Primary keys are sorted to the top of the table symbols
Lines are thicker on hover to make it easier to select the relevant symbol
Query does not filter out empty tables.
This completes the set of databases that I have made this work for, might include DB2 at some point in the future if I ever work on an IBM system.
For this interactive version, hovering over the lines makes them larger so that you can click to highlight the line. This makes it easy to plan out a query by following the links between the relevant tables, regardless of where they are on the screen. A good example of this would be tracing out which language DVDs are rented out in a specified city? This needs seven tables and six relationships to determine this, and it is much easier to have the path highlighted while writing the query than having to remember the path as you write the query.
The experimental section of the paper is worth a read, and again, you can tell that Matzger’s group has good technique because everyone made it intact to the writing of the manuscript. There are pictures of the crystals themselves, which are very nice, until you realize that they’re plotting to blow you into the ceiling crawl space at the first opportunity. It says that “no unplanned detonations were encountered” during the work, which is a nice distinction.
Spoiler Alert! Next to the ice sheets the sea level can actually fall as a result of the ice melting due to the loss of the gravitational pull from the mass of the ice sheet. It will fall even further over geological times due to the rebound of the crust when the weight of the ice is removed. Canada is rebounding approx. 1mm/yr in response to the removal of the ice sheets from the last ice age.
Posted by Pete McBreen Thu, 04 Aug 2016 02:45:00 GMT
In every iteration, have a few bugs that do not get fixed. After five or six iterations you can build up a reasonable size bug backlog without even trying, and the best bit is that you can hide them in the previous iterations so nobody important sees them.
If there is anything left over in the current iteration, move it into the next and increase the priority of that item.
Review all items that overflow into the next iteration to make sure that the team understands what is needed.
Publish the failure up the management chain if a defect survives to iterations.
Posted by Pete McBreen Sat, 19 Dec 2015 22:46:00 GMT
Recently as part of an archaeology task of understanding how some SQL queries were working, I needed to draw an ERD to help with my understanding of the database. After contemplating drawing the diagram by hand for a few seconds, I decided to leverage GraphViz and just draw a diagram of all of the foreign key relationships between the tables.
Since it was an Oracle database, the queries to read the relationships were not that complex ErdCrearion-specific.sql is designed to run in SQLDeveloper and prompt for the :OWNER tablespace name to pick the tables from, and limit the selection to the names mentioned in the tablelist CTE (unfortunately duplicated as I have not rewritten this to make it simpler).
gives us a nice image of the relationship. The table name is prefixed with the schema to make sure that you can identify the table correctly for those cases where the same table exists in multiple schemas, and the columns involved in the relationships are highlighted in their own box. The non-relationship columns appear at the bottom of the symbol (column ordering is maintained and hidden columns are not shown).
The resulting file when uploaded to a webserver that has d3.js in the right place is interactive - see scottsimple.html unlike the image above it can be clicked on to highlight the symbols or relationships - only the outer line of the table is clickable - the rest is left as an exercise for the reader.
Firefox has always had lots of really large extensions, but by deciding that they must be signed and reviewed, the Firefox community has just committed itself to a LOT of extra work reviewing the extensions. Hence the dumb idea of scanning to see if there is anything malicious in it. Now that is an arms race that is going to be lost. The guys in the AdBlock game know that, a continual game of whack a mole. Actively developed extensions like Zotero really lose out because a manual review of a large codebase takes a long time, and scanning is insufficient (as the above link describes, it is easy to create an add-on that passes scanning and does nasty things).
QA Engineer walks into a bar. Orders a beer. Orders 0 beers. Orders 999999999 beers. Orders a lizard. Orders -1 beers. Orders a sfdeljknesv.
I sure wish more programmers would focus a lot of attention on testing their own code before passing it on to QA/Test. That way the QA/Test team can focus on finding the requirements and interaction defects, rather than the simple coding mistakes that are often the bane of their existence
The whole of life is just like watching a film. Only it’s as though you always get in ten minutes after the big picture has started, and no-one will tell you the plot, so you have to work it out all yourself from the clues.
The presence of those seeking the truth is infinitely to be preferred to the presence of those who think they’ve found it.
It’s still magic even if you know how it’s done.
There are times in life when people must know when not to let go. Balloons are designed to teach small children this.
YOU HAVE TO START OUT LEARNING TO BELIEVE THE LITTLE LIES.
