Monday, April 29, 2013

Quick CFML Tips: Script-based Queries And Tag/Script Hybrid CFCs

While refactoring a particular process in a ColdFusion project at work, I learned two things I thought worth passing on:

1.  There are certain scenarios where doing queries in cfscript, instead of using the <cfquery> tag, does come with a significant performance penalty.  In my case, the scenario was one where I was taking two recordsets created by querying the database and running subqueries against those recordsets in a recursive fashion.  My guess is that instantiating the query object needed to perform query functions in cfscript (which I was doing with each recursion) was the main issue.  When I converted the queries and functions involved in the recursive process to use tag-based syntax, the amount of time it took the process to run dropped by over 33%.

Not saying that this means you should avoid doing script-style queries, just that if there are a large number of such queries in a long-running process, you might want to experiment with refactoring them.

2.  I already knew that I could have one or more cfscript blocks inside the body of a CFC function, but I didn't know that I could combine tag-syntax functions and script-syntax functions in the same CFC like so:

<cfcomponent accessors="true">
    <cffunction name="doX" output="false" returntype="void">

        public void function doY () {
</cfcomponent> had never crossed my mind to try it that way. Certainly useful when you need to run a CFML function that has no cfscript equivalent in whatever version of CFML engine you're using (I should note that I was using ColdFusion 9.0.1 in both of the above cases).

Wednesday, April 10, 2013

Overcoming the Cookie Size Limit When Using jQuery DataTables and Saved State

One of the features of the jQuery DataTables plugin is that you can use the configuration option "bStateSave" to store the current view of the table (the sort order, the number of rows displayed, the filter term, etc.) in a cookie, so if the user navigates away from the page then comes back, the table view is the same as how they left it.

However, if your website or web application stores the state of several DataTables, and a user hits all those tables faster than those cookies can expire (their default lifespan is 2 hours but can be customized with the "iCookieDuration" option), the user could hit the browser cookie size limit and start seeing errors on your site.  I ran into this problem today with an application I've been working on.

Fortunately, starting with version 1.9, DataTables provides functions that let developers intercept the process of saving the table state and reloading that state, and the plugin author provides a documentation page on how to use those functions to store the state data in localStorage, which in most browsers allows you to store a few MBs of data per site (far more than the 4K limit per site for cookies):

In my case, I decided that I would store the state data in sessionStorage rather than localStorage, but the principle was the same.