|By Tom Peer||
|April 8, 2002 12:00 AM EDT||
[Ed. Note: We've run articles on this in the past, but - we can never say it enough!]
Cutting ColdFusion code is fun, and therein lies ColdFusion's biggest problem. It's too easy to get carried away writing code to do things that should be happening in the database itself - or often shouldn't be happening at all. It's also just too easy to use. You can get up and running far too quickly, and get into trouble even quicker. Sometimes experienced developers get carried away trying to do too much; beginners often start to run before they can walk.
When I came across a site where a simple query of news stories was taking a quarter of a second, I wasn't sure that writing their own object-caching mechanism in ColdFusion was entirely the right approach. I called a timeout - a morning to go over the basics. One simple run of the Query Analyzer diagnosed the problem: a date field was being used in a sort clause without an index.
The query time was reduced to around 15ms - around 6ms database time plus the ODBC overhead. If you use SQL Server, the Query Analyzer is a tool you should learn to love. As a basic rule, any query that does more than select a single record using a primary as the criterion will probably benefit from some sort of index.
Using it couldn't be simpler - simply open a window, enter your SQL query text and then press Ctrl + I to run an index analysis (see Figure 1). In SQL Server versions 7 and up it's become an invaluable tool. You can also take a look at the path analysis and turn on the "Show stats time" option in the Query->Current Connection Options dialog.
It's useful, but in a publishing application there's only so much you can do to tune database performance. You can get too worried about optimization - you're pushing about large text strings and that takes time. Hard-core optimization is more relevant in financial and engineering applications where the database is summarizing and calculating vast numbers of small records.
You're more likely to achieve better results if you concentrate your efforts on your ColdFusion code. ColdFusion offers two powerful ways of caching queries: the "cached within" feature and caching in a shared scope. Many developers aren't aware that you can cache any ColdFusion object in the application scope; structs and queries can just as easily be cached as scalar variables. You can cache queries that are unlikely to change in application.cfm:
<cfif NOT IsDefined("application.courses")>
<cflock scope="application" type="exclusive" timeout="10">
<cfquery name="courses" datasource="#application.dsn#">
SELECT * FROM COURSES
ORDER BY COURSE
<cfset application.courses = courses>
<cflock scope="application" type="exclusive" timeout="10">
(The locking after the query is vitally important; see article 20370 in the ColdFusion knowledgebase.)
By putting the actual query and assignment above into a separate include file and calling it whenever the table is affected, you can create your own full-fledged cache server. Alternatively, you can convert the query to a struct keyed by the primary key of the database table and put the struct into the application scope. There are custom tags in the developer's exchange to do this, but it's almost quicker to do it yourself.
Don't be scared of using the application scope. Memory's cheap and downtime isn't. If your entire database is only half a gigabyte and you have 2GB in your server, why not load it into the application scope?
Usually it's best to mix this approach with the cached within approach. Say you have a database of two thousand suppliers, listed by region, together with the services they offer. You want to use the "startrow, endrow" parameters of <CFOUTPUT> to show fifty at a time, but this means fetching the entire listing in the query, which takes nearly 150ms.
In this case you could put the fields you need for the listing in an application-level query and then, on a separate "view" page, select the main details in a separate query that you apply the cached within parameter to. This parameter of <CFQUERY> is one of ColdFusion's best features. It can send your sysadmin into a blind panic when he or she sees CF taking up 800MB ("It's got a leak!"), but it's so simple to use compared to rival offerings.
One technique I use all the time, caching formatted output, is a little more contentious. Say, for instance, you have fields in your supplier database for TEL, FAX, EMAIL, WEB - any of which may be blank or need formatting. In a listing page of fifty records this can take time. On one of my pages it was taking too much time just to do a simple list. My solution? Rather than copy the whole query into the application scope, I created a new query (see the Query-New() function) with fields for the primary key and formatted display.
Even more contentious: sometimes I put the formatted output back into the database. I do this all the time where the database is storing XML and I need to convert to HTML. Converting a page on the fly takes around 400ms (assuming XSL doesn't get stuck in an endless loop) and displaying a cached query takes less than 1ms.
This may sound like a lash-up (I less than impressed an old college friend who followed a slightly more formal career), but this is how the really expensive application servers work. Sure, they won't store large chunks of HTML in the database; they'll store serialized Java objects, but at least the HTML will still work when somebody changes the code. (Application servers store objects in a format that depends on the object definition [your code]. When you change that definition, the entire object store can be rendered unusable. It's very problematic, and I've seen plenty of implementations of expensive object servers where almost all the data is stored in plain SQL tables.)