The truth may be out there, but the lies are inside your head.
Goodness is about what you do. Not who you pray to.
I have no use for people who have learned the limits of the possible.
Posted by Pete McBreen Mon, 16 Feb 2015 02:49:00 GMT
Kevlin Henney - of Curly Bracket Languages fame has a good video of his presentation at a recent NDC conference Seven Ineffective Coding Habits of Many Programmers. As usual a very entertaining talk, but Kevlin is also spot on in identifying ways in which we are lead to make incorrect decisions about the code we are writing.
In it he references a paper from Rob Pike Notes on Programming in C. Although Rob Pike wrote that paper back in 1989 it is still relevant, as can be seen by his words about variable names:
Length is not a virtue in a name; clarity of expression is.
The one skill that separates bad programmers from good programmers is attention to detail. In fact, it’s what separates the good from the bad in any profession. Without paying attention to the tiniest details of your work, you will miss key elements of what you create. In programming, this is how you end up with bugs and difficult-to-use systems.
Posted by Pete McBreen Wed, 02 Jul 2014 02:52:00 GMT
Software development is a hard problem.
Books like The Mythical Man Month, Set Phasers on Stun and The Inmates are running the Asylum have all pointed out in their own way that creating software is hard. Fred Brooks focused on the problem of large complex projects, and the problems that face project managers, the other two remind us that even small projects can fail because we still are not able to create software that is both easy to use and powerful enough to do that tasks that we want to do with software.
Until we are able to understand why software development is such a hard problem, we are not going to make much beyond incremental improvement. There will always be a few projects that through the operation of blind luck across millions of projects that results in seemingly reproducible improvement, but the normal regression to the mean will correct that eventually.
Posted by Pete McBreen Mon, 30 Jun 2014 03:17:00 GMT
I didn’t see this when it was first written, but it matches with my recent experiences.
… most programmers simply don’t know where the quality bar is. They don’t know what disciplines they should adopt. They don’t know the difference between good and bad code. And, most importantly, they have not learned that writing good clean code in a disciplined manner is the fastest and best way get the job done well. – Robert Martin
Posted by Pete McBreen Thu, 05 Jun 2014 02:47:00 GMT
Many software developers do not seem to understand the basics of our craft. Recently I’ve seen
SQL queries that were massively more complex than they needed to be - that when simplified, without any database changes ran more than 10 times faster
Client server applications that issue nearly 1000 SQL queries while refreshing what is supposed to be an interactive screen - the end result being that the poor user has to wait 5 to 10 seconds for the screen to refresh after conceptually simple actions
Supposedly secure web applications that sent Active Directory usernames and passwords in cleartext across HTTP connections
Code that created connections to external resources but forgot to free them - made for a very effective rate limiting mechanism since the external resource freed unused handles about an hour after they were last used
There have been lots more examples, but most of them fall into the category of being unbelievable if you were not a direct witness to the utter ignorance of the basics of software development that brought them to my attention.
Maybe it is time that we started to focus on the basics of the craft of coding before we get too far into creating overly complex systems that nobody can understand or fix.
Posted by Pete McBreen Fri, 22 Nov 2013 04:10:00 GMT
But I’m not sure we will learn the right lessons.
In the early 1980’s I worked on applications that had to process 300 transactions per minute. At the time that was considered a heavy load for a Dec Vax to deal with. By the late 1980’s the same applications were dealing with 1,000 transactions per minute because the hardware had got a lot faster. In the mid-1990’s I worked on a small scale credit card processing application, running on a later incarnation of the Dec Vax that was able to handle nearly 20 transactions per second. In the late 1990’s I worked on a stock exchange system that had to deal with what we thought at the time was a stupidly large number of messages per second … little did I know. Fast forward to the early 2000’s and I worked on consumer facing web applications that had to withstand 10,000 requests per second. By 2010 I had the fun of being on a real web scale project, experiencing the joys of being linked to by Digg and CNN and hoping that the ensuing millions of requests per hour would not being the system down.
They’d fully specify the software, the user interface, its internal workings, file formats, even write the user documentation, before a single line of code was written. Then they’d hand the parts off to development teams who would independently of each other create the components. Another team would do the integration.
The sad fact is that the big corporations that are awarded these big government contracts do not have a clue how to build web scale applications that work. They over promise and massively underdeliver. All too often large companies are awarded contracts to build large systems and fail to deliver anything of value except to their own shareholders.