Here's a quick note about SQL temp tables. In SQL Server, there are three kinds of temporary tables you can use. The first kind (my favorite) are known as table variables. They only exist in memory and are not written to disk (unless your OS is low on RAM and starts swapping). Table variable names start with an "@" just like other T-SQL variables and the syntax for one is like so:
You may have a full-time DBA where you work, but a lot of us share the CF developer and DB developer hats. Your SQL Server's performance can be an easy thing to overlook if your database is very small, or your website gets very little traffic. The easy (but not always correct) answer to most performance problems is "add an index". Some indexes are an obvious help, but how do you tell if the less obvious ones are really being used? It is possible to have too many indexes. In addition to bloating the size of your database, they take time to update which can actually slow your application DOWN on inserts and updates.
A recent thread on CF-Talk brought up this very good topic. It deals with the performance hit you can get when SQL Server implicitly converts your data to nchar and nvarchar for you when you have enabled Unicode support in your data sources. Unicode text cannot be stored in normal char or varchar fields. It must use nchar or nvarchar. These data types use two bytes per character, which means you can only store half as much text in them (limit 4,400 instead of 8,800). The problem is two fold:
- SQL Server cannot directly compare a varchar and nvarchar value so it must convert one.
- String manipulation or conversion on an indexed column will render the index useless
I just got out of a session with Jason Delmore talking about some of the new features being looked at in ColdFusion 9. He mostly talked about the ORM features being baked into the next version of ColdFusion courtesy of Hibernate. We also squeezed a few other tidbits of information out of him too.
Sorry I've been quiet for the past few days. My Flex adventures took a quick detour through the massive land of our AS400 and DB2. Now that I had a prototype of my pretty line, bar, and pie charts I needed some real data. My job was to write a process to fetch our sales data from the AS400 server here at work nightly and populate some SQL Server tables with it. Easy Peasy, I thought. I didn't know what I was in for.
So in the past 3 days I have been trying Flex I've had several out of memory errors that crashed my browser. I don't know if it is my operating system, my browser, Flash in general, or Flex, but it sucks. For the record I am using Windows XP Pro, IE 7, Flash 9, and Flex 3. This is what happens: As I develop, I keep hitting save in Flex Builder, waiting for it to recompile in the background, then Alt-tabbing over to IE and whacking F5 to refresh. Well, over the course of 2 or 3 hours of doing this, the memory usage for iexpolore.exe just keeps climbing and climbing as though there is a memory leak or garbage collection isn't happening.
There has been a lot of talk recently about design patterns aimed at circumventing the overhead ColdFusion imposes upon us when creating CFCs. I'm not sure who coined the term "Object Instantiation Penalty", but the first reference to it I can find in the CF community was over at the Dot Matrix blog. Everyone seems to agree that object creation in ColdFusion leaves something to be desired, but I haven't seen anyone really quantify the price yet. I decided some line charts were in order.
I've been staring at my computer monitor trying start this paragraph for about 10 minutes now, so I'm just going to start typing. I've been thinking about system design. Organization versus performance. Design patterns versus efficiency. We adopt some code without thought to its performance because we're talking about milliseconds, and the readability, organization, and structure gains our apps enjoy are well worth it. I'm not sure that is always the case though, and we don't notice it until too late.
On my home PC I have the developer edition of ColdFusion 8 installed along with Apache Web Server and MySQL 5. Apache and MySQL are pretty lightweight, but ColdFusion can get a little bulky when it comes to memory. I don't use my personal Dev sites all the time, so I like to turn it all off when I'm not using it. I only have 1 gig of RAM in this PC after all.
I love infinite loops. They're sort of the black hole of programming. No one really knows what you code does when it reaches the last iteration of an infinite loop, but I speculate it has something to do with String Theory and unbounded time and space increasing proportionately to the rate of dense matter being compressed by gravitational forces so strong even light can't escape. Well, that's what I came up with off the top of my head anyway. Speaking of infinite loops, I found one happening on my server today.