More About Searching
Our pre-indexing solution is, indeed, faster than the search program we examined last month. I did not perform any serious benchmarks on this set of programs, but the difference was readily apparent to the naked eye. Not only that, but our pre-indexed implementation made it easy to rank files according to the number of matches.
However, pre-indexing is not a panacea. For starters, it requires a good deal of disk space, weighing in at 2.6MB for an index of fewer than 400 files. However, given the rapidly dropping price of disk space, even a 10MB index should not prove to be much of a deterrent for most systems.
A bigger problem is the lack of flexibility that pre-indexing forces on a search system. For example, our index programs all used Perl's lc operator to force all of the letters to lowercase. Now that we have removed any trace of case from our index, how can we offer a case-sensitive search? The only real answer is to build the DBM file in a slightly different way, perhaps by storing an additional literal element in the hash for each file. Then we would know that abc appeared five times in a particular file, but that two of these were ABC and the remaining three were abc.
Pre-indexing also means we can no longer offer a phrase search, in addition to AND and OR searches. There are ways to solve this problem; the easiest might be to store “next word” information in the database hash. Then we could search for the first word of a phrase and use the “next word” information to see if the other words were found, one by one.
Finally, pre-indexing always means the index will lag behind other content on a web site. If the index is generated once every 24 hours, it might take up to one day for a new document to be read into the index. One solution is to run the indexer more often, such as every three or six hours.
Searching is an essential part of every good web site. It means users can find what interests them quickly, and can perform analyses that the site's administrators never expected. But as we saw last month, a straight search through a site's files can take a long time to execute. Pre-indexing is the standard solution to this problem, trading additional disk space and a slightly out-of-date index in exchange for faster execution speed. Understanding the trade-offs involved in writing a search engine makes it easier to evaluate free and commercial offerings, and thus make your site a more enjoyable place for users to visit.
Practical Task Scheduling Deployment
One of the best things about the UNIX environment (aside from being stable and efficient) is the vast array of software tools available to help you do your job. Traditionally, a UNIX tool does only one thing, but does that one thing very well. For example, grep is very easy to use and can search vast amounts of data quickly. The find tool can find a particular file or files based on all kinds of criteria. It's pretty easy to string these tools together to build even more powerful tools, such as a tool that finds all of the .log files in the /home directory and searches each one for a particular entry. This erector-set mentality allows UNIX system administrators to seem to always have the right tool for the job.
Cron traditionally has been considered another such a tool for job scheduling, but is it enough? This webinar considers that very question. The first part builds on a previous Geek Guide, Beyond Cron, and briefly describes how to know when it might be time to consider upgrading your job scheduling infrastructure. The second part presents an actual planning and implementation framework.
Join Linux Journal's Mike Diehl and Pat Cameron of Help Systems.
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|The Firebird Project's Firebird Relational Database||Jul 29, 2016|
|Stunnel Security for Oracle||Jul 28, 2016|
|SUSE LLC's SUSE Manager||Jul 21, 2016|
|My +1 Sword of Productivity||Jul 20, 2016|
|Non-Linux FOSS: Caffeine!||Jul 19, 2016|
|Murat Yener and Onur Dundar's Expert Android Studio (Wrox)||Jul 18, 2016|
- The Firebird Project's Firebird Relational Database
- Stunnel Security for Oracle
- My +1 Sword of Productivity
- Non-Linux FOSS: Caffeine!
- SUSE LLC's SUSE Manager
- Managing Linux Using Puppet
- Murat Yener and Onur Dundar's Expert Android Studio (Wrox)
- Doing for User Space What We Did for Kernel Space
- Google's SwiftShader Released
- SuperTuxKart 0.9.2 Released
With all the industry talk about the benefits of Linux on Power and all the performance advantages offered by its open architecture, you may be considering a move in that direction. If you are thinking about analytics, big data and cloud computing, you would be right to evaluate Power. The idea of using commodity x86 hardware and replacing it every three years is an outdated cost model. It doesn’t consider the total cost of ownership, and it doesn’t consider the advantage of real processing power, high-availability and multithreading like a demon.
This ebook takes a look at some of the practical applications of the Linux on Power platform and ways you might bring all the performance power of this open architecture to bear for your organization. There are no smoke and mirrors here—just hard, cold, empirical evidence provided by independent sources. I also consider some innovative ways Linux on Power will be used in the future.Get the Guide