Created
March 25, 2017 09:45
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Snippets for mongoengine upgrade blog post
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from mongoengine import * | |
class UpdatableDocument(Document): | |
schema_version = IntField(default=0) | |
schema_updates = {} # Dictionary to hold all the updates | |
def __init__(self, *args, **kwargs): | |
values = self.schema_update(kwargs) | |
super().__init__(*args, **values) | |
def schema_update(values): | |
version = values.get('schema_version', 0) | |
next_version = version + 1 | |
# Get the n+1 version and perform the delta | |
# keep doing until there are no new versions | |
while self.schema_updates.get(next_version): | |
update = self.schema_updates[next_version] | |
update(values) | |
values['schema_version'] = next_version | |
next_version += 1 | |
return values | |
class IoTProduct(Document): | |
""" Information about all devices of a specific type """ | |
tags = ListField(StringField()) | |
field_d = IntField() | |
def schema_update_add_product_tags(values): | |
"""Adds the tags from the products to the tags field on the device | |
Args: | |
values (dict): A dictionary loaded from the mongodb BSON. | |
Returns: None | |
""" | |
product = IoTProduct.objects.get(id=values['field_c'].id) | |
values['tags'] = product.tags | |
class IoTDevice(UpdatableDocument): | |
""" Information about a specific IoT device """ | |
field_a = StringField() | |
field_b = IntField() | |
field_c = ReferenceField(IoTProduct) | |
tags = ListField(StringField()) | |
schema_updates = { | |
1: schema_update_add_product_tags, | |
} |
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{ | |
"_id": ObjectId("58d5b3000000000000000000"), | |
"field_a": "Tempurature Sensor", | |
"field_b": "21", | |
"field_c": ObjectId("58d5b3011111111111111111") | |
} |
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class IoTProduct(Document): | |
""" Information about all devices of a specific type """ | |
tags = ListField(StringField()) | |
field_d = IntField() | |
class IoTDevice(Document): | |
""" Information about a specific IoT device """ | |
field_a = StringField() | |
field_b = IntField() | |
field_c = ReferenceField(IoTProduct) # Reference to a product |
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class IoTDevice(UpdatableDocument): | |
""" Information about a specific IoT device """ | |
field_a = StringField() | |
field_b = IntField() | |
field_c = ReferenceField(IoTProduct) | |
tags = ListField(StringField()) | |
schema_updates = { | |
1: schema_update_add_product_tags, | |
} |
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def schema_update_add_product_tags(values): | |
"""Adds the tags from the products to the tags field on the device | |
Args: | |
values (dict): A dictionary loaded from the mongodb BSON. | |
Returns: None | |
""" | |
product = IoTProduct.objects.get(id=values['field_c'].id) | |
values['tags'] = product.tags | |
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class UpdatableDocument(Document): | |
schema_version = IntField(default=0) | |
schema_updates = {} # Dictionary to hold all the updates | |
def __init__(self, *args, **kwargs): | |
values = self.schema_update(kwargs) | |
super().__init__(*args, **values) | |
def schema_update(values): | |
version = values.get('schema_version', 0) | |
next_version = version + 1 | |
# Get the n+1 version and perform the delta | |
# keep doing until there are no new versions | |
while self.schema_updates.get(next_version): | |
update = self.schema_updates[next_version] | |
update(values) | |
values['schema_version'] = next_version | |
next_version += 1 | |
return values |
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class IoTDevice(Document): | |
""" Information about a specific IoT device """ | |
field_a = StringField() | |
field_b = IntField() | |
field_c = ReferenceField(IoTProduct) # Reference to a product | |
tags = ListField(StringField()) # !New! field |
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