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Coder's Revolution: MySQL performance: INNER JOIN vs. sub-select. I ran into an interesting behavior with MySQL this week.
I was helping someone speed up a slow page and a sizable increase in performance was achieved by simply re-arranging the SQL statement. The page was calling a SQL statement inside of a loop-- probably around 150 times on a page load. My initial idea (and still the best long-term one I think) was to gather all the information from the database in a single cfquery and not hit the database over and over.
That approach would have required quite a lot more refactoring of code, so first we tried to squeeze some better performance out of the SQL already being called.This site used MySQL which I am not as familiar with compared to MSSQL, but I started by looking at an EXPLAIN statement. In MySQL the placing the keyword EXPLAIN before your select will cause the engine to output a result set which describes how the select was performed. [code]EXPLAIN SELECT * FROM my_table WHERE column = 'foo'[/code]
How to optimize subqueries and joins in MySQL at Xaprb. I have written before about using joins instead of subqueries, especially for NOT IN queries, which can usually be rewritten as exclusion joins – sometimes with huge efficiency gains.
In this article I’ll look more closely at the performance characteristics of a few queries I’ve optimized in MySQL 5.0.3. I’ll also show you some tricks you can use to get MySQL to optimize queries better when you know it’s being inefficient. Updates in a join I wrote recently about the theoretical problems caused by UPDATE statements with FROM clauses (Many-to-one problems in SQL). This particular query shows the performance difference between a “correct” query and a “bad, nonstandard” query I wrote recently at work. The application for this query is to update a table with aggregated clicks per day from a table of click-tracking data for online advertising.
Since the tables are InnoDB, the clustered index is the primary key. For this article, I populated my tables with some pseudo-random data. Troubleshooting Memory and Networking Issues. Many common issues with Linodes are caused by excessive memory consumption or networking configuration errors.
This guide provides suggestions for alleviating these problems. When your VPS is running low on physical memory, it may start to "swap thrash. " This means it's attempting to use your swap partition heavily instead of real RAM. We recommend you limit your swap partition size to 256 MB; heavy use of swap in a virtualized environment will cause major performance problems. Determining Free Memory and Swap Activity. Installing an SSL Certificate in Tomc... When you request an SSL certificate, you must provide a Certificate Signing Request (CSR) from your server.
The CSR includes your public key, and must contain the same details as the online request form in your account. After your request is vetted and your certificate is issued, download and install all of the provided files to complete the installation. SSL Certificate Renewal - Tomcat 4.x/... After we approve your certificate renewal request, you can download your SSL and intermediate certificate.
For more information, see Downloading an SSL Certificate. You must install both files on your Web server. You can also download the intermediate certificate here. Follow the instructions below to download and install signed certificate and intermediate certificates on your Web server. Generating a Certificate Signing Requ... To complete your online request form for an SSL, you need to generat a key pair and a Certificate Signing Request (CSR).
Follow these instructions to generate them for your website. Java 2 SDK 1.2 or above must be installed before you can generate your CSR. Once installed, you can use the "keytool" command to create your key pair and CSR. To Generate the Key Pair For the purposes of this article, we are using PuTTY as our Secure Shell (SSH) client, and we are running Tomcat on a Linux based server. To log in to the server's terminal SSH, double click on your servers SSH client.Enter the Host Name (or IP address), and then the Port the server is using.Select SSH as the Connection type, and then click OpenAt the SSH prompt, enter the server's username, and then press Enter on your keyboard.Enter the server's password, and then press Enter. Open Source Research and Reference. Using suphp To Secure A Shared Server. The challenge with securing a shared hosting server is how to secure the website from attack both from the outside and from the inside.
PHP has built-in features to help, but ultimately it s the wrong place to address the problem. Apache has built-in features too, but the performance cost of these features is prohibitive. This has created a gap that a number of third-party solutions have attempted to fill. One of the oldest of these is suphp, created by Sebastian Marsching. ViewDNS.info - Your one source for DNS related tools! Internet Health Report. SANS Internet Storm Center; Cooperative Network Security Community - Internet Security. New battery design could give electric vehicles a jolt. A radically new approach to the design of batteries, developed by researchers at MIT, could provide a lightweight and inexpensive alternative to existing batteries for electric vehicles and the power grid.
The technology could even make “refueling” such batteries as quick and easy as pumping gas into a conventional car. The new battery relies on an innovative architecture called a semi-solid flow cell, in which solid particles are suspended in a carrier liquid and pumped through the system. In this design, the battery’s active components — the positive and negative electrodes, or cathodes and anodes — are composed of particles suspended in a liquid electrolyte. These two different suspensions are pumped through systems separated by a filter, such as a thin porous membrane. The work was carried out by Mihai Duduta ’10 and graduate student Bryan Ho, under the leadership of professors of materials science W.
Communicating at an unknown rate.
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