Django 5.1 Connection Pooling and Code Structure

Connection Pooling

Based on the Django 5.1 documentation, the native connection pooling feature is indeed only available for PostgreSQL databases using the psycopg library. This is a new feature in Django 5.1 and is not currently available for MariaDB/MySQL databases. The documentation specifically states:

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DATABASES = {
    "default": {
        "ENGINE": "django.db.backends.postgresql",
        # ...
        "OPTIONS": {
            "pool": True,
        },
    },
}

And further notes that "This option requires psycopg[pool] or psycopg-pool to be installed and is ignored with psycopg2."

There's no mention of similar functionality for MariaDB/MySQL in the documentation.

Code Structure Best Practices

Regarding your questions about code structure and organization:

1. Code Structure

Django follows the Model-View-Template (MVT) pattern, which encourages separation of concerns. Best practices generally suggest:

• Separate functions/classes for different tasks: Rather than one large function/class, it's better to have smaller, focused components that handle specific tasks.
• Class-based views (CBVs) are often preferred for complex views as they provide built-in functionality for common tasks and better organization.
• Mixins can be used to share functionality across different view classes.

For example:

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# Instead of one large view handling everything
class ItemListView(ListView):
    model = Item
    paginate_by = 10
    
    def get_queryset(self):
        queryset = super().get_queryset()
        # Apply filters based on request parameters
        return queryset

class ItemCreateView(CreateView):
    model = Item
    form_class = ItemForm
    success_url = reverse_lazy('item-list')

class ItemUpdateView(UpdateView):
    model = Item
    form_class = ItemForm
    success_url = reverse_lazy('item-list')

2. Reusing Queries Across Functions

There are several approaches to share query logic without global variables:

• Create utility functions that generate queries based on parameters
• Use class-based views where query logic can be defined in methods like get_queryset()
• Use Django's built-in filtering with URL parameters

Example utility function:

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def get_filtered_items(request):
    queryset = Item.objects.all()
    
    # Apply filters based on request parameters
    if 'category' in request.GET:
        queryset = queryset.filter(category=request.GET['category'])
    
    # Apply ordering
    order_by = request.GET.get('order_by', 'name')
    queryset = queryset.order_by(order_by)
    
    return queryset

# Then in your views:
def item_list(request):
    items = get_filtered_items(request)
    paginator = Paginator(items, 10)
    page = request.GET.get('page')
    items_page = paginator.get_page(page)
    return render(request, 'items/list.html', {'items': items_page})

def export_items(request):
    items = get_filtered_items(request)
    # Export logic here
    return response

3. Global Variables vs. Configuration

The warning against global variables is primarily about mutable state that can be changed from multiple places, making code harder to reason about and debug.

• Configuration values (like those in .env files) are generally constants and not problematic
• Session or request-scoped data should be stored in the appropriate context (request.session, etc.)
• View-specific state should be encapsulated in the view class or function

For pagination and ordering preferences:

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# In your view
def item_list(request):
    # Store user preferences in session
    if 'order_by' in request.GET:
        request.session['items_order_by'] = request.GET['order_by']
    
    if 'items_per_page' in request.GET:
        request.session['items_per_page'] = int(request.GET['items_per_page'])
    
    # Use stored preferences with defaults
    order_by = request.session.get('items_order_by', 'name')
    items_per_page = request.session.get('items_per_page', 10)
    
    # Apply to query
    items = Item.objects.all().order_by(order_by)
    paginator = Paginator(items, items_per_page)
    
    # Rest of view logic

This approach stores user preferences in their session rather than using global variables, making it user-specific and avoiding shared mutable state.

For the {% querystring %} template tag, it's typically used to preserve query parameters when generating links, especially for pagination. If you're having trouble with the documentation, consider using Django's built-in request.GET.urlencode() method in your templates to achieve similar functionality.