Adding duration field with default <24h raises an error on Oracle.

[Marcello Dalponte]

BUG DESCRIPTION

When adding a DurationField with a default which is smaller than 24h

class Scheduler(models.Model):
    delay = models.DurationField(default=timedelta(minutes=5))

I get this error with the oracle backend

  ORA-01735: invalid ALTER TABLE option

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INVESTIGATION

I dug into the issue and I found that the reason why the query errors is because the query generated by the migration app is

  ALTER TABLE "EXAMPLE_SCHEDULER" ADD "DELAY" INTERVAL DAY(9) TO SECOND(6) DEFAULT 0:05:00 NOT NULL;

this query has two issues:

1. the duration is not enclosed in quotes 0:05:00 -> '0:05:00'
2. oracle requires the day to be in the value '0:05:00' -> '0 0:05:00'

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SUGGESTED FIX

A possible fix would be to ensure we format timedelta into the right format when generating migrations, this means extending DatabaseSchemaEditor.prepare_default to do the formatting before quoting the value, right now prepare_default simply proxies the business logic to quote_value which simply casts the timedelta to string.

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ENVIRONMENT

python venv:

Django==3.1
cx_Oracle==8.3.0

oracle version:
Oracle Database 19c Enterprise Edition Release 19.0.0.0.0 - Production

[Marcello Dalponte]

Here is the fix ​https://github.com/django/django/pull/15183

[Mariusz Felisiak <felisiak.mariusz@…>]

In 3b73f77a:

Fixed #33358 -- Fixed handling timedelta < 1 day in schema operations on Oracle.