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• Twitter's new approach of third party application? How would you see this move as developer.... especially you plan to build a twitter client.

  - by MobileDev123

  Just today morning I have read news that twitter has issued a warning to developers not to make any new third party client, the official announcement can be read here. As a programmer, how do you see this move of twitter? Does it seems that they want to standardize the behavior of third party client or they don't want any new client in favor of the default clients they have made? What if anybody wants to create a new client? Is there any guidelines that-if followed- ensure that we can create a new mobile client? Or we should stop thinking about it? What are the option for the developers who want to build some clients for twitter? I can realize that I have asked too many questions, but I still think that there can be one common answer.

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• anyone doing php-fpm and APC? cache files missing in /tmp

  - by Vangel

  I have been using xcache for a long time. Recently I put together php-fpm and nginx. I see apc is installed and enabled in the configuration. I was assuming that apc will automatically opcode the files and store it somewhere. According to config it should be in /tmp/apx.xxxx but there is no such thing there. What am i missing? any clues to investigate would be of much help. Please note I am using php 5.3 fpm. thanks mates. UPDATE: i looked at apc.php it says things are fine. will just have to take its word for it.

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• Is a larger hard drive with the same cache, rpm, and bus type faster?

  - by Joel Coehoorn

  I recently heard that, all else being equal, larger hard are faster than smaller. It has to do with more bits passing under the read head as the drive spins - since a large drive packs the bits more tightly, the same amount of spin/time presents more data to the read head. I had not heard this before, and was inclined to believe the the read heads expected bits at a specific rate and would instead stagger data, so that the two drives would be the same speed. I now find myself looking at purchasing one of two computer models for the school where I work. One model has an 80GB drive, the other a 400GB (for ~$13 more). The size of the drive is immaterial, since users will keep their files on a file server where they can be backed up. But if the 400GB drive will really deliver a performance boost to the hard drive, the extra money is probably worth it. Thoughts?

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• How much HDD space would I need to cache the web while respecting robot.txts?

  - by Koning Baard XIV

  I want to experiment with creating a web crawler. I'll start with indexing a few medium sized website like Stack Overflow or Smashing Magazine. If it works, I'd like to start crawling the entire web. I'll respect robot.txts. I save all html, pdf, word, excel, powerpoint, keynote, etc... documents (not exes, dmgs etc, just documents) in a MySQL DB. Next to that, I'll have a second table containing all restults and descriptions, and a table with words and on what page to find those words (aka an index). How much HDD space do you think I need to save all the pages? Is it as low as 1 TB or is it about 10 TB, 20? Maybe 30? 1000? Thanks

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• Squid not caching files (Randomly)

  - by Heinrich

  I want to use an intercepting squid server to cache specific large zip files that users in my network download frequently. I have configured squid on a gateway machine and caching is working for "static" zip files that are served from an Apache web server outside our network. The files that I want to have cached by squid are zip files 100MB which are served from a heroku-hosted Rails application. I set an ETag header (SHA hash of the zip file on the server) and Cache-Control: public header. However, these files are not cached by squid. This, for example, is a request that is not cached: $ curl --no-keepalive -v -o test.zip --header "X-Access-Key: 20767ed397afdea90601fda4513ceb042fe6ab4e51578da63d3bc9b024ed538a" --header "X-Customer: 5" "http://MY_APP.herokuapp.com/api/device/v1/media/download?version=latest" * Adding handle: conn: 0x7ffd4a804400 * Adding handle: send: 0 * Adding handle: recv: 0 ... > GET /api/device/v1/media/download?version=latest HTTP/1.1 > User-Agent: curl/7.30.0 > Host: MY_APP.herokuapp.com > Accept: */* > X-Access-Key: 20767ed397afdea90601fda4513ceb042fe6ab4e51578da63d3bc9b024ed538a > X-Customer: 5 > 0 0 0 0 0 0 0 0 --:--:-- 0:00:09 --:--:-- 0< HTTP/1.1 200 OK * Server Cowboy is not blacklisted < Server: Cowboy < Date: Mon, 18 Aug 2014 14:13:27 GMT < Status: 200 OK < X-Frame-Options: SAMEORIGIN < X-Xss-Protection: 1; mode=block < X-Content-Type-Options: nosniff < ETag: "95e888938c0d539b8dd74139beace67f" < Content-Disposition: attachment; filename="e7cce850ae728b81fe3f315d21a560af.zip" < Content-Transfer-Encoding: binary < Content-Length: 125727431 < Content-Type: application/zip < Cache-Control: public < X-Request-Id: 7ce6edb0-013a-4003-a331-94d2b8fae8ad < X-Runtime: 1.244251 < X-Cache: MISS from AAA.fritz.box < Via: 1.1 vegur, 1.1 AAA.fritz.box (squid/3.3.11) < Connection: keep-alive In the logs squid is reporting a TCP_MISS. This is the relevant excerpt from my squid file: # Squid normally listens to port 3128 http_port 3128 http_port 3129 intercept # Uncomment and adjust the following to add a disk cache directory. maximum_object_size 1000 MB maximum_object_size_in_memory 1000 MB cache_dir ufs /usr/local/var/cache/squid 10000 16 256 cache_mem 2000 MB # Leave coredumps in the first cache dir coredump_dir /usr/local/var/cache/squid cache_store_log daemon:/usr/local/var/logs/cache_store.log #refresh_pattern -i (/cgi-bin/|\?) 0 0% 0 refresh_pattern -i .(zip) 525600 100% 525600 override-expire ignore-no-cache ignore-no-store refresh_pattern . 0 20% 4320 ## DNS Configuration dns_nameservers 8.8.8.8 8.8.4.4 After trying around for some time I realized that squid is sometimes deciding that my file is cacheable, sometimes not, depending on whether and when I enable/disable the dns_nameservers directive. What could be wrong here?

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• What's wrong with this vcl config for varnish-cache as load balancer?

