Planet Bluesmoon

Deleting From Self-Referencing Tables

2012-05-17T19:58:41+00:00

Today, I ran into a common issue when deleting records from a table. I was using Doctrine 1.2 on top of MySQL. Deleting a certain number of records failed due to an integrity constraint.

Self-Referencing Tables

A self-referencing table is one that has a foreign key pointing to the same table. For example, a folder hierarchy might have a parent_id column referring to its parent folder. Deleting a single row that has children should normally fail. But what if you wanted to delete a whole tree at once? Would you go recursively from the bottom up?

Solution

A simple way to achieve this is to use the following statement before: SET FOREIGN_KEY_CHECKS=0; This will prevent the MySQL database from complaining about the integrity constraint.

To achieve this using Doctrine, you can execute a raw query using the currently opened connection. Use the table name from which you expect to delete later, to make sure that the right connection is used.

Doctrine::getTable("TableName")
  ->getConnection()
  ->getDbh()
  ->query("SET FOREIGN_KEY_CHECKS=0;");

Now run your delete queries. Don’t forget to SET FOREIGN_KEY_CHECKS=1; at the end if you expect to execute more queries later on using the same connection.

Here’s an example of a delete query with Doctrine:

Doctrine_Query::create()
  ->delete()
  ->from("Folder")
  ->where("id > 25")
  ->execute();

Best Practices

You add database constraints for a reason and pointing to inexistant records compromises your data’s integrity. This approach assumes that you know in advance that removing the row set is alright. I only use this method in maintenance scripts, not in the normal application flow.

brvty++ ?

2012-05-17T18:16:27+00:00

Discussion. Responsive images. Picture too much? Srcset weird syntax? Brevity argument. Typing hard. People lazy. Let’s go shopping?

In other, more human, words: in the wake of the current discussion about responsive images and solutions using a picture element or the srcset attribute I came across an argument that always annoys me. And I fear that the more we use that argument the more we alienate ourselves from what the web is and how it became what it is now.

It is the argument for brevity in code above everything, especially markup. Shorter is better as it means people can type more and faster and there is less opportunity for doing things wrong. I call shenanigans on this.

XHTML’s failure was not the amount of code

The argument is based on the assumption that XHTML failed because it was far too much to type and too much work. HTML5 is considered superior as we only type what we need and we can even omit a lot of “optional” code as browsers are superb and will fix our omissions for us. We write much less and it still works. We call this pragmatism. Except it isn’t. It is laziness and the arrogant assumption that we write code for browsers to execute instead of people to read.

XHTML did not fail because of the amount of things you had to write. It failed because of the redundant things you had to write, its over-complexity and that it wasn’t supported the way it was meant to in the most used browser at the time.

And even that wasn’t the issue as nobody wrote all these overly complex constructs by hand – we have editors, templates and snippets for that. Code autocompletion is quite common. We were happy adding truckloads of Object/Embed code for movies until video came around and we never typed any of that by hand. We had tools for that.

Be productively lazy

Good developers are lazy in the sense that they don’t want to repeat themselves. Instead of doing the same boring and tedious task over and over again by hand we write a script to do it for us. This is what programming is for: allow humans to do better things than the repetitive tasks computers were made for.

If you write a lot of code and it never gets used that is frustrating. Very much so. It is also pointless work. However, the mistakes of XHTML should not push us into the other extreme of writing code for computers instead of writing code that executes and is easy to understand for people who want to learn or people who will have to maintain what we wrote.

Markup is different to other code

I love markup. I love the idea of – get this – marking up a document. Adding those funky bracket things around text and URLs is not about shifting bytes, accessing a chipset or setting an interrupt. They are there to give meaning to the texts and to the URLs they contain.

Think of them as highlighting texts with a marker and writing lots of explanations in the margins explaining the meaning of the highlighted texts. Think of them as the little booklet you get with Shakespeare’s Julius Caesar explaining to you what political, social or historical tidbits the author talks about that you would never get as you don’t live in that time.

Good markup brings meaning to text. Don’t take that away from the web for the sake of brevity and technical use cases that are possibly very short-lived.

The web we all work in right now isn’t the result of writing very clever and beautiful code nor is it the result of squeezing the last byte out of our documents to make them work perfect in a certain environment. Most of the atomic micro-optimisations and performance testing and tweaking we do can be undone by a single, badly coached and still well-meaning maintainer.

