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  • Not allow a href tags in form textarea

    - by saquib
    Hello friends, How can i prevent user to enter any url or link in contact form text area, i have tried it with this but its not working - if (!isset($_POST['submit']) && preg_match_all('/<a.*>.*<\/a>/', $_POST['query'])) { echo "<h1 style='color:red;'>HTML Tag Not allowed </h1>"; } else { //sendmail } Please help me

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  • Gradually enlarging text

    - by WCoastGuynCA
    I want to create a Flash or animated video that starts with a red dot on a black background. Gradually the dot increases in size and is actually text which says something such as "Buy American". How can this be done?

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  • Best way to add/change 1 GET value while keeping others?

    - by John Isaacks
    How can I make a link that justs adds or changes 1 GET var while maintaining all others? I have a page that is created using different GET vars. So it will be like mypage.php?color=red&size=7&brand=some%20brand So I want to have a link that sets it to page=2 or size=8. Whats the easiest way to have a link do that without reseting all the other vars? I hope that makes sense, let me know if I need to further explain anything

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  • getting panel color

    - by user161004
    I have a program where i have a button to change the background color to red and another button to set back the default panel color. How do i get back the default color for panel??

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  • sonar code coverage issue

    - by user1490244
    Hi I am running sonar for my impl class, i have written junit for all the methods of impl class but when i ran the sonar the code coverage is just 11% and all the file is in red color. stating that the code is not covered. I really dont understand inspite of writing all the test methods for all the impl methods why is it showing such a less percentage. Any help or tips or guidelines will be greatly appreciated. Thanks

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  • Multiple certs with one private key on apache?

    - by tenbatsu
    Really fundamental question here, but nothing a quick google search is lending itself to. Do I need to generate a separate private key for each cert I use in apache? Server details: % /usr/sbin/httpd -v Server version: Apache/2.2.8 (Unix) Server built: Jan 24 2008 10:44:19 % uname -a Linux *.com 2.6.23.15-80.fc7 #1 SMP Sun Feb 10 17:29:10 EST 2008 i686 i686 i386 GNU/Linux % cat /proc/versionversion 2.6.23.15-80.fc7 ([email protected]) (gcc version 4.1.2 20070925 (Red Hat 4.1.2-27)) #1 SMP Sun Feb 10 17:29:10 EST 2008

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  • GMail suspects confirmation email in stealing personal information