  - by dabito

  I have the current configurations active on my default.vcl varnish file on the machine that balances the load for other two machines (the other two machines also have varnish active). My intention is to have this server do only the load balancing and the other machines do the processing and also their own caching. My problem is that even with the config testing (not even a stress test or anything, just a few requests a minute) I get the guru meditation error and have to restart varnish. This is the default.vcl for the load balancing server: backend vader { .host = "app1.server.com"; .probe = { .url = "/"; .interval = 10s; .timeout = 4s; .window = 5; .threshold = 3; } } backend malgus { .host = "app2.server.com"; .probe = { .url = "/"; .interval = 10s; .timeout = 4s; .window = 5; .threshold = 3; } } director dooku round-robin { { .backend = vader; } { .backend = malgus; } } sub vcl_recv { if (req.http.host ~ "^balancer.server.com$") { set req.backend = dooku; } } Am I doing something wrong or missing something? EDIT: This is varnishlog's output: 0 CLI - Rd ping 0 CLI - Wr 200 19 PONG 1345839995 1.0 0 CLI - Rd ping 0 CLI - Wr 200 19 PONG 1345839998 1.0 0 CLI - Rd ping 0 CLI - Wr 200 19 PONG 1345840001 1.0 0 Backend_health - malgus Still sick 4--X--- 0 3 5 0.000000 3.846876 0 Backend_health - vader Still sick 4--X--- 0 3 5 0.000000 3.839194 0 CLI - Rd ping 0 CLI - Wr 200 19 PONG 1345840004 1.0 14 SessionOpen c 10.150.7.151 38272 :80 14 ReqStart c 10.150.7.151 38272 458200540 14 RxRequest c GET 14 RxURL c / 14 RxProtocol c HTTP/1.1 14 RxHeader c Host: dooku-dev.excelsior.com 14 RxHeader c Connection: keep-alive 14 RxHeader c User-Agent: Mozilla/5.0 (X11; Linux x86_64) AppleWebKit/536.11 (KHTML, like Gecko) Chrome/20.0.1132.47 Safari/536.11 14 RxHeader c Accept: text/html,application/xhtml+xml,application/xml;q=0.9,*/*;q=0.8 14 RxHeader c Accept-Encoding: gzip,deflate,sdch 14 RxHeader c Accept-Language: en-US,en;q=0.8,es-419;q=0.6,es;q=0.4 14 RxHeader c Accept-Charset: ISO-8859-1,utf-8;q=0.7,*;q=0.3 14 RxHeader c Cookie: SESSa87d6c6da0c61037a9169122dc5e4a19=HR_0Srhgc-uDArT3aJFzOBy31FtzneTXg38byr1eGMU; __atuvc=4%7C33 14 VCL_call c recv pass 14 VCL_call c hash 14 Hash c / 14 Hash c dooku-dev.excelsior.com 14 VCL_return c hash 14 VCL_call c pass pass 14 FetchError c no backend connection 14 VCL_call c error deliver 14 VCL_call c deliver deliver 14 TxProtocol c HTTP/1.1 14 TxStatus c 503 14 TxResponse c Service Unavailable 14 TxHeader c Server: Varnish 14 TxHeader c Content-Type: text/html; charset=utf-8 14 TxHeader c Retry-After: 5 14 TxHeader c Content-Length: 418 14 TxHeader c Accept-Ranges: bytes 14 TxHeader c Date: Fri, 24 Aug 2012 20:26:44 GMT 14 TxHeader c X-Varnish: 458200540 14 TxHeader c Age: 0 14 TxHeader c Via: 1.1 varnish 14 TxHeader c Connection: close 14 Length c 418 14 ReqEnd c 458200540 1345840004.916415691 1345840004.965190172 0.020933390 0.048741817 0.000032663 14 SessionClose c error 14 StatSess c 10.150.7.151 38272 0 1 1 0 1 0 256 418 14 SessionOpen c 10.150.7.151 38273 :80 14 ReqStart c 10.150.7.151 38273 458200541 14 RxRequest c GET 14 RxURL c /favicon.ico 14 RxProtocol c HTTP/1.1 14 RxHeader c Host: dooku-dev.excelsior.com 14 RxHeader c Connection: keep-alive 14 RxHeader c Accept: */* 14 RxHeader c User-Agent: Mozilla/5.0 (X11; Linux x86_64) AppleWebKit/536.11 (KHTML, like Gecko) Chrome/20.0.1132.47 Safari/536.11 14 RxHeader c Accept-Encoding: gzip,deflate,sdch 14 RxHeader c Accept-Language: en-US,en;q=0.8,es-419;q=0.6,es;q=0.4 14 RxHeader c Accept-Charset: ISO-8859-1,utf-8;q=0.7,*;q=0.3 14 RxHeader c Cookie: SESSa87d6c6da0c61037a9169122dc5e4a19=HR_0Srhgc-uDArT3aJFzOBy31FtzneTXg38byr1eGMU; __atuvc=4%7C33 14 VCL_call c recv pass 14 VCL_call c hash 14 Hash c /favicon.ico 14 Hash c dooku-dev.excelsior.com 14 VCL_return c hash 14 VCL_call c pass pass 14 FetchError c no backend connection 14 VCL_call c error deliver 14 VCL_call c deliver deliver 14 TxProtocol c HTTP/1.1 14 TxStatus c 503 14 TxResponse c Service Unavailable 14 TxHeader c Server: Varnish 14 TxHeader c Content-Type: text/html; charset=utf-8 14 TxHeader c Retry-After: 5 14 TxHeader c Content-Length: 418 14 TxHeader c Accept-Ranges: bytes 14 TxHeader c Date: Fri, 24 Aug 2012 20:26:45 GMT 14 TxHeader c X-Varnish: 458200541 14 TxHeader c Age: 0 14 TxHeader c Via: 1.1 varnish 14 TxHeader c Connection: close 14 Length c 418 14 ReqEnd c 458200541 1345840005.226389885 1345840005.226457834 0.000026941 0.000043154 0.000024796 14 SessionClose c error 14 StatSess c 10.150.7.151 38273 0 1 1 0 1 0 256 418

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• Does Exchange Cache Mode affect email markers refresh time in other Outlook clients?