Note: With reference to Ben Forta's February CFDJ article ("Faster and Safer Database Queries," Vol. 4, issue 2), you can't cache a query that uses a QUERYPARAM tag. You can, though, achieve the same security against malicious URLs by ensuring that all your tables have a numeric primary key and then validating any variables used in SQL queries with an "IsNumeric()" test. It's one more reason why all database tables should have a numeric primary key.
No matter how cheap memory gets, you do still need to apply a certain amount of discipline to your coding. One of the most common causes of database problems is fetching too much data from the database. Using derived tables and other advanced SQL constructs, you should be able to avoid fetching vast amounts of query data and looping over it.
A typical derived table query looks something like this:
SELECT TOP 1 A.NEWS_ID, A.HEADLINE, A.STORY FROM NEWS AS A,
(SELECT NEWS_ID FROM NEWS_CATEGORIES_JOIN
WHERE CATEGORY_ID IN (#cat_list#)) AS B
WHERE A.NEWS_ID = B.NEWS_ID
ORDER BY A.PUBDATE DESC
This will select a record from a correctly built many-to-many join (of which much more later) when a GROUP BY can't be used (i.e., with long text fields). This is just a simple example (a subselect could be used equally well here and run as quickly); derived tables are most effective when some sort of calculation needs to be performed, perhaps a summation or a count. If you find the idea of working with tables that don't exist a little frightening, you can often achieve the same affect by using a view, a stored query that can be queried and joined just like a standard table (see Figure 2).
Often underused, views are a great tool for making both your SQL and your CF code as simple as possible. They're second nature to anyone who's come to SQL Server from Access (where they're known as queries), but experienced programmers who have been using old-style databases often prefer to do everything in one query. Using views is usually quicker than performing joins or summaries at runtime. I saw a job advertisement recently that said "must be able to write join queries without using visual tools" and I thought: "Why?" There's no benefit, save a few techy kudos.
If you do need to loop over entire tables, try to avoid fetching the data into ColdFusion. Database cursors (described by Ian Rutherford in "Using MS-SQL Stored Procedures with ColdFusion," CFDJ Vol. 4, issue 2) will run much faster than dragging data into ColdFusion, processing it, and then running an update. It also won't take up a ColdFusion thread or valuable network capacity.
Speed Isn't Everything
As important as optimization is, sometimes there's too much focus on saving a millisecond here or cutting down white space there at the expense of properly structured code and databases. The key to software engineering, as in all engineering, is to keep it simple, and the main aim in a ColdFusion development should be no different from any other project: to keep the code to a minimum.
It's this discipline of keeping things simple that's the most important part of building reliable and scalable sites. It may seem strange, but sometimes code that runs slower can make for better Web sites. Take, for example, what for me is the litmus test of good database design: the use of many-to-many joins. A typical database application might be a listing of schools and the courses they offer. The original data, as always, is in Excel, looking something like the example in Figure 3. The experienced developer will recognize the need for a separate table of courses and a third "join" table indicating which schools have which courses.
The temptation, though, is simply to import it into the database and use it as is, relying on ColdFusion's list handling to determine which courses are offered by which schools. That would be bad, but what would be even worse would be some attempt to code the courses offered as separate database fields (see Figure 4).
Why you shouldn't do this is hard to explain, although it's simple: in a SELECT query it'll run two to three times as fast as using a many-to-many join, and it's easy to program using ColdFusion Studio. You just point the wizards at the right table and five minutes later you're done. But by doing something like this, you have hard-coded "data" into the "structure" of your system. To build truly scalable systems, you need to keep a very definite division between the structure and the data. The Golden Rule is this: if your ColdFusion code is completely separate from your database, then your system will scale. If you've hard-coded data as fieldnames - you just can't do this - your data is inextricably tied up with your application.
Using ColdFusion, it isn't always possible to adhere to the strict three-tier model (database, application, presentation), but creating a division between the structure and the data is still a must. You should be able to edit the data directly without using your ColdFusion application and still see the changes reflected on your site.
So, for instance, were you to add a new course to the table of courses, your site should display that course wherever relevant. Often this doesn't happen; data fields are hard-coded and the layout of the pages is dependent on the data structure.
Sometimes you might use the ColdFusion application to enforce certain database rules - for instance, that a salesperson can have a maximum of only 10 customers. This is fine. In fact, database theorists call such a rule an application rule for the very reason that it doesn't affect the underlying data. If a salesperson had 11 clients it wouldn't affect the data in any way. But if the only way you could add or remove clients was through the ColdFusion-based Web interface, then something would be amiss.