    - by Dennis Gorelik
    When user registers on my web site, web site sends user email confirmation link. Subject: Please confirm your email address Body:Please open this link in your browser to confirm your email address: http://www.postjobfree.com/a/c301718062444f96ba0e358ea833c9b3 This link will expire on: 6/9/2012 8:04:07 PM EST. If my web site sends that email to GMaill (either @gmail.com or another domain that's handled by Google Apps) and that user never emailed to email -- then GMail not only puts the email to spam folder, but also adds prominent red warning:Be careful with this message. Similar messages were used to steal people's personal information. Unless you trust the sender, don't click links or reply with personal information. Learn more That warning really scares many of my users, so they are afraid to open that link and confirm their email. What can I do about it? Ideally I would like that message end up in user's inbox, not spam folder. But at least how do I prevent that scary message? IP address of my mailing server is not blacklisted: http://www.mxtoolbox.com/SuperTool.aspx?action=blacklist%3a208.43.198.72 I use SPF and DKIM signature. Below is the email that ended up in spam folder with that scary red message. Delivered-To: [email protected] Received: by 10.112.84.98 with SMTP id x2csp36568lby; Fri, 8 Jun 2012 17:04:15 -0700 (PDT) Received: by 10.60.25.6 with SMTP id y6mr9110318oef.42.1339200255375; Fri, 08 Jun 2012 17:04:15 -0700 (PDT) Return-Path: Received: from smtp.postjobfree.com (smtp.postjobfree.com. [208.43.198.72]) by mx.google.com with ESMTP id v8si6058193oev.44.2012.06.08.17.04.14; Fri, 08 Jun 2012 17:04:15 -0700 (PDT) Received-SPF: pass (google.com: domain of [email protected] designates 208.43.198.72 as permitted sender) client-ip=208.43.198.72; Authentication-Results: mx.google.com; spf=pass (google.com: domain of [email protected] designates 208.43.198.72 as permitted sender) [email protected]; dkim=pass [email protected] DomainKey-Signature: a=rsa-sha1; c=nofws; q=dns; d=postjobfree.com; s=postjobfree.com; h= received:message-id:mime-version:from:to:date:subject:content-type; b=TCip/3hP1WWViWB1cdAzMFPjyi/aUKXQbuSTVpEO7qr8x3WdMFhJCqZciA69S0HB4 Koatk2cQQ3fOilr4ledCgZYemLSJgwa/ZRhObnqgPHAglkBy8/RAwkrwaE0GjLKup 0XI6G2wPlh+ReR+inkMwhCPHFInmvrh4evlBx/VlA= DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=postjobfree.com; s=postjobfree.com; h=content-type:subject:date:to:from:mime-version:message-id; bh=N59EIgRECIlAnd41LY4HY/OFI+v1p7t5M9yP+3FsKXY=; b=J3/BdZmpjzP4I6GA4ntmi4REu5PpOcmyzEL+6i7y7LaTR8tuc2h7fdW4HaMPlB7za Lj4NJPed61ErumO66eG4urd1UfyaRDtszWeuIbcIUqzwYpnMZ8ytaj8DPcWPE3JYj oKhcYyiVbgiFjLujib3/2k2PqDIrNutRH9Ln7puz4= Received: from sv3035 (sv3035 [208.43.198.72]) by smtp.postjobfree.com with SMTP; Fri, 8 Jun 2012 20:04:07 -0400 Message-ID: MIME-Version: 1.0 From: "PostJobFree Notification" To: [email protected] Date: 8 Jun 2012 20:04:07 -0400 Subject: Please confirm your email address Content-Type: multipart/alternative; boundary=--boundary_107_ffa6a9ea-01dc-40f5-a50c-4c3b3d113f08 ----boundary_107_ffa6a9ea-01dc-40f5-a50c-4c3b3d113f08 Content-Type: text/plain; charset=us-ascii Content-Transfer-Encoding: quoted-printable Please open this link in your browser to confirm your email addre= ss: =0D=0Ahttp://www.postjobfree.com/a/c301718062444f96ba0e358ea8= 33c9b3 =0D=0AThis link will expire on: 6/9/2012 8:04:07 PM EST. =0D=0A ----boundary_107_ffa6a9ea-01dc-40f5-a50c-4c3b3d113f08 Content-Type: text/html; charset=utf-8 Content-Transfer-Encoding: base64 PGh0bWw+PGhlYWQ+PG1ldGEgaHR0cC1lcXVpdj1Db250ZW50LVR5cGUgY29udGVu dD0idGV4dC9odG1sOyBjaGFyc2V0PXV0Zi04Ij48L2hlYWQ+DQo8Ym9keT48ZGl2 Pg0KUGxlYXNlIG9wZW4gdGhpcyBsaW5rIGluIHlvdXIgYnJvd3NlciB0byBjb25m aXJtIHlvdXIgZW1haWwgYWRkcmVzczo8YnIgLz48YSBocmVmPSJodHRwOi8vd3d3 LnBvc3Rqb2JmcmVlLmNvbS9hL2MzMDE3MTgwNjI0NDRmOTZiYTBlMzU4ZWE4MzNj OWIzIj5odHRwOi8vd3d3LnBvc3Rqb2JmcmVlLmNvbS9hL2MzMDE3MTgwNjI0NDRm OTZiYTBlMzU4ZWE4MzNjOWIzPC9hPjxiciAvPlRoaXMgbGluayB3aWxsIGV4cGly ZSBvbjogNi85LzIwMTIgODowNDowNyBQTSBFU1QuPGJyIC8+DQo8L2Rpdj48L2Jv ZHk+PC9odG1sPg== ----boundary_107_ffa6a9ea-01dc-40f5-a50c-4c3b3d113f08--

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  • "Possible SYN flooding" in log despite low number of SYN_RECV connections