  - by David

  We have users who share a single email account by using the Additional Email option under their accounts. Now, they want to assign emails to one another using the markers alongside the emails. We noticed that when changing the color of a marker, one Outlook client updated immediately, but another Outlook client did not. It looked like they were both set to "Cached Mode". Is it likely that caching effected the refresh of the client? Would it be better to turn off cached mode if we are using Outlook this way?

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• How i can setup a nginx cache strategy that first try amazon s3, then memcache and do a fallback on miss?

  - by Tim

  i have a large site with lot of pages that almost never change, right now i am using two memcache servers (amazon elasticache), but this its really expensive. Thats why for this files that barely never change i want to upload them to amazon s3 and shutdown 1 memcache server. Here is my conf; location ~ /longterm/(.*){ proxy_pass http://amazonS3bucket; proxy_intercept_errors on; proxy_next_upstream http_404; error_page 404 503 = @fallback_memcached } location @fallback_memcache { set $memcached_key $uri; memcached_pass name:11211; error_page 404 @fallback; } location @fallback { try_files $uri $uri/index.html } I dont know why but the config doesnt work on the final fallback; if i got an amazon S3 hit it works, if i got an amazon S3 miss and a memcache hit it works, but if i got an amazon S3 miss then a memcache miss when it try to resolve the las fallback it fails. I am also thinking in use the amazon s3 fuse http://code.google.com/p/s3fs/ instead of the proxy pass i think it would be easier for implement, i would also be less performant?

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• Making a Login Work After Cache, Cookies, etc. Have Been Cleared

  - by John

  Hello, I am using the code below for a user login. The first I try to login after cache / cookies, etc. have been cleared, the browser refreshes and the user name is not logged in. After that, logging in works fine. Any idea how I can make it work the first time? Thanks in advance, John index.php: <?php if($_SERVER['REQUEST_METHOD'] == "POST"){header('Location: http://www...com/.../index.php?username='.$username.'&password='.$password.'');} require_once "header.php"; include "login.php"; require_once "footer.php"; ?> login.php: <?php if (!isLoggedIn()) { if (isset($_POST['cmdlogin'])) { if (checkLogin($_POST['username'], $_POST['password'])) { show_userbox(); } else { echo "Incorrect Login information !"; show_loginform(); } } else { show_loginform(); } } else { show_userbox(); } ?> show_loginform function: function show_loginform($disabled = false) { echo '<form name="login-form" id="login-form" method="post" action="./index.php?'.$_SERVER['QUERY_STRING'].'"> <div class="usernameformtext"><label title="Username">Username: </label></div> <div class="usernameformfield"><input tabindex="1" accesskey="u" name="username" type="text" maxlength="30" id="username" /></div> <div class="passwordformtext"><label title="Password">Password: </label></div> <div class="passwordformfield"><input tabindex="2" accesskey="p" name="password" type="password" maxlength="15" id="password" /></div> <div class="registertext"><a href="http://www...com/.../register.php" title="Register">Register</a></div> <div class="lostpasswordtext"><a href="http://www...com/.../lostpassword.php" title="Lost Password">Lost password?</a></div> <p class="loginbutton"><input tabindex="3" accesskey="l" type="submit" name="cmdlogin" value="Login" '; if ($disabled == true) { echo 'disabled="disabled"'; } echo ' /></p></form>'; }

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• Suggestions In Porting ASP.NET to MVC.NET - Is storing SiteConfiguration in Cache RESTful?

  - by DaveDev

  I've been tasked with porting/refactoring a Web Application Platform that we have from ASP.NET to MVC.NET. Ideally I could use all the existing platform's configurations to determine the properties of the site that is presented. Is it RESTful to keep a SiteConfiguration object which contains all of our various page configuration data in the System.Web.Caching.Cache? There are a lot of settings that need to be loaded when the user acceses our site so it's inefficient for each user to have to load the same settings every time they access. Some data the SiteConfiguration object contains is as follows and it determines what Master Page / site configuration / style / UserControls are available to the client, public string SiteTheme { get; set; } public string Region { private get; set; } public string DateFormat { get; set; } public string NumberFormat { get; set; } public int WrapperType { private get; set; } public string LabelFileName { get; set; } public LabelFile LabelFile { get; set; } // the following two are the heavy ones // PageConfiguration contains lots of configuration data for each panel on the page public IList<PageConfiguration> Pages { get; set; } // This contains all the configurations for the factsheets we produce public List<ConfiguredFactsheet> ConfiguredFactsheets { get; set; } I was thinking of having a URL structure like this: www.MySite1.com/PageTemplate/UserControl/ the domain determines the SiteConfiguration object that is created, where MySite1.com is SiteId = 1, MySite2.com is SiteId = 2. (and in turn, style, configurations for various pages, etc.) PageTemplate is the View that will be rendered and simply defines a layout for where I'm going to inject the UserControls Can somebody please tell me if I'm completely missing the RESTful point here? I'd like to refactor the platform into MVC because it's better to work in but I want to do it right but with a minimum of reinventing-the-wheel because otherwise it won't get approval. Any suggestions otherwise? Thanks

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• SQL SERVER – Subquery or Join – Various Options – SQL Server Engine Knows the Best – Part 2