The web is easy to get into – let’s start with a clean slate

The web we have right now is the result of it being the most accessible media out there. You wouldn’t know how to put your photo and a big heading with your name in the newspaper or TV. But you can learn in a few minutes flat how to write a:

<!DOCTYPE html>
<html lang="en">
<head>
  <meta charset="UTF-8">
  <title>Chris' page</title>
</head>
<body>
<h1>Chris rules!</h1>
<img src="http://example.com/chris.jpg" alt="Photo of Chris" 
     title="that's me, that is">
</body>
</html>

Why the doctype, the head, the charset definition and the body? Surely the browser will do that for us?

Because the code above should be the result of someone caring about the web telling you that:

The doctype ensures predictability in displaying your page
Defining the language means search engines have it easier to index the page and blind users don’t suffer hearing text pronounced in a different language
The UTF-8 means that if you need international characters they will show up instead of rectangles or question marks and
The head and body makes a clear distinction where your visible content and the instructions for the browser go.

All of this can be violated with intelligent and amazing tricks and still be valid HTML5 and cool. I am quite sure that a few people twitched at the last point and disagreed as you can style title to be visible and scripts can go in the body and there are use cases for inline styles and so on.

The point though is that none of the above hurts a web developer to write and all of it has a purpose. A structure like that makes it easier for people to learn the basics of what we do. It makes our work predictable, clean, maintainable and – at least to me – professional workmanship instead of crazy and cool geek stuff. We get tied up in the latter and one-up each other showing just what is possible and we forget that people are watching and don’t spend the time to learn the basics. Case in point? The excellent learning resource Codecademy lately added a HTML 101 course, omitting the doctype and alternative text for images in the first steps. We start to see teaching as “showing the quickest way” rather than “showing the cleanest way that explains and yields results”.

We value instant gratification over working for achieving a goal. And the gratification you feel when you achieve something you had to work for lasts longer and feels better than the fast variant. This includes making mistakes and learning from them. Giving people an environment that is incredibly forgiving as the first barrier to entry doesn’t help people grow or reach the goal on their own terms.

Fostering a new generation of webmakers

At Mozilla we have a very interesting thing going: we set a goal for ourselves to foster a community of web makers. We do workshops with journalists on how to use the web as a platform for news and entertainment. We show Popcorn as a way to produce news items that can be maintained without re-shooting. We talk to children and find playful ways to get them into making the web rather than ploughing through apps buying them, playing them for a day or so and discarding them to buy the next one. For this, we use markup and a live editor in the browser. Check out the web arcade to see what I mean.

The next generation of people coming into our market should not be virtual couch potatoes who want everything to work magically and discard it when it breaks or gets slow. Tinkering with the web is what got us where we are. Playing with the open technologies and learning from what others did made us the developers we are now. The next generation should be allowed to feel the same excitement about making that we feel now.

Be brief, but stay comprehensible

Writing not much to achieve something isn’t cool. Writing the least amount possible, getting your message across and making it easy for others to build on what you did is. It means you are free to do other, better, and – for you – much more interesting things.

Let’s focus on tools instead of muddling the basics

If you really want people to write less and achieve more, help improve and build tools for creating in a way that shortens the distance between creation and seeing the result. There is a lot of exciting work being done in this field and we need something for those who don’t want to write code. As people in the know we scoff at the Dreamweavers out there, but it is also our fault when bad code ends up on the web as we were too arrogant to help those who simply want to get their content onto the web.

Marketing is a River

2012-05-17T08:55:11+00:00

It is interesting how misunderstood the concept of “marketing” is. Way too many people equate marketing with selling, creating awareness about a product, a campaign, etc. Something that you do at a specific time, when you are trying to achieve an objective. And usually something negative. Let me try and explain how I see the [...]

Comic for May 17, 2012

2012-05-17T05:00:00+00:00

Enounce MySpeed

2012-05-16T10:22:56+00:00

As an update to an earlier post about listening faster I have been using MySpeed for about 6 weeks now. It hooks into Flash player and gives you a little desktop control that lets you speed up any Flash video from 0.5x (slow down) to 5x.