    - by al4
    Recently we had an apache server which was responding very slowly due to SYN flooding. The workaround for this was to enable tcp_syncookies (net.ipv4.tcp_syncookies=1 in /etc/sysctl.conf). I posted a question about this here if you want more background. After enabling syncookies we started seeing the following message in /var/log/messages approximately every 60 seconds: [84440.731929] possible SYN flooding on port 80. Sending cookies. Vinko Vrsalovic informed me that this means the syn backlog is getting full, so I raised tcp_max_syn_backlog to 4096. At some point I also lowered tcp_synack_retries to 3 (down from the default of 5) by issuing sysctl -w net.ipv4.tcp_synack_retries=3. After doing this, the frequency seemed to drop, with the interval of the messages varying between roughly 60 and 180 seconds. Next I issued sysctl -w net.ipv4.tcp_max_syn_backlog=65536, but am still getting the message in the log. Throughout all this I've been watching the number of connections in SYN_RECV state (by running watch --interval=5 'netstat -tuna |grep "SYN_RECV"|wc -l'), and it never goes higher than about 240, much much lower than the size of the backlog. Yet I have a Red Hat server which hovers around 512 (limit on this server is the default of 1024). Are there any other tcp settings which would limit the size of the backlog or am I barking up the wrong tree? Should the number of SYN_RECV connections in netstat -tuna correlate to the size of the backlog? Update As best I can tell I'm dealing with legitimate connections here, netstat -tuna|wc -l hovers around 5000. I've been researching this today and found this post from a last.fm employee, which has been rather useful. I've also discovered that the tcp_max_syn_backlog has no effect when syncookies are enabled (as per this link) So as a next step I set the following in sysctl.conf: net.ipv4.tcp_syn_retries = 3 # default=5 net.ipv4.tcp_synack_retries = 3 # default=5 net.ipv4.tcp_max_syn_backlog = 65536 # default=1024 net.core.wmem_max = 8388608 # default=124928 net.core.rmem_max = 8388608 # default=131071 net.core.somaxconn = 512 # default = 128 net.core.optmem_max = 81920 # default = 20480 I then setup my response time test, ran sysctl -p and disabled syncookies by sysctl -w net.ipv4.tcp_syncookies=0. After doing this the number of connections in the SYN_RECV state still remained around 220-250, but connections were starting to delay again. Once I noticed these delays I re-enabled syncookies and the delays stopped. I believe what I was seeing was still an improvement from the initial state, however some requests were still delayed which is much worse than having syncookies enabled. So it looks like I'm stuck with them enabled until we can get some more servers online to cope with the load. Even then, I'm not sure I see a valid reason to disable them again as they're only sent (apparently) when the server's buffers get full. But the syn backlog doesn't appear to be full with only ~250 connections in the SYN_RECV state! Is it possible that the SYN flooding message is a red herring and it's something other than the syn_backlog that's filling up? If anyone has any other tuning options I haven't tried yet I'd be more than happy to try them out, but I'm starting to wonder if the syn_backlog setting isn't being applied properly for some reason.

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  • How to use more than 3 virtual disks in Linux using CentOS and XenServer