  - by pinaldave

  This blog post is part 2 of the earlier written article SQL SERVER – Subquery or Join – Various Options – SQL Server Engine knows the Best by Paulo R. Pereira. Paulo has left excellent comment to earlier article once again proving the point that SQL Server Engine is smart enough to figure out the best plan itself and uses the same for the query. Let us go over his comment as he has posted. “I think IN or EXISTS is the best choice, because there is a little difference between ‘Merge Join’ of query with JOIN (Inner Join) and the others options (Left Semi Join), and JOIN can give more results than IN or EXISTS if the relationship is 1:0..N and not 1:0..1. And if I try use NOT IN and NOT EXISTS the query plan is different from LEFT JOIN too (Left Anti Semi Join vs. Left Outer Join + Filter). So, I found a case where EXISTS has a different query plan than IN or ANY/SOME:” USE AdventureWorks GO -- use of SOME SELECT * FROM HumanResources.Employee E WHERE E.EmployeeID = SOME ( SELECT EA.EmployeeID FROM HumanResources.EmployeeAddress EA UNION ALL SELECT EA.EmployeeID FROM HumanResources.EmployeeDepartmentHistory EA ) -- use of IN SELECT * FROM HumanResources.Employee E WHERE E.EmployeeID IN ( SELECT EA.EmployeeID FROM HumanResources.EmployeeAddress EA UNION ALL SELECT EA.EmployeeID FROM HumanResources.EmployeeDepartmentHistory EA ) -- use of EXISTS SELECT * FROM HumanResources.Employee E WHERE EXISTS ( SELECT EA.EmployeeID FROM HumanResources.EmployeeAddress EA UNION ALL SELECT EA.EmployeeID FROM HumanResources.EmployeeDepartmentHistory EA ) When looked into execution plan of the queries listed above indeed we do get different plans for queries and SQL Server Engines creates the best (least cost) plan for each query. Click on image to see larger images. Thanks Paulo for your wonderful contribution. Reference : Pinal Dave (http://blog.SQLAuthority.com) Filed under: Pinal Dave, Readers Contribution, SQL, SQL Authority, SQL Joins, SQL Optimization, SQL Performance, SQL Query, SQL Scripts, SQL Server, SQL Tips and Tricks, T SQL, Technology

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• Nginx compiled --with-http_spdy_module yet raise errors complains ngx_http_spdy_module

  - by c19

  [emerg] 21101#0: the "spdy" parameter requires ngx_http_spdy_module in /etc/nginx/conf.d/cc.conf isn't it the same module? and it causes multi-redirection error too. I have no idea what is going on. Full configure arg: nginx version: nginx/1.4.2 built by gcc 4.4.6 20120305 (Red Hat 4.4.6-4) (GCC) TLS SNI support enabled configure arguments: --prefix=/etc/nginx --sbin-path=/usr/sbin/nginx --conf-path=/etc/nginx/nginx.conf --error-log-path=/var/log/nginx/error.log --http-log-path=/var/log/nginx/access.log --pid-path=/var/run/nginx.pid --lock-path=/var/run/nginx.lock --http-client-body-temp-path=/var/cache/nginx/client_temp --http-proxy-temp-path=/var/cache/nginx/proxy_temp --http-fastcgi-temp-path=/var/cache/nginx/fastcgi_temp --http-uwsgi-temp-path=/var/cache/nginx/uwsgi_temp --http-scgi-temp-path=/var/cache/nginx/scgi_temp --user=nginx --group=nginx --with-http_ssl_module --with-http_realip_module --with-http_addition_module --with-http_sub_module --with-http_dav_module --with-http_flv_module --with-http_mp4_module --with-http_gunzip_module --with-http_gzip_static_module --with-http_random_index_module --with-http_secure_link_module --with-http_stub_status_module --with-mail --with-mail_ssl_module --with-file-aio --with-ipv6 --with-cc-opt='-O2 -g -pipe -Wp,-D_FORTIFY_SOURCE=2 -fexceptions -fstack-protector --param=ssp-buffer-size=4 -m64 -mtune=generic' --with-pcre --with-http_ssl_module `--with-http_spdy_module` --with-http_gunzip_module --with-http_gzip_static_module --with-http_stub_status_module --with-openssl=/usr/local/src/openssl-1.0.1e

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• C# 4: The Curious ConcurrentDictionary

