate the average of all the duration fields - all in a single query.
What I want to do is trigger an action when one of the fields on my field collection is changed to a certain value. For example, my 'campaign' node has a field collection with a field called 'status' This status is a list containing 3 options; 'onboard', 'live', or 'dead'. When the field on a campaign node field collection is set to 'live' I want to trigger an action.
So I start by saying:
Events: After node is updated
Conditions: This is the bit I am struggling to work out as I cannot do a data comparison with this particular field.
Action: send email
How can I achieve this?
You may get it to work by using an approach similar to what is mentioned in comment # 4 of issue # 1315566, i.e.:
Create an "entity has field" condition on your Rule.
For the "Data Selector," select the entity that contains the field (in my case, a node). For the "Field" value, select the machine name of the field collection in question.
Go to your action. Using the "Data Selector" mode, you should be able to drill down through the entity in question to all the values contained within the field collection. In my case, the end result is "node:field-enrollee:field-school-district:0:tid"
In your case you try to do what is mentioned in step 3 above as a Rules Condition (instead of a Rules Action). So add a Rules Condition "Entity has field" (prior to being able to use it anywhere later on in your rule), which refers to your field collection field.
For way more details about this, refer to "How to iterate over all field collection items in the Rules module?" (which also includes a rule in export format you may want to experiment with, if you only adapt some machine names of the used fields).
This is an APEX code related question and is specific to a VisualForce controller class.
Question
I am trying to update a record with a known AccountId. However, when I set the ID in the sObject declaration SalesForce is appending the string "IAR" to the end of the ID!
Can someone please let me know what I am doing that is wrong and if I am going about this in the wrong way than what is the correct way to update a record from a custom method, outside of quicksave() or update().
Description
So basically, the user will come to this page with the id encoded and it will either have an id or a level. This is handled by the function decode() which takes a string; "id" / "level". I then create an Account variable "acc" which will be used to store all of the Account information before we insert or update it with the statement "insert acc;". Since, I cannot set the ID for "acc" with "acc.id = salesForceID" I have decided to set it when "acc" is created. The following APEX code occurs in the constructor when it is declaring the "acc" variable.
URL Variable Passed
/application?id=001Q000000OognA
APEX Controller Class (Abridged)
salesForceID = decode('id');
debug1 = 'salesForceID: ' + salesForceID;
acc = new Account(id = salesForceID);
debug2 = 'Account ID: ' + acc.id;
Debug Output
salesForceID: 001Q000000OognA
Account ID: 001Q000000OognAIAR
Comments
I apologise for the brevity of the code given, this is for security reasons. I am basically trying to set the ID of the acc before I insert/upsert/update it. I appreciate any explanations for why it could be appending "IAR" and or any alternate ways to update a record given an input AccountId. I do understand that if you pass the id in as a URL variable that SalesForce will automatically do this for you. However, I am passing more than one variable to the page as there are three separate use cases.
Thanks for your help.
001Q000000OognA is the "standard" 15-character Salesforce ID. 15-character ID's are case-sensitive.
001Q000000OognAIAR is the case-insensitive 18-character version of that ID.
Either one is fine. You do not need to worry about the difference. If for some reason you really need to use the 15-character version in parameters etc, you can safely truncate the last 3 digits.
More information here: http://www.salesforce.com/us/developer/docs/api/Content/field_types.htm
Let's take the Django tutorial. In the first part we can find this model:
class Poll(models.Model):
question = models.CharField(max_length=200)
pub_date = models.DateTimeField('date published')
with which Django generates the following SQL:
CREATE TABLE "polls_poll" (
"id" serial NOT NULL PRIMARY KEY,
"question" varchar(200) NOT NULL,
"pub_date" timestamp with time zone NOT NULL
);
One can note that Django automatically added an AutoField, gloriously named id, which is akin to an IntegerField in that it handles integers.
On part 3, we build a custom view, reachable through the following url pattern:
(r'^polls/(?P<poll_id>\d+)/$', 'polls.views.detail'),
The tutorial helpfully explains that a subsequent HTTP request will result in the following call:
detail(request=<HttpRequest object>, poll_id='23')
A few scrolls later, we can find this snippet:
def detail(request, poll_id):
try:
p = Poll.objects.get(pk=poll_id)
Notice how the URL tail component becomes the poll_id argument with a string value of '23', happily churned by the Manager (and therefore QuerySet) get method to produce the result of an SQL query containing a WHERE clause with an integer value of 23 certainly looking like that one:
SELECT * FROM polls_poll WHERE id=23
Certainly Django performed the conversion from the fact that the id field is an AutoField one. The question is how, and when. Specifically, I want to know which internal methods are called, and in what order (kind of like what the doc explains for form validation).
Note: I took a look at sources in django.db.models and found a few *prep* methods, but don't know neither when or where they are called, let alone if they're what I'm looking for.
PS: I know it's not casting stricto sensu, but I think you get the idea.
I think it's in django.db.models.query.get_where_clause