    - by 010110110101
    I've attached 5 virtual disks to a Virtual Machine in Citrix XenServer. The VM has the xs-tools installed. Initially it said that it couldn't add so many disks. After I installed the xs-tools, it let me add all the disks. But /dev doesn't show all the disks. It shows these: /dev/xvda /dev/xvdb /dev/xvdc /dev/cdrom Perhaps it is bound by the limits of an IDE bus? (3 disks + CD-ROM) If so, how does one change the VM to use SCSI? Edit: According to the documentation: 2.6.3. VM Block Devices In the PV Linux case, block devices are passed through as PV devices. XenServer does not attempt to emulate SCSI or IDE, but instead provides a more suitable interface in the virtual environment in the form of xvd* devices. It is also possible to get an sd* device using the same mechanism, where the PV driver inside the VM takes over the SCSI device namespace. This is not desirable so it is best to use xvd* where possible for PV guests (this is the default for Debian and RHEL). For Windows or other fully virtualized guests, XenServer emulates an IDE bus in the form of an hd* device. When using Windows, installing the Citrix Tools for Virtual Machines installs a special PV driver that works in a similar way to Linux, except in the fully virtualized environment. Still, with 5 virtual disks attached, I don't see the other xvd devices. Edit #2: (attached requested info) Host Machine: XenServer 6.1 Linux version 2.6.32.43-0.4.1.xs1.6.10.777.170770xen (geeko@buildhost) (gcc version 4.1.2 20080704 (Red Hat 4.1.2-51)) #1 SMP Wed Apr 17 05:52:03 EDT 2013 Guest Machine: CentOS release 6.4 (Final) Linux version 2.6.32-358.6.2.el6.x86_64 ([email protected]) (gcc version 4.4.7 20120313 (Red Hat 4.4.7-3) (GCC) ) #1 SMP Thu May 16 20:59:36 UTC 2013 Output of 'fdisk -l' on Guest Machine: Note, the disk beyond the first 3 attached are not displaying -- there should be 4 100GB disks. (There are a total of 5 disks displayed in XenCenter -- 16GB, 100GB, 100GB, 100GB, 100GB) Disk /dev/xvdb: 107.4 GB, 107374182400 bytes 255 heads, 63 sectors/track, 13054 cylinders Units = cylinders of 16065 * 512 = 8225280 bytes Sector size (logical/physical): 512 bytes / 512 bytes I/O size (minimum/optimal): 512 bytes / 512 bytes Disk identifier: 0xfb6c95b9 Device Boot Start End Blocks Id System /dev/xvdb1 1 13054 104856223+ 83 Linux Disk /dev/xvda: 17.2 GB, 17179869184 bytes 255 heads, 63 sectors/track, 2088 cylinders Units = cylinders of 16065 * 512 = 8225280 bytes Sector size (logical/physical): 512 bytes / 512 bytes I/O size (minimum/optimal): 512 bytes / 512 bytes Disk identifier: 0x000e5f41 Device Boot Start End Blocks Id System /dev/xvda1 * 1 64 512000 83 Linux Partition 1 does not end on cylinder boundary. /dev/xvda2 64 2089 16264192 8e Linux LVM Disk /dev/xvdc: 107.4 GB, 107374182400 bytes 255 heads, 63 sectors/track, 13054 cylinders Units = cylinders of 16065 * 512 = 8225280 bytes Sector size (logical/physical): 512 bytes / 512 bytes I/O size (minimum/optimal): 512 bytes / 512 bytes Disk identifier: 0xed249ced Device Boot Start End Blocks Id System /dev/xvdc1 1 13054 104856223+ 83 Linux Disk /dev/mapper/vg_blue-lv_root: 14.6 GB, 14571012096 bytes 255 heads, 63 sectors/track, 1771 cylinders Units = cylinders of 16065 * 512 = 8225280 bytes Sector size (logical/physical): 512 bytes / 