  - by James Michael Hare

  In my previous post (here) I did a comparison of the new ConcurrentQueue versus the old standard of a System.Collections.Generic Queue with simple locking.  The results were exactly what I would have hoped, that the ConcurrentQueue was faster with multi-threading for most all situations.  In addition, concurrent collections have the added benefit that you can enumerate them even if they're being modified. So I set out to see what the improvements would be for the ConcurrentDictionary, would it have the same performance benefits as the ConcurrentQueue did?  Well, after running some tests and multiple tweaks and tunes, I have good and bad news. But first, let's look at the tests.  Obviously there's many things we can do with a dictionary.  One of the most notable uses, of course, in a multi-threaded environment is for a small, local in-memory cache.  So I set about to do a very simple simulation of a cache where I would create a test class that I'll just call an Accessor.  This accessor will attempt to look up a key in the dictionary, and if the key exists, it stops (i.e. a cache "hit").  However, if the lookup fails, it will then try to add the key and value to the dictionary (i.e. a cache "miss").  So here's the Accessor that will run the tests: 1: internal class Accessor 2: { 3: public int Hits { get; set; } 4: public int Misses { get; set; } 5: public Func<int, string> GetDelegate { get; set; } 6: public Action<int, string> AddDelegate { get; set; } 7: public int Iterations { get; set; } 8: public int MaxRange { get; set; } 9: public int Seed { get; set; } 10:  11: public void Access() 12: { 13: var randomGenerator = new Random(Seed); 14:  15: for (int i=0; i<Iterations; i++) 16: { 17: // give a wide spread so will have some duplicates and some unique 18: var target = randomGenerator.Next(1, MaxRange); 19:  20: // attempt to grab the item from the cache 21: var result = GetDelegate(target); 22:  23: // if the item doesn't exist, add it 24: if(result == null) 25: { 26: AddDelegate(target, target.ToString()); 27: Misses++; 28: } 29: else 30: { 31: Hits++; 32: } 33: } 34: } 35: } Note that so I could test different implementations, I defined a GetDelegate and AddDelegate that will call the appropriate dictionary methods to add or retrieve items in the cache using various techniques. So let's examine the three techniques I decided to test: Dictionary with mutex - Just your standard generic Dictionary with a simple lock construct on an internal object. Dictionary with ReaderWriterLockSlim - Same Dictionary, but now using a lock designed to let multiple readers access simultaneously and then locked when a writer needs access. ConcurrentDictionary - The new ConcurrentDictionary from System.Collections.Concurrent that is supposed to be optimized to allow multiple threads to access safely. So the approach to each of these is also fairly straight-forward.  Let's look at the GetDelegate and AddDelegate implementations for the Dictionary with mutex lock: 1: var addDelegate = (key,val) => 2: { 3: lock (_mutex) 4: { 5: _dictionary[key] = val; 6: } 7: }; 8: var getDelegate = (key) => 9: { 10: lock (_mutex) 11: { 12: string val; 13: return _dictionary.TryGetValue(key, out val) ? val : null; 14: } 15: }; Nothing new or fancy here, just your basic lock on a private object and then query/insert into the Dictionary. Now, for the Dictionary with ReadWriteLockSlim it's a little more complex: 1: var addDelegate = (key,val) => 2: { 3: _readerWriterLock.EnterWriteLock(); 4: _dictionary[key] = val; 5: _readerWriterLock.ExitWriteLock(); 6: }; 7: var getDelegate = (key) => 8: { 9: string val; 10: _readerWriterLock.EnterReadLock(); 11: if(!_dictionary.TryGetValue(key, out val)) 12: { 13: val = null; 14: } 15: _readerWriterLock.ExitReadLock(); 16: return val; 17: }; And finally, the ConcurrentDictionary, which since it does all it's own concurrency control, is remarkably elegant and simple: 1: var addDelegate = (key,val) => 2: { 3: _concurrentDictionary[key] = val; 4: }; 5: var getDelegate = (key) => 6: { 7: string s; 8: return _concurrentDictionary.TryGetValue(key, out s) ? s : null; 9: };                    Then, I set up a test harness that would simply ask the user for the number of concurrent Accessors to attempt to Access the cache (as specified in Accessor.Access() above) and then let them fly and see how long it took them all to complete.  Each of these tests was run with 10,000,000 cache accesses divided among the available Accessor instances.  All times are in milliseconds. 1: Dictionary with Mutex Locking 2: --------------------------------------------------- 3: Accessors Mostly Misses Mostly Hits 4: 1 7916 3285 5: 10 8293 3481 6: 100 8799 3532 7: 1000 8815 3584 8:  9:  10: Dictionary with ReaderWriterLockSlim Locking 11: --------------------------------------------------- 12: Accessors Mostly Misses Mostly Hits 13: 1 8445 3624 14: 10 11002 4119 15: 100 11076 3992 16: 1000 14794 4861 17:  18:  19: Concurrent Dictionary 20: --------------------------------------------------- 21: Accessors Mostly Misses Mostly Hits 22: 1 17443 3726 23: 10 14181 1897 24: 100 15141 1994 25: 1000 17209 2128 The first test I did across the board is the Mostly Misses category.  The mostly misses (more adds because data requested was not in the dictionary) shows an interesting trend.  In both cases the Dictionary with the simple mutex lock is much faster, and the ConcurrentDictionary is the slowest solution.  But this got me thinking, and a little research seemed to confirm it, maybe the ConcurrentDictionary is more optimized to concurrent "gets" than "adds".  So since the ratio of misses to hits were 2 to 1, I decided to reverse that and see the results. So I tweaked the data so that the number of keys were much smaller than the number of iterations to give me about a 2 to 1 ration of hits to misses (twice as likely to already find the item in the cache than to need to add it).  And yes, indeed here we see that the ConcurrentDictionary is indeed faster than the standard Dictionary here.  I have a strong feeling that as the ration of hits-to-misses gets higher and higher these number gets even better as well.  This makes sense since the ConcurrentDictionary is read-optimized. Also note that I tried the tests with capacity and concurrency hints on the ConcurrentDictionary but saw very little improvement, I think this is largely because on the 10,000,000 hit test it quickly ramped up to the correct capacity and concurrency and thus the impact was limited to the first few milliseconds of the run. So what does this tell us?  Well, as in all things, ConcurrentDictionary is not a panacea.  It won't solve all your woes and it shouldn't be the only Dictionary you ever use.  So when should we use each? Use System.Collections.Generic.Dictionary when: You need a single-threaded Dictionary (no locking needed). You need a multi-threaded Dictionary that is loaded only once at creation and never modified (no locking needed). You need a multi-threaded Dictionary to store items where writes are far more prevalent than reads (locking needed). And use System.Collections.Concurrent.ConcurrentDictionary when: You need a multi-threaded Dictionary where the writes are far more prevalent than reads. You need to be able to iterate over the collection without locking it even if its being modified. Both Dictionaries have their strong suits, I have a feeling this is just one where you need to know from design what you hope to use it for and make your decision based on that criteria.

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• External HDD USB 3.0 failure

