Django TruncDate gives null

Question

I'm using Django 2.2

I'm filtering records using Django query like

from datetime import datetime
from django.db.models.functions import TruncDate

start_date = datetime.strptime('2020-02-01', '%Y-%m-%d').date()
end_date = datetime.strptime('2020-03-31', '%Y-%m-%d').date()

lead_list = LeadList.objects.all()

# Filter query
query = LeadListEntry.objects.filter(
    lead_list__in=lead_list
  )

# Filter by start date
query = query.filter(
    created__gte=start_date
  )

# Filter by end date
query = query.filter(
    created__lte=end_date
  )

# Annotate date
query = query.annotate(
     created_date=TruncDate('created')
   ).order_by(
     'created_date'
   ).values('created_date').annotate(
     **{'total': Count('created')}
   )

The SQL query generated is

SELECT 
    DATE(CONVERT_TZ(`lead_generation_leadlistentry`.`created`, 'UTC', 'UTC')) AS `created_date`, 
    COUNT(`lead_generation_leadlistentry`.`created`) AS `total`
FROM `lead_generation_leadlistentry` 
WHERE (
    `lead_generation_leadlistentry`.`lead_list_id` IN (
        SELECT 
            U0.`id` FROM `lead_generation_leadlist` U0 
        WHERE 
            U0.`deleted` IS NULL
    )
    AND `lead_generation_leadlistentry`.`created` >= '2020-02-01 00:00:00' 
    AND `lead_generation_leadlistentry`.`created` <= '2020-03-31 00:00:00'
)
GROUP BY DATE(CONVERT_TZ(`lead_generation_leadlistentry`.`created`, 'UTC', 'UTC'))
ORDER BY `created_date` ASC

This is behaving different on local and staging server

Local Development server

+--------------+-------+
| created_date | total |
| ------------ | ----- |
| 2020-02-25   | 15    |
| 2020-02-27   | 10    |
+--------------+-------+

Staging server

+--------------+-------+
| created_date | total |
| ------------ | ----- |
| null         | 15    |
+--------------+-------+

The date column is null

NOTE: Django has timezone enabled by USE_TZ=True

LeadListEntry model

class LeadListEntry(models.Model):
    lead_list = models.ForeignKey(LeadList, on_delete=models.CASCADE, related_name='lead_list_entry')
    data = models.TextField(help_text='Lead List entry data. (JSON data)', blank=False)

    created = models.DateTimeField(auto_now_add=True)
    modified = models.DateTimeField(auto_now=True)

Answer 1

Here is the solution for the users getting the same error

The error was not with the Django, instead it was with the MySQL database setup.

The date field returns null because CONVERT_TZ does not work. This can be due to no timezone data in the MySQL database.

To import the timezone data, execute following command

mysql_tzinfo_to_sql /usr/share/zoneinfo | mysql -u root -p mysql

After importing, restart the mysql server.