512 bytes I/O size (minimum/optimal): 512 bytes / 512 bytes Disk identifier: 0x00000000 Disk /dev/mapper/vg_blue-lv_swap: 2080 MB, 2080374784 bytes 255 heads, 63 sectors/track, 252 cylinders Units = cylinders of 16065 * 512 = 8225280 bytes Sector size (logical/physical): 512 bytes / 512 bytes I/O size (minimum/optimal): 512 bytes / 512 bytes Disk identifier: 0x00000000 I see that the Linux versions say SMP. The Guest VM doesn't say "xen" in the name. However, I have already run yum install kernel-xen. Could be a clue?

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  • My 3D Games crashing in these scenarios

    - by desaivv
    I have a situation here which I am unable to solve. I bought a PC last year March, here are my specs: Intel Core i3 550 @ 3GHz 4 GB RAM @400 MHz XFX GeForce 9500 GT graphics card 1GB @550MHz 500 GB HDD Lately as soon as I load my save game of Skyrim, it crashes. I have been playing Skyrim since I joined Gaming.SE site. Crashes as in the entire scene gets red lines. I can not ALT + TAB back or even CTRL + ALT + DEL either. My only recourse is a hard reset via the power button. Can not take a screen shot either. I have the latest Forceware 296.10 drivers also. This has been happening since the last 2 weeks. I always use Driver Sweeper to clean my old drivers, since that is what XFXForce recommends before installing new drivers. I installed MSI Afterburner lately to see my GPU temperature. My GPU is default, never over-clocked it. In MSI's Afterburner, I can not adjust fan speed. It is greyed out. Also in settings there is no fan tab. With normal Internet browsing it stays at 51 C. Ran Memtest86 over night with level 11. Took about 13 hours, but no errors in my RAM. I even re-installed my OS, with just the 296 drivers. The fan for the GPU does come on. I can play Diablo 2. I can not get past Warcraft 3's menu selection. There WAS some dust in my machine, but I always try and keep everything clean, since in my home town dust is an issue. Always keep cool my entire PC cabinet. My friend came with his functioning graphics card, we bought our PCs at the same time with exact same specifications. His card did not work either. Same problem with the scene freezing with red lines. I did do my research before posting here. That is how I was able to learn about MSI Afterburner, Driver Sweeper, SpeedFan etc. I followed posts on Tom's Hardware too regarding people that had similar problems. One person suggested and was followed by worked as well the suggestion to "Bake the card in an oven". Since I bought it, played Diablo 2 for months, Starcraft 2 campaign for months and Skyrim recently for months. Bought ME3 also. I am at my wits end. I do not know what else to do. I can go out and buy a card, but my friend's card did not work either. I can use the machine for Eclipse or VS2010 development just fine. Just not with 3D gaming. I originally posted this question on Gaming.SE But I was directed here. I have browsed the SU database for my problem and found this, this, and this. But none of these cover my question. My machine is only one year old. Can some experienced superuser(s) shed some light on this scenario? Is it a 3D graphics card problem? Will a brand new card work? What else can I try to pin point the problem? Can it be the Motherboard? Thanks.