  - by Philip

  [ 2560.376113] usb 9-1: new high-speed USB device number 2 using xhci_hcd [ 2560.376186] usb 9-1: Device not responding to set address. [ 2560.580136] usb 9-1: Device not responding to set address. [ 2560.784104] usb 9-1: device not accepting address 2, error -71 [ 2560.840127] hub 9-0:1.0: unable to enumerate USB device on port 1 [ 2561.080182] usb 10-1: new SuperSpeed USB device number 5 using xhci_hcd [ 2566.096163] usb 10-1: device descriptor read/8, error -110 [ 2566.200096] usb 10-1: new SuperSpeed USB device number 5 using xhci_hcd [ 2571.216175] usb 10-1: device descriptor read/8, error -110 [ 2571.376138] hub 10-0:1.0: unable to enumerate USB device on port 1 [ 2571.744174] usb 10-1: new SuperSpeed USB device number 7 using xhci_hcd [ 2576.760116] usb 10-1: device descriptor read/8, error -110 [ 2576.864074] usb 10-1: new SuperSpeed USB device number 7 using xhci_hcd [ 2581.880153] usb 10-1: device descriptor read/8, error -110 [ 2582.040123] hub 10-0:1.0: unable to enumerate USB device on port 1 [ 2582.224139] hub 9-0:1.0: unable to enumerate USB device on port 1 [ 2582.464177] usb 10-1: new SuperSpeed USB device number 9 using xhci_hcd [ 2587.480122] usb 10-1: device descriptor read/8, error -110 [ 2587.584079] usb 10-1: new SuperSpeed USB device number 9 using xhci_hcd [ 2592.600150] usb 10-1: device descriptor read/8, error -110 [ 2592.760134] hub 10-0:1.0: unable to enumerate USB device on port 1 [ 2593.128175] usb 10-1: new SuperSpeed USB device number 11 using xhci_hcd [ 2598.144183] usb 10-1: device descriptor read/8, error -110 [ 2598.248109] usb 10-1: new SuperSpeed USB device number 11 using xhci_hcd [ 2603.264171] usb 10-1: device descriptor read/8, error -110 [ 2603.480157] usb 10-1: new SuperSpeed USB device number 12 using xhci_hcd [ 2608.496162] usb 10-1: device descriptor read/8, error -110 [ 2608.600091] usb 10-1: new SuperSpeed USB device number 12 using xhci_hcd [ 2613.616166] usb 10-1: device descriptor read/8, error -110 [ 2613.832170] usb 10-1: new SuperSpeed USB device number 13 using xhci_hcd [ 2618.848135] usb 10-1: device descriptor read/8, error -110 [ 2618.952079] usb 10-1: new SuperSpeed USB device number 13 using xhci_hcd [ 2623.968155] usb 10-1: device descriptor read/8, error -110 [ 2624.184176] usb 10-1: new SuperSpeed USB device number 14 using xhci_hcd [ 2629.200124] usb 10-1: device descriptor read/8, error -110 [ 2629.304075] usb 10-1: new SuperSpeed USB device number 14 using xhci_hcd [ 2634.320172] usb 10-1: device descriptor read/8, error -110 [ 2634.424135] hub 10-0:1.0: unable to enumerate USB device on port 1 [ 2634.776186] usb 10-1: new SuperSpeed USB device number 15 using xhci_hcd [ 2639.792105] usb 10-1: device descriptor read/8, error -110 [ 2639.896090] usb 10-1: new SuperSpeed USB device number 15 using xhci_hcd [ 2644.912172] usb 10-1: device descriptor read/8, error -110 [ 2645.128174] usb 10-1: new SuperSpeed USB device number 16 using xhci_hcd [ 2650.144160] usb 10-1: device descriptor read/8, error -110 [ 2650.248062] usb 10-1: new SuperSpeed USB device number 16 using xhci_hcd [ 2655.264120] usb 10-1: device descriptor read/8, error -110 [ 2655.480182] usb 10-1: new SuperSpeed USB device number 17 using xhci_hcd [ 2660.496121] usb 10-1: device descriptor read/8, error -110 [ 2660.600086] usb 10-1: new SuperSpeed USB device number 17 using xhci_hcd [ 2665.616167] usb 10-1: device descriptor read/8, error -110 [ 2665.832177] usb 10-1: new SuperSpeed USB device number 18 using xhci_hcd [ 2670.848110] usb 10-1: device descriptor read/8, error -110 [ 2670.952066] usb 10-1: new SuperSpeed USB device number 18 using xhci_hcd [ 2675.968081] usb 10-1: device descriptor read/8, error -110 [ 2676.072124] hub 10-0:1.0: unable to enumerate USB device on port 1 [ 2786.104531] xhci_hcd 0000:02:00.0: remove, state 4 [ 2786.104546] usb usb10: USB disconnect, device number 1 [ 2786.104686] xHCI xhci_drop_endpoint called for root hub [ 2786.104692] xHCI xhci_check_bandwidth called for root hub [ 2786.104942] xhci_hcd 0000:02:00.0: USB bus 10 deregistered [ 2786.105054] xhci_hcd 0000:02:00.0: remove, state 4 [ 2786.105065] usb usb9: USB disconnect, device number 1 [ 2786.105176] xHCI xhci_drop_endpoint called for root hub [ 2786.105181] xHCI xhci_check_bandwidth called for root hub [ 2786.109787] xhci_hcd 0000:02:00.0: USB bus 9 deregistered [ 2786.110134] xhci_hcd 0000:02:00.0: PCI INT A disabled [ 2794.268445] pci 0000:02:00.0: [1b73:1000] type 0 class 0x000c03 [ 2794.268483] pci 0000:02:00.0: reg 10: [mem 0x00000000-0x0000ffff] [ 2794.268689] pci 0000:02:00.0: PME# supported from D0 D3hot [ 2794.268700] pci 0000:02:00.0: PME# disabled [ 2794.276383] pci 0000:02:00.0: BAR 0: assigned [mem 0xd7800000-0xd780ffff] [ 2794.276398] pci 0000:02:00.0: BAR 0: