Combination of two fields to be unique in Python Eve
Question:
In Python Eve framework, is it possible to have a condition which checks combination of two fields to be unique?
For example the below definition restricts only firstname and lastname to be unique for items in the resource.
people = {
# 'title' tag used in item links.
'item_title': 'person',
'schema': {
'firstname': {
'type': 'string',
'required': True,
'unique': True
},
'lastname': {
'type': 'string',
'required': True,
'unique': True
}
}
Instead, is there a way to restrict firstname and lastname combination to be unique?
Or is there a way to implement a CustomValidator for this?
Answers:
You can probably achieve what you want by overloading the _validate_unique
and implementing custom logic there, taking advantage of self.document
in order to retrieve the other field value.
However, since _validate_unique
is called for every unique field, you would end up performing your custom validation twice, once for firstname
and then for lastname
. Not really desirable. Of course the wasy way out is setting up fullname
field, but I guess that’s not an option in your case.
Have you considered going for a slighty different design? Something like:
{'name': {'first': 'John', 'last': 'Doe'}}
Then all you need is make sure that name
is required and unique:
{
'name': {
'type':'dict',
'required': True,
'unique': True,
'schema': {
'first': {'type': 'string'},
'last': {'type': 'string'}
}
}
}
Inspired by Nicola and _validate_unique
.
from eve.io.mongo import Validator
from eve.utils import config
from flask import current_app as app
class ExtendedValidator(Validator):
def _validate_unique_combination(self, unique_combination, field, value):
""" {'type': 'list'} """
self._is_combination_unique(unique_combination, field, value, {})
def _is_combination_unique(self, unique_combination, field, value, query):
""" Test if the value combination is unique.
"""
if unique_combination:
query = {k: self.document[k] for k in unique_combination}
query[field] = value
resource_config = config.DOMAIN[self.resource]
# exclude soft deleted documents if applicable
if resource_config['soft_delete']:
query[config.DELETED] = {'$ne': True}
if self.document_id:
id_field = resource_config['id_field']
query[id_field] = {'$ne': self.document_id}
datasource, _, _, _ = app.data.datasource(self.resource)
if app.data.driver.db[datasource].find_one(query):
key_names = ', '.join([k for k in query])
self._error(field, "value combination of '%s' is not unique" % key_names)
The way I solved this issue is by creating a dynamic field using a combination of functions and lambdas to create a hash that will use
which ever fields you provide
def unique_record(fields):
def is_lambda(field):
# Test if a variable is a lambda
return callable(field) and field.__name__ == "<lambda>"
def default_setter(doc):
# Generate the composite list
r = [
str(field(doc)
# Check is lambda
if is_lambda(field)
# jmespath is not required, but it enables using nested doc values
else jmespath.search(field, doc))
for field in fields
]
# Generate MD5 has from composite string (Keep it clean)
return hashlib.md5(''.join(r).encode()).hexdigest()
return {
'type': 'string',
'unique': True,
'default_setter': default_setter
}
Practical Implementation
My use case was to create a collection that limits the amount of key value pairs a user can create within the collection
domain = {
'schema': {
'key': {
'type': 'string',
'minlength': 1,
'maxlength': 25,
'required': True,
},
'value': {
'type': 'string',
'minlength': 1,
'required': True
},
'hash': unique_record([
'key',
lambda doc: request.USER['_id']
]),
'user': {
'type': 'objectid',
'default_setter': lambda doc: request.USER['_id'] # User tenant ID
}
}
}
}
The function will receive a list of either string or lambda function for dynamic value setting at request time, in my case the user’s "_id"
The function supports the use of JSON query with the JMESPATH package, this isn’t mandatory, but leave the door open for nested doc flexibility in other usecases
NOTE: This will only work with values that are set by the USER at request time or injected into the request body using the pre_GET trigger pattern, like the USER object I inject in the pre_GET trigger which represents the USER currently making the request
In Python Eve framework, is it possible to have a condition which checks combination of two fields to be unique?
For example the below definition restricts only firstname and lastname to be unique for items in the resource.
people = {
# 'title' tag used in item links.
'item_title': 'person',
'schema': {
'firstname': {
'type': 'string',
'required': True,
'unique': True
},
'lastname': {
'type': 'string',
'required': True,
'unique': True
}
}
Instead, is there a way to restrict firstname and lastname combination to be unique?
Or is there a way to implement a CustomValidator for this?
You can probably achieve what you want by overloading the _validate_unique
and implementing custom logic there, taking advantage of self.document
in order to retrieve the other field value.
However, since _validate_unique
is called for every unique field, you would end up performing your custom validation twice, once for firstname
and then for lastname
. Not really desirable. Of course the wasy way out is setting up fullname
field, but I guess that’s not an option in your case.
Have you considered going for a slighty different design? Something like:
{'name': {'first': 'John', 'last': 'Doe'}}
Then all you need is make sure that name
is required and unique:
{
'name': {
'type':'dict',
'required': True,
'unique': True,
'schema': {
'first': {'type': 'string'},
'last': {'type': 'string'}
}
}
}
Inspired by Nicola and _validate_unique
.
from eve.io.mongo import Validator
from eve.utils import config
from flask import current_app as app
class ExtendedValidator(Validator):
def _validate_unique_combination(self, unique_combination, field, value):
""" {'type': 'list'} """
self._is_combination_unique(unique_combination, field, value, {})
def _is_combination_unique(self, unique_combination, field, value, query):
""" Test if the value combination is unique.
"""
if unique_combination:
query = {k: self.document[k] for k in unique_combination}
query[field] = value
resource_config = config.DOMAIN[self.resource]
# exclude soft deleted documents if applicable
if resource_config['soft_delete']:
query[config.DELETED] = {'$ne': True}
if self.document_id:
id_field = resource_config['id_field']
query[id_field] = {'$ne': self.document_id}
datasource, _, _, _ = app.data.datasource(self.resource)
if app.data.driver.db[datasource].find_one(query):
key_names = ', '.join([k for k in query])
self._error(field, "value combination of '%s' is not unique" % key_names)
The way I solved this issue is by creating a dynamic field using a combination of functions and lambdas to create a hash that will use
which ever fields you provide
def unique_record(fields):
def is_lambda(field):
# Test if a variable is a lambda
return callable(field) and field.__name__ == "<lambda>"
def default_setter(doc):
# Generate the composite list
r = [
str(field(doc)
# Check is lambda
if is_lambda(field)
# jmespath is not required, but it enables using nested doc values
else jmespath.search(field, doc))
for field in fields
]
# Generate MD5 has from composite string (Keep it clean)
return hashlib.md5(''.join(r).encode()).hexdigest()
return {
'type': 'string',
'unique': True,
'default_setter': default_setter
}
Practical Implementation
My use case was to create a collection that limits the amount of key value pairs a user can create within the collection
domain = {
'schema': {
'key': {
'type': 'string',
'minlength': 1,
'maxlength': 25,
'required': True,
},
'value': {
'type': 'string',
'minlength': 1,
'required': True
},
'hash': unique_record([
'key',
lambda doc: request.USER['_id']
]),
'user': {
'type': 'objectid',
'default_setter': lambda doc: request.USER['_id'] # User tenant ID
}
}
}
}
The function will receive a list of either string or lambda function for dynamic value setting at request time, in my case the user’s "_id"
The function supports the use of JSON query with the JMESPATH package, this isn’t mandatory, but leave the door open for nested doc flexibility in other usecases
NOTE: This will only work with values that are set by the USER at request time or injected into the request body using the pre_GET trigger pattern, like the USER object I inject in the pre_GET trigger which represents the USER currently making the request