I've had a couple of instances where it has failed -- it tells you when it's active and occasionally I'll be watching a YouTube video and it will say "No Flash Video Playing ..." But for the most part it works as advertised and I would recommend it.

I now watch most video at a minimum of 1.3x. MySpeed has hot keys so you can quickly dial the speed up or down in 0.1x increments. With practice I'm starting to understand speech at a faster pace so sometimes I'll ramp it up to 2x.

Most YouTube videos are much more amusing if you watch them at 1.3x or faster.

TED talks feature some of the world's slowest presentations. You can watch most TED talks at 2x, often 3x. I understand they are trying to convey big ideas but once you start watching video at your preferred pace you start to realise just how much time is being wasted for the sake of dramatic effect (and clarity; I'll note that both speakers & audience are not native English speakers).

A nifty side effect for those of us who don't want to run an ad blocker: you can use this to fast forward all Flash video ads.

I was a bit dubious about MySpeed when I first discovered it via Google. It looks like such a spam site. So this post is mostly for the benefit of others like me who may have hesitated to try a Flash hook from such a random looking site.

Peacock Pansy…

2012-05-16T10:02:10+00:00

Posted in Tumblog

Peacock Pansy by Tarique Sani Tweet

Comic for May 16, 2012

2012-05-16T05:00:00+00:00

Felidae

2012-05-16T04:00:00+00:00

05/14/12 PHD comic: 'The Avoidance Cycle'

2012-05-15T18:49:59+00:00

Piled Higher & Deeper by Jorge Cham		www.phdcomics.com

title: "The Avoidance Cycle" - originally published 5/14/2012 For the latest news in PHD Comics, CLICK HERE!

Ignite London: Crowd Sourcing a Map of the World

2012-05-15T08:47:00+00:00

Ignite London: Crowd Sourcing a Map of the World

London, UK

Tuesday, May 15th 2012, 09:47 BST

Almost two weeks ago, I gave a talk at Ignite London about OpenStreetMap, titled "Crowd Sourcing a Map of the World". Ignite's presentation style is 20 slides which automatically advance every 15 seconds. Having never done this before I actually wrote the whole talk out. The presentation that I gave slightly diverges from this but I thought it'd still be good to reproduce here. I did add some links to more information, and if you want to see the recording, you can find it at the end of this post.

1. This talk is about a project, started here in the UK with as its major goal to create a free map of the whole planet. From roads and motorways to country-side footpaths, restaurants and of course pubs. This talk is about OpenStreetMap, the free map of the world.

2. There are of course already plenty of mapping solutions available. Maybe one of the best maps can be acquired through Ordnance Survey. They can be regarded as the national authority on this subject. It's however expensive to get access to their maps, especially the very detailed maps from OS MasterMap. Additionally, it's only for the UK.

3. Besides the commercial solutions, you might wonder why we simply can't do with GoogleMaps? It's mostly freely available for use and also provides you with satellite imagery and StreetView. They even allow you in some areas to update the map through Google MapMaker.

4. But one thing Google doesn't give you access to, is the data behind the map. All you will ever see, is the rendered map tiles and perhaps some APIs to lookup locations and points of interest. Even for data that you have added yourself through MapMaker.

5. Both aspects; the cost of commercial maps, as well as the access to the data that is behind the map tiles is something that the OpenStreetMap project addresses. But which steps have to be taken to obtain this enormous amount of geographical data?

6. We start by getting our wellies and trusty GPS out. Maybe even some pen and paper. We find a location that looks rather empty on the map and travel to that area to see what's on the ground. This is step one: data gathering in the field.

7. In urban areas such as London the roads have often already been mapped and a GPS is not accurate enough to be useful. Then we just use pen and paper to record points of interest, such as shops, landmarks, restaurants and postboxes, my personal favourite.

8. In the country side, donated aerial imagery makes it possible for us to easily trace tracks and footpaths. However, you can't be sure whether the imagery is up-to-date, and you can't always see where fences, streams and local wild life create barriers.

9. In both situations, surveys are best done in groups: at mapping parties. It helps spread the workload and a larger area can be surveyed in one go. As an additional benefit, it allows us to go the pub and discuss our mapping adventures!