A simple example like the one shown in Figure 4 doesn't really illustrate the necessity of relational design. Once you're bug-free, the example will run faster than a relational design, and it will scale. It's simple and, above all, that's what matters.
You wouldn't have to get much more complicated before a flat file system like this would start to break down, though. It's not just raw performance that's the issue - the extra complexity of the code and the difficulties in making changes will all contribute in different ways to a lack of scalability. If a system relies on a single overworked developer to make simple changes, then it won't be scalable no matter how optimized the code.
As with any rule, the one about keeping the data separate from the code is easily broken. It's quite possible to make such a convoluted mess of triggers, derived tables, cursor loops, and other database constructs that no amount of processing power will save you. Keep it simple, though, and it will scale.
Easy in Theory
Although it makes things simpler in the database system, relational design can, if you're not careful, make things more complicated in the Web application. Using separate tables for many-to-many joins requires extra INSERT queries, and SELECT functions often have to employ grouping, subselects, or derived tables.
Perhaps the principal reason many-to-many joins don't get used is that most database editing systems don't have a standard component for implementing them. Access doesn't (you have to create a subform or use some VB), and if you're using HTML forms, you unfortunately can't use the "query" attribute of <CFSELECT> as it doesn't support multiple values for "selected". You can, however, use a simple loop:
<cfselect name="course_id" multiple="Yes">
DE("selected"), DE(""))# value="#courses_id#">#course#
Alternatively, you can use checkboxes; another effective device for editing many-to-many joins is a swap box. It's especially useful when you have many possible options to choose from, and it's more intuitive than multiple select boxes where the user has to control-click (see Figure 5).
There are several custom tags to do this in the developer's exchange, and my own <CF_SWAPBOX> is available from my site (see "Resources" section). It has almost identical syntax to CFSELECT, and also supports multiple values for "selected".
One thing you can't do much about is the complexity of inserting and updating the "join" tables (the third table used for many-to-many joins). You can cut down the number of queries needed by using an "insert into" with a subselect, for example:
INSERT INTO COURSES_SCHOOLS_JOIN
SELECT COURSES_ID, #form.SCHOOLS_ID#
WHERE COURSES_ID IN (#form.courses_id#)
but this won't run any faster than using multiple inserts in the same query. Nor can you run this as a stored procedure (you can't pass a list of integer primary keys as a VARCHAR and then use it in a subselect), nor can you use the <CFQUERYPARAM> tag. It's best just to run a separate insert for each row of the join table.
Perhaps, though, the biggest obstacle to correct database design isn't a technical one, but the very familiar problem of client demands. Before you can build a sound database, you need to convince the client that that's what's needed. The temptation for clients is to think of their Web site like a magazine: "I want to put that over there, that over there." Convincing clients they need to "think data" is the hardest part of any project.
In the most difficult project I ever worked on, the editor of the site was so incensed at no longer being able to work on the HTML pages himself that he got hold of the administrator password and replaced all the ColdFusion code with HTML pages he'd "saved as" from his browser. All the dynamic functions duly broke, but because the site still looked the same as it did before, the client never really understood what had happened. As far as he was concerned, my code didn't work. The editor was there to edit pages and that was what he was doing.
The concept of changing a page not by editing the page itself, but by editing a separate data system, is a surprisingly difficult conceptual hurdle for many people. It's such a simple concept that it's easy to forget how revolutionary it is. Those who have come from a print media background aren't going to buy into the database idea until they've had that hallelujah moment and seen just what an impact information systems can have. Until that time they're going to find using a database frustrating and too inflexible.
If your client isn't of the database mind-set when you start a project, it's vital that you help him or her see the light before you start programming. Otherwise you'll end up putting in hooks and hacks to try and satisfy client demands ("sometimes we might want to do something different"). They'll come back to haunt you.
I've found that the most important ingredient of a successful site isn't the design or my code, but getting the client used to the idea of editing a database. A client who comes to you not with ideas for "new pages" but a "new section" and a sketch of the underlying data is worth more than any amount of milliseconds saved from a database query.
The 3rd International Internet of @ThingsExpo, co-located with the 16th International Cloud Expo - to be held June 9-11, 2015, at the Javits Center in New York City, NY - announces that its Call for Papers is now open. The Internet of Things (IoT) is the biggest idea since the creation of the Worldwide Web more than 20 years ago.
