Odoo Constraints

Odoo Constraints

Goal

Prevent invalid data from being saved to the database.

1. SQL Constraints

Enforced by the PostgreSQL database. Efficient and atomic.

• Defined via _sql_constraints model attribute.
• List of tuples: ('constraint_name', 'SQL CHECK/UNIQUE', 'Error Message').

Example:

class EstateProperty(models.Model):
    _name = "estate.property"

    _sql_constraints = [
        ('check_expected_price', 'CHECK(expected_price > 0)', 'The expected price must be positive.'),
        ('check_selling_price', 'CHECK(selling_price >= 0)', 'The selling price must be positive.'),
        ('name_uniq', 'UNIQUE(name)', 'Property name must be unique!'),
    ]

• Note: If existing data violates the constraint, the module update/install will fail. You must fix the data first.

2. Python Constraints

Enforced by Odoo server application logic. Used for complex validations that SQL cannot handle easily.

• Decorator: @api.constrains('field1', 'field2')
• Exception: Raise odoo.exceptions.ValidationError if check fails.

Example:

from odoo.exceptions import ValidationError
from odoo.tools.float_utils import float_compare

@api.constrains('selling_price', 'expected_price')
def _check_selling_price(self):
    for record in self:
        # Skip check if no selling price is set
        if float_is_zero(record.selling_price, precision_digits=2):
            continue

        # Check if selling price is lower than 90% of expected
        if float_compare(record.selling_price, record.expected_price * 0.9, precision_digits=2) == -1:
            raise ValidationError("Selling price cannot be lower than 90% of the expected price.")

• Float Comparison: ALWAYS use float_compare and float_is_zero when working with monetary fields to avoid rounding errors.
• Trigger: The method runs whenever any of the fields in @api.constrains are modified.

3. SQL vs Python

• SQL: Faster, strictly enforced at DB level. Use for simple checks (ranges, uniqueness).
• Python: Slower, enforced at app level. Use for complex logic involving multiple records or python-specific calculations.

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