set to [mem 0xd7800000-0xd780ffff] (PCI address [0xd7800000-0xd780ffff]) [ 2794.276419] pci 0000:02:00.0: no hotplug settings from platform [ 2794.276658] xhci_hcd 0000:02:00.0: enabling device (0000 -> 0002) [ 2794.276675] xhci_hcd 0000:02:00.0: PCI INT A -> GSI 16 (level, low) -> IRQ 16 [ 2794.276762] xhci_hcd 0000:02:00.0: setting latency timer to 64 [ 2794.276771] xhci_hcd 0000:02:00.0: xHCI Host Controller [ 2794.276913] xhci_hcd 0000:02:00.0: new USB bus registered, assigned bus number 9 [ 2794.395760] xhci_hcd 0000:02:00.0: irq 16, io mem 0xd7800000 [ 2794.396141] xHCI xhci_add_endpoint called for root hub [ 2794.396144] xHCI xhci_check_bandwidth called for root hub [ 2794.396195] hub 9-0:1.0: USB hub found [ 2794.396203] hub 9-0:1.0: 1 port detected [ 2794.396305] xhci_hcd 0000:02:00.0: xHCI Host Controller [ 2794.396371] xhci_hcd 0000:02:00.0: new USB bus registered, assigned bus number 10 [ 2794.396496] xHCI xhci_add_endpoint called for root hub [ 2794.396499] xHCI xhci_check_bandwidth called for root hub [ 2794.396547] hub 10-0:1.0: USB hub found [ 2794.396553] hub 10-0:1.0: 1 port detected [ 2798.004084] usb 1-3: new high-speed USB device number 8 using ehci_hcd [ 2798.140824] scsi21 : usb-storage 1-3:1.0 [ 2820.176116] usb 1-3: reset high-speed USB device number 8 using ehci_hcd [ 2824.000526] scsi 21:0:0:0: Direct-Access BUFFALO HD-PZU3 0001 PQ: 0 ANSI: 6 [ 2824.002263] sd 21:0:0:0: Attached scsi generic sg2 type 0 [ 2824.003617] sd 21:0:0:0: [sdb] 1953463728 512-byte logical blocks: (1.00 TB/931 GiB) [ 2824.005139] sd 21:0:0:0: [sdb] Write Protect is off [ 2824.005149] sd 21:0:0:0: [sdb] Mode Sense: 1f 00 00 08 [ 2824.009084] sd 21:0:0:0: [sdb] No Caching mode page present [ 2824.009094] sd 21:0:0:0: [sdb] Assuming drive cache: write through [ 2824.011944] sd 21:0:0:0: [sdb] No Caching mode page present [ 2824.011952] sd 21:0:0:0: [sdb] Assuming drive cache: write through [ 2824.049153] sdb: sdb1 [ 2824.051814] sd 21:0:0:0: [sdb] No Caching mode page present [ 2824.051821] sd 21:0:0:0: [sdb] Assuming drive cache: write through [ 2824.051825] sd 21:0:0:0: [sdb] Attached SCSI disk [ 2839.536624] usb 1-3: USB disconnect, device number 8 [ 2844.620178] usb 10-1: new SuperSpeed USB device number 2 using xhci_hcd [ 2844.640281] scsi22 : usb-storage 10-1:1.0 [ 2850.326545] scsi 22:0:0:0: Direct-Access BUFFALO HD-PZU3 0001 PQ: 0 ANSI: 6 [ 2850.327560] sd 22:0:0:0: Attached scsi generic sg2 type 0 [ 2850.329561] sd 22:0:0:0: [sdb] 1953463728 512-byte logical blocks: (1.00 TB/931 GiB) [ 2850.329889] sd 22:0:0:0: [sdb] Write Protect is off [ 2850.329897] sd 22:0:0:0: [sdb] Mode Sense: 1f 00 00 08 [ 2850.330223] sd 22:0:0:0: [sdb] No Caching mode page present [ 2850.330231] sd 22:0:0:0: [sdb] Assuming drive cache: write through [ 2850.331414] sd 22:0:0:0: [sdb] No Caching mode page present [ 2850.331423] sd 22:0:0:0: [sdb] Assuming drive cache: write through [ 2850.384116] usb 10-1: USB disconnect, device number 2 [ 2850.392050] sd 22:0:0:0: [sdb] Unhandled error code [ 2850.392056] sd 22:0:0:0: [sdb] Result: hostbyte=DID_NO_CONNECT driverbyte=DRIVER_OK [ 2850.392061] sd 22:0:0:0: [sdb] CDB: Read(10): 28 00 00 00 00 00 00 00 08 00 [ 2850.392074] end_request: I/O error, dev sdb, sector 0 [ 2850.392079] quiet_error: 70 callbacks suppressed [ 2850.392082] Buffer I/O error on device sdb, logical block 0 [ 2850.392194] ldm_validate_partition_table(): Disk read failed. [ 2850.392271] Dev sdb: unable to read RDB block 0 [ 2850.392377] sdb: unable to read partition table [ 2850.392581] sd 22:0:0:0: [sdb] READ CAPACITY failed [ 2850.392584] sd 22:0:0:0: [sdb] Result: hostbyte=DID_NO_CONNECT driverbyte=DRIVER_OK [ 2850.392588] sd 22:0:0:0: [sdb] Sense not available. [ 2850.392613] sd 22:0:0:0: [sdb] Asking for cache data failed [ 2850.392617] sd 22:0:0:0: [sdb] Assuming drive cache: write through [ 2850.392621] sd 22:0:0:0: [sdb] Attached SCSI disk [ 2850.732182] usb 10-1: new SuperSpeed USB device number 3 using xhci_hcd [ 2850.752228] scsi23 : usb-storage 10-1:1.0 [ 2851.752709] scsi 23:0:0:0: Direct-Access BUFFALO HD-PZU3 0001 PQ: 0 ANSI: 6 [ 2851.754481] sd 23:0:0:0: Attached scsi generic sg2 type 0 [ 2851.756576] sd 23:0:0:0: [sdb] 1953463728 512-byte logical blocks: (1.00 TB/931 GiB) [ 2851.758426] sd 23:0:0:0: [sdb] Write Protect is off [ 2851.758436] sd 23:0:0:0: [sdb] Mode Sense: 1f 00 00 08 [ 2851.758779] sd 23:0:0:0: [sdb] No Caching mode page present [ 2851.758787] sd 23:0:0:0: [sdb] Assuming drive cache: write through [ 2851.759968] sd 23:0:0:0: [sdb] No Caching mode page present [ 2851.759977] sd 23:0:0:0: [sdb] Assuming drive cache: write through [ 2851.817710] sdb: sdb1 [ 2851.820562] sd 23:0:0:0: [sdb] No Caching mode page present [ 2851.820568] sd 23:0:0:0: [sdb] Assuming drive cache: write through [ 