Nov. 28, 2014 11:00 AM EST Reads: 1,791
Cultural, regulatory, environmental, political and economic (CREPE) conditions over the past decade are creating cross-industry solution spaces that require processes and technologies from both the Internet of Things (IoT), and Data Management and Analytics (DMA). These solution spaces are evolving into Sensor Analytics Ecosystems (SAE) that represent significant new opportunities for organizations of all types. Public Utilities throughout the world, providing electricity, natural gas and water, are pursuing SmartGrid initiatives that represent one of the more mature examples of SAE. We have s...
Nov. 27, 2014 04:00 PM EST Reads: 1,978
The security devil is always in the details of the attack: the ones you've endured, the ones you prepare yourself to fend off, and the ones that, you fear, will catch you completely unaware and defenseless. The Internet of Things (IoT) is nothing if not an endless proliferation of details. It's the vision of a world in which continuous Internet connectivity and addressability is embedded into a growing range of human artifacts, into the natural world, and even into our smartphones, appliances, and physical persons. In the IoT vision, every new "thing" - sensor, actuator, data source, data con...
Nov. 27, 2014 04:00 PM EST Reads: 2,066
The Internet of Things is tied together with a thin strand that is known as time. Coincidentally, at the core of nearly all data analytics is a timestamp. When working with time series data there are a few core principles that everyone should consider, especially across datasets where time is the common boundary. In his session at Internet of @ThingsExpo, Jim Scott, Director of Enterprise Strategy & Architecture at MapR Technologies, discussed single-value, geo-spatial, and log time series data. By focusing on enterprise applications and the data center, he will use OpenTSDB as an example t...
Nov. 27, 2014 03:00 PM EST Reads: 2,230
How do APIs and IoT relate? The answer is not as simple as merely adding an API on top of a dumb device, but rather about understanding the architectural patterns for implementing an IoT fabric. There are typically two or three trends: Exposing the device to a management framework Exposing that management framework to a business centric logic Exposing that business layer and data to end users. This last trend is the IoT stack, which involves a new shift in the separation of what stuff happens, where data lives and where the interface lies. For instance, it's a mix of architectural styles ...
Nov. 27, 2014 03:00 PM EST Reads: 2,084
An entirely new security model is needed for the Internet of Things, or is it? Can we save some old and tested controls for this new and different environment? In his session at @ThingsExpo, New York's at the Javits Center, Davi Ottenheimer, EMC Senior Director of Trust, reviewed hands-on lessons with IoT devices and reveal a new risk balance you might not expect. Davi Ottenheimer, EMC Senior Director of Trust, has more than nineteen years' experience managing global security operations and assessments, including a decade of leading incident response and digital forensics. He is co-author of t...
Nov. 27, 2014 01:00 PM EST Reads: 2,125
The Internet of Things will greatly expand the opportunities for data collection and new business models driven off of that data. In her session at @ThingsExpo, Esmeralda Swartz, CMO of MetraTech, discussed how for this to be effective you not only need to have infrastructure and operational models capable of utilizing this new phenomenon, but increasingly service providers will need to convince a skeptical public to participate. Get ready to show them the money!
Nov. 27, 2014 11:00 AM EST Reads: 1,951
The Internet of Things will put IT to its ultimate test by creating infinite new opportunities to digitize products and services, generate and analyze new data to improve customer satisfaction, and discover new ways to gain a competitive advantage across nearly every industry. In order to help corporate business units to capitalize on the rapidly evolving IoT opportunities, IT must stand up to a new set of challenges. In his session at @ThingsExpo, Jeff Kaplan, Managing Director of THINKstrategies, will examine why IT must finally fulfill its role in support of its SBUs or face a new round of...
Nov. 27, 2014 10:00 AM EST Reads: 1,947
One of the biggest challenges when developing connected devices is identifying user value and delivering it through successful user experiences. In his session at Internet of @ThingsExpo, Mike Kuniavsky, Principal Scientist, Innovation Services at PARC, described an IoT-specific approach to user experience design that combines approaches from interaction design, industrial design and service design to create experiences that go beyond simple connected gadgets to create lasting, multi-device experiences grounded in people's real needs and desires.
Nov. 27, 2014 08:00 AM EST Reads: 1,924
Enthusiasm for the Internet of Things has reached an all-time high. In 2013 alone, venture capitalists spent more than $1 billion dollars investing in the IoT space. With "smart" appliances and devices, IoT covers wearable smart devices, cloud services to hardware companies. Nest, a Google company, detects temperatures inside homes and automatically adjusts it by tracking its user's habit. These technologies are quickly developing and with it come challenges such as bridging infrastructure gaps, abiding by privacy concerns and making the concept a reality. These challenges can't be addressed w...
