Django bulk_create ignore_conflicts=True leaks memory

We are using Django 2.2, python 3.6 and mysql 5.6 for scheduling data intensive jobs.

Memory is increasing over time for a long running job. DEBUG=False in settings.py

why use ignore_conflicts?

we set up a unique key for the table, so ignore_conflicts can filter out those records already in the table.

simple code like this

for record_batch in readFromSomewhere(batch_size):
    for record in record_batch:
        product = parse(record)
        product_list.append(product)
    
    # memory increase and leak
    Product.objects.bulk_create(product_list, ignore_conflicts=True) 
    
    # memory does not increase
    #Product.objects.bulk_create(product_list)  

    #db.reset_queries()
    #gc.collect()

I read a lots of stackoverflow post and put gc.collect() and django.db.reset_query(), but it does not prevent the increase. If I use Product.objects.bulk_create(products), memory does not increase. but if I use Product.objects.bulk_create(products,ignore_conflicts=True) the memory increase over time.

the batch size is very small, around 100. I notice if the batch size is smaller, which means the number of bulk_create calls is larger, memory increases faster. If the batch size is larger, then memory increase slower.

Any thoughts to release the memory after batch created(ignore_conflict=True) into db?