issue2551328/issue2551264 unneeded next link and total_count incorrect Fix: issue2551328 - REST results show next link if number of results is a multiple of page size. (Found by members of team 3 in the UMass-Boston CS682 Spring 2024 class.) issue2551264 - REST X-Total-Count header and @total_size count incorrect when paginated These issues arose because we retrieved the exact number of rows from the database as requested by the user using the @page_size parameter. With this changeset, we retrieve up to 10 million + 1 rows from the database. If the total number of rows exceeds 10 million, we set the total_count indicators to -1 as an invalid size. (The max number of requested rows (default 10 million +1) can be modified by the admin through interfaces.py.) By retrieving more data than necessary, we can calculate the total count by adding @page_index*@page_size to the number of rows returned by the query. Furthermore, since we return more than @page_size rows, we can determine the existence of a row at @page_size+1 and use that information to determine if a next link should be provided. Previously, a next link was returned if @page_size rows were retrieved. This change does not guarantee that the user will get @page_size rows returned. Access policy filtering occurs after the rows are returned, and discards rows inaccessible by the user. Using the current @page_index/@page_size it would be difficult to have the roundup code refetch data and make sure that a full @page_size set of rows is returned. E.G. @page_size=100 and 5 of them are dropped due to access restrictions. We then fetch 10 items and add items 1-4 and 6 (5 is inaccessible). There is no way to calculate the new database offset at: @page_index*@page_size + 6 from the URL. We would need to add an @page_offset=6 or something. This could work since the client isn't adding 1 to @page_index to get the next page. Thanks to HATEOAS, the client just uses the 'next' url. But I am not going to cross that bridge without a concrete use case. This can also be handled client side by merging a short response with the next response and re-paginating client side. Also added extra index markers to the docs to highlight use of interfaces.py.

.. meta::
    :description:
        Additional implementation notes for the Roundup Issue Tracker.
        Supplement for docstrings in the Roundup package.

====================
Implementation notes
====================

[see also the roundup package docstring]

There have been some modifications to the spec. I've marked these in the
source with 'XXX' comments when I remember to.

In short:
 Class.find() - may match multiple properties, uses keyword args.

 Class.filter() - isn't in the spec and it's very useful to have at the
    Class level.

 CGI interface index view specifier layout part - lose the '+' from the
    sorting arguments (it's a reserved URL character ;). Just made no
    prefix mean ascending and '-' prefix descending.

 ItemClass - renamed to IssueClass to better match it only having one
    hypderdb class "issue". Allowing > 1 hyperdb class breaks the
    "superseder" multilink (since it can only link to one thing, and
    we'd want bugs to link to support and vice-versa).

 template - the call="link()" is handled by special-case mechanisms in
    my top-level CGI handler. In a nutshell, the handler looks for a
    method on itself called 'index%s' or 'item%s' where %s is a class.
    Most items pass on to the templating mechanism, but the file class
    _always_ does downloading. It'll probably stay this way too...

 template - call="link(property)" may be used to link "the current item"
    (from an index) - the link text is the property specified.

 template - added functions that I found very useful: List, History and
    Submit.

 template - items must specify the message lists, history, etc. Having
    them by default was sometimes not wanted.

 template - index view determines its default columns from the
    template's ``tal:condition="request/show/<property>"`` directives.

 template - menu() and field() look awfully similar now .... ;)

 roundup_admin.py - the command-line tool has a lot more commands at its
    disposal

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