# Troubleshooting

Don't Paginate Unordered PostgreSQL Collections!

@pagy, @records = pagy(unordered)

# behind the scenes, pagy selects the page of records with: 
unordered.offset(pagy.offset).limit(pagy.limit)

From the PostgreSQL Documentation

When using LIMIT, it is important to use an ORDER BY clause that constrains the result rows into a unique order. Otherwise you will get an unpredictable subset of the query's rows.

Ensure the PostgreSQL collection is ordered!

# results will be predictable with #order
ordered         = unordered.order(:id)
@pagy, @records = pagy(ordered)

Don't rely on ARIA default with multiple nav elements!

Pagy sets the aria-label attribute of its nav elements with the translated and pluralized pagy.aria_label.nav that finds in the locale files. That would be (always) "Page"/"Pages" for the en locale.

Since the nav or role="navigation" elements of a HTML document are considered landmark roles, they should be uniquely aria-identified in the page.

Pass your own `aria_label` to each nav!

<%# Explicitly set the aria_label string %> 
<%== pagy_nav(@pagy, aria_label: 'Search result pages') %>

Don't duplicate attributes with the `:anchor_string`!

<%== pagy_bootstrap_nav(@pagy, anchor_string: 'class="my-class"', **vars) %>

The class attribute with a value of "pagination" is already added by the pagy_bootstrap_nav so it's a duplicate HTML attribute which is invalid html.

Easily check the native component attributes!

pagy demo
# or: bundle exec pagy demo
# ...and point your browser at http://0.0.0.0:8000

In the specific bootstrap example you could override the default bootstrap "pagination" class by adding other classes with:

@pagy, @records = pagy_bootstrap_nav(collection, classes: 'pagination my-class')

There has been a single report of a slow last page using very big DB tables. It's a pure DB problem and it's not caused by pagy or by any other ruby code (#696, #704), but a simple pagy override may avoid it:

## override pagy_get_items
def pagy_get_items(collection, pagy)
  limit = pagy.last == pagy.page ? pagy.in : pagy.limit
  collection.offset(pagy.offset).limit(limit)
end