Changing StringProperty to TextProperty of existing AppEngine DataStore entity without losing data

[Heisenberg W]

I have a django project and I want to change property type of one of the models. My current model.py is:

class Person(ndb.Model):

    property_one= ndb.StringProperty()

    property_two= ndb.StringProperty()

and I want to change it to:

class Person(ndb.Model):

    property_one= ndb.TextProperty()

    property_two= ndb.TextProperty()

Both of my properties already have data and I cannot store more than 1500 bytes. So I want to convert from string to text without losing any data. How can I achieve this?

[Harmit Rishi (Cloud Platform Support)]

Hi, 

The following documentation here provides an example for db.TextProperty() which may be of some use for you. However before moving forward, would you be able to clarify your use case of converting StringProperty() to TextProperty()? 

I ask this because indeed TextProperty value can be more than 1500 bytes long. However, these values are not indexed and cannot be used in filters or sort orders. Additionally, TextProperty values store text with text encoding. Due to this, I am trying to determine if you require binary data. If so, you may consider BlobProperty. 

[Vitaly Bogomolov]

Hi.

The key thing is usage an Expando subclass. For example, as described here:

Change IntegerProperty to FloatProperty of existing AppEngine DataStore

https://stackoverflow.com/questions/4742875/change-integerproperty-to-floatproperty-of-existing-appengine-datastore

Also, these links may be useful:

https://medium.com/engineering-workzeit/migrating-versioned-entities-in-google-app-engine-e21938a2e2ec

https://stackoverflow.com/questions/19842671/migrating-data-when-changing-an-ndb-fields-property-type

WBR, Vitaly

[Heisenberg W]

Thanks for the response.

I have already seen that expando answer in stackoverflow and I was having trouble with one thing.

From stackoverflow:

Before:

class Person(db.Model):
    name = db.StringProperty()
    age = db.StringProperty() #this will go to int

After

class Person(db.Expando):
    pass

for person in Person.all():
    person.age = int(person.age)
    person.put()

Very after:

class Person(db.Model):
    name = db.StringProperty()
    age = db.IntegerProperty() 

Do I have to write all this in models.py file? Including the for loop? I put the similar code in models.py file and nothing happened. I want to use expando but it doesn't work.

[Heisenberg W]

The project is storing references to photo links stored in filestack. I want neither indexing nor encoding.

[Tiago (Google Cloud Platform Support)]

Google Groups hosts discussion forums where you can find information like service status updates, release notes and high-level discussions on the state of the platform. For coding and programming assistance, you're better served in dedicated forums such as Stack Overflow, where experienced programmers are within reach and ready to help. 

Thank you for understanding.