Nov. 27, 2014 07:45 AM EST Reads: 2,052
The Domain Name Service (DNS) is one of the most important components in networking infrastructure, enabling users and services to access applications by translating URLs (names) into IP addresses (numbers). Because every icon and URL and all embedded content on a website requires a DNS lookup loading complex sites necessitates hundreds of DNS queries. In addition, as more internet-enabled ‘Things' get connected, people will rely on DNS to name and find their fridges, toasters and toilets. According to a recent IDG Research Services Survey this rate of traffic will only grow. What's driving t...
Nov. 27, 2014 07:00 AM EST Reads: 2,107
Scott Jenson leads a project called The Physical Web within the Chrome team at Google. Project members are working to take the scalability and openness of the web and use it to talk to the exponentially exploding range of smart devices. Nearly every company today working on the IoT comes up with the same basic solution: use my server and you'll be fine. But if we really believe there will be trillions of these devices, that just can't scale. We need a system that is open a scalable and by using the URL as a basic building block, we open this up and get the same resilience that the web enjoys.
Nov. 27, 2014 06:45 AM EST Reads: 2,168
Connected devices and the Internet of Things are getting significant momentum in 2014. In his session at Internet of @ThingsExpo, Jim Hunter, Chief Scientist & Technology Evangelist at Greenwave Systems, examined three key elements that together will drive mass adoption of the IoT before the end of 2015. The first element is the recent advent of robust open source protocols (like AllJoyn and WebRTC) that facilitate M2M communication. The second is broad availability of flexible, cost-effective storage designed to handle the massive surge in back-end data in a world where timely analytics is e...
Nov. 27, 2014 06:45 AM EST Reads: 2,091
We are reaching the end of the beginning with WebRTC, and real systems using this technology have begun to appear. One challenge that faces every WebRTC deployment (in some form or another) is identity management. For example, if you have an existing service – possibly built on a variety of different PaaS/SaaS offerings – and you want to add real-time communications you are faced with a challenge relating to user management, authentication, authorization, and validation. Service providers will want to use their existing identities, but these will have credentials already that are (hopefully) i...
Nov. 27, 2014 04:00 AM EST Reads: 1,761
"Matrix is an ambitious open standard and implementation that's set up to break down the fragmentation problems that exist in IP messaging and VoIP communication," explained John Woolf, Technical Evangelist at Matrix, in this SYS-CON.tv interview at @ThingsExpo, held Nov 4–6, 2014, at the Santa Clara Convention Center in Santa Clara, CA.
Nov. 27, 2014 04:00 AM EST Reads: 1,823
P2P RTC will impact the landscape of communications, shifting from traditional telephony style communications models to OTT (Over-The-Top) cloud assisted & PaaS (Platform as a Service) communication services. The P2P shift will impact many areas of our lives, from mobile communication, human interactive web services, RTC and telephony infrastructure, user federation, security and privacy implications, business costs, and scalability. In his session at @ThingsExpo, Robin Raymond, Chief Architect at Hookflash, will walk through the shifting landscape of traditional telephone and voice services ...
Nov. 26, 2014 02:00 PM EST Reads: 2,093
Explosive growth in connected devices. Enormous amounts of data for collection and analysis. Critical use of data for split-second decision making and actionable information. All three are factors in making the Internet of Things a reality. Yet, any one factor would have an IT organization pondering its infrastructure strategy. How should your organization enhance its IT framework to enable an Internet of Things implementation? In his session at Internet of @ThingsExpo, James Kirkland, Chief Architect for the Internet of Things and Intelligent Systems at Red Hat, described how to revolutioniz...
Nov. 24, 2014 07:00 PM EST Reads: 2,254
Bit6 today issued a challenge to the technology community implementing Web Real Time Communication (WebRTC). To leap beyond WebRTC’s significant limitations and fully leverage its underlying value to accelerate innovation, application developers need to consider the entire communications ecosystem.
Nov. 24, 2014 12:00 PM EST Reads: 2,019
The definition of IoT is not new, in fact it’s been around for over a decade. What has changed is the public's awareness that the technology we use on a daily basis has caught up on the vision of an always on, always connected world. If you look into the details of what comprises the IoT, you’ll see that it includes everything from cloud computing, Big Data analytics, “Things,” Web communication, applications, network, storage, etc. It is essentially including everything connected online from hardware to software, or as we like to say, it’s an Internet of many different things. The difference ...
Nov. 24, 2014 11:00 AM EST Reads: 2,370
Cloud Expo 2014 TV commercials will feature @ThingsExpo, which was launched in June, 2014 at New York City's Javits Center as the largest 'Internet of Things' event in the world.
Nov. 24, 2014 09:00 AM EST Reads: 2,242