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  • Week in Geek: USDA Chooses Microsoft for Cloud Services Edition

    - by Asian Angel
    This week we learned how to create geeky LED holiday lights with old bottles, dig deeper in Windows Defrag via the command prompt, use Google Chrome’s drag/drop feature to upload files easier, find great gift recommendations by looking through the How-To Geek holiday gift guide, and have fun adding Merry Christmas fonts to our computers. Photo by ntr23. Random Geek Links It has been a busy week, so we have extra news link goodness with information that is good for you to know. USDA making the move to Microsoft The U.S. Department of Agriculture has announced that it has chosen Microsoft to host things like e-mail, instant messaging, and collaboration through the software giant’s Business Productivity Online Suite. Google says it was cut off from USDA project bid Google is claiming that it was not given a chance to bid on a cloud-computing project for the U.S. Department of Agriculture, for which the contract was awarded to rival Microsoft. Apache is being forced into a Java Fork When Oracle rolled over Apache and Google’s objections to its Java plans in December, the scene was set for Apache to leave and, eventually, force a Java code fork. Tumblr explains daylong outage After experiencing an outage that started on Sunday afternoon and stretched through most of the day yesterday, Tumblr has explained what happened. Google demos Chrome OS, launches pilot program During a press briefing this week in San Francisco, Google launched the Chrome application store and demonstrated Chrome OS, its browser-centric netbook operating system. Don’t expect Spotify in U.S. this holiday season As of last week, Spotify had yet to sign a single licensing deal with a major label, after spending more than a year negotiating, multiple music sources told CNET. December 2010 Patch Tuesday will come with most bulletins ever According to the Microsoft Security Response Center, Microsoft will issue 17 Security Bulletins addressing 40 vulnerabilities on Tuesday, December 14. It will also host a webcast to address customer questions the following day. Hacker plants back door in Symbian firmware Indian hacker Atul Alex has had a look at the firmware for Symbian S60 smartphones and come up with a back door for it. PC quarantines raise tough complexities The concept of quarantining PCs to prevent widespread infection is “interesting, but difficult to implement, with far too many problems”, said security experts. Symantec: DDoS attacks hard to defend It has surfaced that the distributed denial of service (DDoS) attacks on Visa and MasterCard Web sites on Wednesday were carried out by a toolkit known as low orbit ion cannon (LOIC). Web Sockets and the risks of unfinished standards Enthusiasm for a promising new standard called Web Sockets has quickly cooled in some quarters as a potential security problem led some browser makers to hastily postpone support. Internet Explorer 9 to get tracking protection Microsoft is making changes to Internet Explorer 9’s security features that will better enable users to keep sites from tracking their activity across browsing sessions. NASA sold PCs with sensitive data NASA failed to remove sensitive data from computers that it sold, according to an audit report released this week. Cybercrooks create fake Amazon receipts The bad guys have created yet another online scam, this one involving fake Amazon receipts. World of Warcraft character move fees waived Until December 22, Blizzard will allow free realm transfers from 25 highly populated servers to alleviate log-in queues or performance issues. (The free transfers are one-way and one-time only.) SpaceX Dragon reaches orbit atop a Falcon with a fiery tail The Space Exploration Technologies corporation has become the first nongovernmental entity to put a vehicle into low Earth orbit. Geek Video of the Week If birds have wings, then why are the Angry Birds using slingshots? Photo by Dorkly Bits. Wait… Birds have Wings, Why are the Angry Ones Using Slingshots? Sysadmin Geek Tips How To Setup Email Alerts on Linux Using Gmail or SMTP Linux machines may require administrative intervention in countless ways, but without manually logging into them how would you know about it? Here’s how to setup emails to get notified when your machines want some tender love and attention. Random TinyHacker Links Red Panda Webcam Support Firefox and the Knoxville Zoo’s Red Panda program. Christmas Icons (Icons we like) Superb set of holiday icons by lgp85 at deviantArt. Download the .zip and use as .png or convert to .ico at Convertico.com or with tiny app Imagicon. Super User Questions Enjoy reading the great answers to this week’s popular questions from Super User Useful USB boot disks? DVD/CD burning .zip: is it more reliable, faster, longer lasting to burn a zip of files rather than the files as a folder? What are other ways to backup my files if I do not have an external drive? Anti virus what is the difference between these all? How can I block all Facebook elements/content? How-To Geek Weekly Article Recap Have you had a busy week between work and preparing for the holidays? Get caught up on your HTG reading with our hottest articles of the week. 20 Windows Keyboard Shortcuts You Might Not Know The 50 Best Registry Hacks that Make Windows Better LCD? LED? Plasma? The How-To Geek Guide to HDTV Technology HTG Explains: Which Linux File System Should You Choose? How to Use and Customize Google Chrome Web Apps One Year Ago on How-To Geek This week’s batch of retro geeky goodness is all about customizing Windows 7. ClassicShell Adds Classic Start Menu and Explorer Features to Windows 7 Get an Aero-Styled Classic Start Menu in Windows 7 Customize the Windows 7 Logon Screen Get the Classic Style Network Activity Indicator Back in Windows 7 How To Enable Check Boxes for Items In Windows 7 The Geek Note We would like you to join us in welcoming Jason Fitzpatrick to the writing staff here at How-To Geek. He started with us this past week, so take some time to read through his articles about the Wii, Kindle, & PlayStation 2 Peripherals and leave a friendly comment to say “Hi”! Got a great tip to share? Make sure to send it in to us at [email protected]. Photo by real00. Latest Features How-To Geek ETC The 50 Best Registry Hacks that Make Windows Better The How-To Geek Holiday Gift Guide (Geeky Stuff We Like) LCD? LED? Plasma? The How-To Geek Guide to HDTV Technology The How-To Geek Guide to Learning Photoshop, Part 8: Filters Improve Digital Photography by Calibrating Your Monitor Our Favorite Tech: What We’re Thankful For at How-To Geek Settle into Orbit with the Voyage Theme for Chrome and Iron Awesome Safari Compass Icons Set Escape from the Exploding Planet Wallpaper Move Your Tumblr Blog to WordPress Pytask is an Easy to Use To-Do List Manager for Your Ubuntu System Snowy Christmas House Personas Theme for Firefox

