odoo add validation for double field

Question

I have this odoo py

class CrmProject(models.Model):
_name='crm.project'
customer_id = fields.Many2one('res.partner','Customer')
project_product_id = fields.Many2one('crm.project.product','Project Product')

how to validate and show a warning when the customer_id and project_product_id are inputted together with the same value as the one in the crm.project database? so it must be checked with the database first then show warning if it have the same value with the one in customer_id AND project_product_id input.
For example:

Database table crm.project
customer_id = 1
project_product_id = 2

Will create warning ONLY if input:

customer_id = 1
project_product_id = 2

Beside that no warning will be create

I have tried this but no warning created (update 25-04-2021)

@api.model
def create(self,vals):
    vals['name'] = self.env['ir.sequence'].next_by_code('crm.project')
    res = super(CrmProject,self).create(vals)
    # Add code here
    #res= super(CrmProject,self).create(vals)
    customer_id = vals.get('crm.project.customer_id')
    project_product_id = vals.get('crm.project.project_product_id')
    get_customer_id = self.env['crm.project'].search([('customer_id','=',customer_id)])
    get_project_product_id = self.env['crm.project'].search([('project_product_id','=',project_product_id)])
    if get_customer_id and get_project_product_id:
        raise UserError(_('The project has already been set before'))
    else:
        return res

Any help will be grateful

Answer 1

you can create constraint in your db with :

create unique index name_your_constraint
on crm_project (customer_id, project_product_id);