10. Doing a survey is important. We take photographs, video and notes with pen and paper of everything that seems to be of interest. This leaves a record that everything we map is actually existing and we can prove that nothing has been copied from other copyrighted maps.

11. After collecting the data, we enter it into the database. This includes basic information such as street names, but we also record whether a café has wheelchair access, or whether a pub has wifi. Updates to the map show up on the site close to real time.

12. Every map object has tags associated with it. Tags tell whether a line is a road, or perhaps a fence. All the tags are free form so you can generally add as much information about an object as you want. Sometimes however, this gets slightly out of hand and people tag pandas in trees and eyes on postboxes.

13. Once the data has been added to the map, we can make use of it. One of the primary uses is obviously showing the data as map tiles. But with all the extra data, we can generate maps that show all the information you're interested in-and nothing more.

14. Clockwise, we have four different visualisations of the map data: we have a cycling-specific style, a style that shows transport routes, a rendering with MapQuest's style sheets and even a water colours inspired style.

15. Having mentioned MapQuest; they were one of the first companies to make use of OpenStreetMap data. They provide, free of charge, map tiles with their own rendering style as well as an instance of Nominatim, OpenStreetMap's geolocation sister project.

16. Lots of companies have already switched to OpenStreetMap. The property search site Nestoria recently switched from using GoogleMaps to OpenStreetMap. Partly because of their costs, but also partly because "The maps are equal or better". geocaching.com, TfL's countdown website and Apple also use OpenStreetMap maps and data.

17. Although OpenStreetMap provides a free and editable map of the world, there are certain requirements for using the data as well. The most important one is that you always need to attribute the OpenStreetMap project.

18. In order to help people start using OpenStreetMap for their mapping needs, the Switch2OSM site has been launched. This website provides background information, case studies and technical information on how to use OpenStreetMap data.

19. Right now, OpenStreetMap has very good data coverage in the country, but we are not nearly finished. A lot of work still has to be done, and we rely on you to improve the data too, even if you add just a postbox.

20. In the last 5 minutes we have looked at what OpenStreetMap is, how the data is gathered and how the data is added to the map. Further more, we had a look at different use cases of the data. OpenStreetMap in the UK: Footpaths and pubs a speciality!

And then I planned showing the "Year of Edits" video, but that sadly didn't work out. I'm including it for good measure here though. (If you want it in HD, follow the link).

OpenStreetMap: A Year of Edits (2011)

The video of the talk itself is at http://vimeo.com/41626116 and is embedded here:

Crowdsourcing a Map of the World

Morning Parade

2012-05-15T07:37:43+00:00

Posted in Tumblog

Comic for May 15, 2012

2012-05-15T05:00:00+00:00

Just another day in…

2012-05-14T08:04:39+00:00

Posted in Tumblog

Just another day in… by Tarique Sani Tweet

Comic for May 14, 2012

2012-05-14T05:00:00+00:00

Kickstarter

2012-05-14T04:00:00+00:00

Comic for May 13, 2012

2012-05-13T05:00:00+00:00

Twitter Weekly Updates for 2012-05-13

2012-05-13T02:19:00+00:00

Posted in Twitter Digests

@duaakhil Glad you know you enjoyed! It is even more amazing after the first rains when all the waterfalls start # I'm watching We Bought a Zoo http://t.co/LmSU5Qsj @GetGlue @weboughtazoo # CSS Tricks: How to Speed Up CSS Rendering http://t.co/egG94K3h # Is Google Burying Firefox With User Agent Strings? http://t.co/TkEFl68S # I'm watching Moneyball http://t.co/VubZvQqk [...]

Comic for May 12, 2012

2012-05-12T05:00:00+00:00

To hell with browser wars panels

2012-05-11T15:23:47+00:00

Summary: Browser War panels have become predictable and non-informative. Instead they are there to entertain the audience but cause much more drama than good.

I go to a lot of conferences. I organised events, a conference and a few unconferences and I spoke at a lot of them. Lately I also stepped back a bit to coach people to speak instead of me going everywhere.

I think conferences should do a few things: educate, entertain, allow people to network and make speakers and experts available to attendees.

You don’t need to go to conferences to learn things – all the information is on the internet and signing up to a few good feeds, groups and lists will get you all the info you want.

