CODEWITHSUNDEEP
google-app-engine
Manas Chaturvedi
Manas Chaturvedi

Reputation: 5540

Google app engine datastore: Summing the values stored inside a single column

I have a database named 'Employee' in my application:

class Employee(db.Model):
    id = db.IntegerProperty(required = True)
    name = db.StringProperty(required = True)
    role = db.StringProperty()
    date_of_joining = db.StringProperty()
    salary = db.IntegerProperty()
    current_task = db.TextProperty()
    percentage_task = db.FloatProperty()

Now, how could I sum the salary of all the employees whose entries are stored in the 'Employee' database?

Upvotes: 0

Views: 67

Answers (1)

Patrice
Patrice

Reputation: 4692

If that's what you currently have, you'd have to get the whole list of 'Employee' and then iterate through them to get a running total, as the datastore doesn't natively support aggregation functions.

Something like :

employees = db.Query(Employee, projection=('salary'))
for employee in employees:
    salarySum += employee.salary

On the other hand, if the salary sum is something you need relatively often, it might be a better idea to keep a counter totaling the salaries, updating it at the same time you update salaries (if the updates are frequent, you might need to look into sharding counters to make sure you don't run into contention problems).

Upvotes: 2

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