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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.
| author | John Rouillard <rouilj@ieee.org> |
|---|---|
| date | Mon, 01 Apr 2024 09:57:16 -0400 |
| parents | 2ab234484708 |
| children |
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<head> <title>Roundup: A Simple and Effective Issue Tracker in Python</title> </head> <body bgcolor="#efefef"> <table bgcolor="#4040a0" width="100%" border=0 cellspacing=0 ><tr valign=bottom><td> <br> <br ><font face="helvetica, arial" color="#ffffff"><big><big><strong >Roundup Short Paper</strong></big></big></font></td><td align=right ><a href="http://www.lfw.org/" ><img src="/images/lfwblue.gif" border=0 width=33 height=22 alt="[LFW]" ></a></td></tr></table> <h3>Roundup: A Simple and Effective Issue Tracker in Python</h3> <small><em>Ka-Ping Yee</em> (<a href="http://www.lfw.org/ping/roundup.html">original site: http://www.lfw.org/ping/roundup.html</a></small>) <p>Please note that <strong>there is a new, active Roundup project</strong> led by Richard Jones. Please <a href="http://roundup.sf.net/">visit them at SourceForge</a>. <p>The Roundup prototype is open source. You can <a href="roundup.tar.gz"><strong>download it here</strong> (roundup.tar.gz, 32 kb)</a>. Or <strong><a href="roundup/roundup.cgi">play with the live prototype!</a> </strong> When prompted for authentication, you can use one of the test accounts: "test", "spam", or "eggs" (password same as account name). Roundup's e-mail address is <a href="mailto:roundup---lfw.org">roundup---lfw.org</a>. You can't create new accounts, but you can read the mail spools for <a href="test.spool">test</a>, <a href="spam.spool">spam</a>, or <a href="eggs.spool">eggs</a> here to see what they're getting. <p><em>A <a href="sc-roundup.html">detailed design proposal for a more advanced issue-tracking system based on Roundup</a> has been submitted to <a href="http://www.software-carpentry.com/">Software Carpentry</a>'s open source software design competition.</em> This first-round submission was <a href="http://software-carpentry.codesourcery.com/first-round-results.html" >selected as a finalist</a>. A <a href="sc-roundup-2.html">more detailed implementation guide</a> was submitted to the <a href="http://software-carpentry.codesourcery.com/second-round-entries.html" >second round of the competition</a>. <p><em>You might also want to check out <a href="/python/">other Python-related stuff on this site</a>.</em> <hr> <p>This short talk will share some experiences from developing and using the issue tracking system used by my development group at ILM. It integrates two modes of access: e-mail for gathering information, and the Web for search and retrieval. We currently work with it daily and it does its job pretty well. <h4>Fine-Grained Mailing Lists</h4> <p>The key strength of Roundup is that it generates a small virtual mailing list for each new issue. In a way, this is like implementing private conversation rooms in e-mail. Although the mechanism is very simple, the emergent properties are quite effective. Here's how it works: <ol type="a"> <li>New issues are always submitted by sending an e-mail message. This message is saved in a mail spool attached to the newly-created issue record, and copied to the relatively large user community of the application so everyone knows the issue has been raised. <li>All e-mail messages sent by Roundup have their "Reply-To" field set to send mail back to Roundup, and have the issue's ID number in the Subject field. So, any replies to the initial announcement and subsequent threads are all received by Roundup and appended to the spool. <li>Each issue has a "nosy list" of people interested in the issue. Any mail tagged with the issue's ID number is copied to this list of people, and any users found in the From:, To:, or Cc: fields of e-mail about the issue are automatically added to the nosy list. Whenever a user edits an item in the Web interface, they are also added to the list. </ol> <p>The result is that no one ever has to worry about subscribing to anything. Indicating interest in an issue is sufficient, and if you want to bring someone new into the conversation, all you need to do is Cc: a message to them. It turns out that no one ever has to worry about unsubscribing, either: the nosy lists are so specific in scope that the conversation tends to die down by itself when the issue is resolved or people no longer find it sufficiently important. The transparent capture of the mail spool attached to each issue also yields a nice searchable knowledge repository over time. <h4>User Interface Decisions</h4> <p>The web interface to Roundup aims to maximize the density of useful information. Although this principle is important to all information presentation, it is especially vital in a web browser because of the limited window real estate. Hence Roundup avoids repetitive or unnecessary information and tries to fit as many items as possible on the first screen. For example, Bugzilla initially displays seven or eight items of the index; Jitterbug can't even manage to fit any items at all in the first screenful, as it's taken up by artwork and adminstrative debris. In contrast, Roundup shows you about 25 high-priority issues right away. Colour indicates the status of each item to help the eye sift through the index quickly. <p>In both Jitterbug and Bugzilla, items are sorted by default by ID, a meaningless field. Sorting by ID puts the issues in order by ascending submission date, which banishes recent issues as <em>far</em> away as possible at the bottom of the list. Roundup sorts items in sections by priority so the high-priority items are immediately visible; within sections, items are sorted by date of last activity. This reveals at a glance where discussion is most active, and provides an easy way for anyone to move an issue up in the list without changing its priority. <p><hr> (The following has been added for this web page and was not part of the short paper in the IPC8 proceedings.) <h4>Screenshots of the Web Interface</h4> <p>Here is the <a href="images/roundup-1.png">Roundup index</a>, the first thing presented to you when you go to Roundup. Note the use of colour coding and the attempt to dedicate maximum space to the description of each issue. <p>In comparison, here is the <a href="images/jitterbug-1.gif">first screen you see when you use Jitterbug</a>. No information is actually visible! You have to scroll down to the <a href="images/jitterbug-2.gif">second screen</a> before you get to see any bugs, and even then your view is limited to a paltry eight entries. The boldface on the item descriptions helps, but the visual effect of the table is still swamped by the powerful green header line -- which contains zero bits of new information. <p>As another example, Bugzilla presents somewhat more information than Jitterbug in its <a href="images/bugzilla-4.gif">index view</a>, but forces you to go through three bewildering screens replete with form widgets (<a href="images/bugzilla-1.gif">one</a>, <a href="images/bugzilla-2.gif">two</a>, <a href="images/bugzilla-3.gif">three</a>) before you even get to see anything. Examination of the <a href="images/bugzilla-4.gif">index view</a> shows that one-third to one-half of the screen area (depending how you count it) is wasted on trivialities or empty space, and the most important column, the description of each issue, is shoved off of the right side of the page. <p><table bgcolor="#4040a0" width="100%" border=0 cellspacing=0 ><tr valign=bottom><td ><font face="helvetica, arial" color="#c0c0e0"><small >copyright © by <a href="http://www.lfw.org/ping/" ><font color="#c0c0e0">Ka-Ping Yee</font></a> updated Sun 2 Jul 2000</td><td align=right ><font face="helvetica, arial" color="#c0c0e0" ><small><small> </small></small></font></td></tr></table> </body>