What conferences do is bring the human factor into it. A good speaker can make a topic come to life and show you an angle you had not thought about and inspire you to play with it. A good workshop gives you guidance how to use a technology and gives you a way in without being overwhelmed by a big scary topic. A conference gives you time out from the day to day delivery and allows you to do things that are not yet on the radar of your company but might be soon.

And then there are “browser war panels”. The original premise of the browser war panels was that an audience could hear the latest and coolest about different browsers and ask questions. The first ones were held at Yahoo and had lead engineers from the different browsers to show how the different products work as that was dark magic back then.

HTML5 defines how a browser should deal with the content it gets – we have a lot more predictability already in the standard. A lot of great information on this topic is out on the web and the accelerated speed of delivery of browsers makes the appearance of platform engineers not happening much. There is no need to repeat the standards, instead the discussions are much more about what makes which browser stand out and in a lot of cases this means what the company wants to promote – not what developers want to use now and get stuck as it doesn’t work.

Browser panels these days get people from companies who are either product evangelists of the browsers or general tech evangelists, advocates, or – in the worst case – sales people. This could be good, they can point out features that are in the browsers people don’t know about and they can show some of the plans for the future of the browser. It can also be awful. As browsers are interesting to the media out of a sudden you see a lot of patterns being followed. Instead of giving information about the browsers, dealing with concerns of developers and implementers or showing changes panelists begin to fall into predefined roles and repeat the messages of the companies they represent.

It becomes predictable to see which company representative will value speed over everything else, which one will praise a great experience in the browser as part of a bigger OS experience, which one will talk about following standards and complain about sites blocking out browsers and which one will point out that the browser is the choice of the user and should keep them in control by being open about everything whilst following standards.

The bigger focus on browsers we have these days makes a panel much less of an educational part of the conference (many a time you will get “I have to go back to the engineering team for this”) but pushes it into the entertainment part of a conference. It is a veiled sales pitch.

Everybody loves a good drama. You could go as far as saying that we have a whole tech journalism market that lives on drama. It is fun to see people disagree on topics and make good arguments about one side or another.

A quite open, unscripted and unplanned format like a panel makes for great drama. It is easy to take potshots at each other and score browny points with the audience with pointing out flaws of the other browsers in a glib fashion. It also gives browny points with the audience to make sweeping statements or deliver soundbites.

Soundbites, being witty and fast are becoming the most important part. If you look at the Twitter stream of a browser panel you will hardly ever find a “oh feature $x will ship in browser $y – so cool” but you will get more “$x of browser $y just called $z out on the $a issue”.

Soundbites are also loved by the press. And as drama brings headlines many a time you will find a sarcastic remark or glib retort show up as “Company representative $x said $y about the competition”. A quick shot to get a giggle out of the audience can cause the communications team of a company to get a lot of unnecessary work. Is that worth it?

I’ve even been on panels where the organisers deliberately asked panelists to find topics to disagree on or seen panel moderators throw out one loaded question after another to entice people to disagree and get the drama going. We call this trolling or baiting, and not a way for conference participants to learn about what is going on in the browser world.

It is not hard to find what is going on in the browser world when you look at the open source engines. You hear much less about the closed ones and to me a panel that has no participant of Apple on it is not a “browser wars” panel as it lacks a massive player who should answer quite a few questions web developers have.

There are exceptions. I thoroughly enjoyed being on the panel at State of the Browser 2 in London and I think as there were no egos and no artificial drama we managed to answer quite a few questions from the audience. But on the whole, these are few and far between and many a “Browser Wars” panel is entertainment and cheap laughs or “wow, did he just say that” moments.

This, in the long run, is not fair to the audience who paid good money (and should get real comedians or entertainers if entertainment is the goal), it is not fair to the platform engineers (as they are misrepresented instead of allowing people to peek under the hood with them) and it does not get us anywhere in the real “browser wars”.

As developers you should not be tempted to build for one browser only and you should not have to build different versions for different browsers. Keeping it all about drama and who shouts the loudest and comes across as most witty doesn’t make that happen. It is a waste of time.

Aslan, the great!

2012-05-11T08:11:04+00:00

Posted in Tumblog

Comic for May 11, 2012

2012-05-11T05:00:00+00:00

The bacon

2012-05-11T04:00:00+00:00