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  • Basics of Join Predicate Pushdown in Oracle

    - by Maria Colgan
    Happy New Year to all of our readers! We hope you all had a great holiday season. We start the new year by continuing our series on Optimizer transformations. This time it is the turn of Predicate Pushdown. I would like to thank Rafi Ahmed for the content of this blog.Normally, a view cannot be joined with an index-based nested loop (i.e., index access) join, since a view, in contrast with a base table, does not have an index defined on it. A view can only be joined with other tables using three methods: hash, nested loop, and sort-merge joins. Introduction The join predicate pushdown (JPPD) transformation allows a view to be joined with index-based nested-loop join method, which may provide a more optimal alternative. In the join predicate pushdown transformation, the view remains a separate query block, but it contains the join predicate, which is pushed down from its containing query block into the view. The view thus becomes correlated and must be evaluated for each row of the outer query block. These pushed-down join predicates, once inside the view, open up new index access paths on the base tables inside the view; this allows the view to be joined with index-based nested-loop join method, thereby enabling the optimizer to select an efficient execution plan. The join predicate pushdown transformation is not always optimal. The join predicate pushed-down view becomes correlated and it must be evaluated for each outer row; if there is a large number of outer rows, the cost of evaluating the view multiple times may make the nested-loop join suboptimal, and therefore joining the view with hash or sort-merge join method may be more efficient. The decision whether to push down join predicates into a view is determined by evaluating the costs of the outer query with and without the join predicate pushdown transformation under Oracle's cost-based query transformation framework. The join predicate pushdown transformation applies to both non-mergeable views and mergeable views and to pre-defined and inline views as well as to views generated internally by the optimizer during various transformations. The following shows the types of views on which join predicate pushdown is currently supported. UNION ALL/UNION view Outer-joined view Anti-joined view Semi-joined view DISTINCT view GROUP-BY view Examples Consider query A, which has an outer-joined view V. The view cannot be merged, as it contains two tables, and the join between these two tables must be performed before the join between the view and the outer table T4. A: SELECT T4.unique1, V.unique3 FROM T_4K T4,            (SELECT T10.unique3, T10.hundred, T10.ten             FROM T_5K T5, T_10K T10             WHERE T5.unique3 = T10.unique3) VWHERE T4.unique3 = V.hundred(+) AND       T4.ten = V.ten(+) AND       T4.thousand = 5; The following shows the non-default plan for query A generated by disabling join predicate pushdown. When query A undergoes join predicate pushdown, it yields query B. Note that query B is expressed in a non-standard SQL and shows an internal representation of the query. B: SELECT T4.unique1, V.unique3 FROM T_4K T4,           (SELECT T10.unique3, T10.hundred, T10.ten             FROM T_5K T5, T_10K T10             WHERE T5.unique3 = T10.unique3             AND T4.unique3 = V.hundred(+)             AND T4.ten = V.ten(+)) V WHERE T4.thousand = 5; The execution plan for query B is shown below. In the execution plan BX, note the keyword 'VIEW PUSHED PREDICATE' indicates that the view has undergone the join predicate pushdown transformation. The join predicates (shown here in red) have been moved into the view V; these join predicates open up index access paths thereby enabling index-based nested-loop join of the view. With join predicate pushdown, the cost of query A has come down from 62 to 32.  As mentioned earlier, the join predicate pushdown transformation is cost-based, and a join predicate pushed-down plan is selected only when it reduces the overall cost. Consider another example of a query C, which contains a view with the UNION ALL set operator.C: SELECT R.unique1, V.unique3 FROM T_5K R,            (SELECT T1.unique3, T2.unique1+T1.unique1             FROM T_5K T1, T_10K T2             WHERE T1.unique1 = T2.unique1             UNION ALL             SELECT T1.unique3, T2.unique2             FROM G_4K T1, T_10K T2             WHERE T1.unique1 = T2.unique1) V WHERE R.unique3 = V.unique3 and R.thousand < 1; The execution plan of query C is shown below. In the above, 'VIEW UNION ALL PUSHED PREDICATE' indicates that the UNION ALL view has undergone the join predicate pushdown transformation. As can be seen, here the join predicate has been replicated and pushed inside every branch of the UNION ALL view. The join predicates (shown here in red) open up index access paths thereby enabling index-based nested loop join of the view. Consider query D as an example of join predicate pushdown into a distinct view. We have the following cardinalities of the tables involved in query D: Sales (1,016,271), Customers (50,000), and Costs (787,766).  D: SELECT C.cust_last_name, C.cust_city FROM customers C,            (SELECT DISTINCT S.cust_id             FROM sales S, costs CT             WHERE S.prod_id = CT.prod_id and CT.unit_price > 70) V WHERE C.cust_state_province = 'CA' and C.cust_id = V.cust_id; The execution plan of query D is shown below. As shown in XD, when query D undergoes join predicate pushdown transformation, the expensive DISTINCT operator is removed and the join is converted into a semi-join; this is possible, since all the SELECT list items of the view participate in an equi-join with the outer tables. Under similar conditions, when a group-by view undergoes join predicate pushdown transformation, the expensive group-by operator can also be removed. With the join predicate pushdown transformation, the elapsed time of query D came down from 63 seconds to 5 seconds. Since distinct and group-by views are mergeable views, the cost-based transformation framework also compares the cost of merging the view with that of join predicate pushdown in selecting the most optimal execution plan. Summary We have tried to illustrate the basic ideas behind join predicate pushdown on different types of views by showing example queries that are quite simple. Oracle can handle far more complex queries and other types of views not shown here in the examples. Again many thanks to Rafi Ahmed for the content of this blog post.

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