# Default\_field (with random data) and batch save. Expected behaviour?
**URL:** https://discuss.tryton.org/t/default-field-with-random-data-and-batch-save-expected-behaviour/624
**Category:** Developer
**Created:** [July 30, 2018, 11:06am UTC](https://discuss.tryton.org/t/default-field-with-random-data-and-batch-save-expected-behaviour/624 "2018-07-30T11:06:56Z")
**Posts on this page:** 3
**Page:** 1
### Author:  [@fgui](https://discuss.tryton.org/u/fgui)
#### Post date: [July 30, 2018, 11:06am UTC](https://discuss.tryton.org/t/default-field-with-random-data-and-batch-save-expected-behaviour/624/1 "2018-07-30T11:06:56Z")
I have a get\_default which generates random data (per design), it works ok when models are saved one by one.
If I create a bunch of instances of the model and save them all at once with Model.save(models) I get the same default value for all of them. Is this the expected behavior?
I am guessing that the get\_default is only called once for all the models instead of one time for each model. I can see how this can save time in some scenarios but it’s not what I expected.
I am working on 4.8 (not default)
In the following test test\_default\_save\_all fails. That was an unexpected behavior for me.
> class TestDefault(ModelSQL):
> **doc** = u’Test’
> **name** = u’test.default’
> default = fields.Integer(u’Default’)
>
> ```
> @classmethod
> def default_default(cls):
> return random.randint(1L, 1024L)
>
> ```
> class TestCase(ModuleTestCase):
> **doc** = u’Test’
> module = u’scratch’
>
> ```
> @with_transaction()
> def test_default_save_one_at_time(self):
> Test = Pool().get(u'test.default')
> test1 = Test()
> test2 = Test()
> test1.save()
> test2.save()
> tests = Test.search([])
> return self.assertFalse(test1.default == test2.default)
>
> @with_transaction()
> def test_default_save_all(self):
> Test = Pool().get(u'test.default')
> Test.save([Test(), Test()])
> tests = Test.search([])
> return self.assertFalse(first(tests).default == second(tests).default)
>
> ```
(note: there may be some code like first and second which seems estrange but does not affect the test, I write most of my code in hy and this is the python translation)
As a work around I ended up setting the default fields before calling save.
---
### Author:  [@ced](https://discuss.tryton.org/u/ced)
#### Post date: [July 30, 2018, 11:42am UTC](https://discuss.tryton.org/t/default-field-with-random-data-and-batch-save-expected-behaviour/624/2 "2018-07-30T11:42:50Z")
> [@fgui](#):
>
> If I create a bunch of instances of the model and save them all at once with Model.save(models) I get the same default value for all of them. Is this the expected behavior?
Yes it is. We should probably document it on: [https://tryton-readthedocs.readthedocs.io/projects/server/en/latest/topics/models/fields\_default\_value.html](https://tryton-readthedocs.readthedocs.io/projects/server/en/latest/topics/models/fields_default_value.html)
> [@fgui](#):
>
> I am guessing that the get\_default is only called once for all the models instead of one time for each model. I can see how this can save time in some scenarios but it’s not what I expected.
Yes this is for performance reason (server and client side). But also when a new column is added we need to have a single value to use in the update query.
> [@fgui](#):
>
> As a work around I ended up setting the default fields before calling save.
The best is probably to override `ModelStorage.create` method and fill the missing value like it is done in [`ir.session`](http://hg.tryton.org/trytond/file/bf4fbc73abde/trytond/ir/session.py#l107).
---
### Author:  [@system](https://discuss.tryton.org/u/system)
#### Post date: [July 30, 2018, 11:42pm UTC](https://discuss.tryton.org/t/default-field-with-random-data-and-batch-save-expected-behaviour/624/3 "2018-07-30T23:42:51Z")
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