CODEWITHSUNDEEP
pythondjangoormsql-update
Evg
Evg

Reputation: 3080

generate update query using django orm

I need to implement this query using django orm:

update table set field=field+1 where id=id

I don't whant to use this:

o = model.objects.get(id=id)
o.field+=1
o.save()

because it use select and when update, and not thread safe.

How to implement this via orm?

Upvotes: 11

Views: 26301

Answers (4)

Stamper
Stamper

Reputation: 21

for django v 2.2 (and maybe 3+) SQL statement compilation function could be:

from django.db.models.sql.subqueries import UpdateQuery

def compile_update_query(query_set, update_kwargs):
    query = query_set.query.chain(UpdateQuery)
    query.add_update_values(update_kwargs)
    return str(query)

where query_set is MyShinyModel.objects.filter(id=42) and update_kwargs is a dictionary of model fields to update

Upvotes: 1

pymen
pymen

Reputation: 6569

If you need to convert the UPDATE ORM query to UPDATE SQL statement without performing it

The update() method is applied instantly and returns the number of rows matched by the query (django 1.8 docs)

def generate_update_sql(queryset, update_kwargs):
    """  [checked on django 1.8]
    Converts queryset with update_kwargs
    like if was: queryset.update(**update_kwargs)
    """
    from django.db.models import sql

    query = queryset.query.clone(sql.UpdateQuery)
    query.add_update_values(update_kwargs)
    compiler = query.get_compiler(queryset.db)
    sql, params = compiler.as_sql()
    return sql % params

Usage

qs = Event.objects.exclude(app='some')
update_kwargs = dict(description='test', action='action')
generate_update_sql(qs, update_kwargs)

Will return

UPDATE `api_event` SET `description` = test, `action` = action WHERE NOT (`api_event`.`app` = some)

Upvotes: 0

linbo
linbo

Reputation: 2431

You can use update, details can be found in the documentation

Upvotes: 2

Daniel Roseman
Daniel Roseman

Reputation: 600041

Both the previous answerers have part of the solution: you should use update in conjunction with F():

Model.objects.filter(id=id).update(field=F('field') +1))

Note this does an in-place UPDATE without any need for SELECT at all.

Upvotes: 37

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