2851.820572] sd 23:0:0:0: [sdb] Attached SCSI disk [ 2852.060352] usb 10-1: reset SuperSpeed USB device number 3 using xhci_hcd [ 2852.076533] xhci_hcd 0000:02:00.0: xHCI xhci_drop_endpoint called with disabled ep f6b19060 [ 2852.076538] xhci_hcd 0000:02:00.0: xHCI xhci_drop_endpoint called with disabled ep f6b1908c [ 2852.196329] usb 10-1: reset SuperSpeed USB device number 3 using xhci_hcd [ 2852.212593] xhci_hcd 0000:02:00.0: xHCI xhci_drop_endpoint called with disabled ep f6b19060 [ 2852.212599] xhci_hcd 0000:02:00.0: xHCI xhci_drop_endpoint called with disabled ep f6b1908c [ 2852.456290] usb 10-1: reset SuperSpeed USB device number 3 using xhci_hcd [ 2852.472402] xhci_hcd 0000:02:00.0: xHCI xhci_drop_endpoint called with disabled ep f6b19060 [ 2852.472408] xhci_hcd 0000:02:00.0: xHCI xhci_drop_endpoint called with disabled ep f6b1908c [ 2852.624304] usb 10-1: reset SuperSpeed USB device number 3 using xhci_hcd [ 2852.640531] xhci_hcd 0000:02:00.0: xHCI xhci_drop_endpoint called with disabled ep f6b19060 [ 2852.640536] xhci_hcd 0000:02:00.0: xHCI xhci_drop_endpoint called with disabled ep f6b1908c [ 2852.772296] usb 10-1: reset SuperSpeed USB device number 3 using xhci_hcd [ 2852.788536] xhci_hcd 0000:02:00.0: xHCI xhci_drop_endpoint called with disabled ep f6b19060 [ 2852.788541] xhci_hcd 0000:02:00.0: xHCI xhci_drop_endpoint called with disabled ep f6b1908c [ 2852.920349] usb 10-1: reset SuperSpeed USB device number 3 using xhci_hcd [ 2852.936536] xhci_hcd 0000:02:00.0: xHCI xhci_drop_endpoint called with disabled ep f6b19060 [ 2852.936540] xhci_hcd 0000:02:00.0: xHCI xhci_drop_endpoint called with disabled ep f6b1908c [ 2853.072287] usb 10-1: reset SuperSpeed USB device number 3 using xhci_hcd [ 2853.088565] xhci_hcd 0000:02:00.0: xHCI xhci_drop_endpoint called with disabled ep f6b19060 [ 2853.088570] xhci_hcd 0000:02:00.0: xHCI xhci_drop_endpoint called with disabled ep f6b1908c [ 2884.176339] usb 10-1: reset SuperSpeed USB device number 3 using xhci_hcd [ 2884.192561] xhci_hcd 0000:02:00.0: xHCI xhci_drop_endpoint called with disabled ep f6b19060 [ 2884.192567] xhci_hcd 0000:02:00.0: xHCI xhci_drop_endpoint called with disabled ep f6b1908c [ 2884.320349] usb 10-1: reset SuperSpeed USB device number 3 using xhci_hcd [ 2884.336526] xhci_hcd 0000:02:00.0: xHCI xhci_drop_endpoint called with disabled ep f6b19060 [ 2884.336531] xhci_hcd 0000:02:00.0: xHCI xhci_drop_endpoint called with disabled ep f6b1908c [ 2884.468344] usb 10-1: reset SuperSpeed USB device number 3 using xhci_hcd [ 2884.484551] xhci_hcd 0000:02:00.0: xHCI xhci_drop_endpoint called with disabled ep f6b19060 [ 2884.484556] xhci_hcd 0000:02:00.0: xHCI xhci_drop_endpoint called with disabled ep f6b1908c [ 2884.612349] usb 10-1: reset SuperSpeed USB device number 3 using xhci_hcd [ 2884.628540] xhci_hcd 0000:02:00.0: xHCI xhci_drop_endpoint called with disabled ep f6b19060 [ 2884.628545] xhci_hcd 0000:02:00.0: xHCI xhci_drop_endpoint called with disabled ep f6b1908c [ 2884.756350] usb 10-1: reset SuperSpeed USB device number 3 using xhci_hcd [ 2884.772528] xhci_hcd 0000:02:00.0: xHCI xhci_drop_endpoint called with disabled ep f6b19060 [ 2884.772533] xhci_hcd 0000:02:00.0: xHCI xhci_drop_endpoint called with disabled ep f6b1908c [ 2884.848116] usb 10-1: USB disconnect, device number 3 [ 2884.851493] scsi 23:0:0:0: [sdb] killing request [ 2884.851501] scsi 23:0:0:0: [sdb] killing request [ 2884.851699] scsi 23:0:0:0: [sdb] Unhandled error code [ 2884.851702] scsi 23:0:0:0: [sdb] Result: hostbyte=DID_NO_CONNECT driverbyte=DRIVER_OK [ 2884.851708] scsi 23:0:0:0: [sdb] CDB: Read(10): 28 00 00 5f 2b ee 00 00 3e 00 [ 2884.851721] end_request: I/O error, dev sdb, sector 6237166 [ 2884.851726] Buffer I/O error on device sdb1, logical block 6237102 [ 2884.851730] Buffer I/O error on device sdb1, logical block 6237103 [ 2884.851738] Buffer I/O error on device sdb1, logical block 6237104 [ 2884.851741] Buffer I/O error on device sdb1, logical block 6237105 [ 2884.851744] Buffer I/O error on device sdb1, logical block 6237106 [ 2884.851747] Buffer I/O error on device sdb1, logical block 6237107 [ 2884.851750] Buffer I/O error on device sdb1, logical block 6237108 [ 2884.851753] Buffer I/O error on device sdb1, logical block 6237109 [ 2884.851757] Buffer I/O error on device sdb1, logical block 6237110 [ 2884.851807] scsi 23:0:0:0: [sdb] Unhandled error code [ 2884.851810] scsi 23:0:0:0: [sdb] Result: hostbyte=DID_NO_CONNECT driverbyte=DRIVER_OK [ 2884.851813] scsi 23:0:0:0: [sdb] CDB: Read(10): 28 00 00 5f 2c 2c 00 00 3e 00 [ 2884.851824] end_request: I/O error, dev sdb, sector 6237228 [ 2885.168190] usb 10-1: new SuperSpeed USB device number 4 using xhci_hcd [ 2885.188268] scsi24 : usb-storage 10-1:1.0 Please help me with my problem. I got this after running dmesg.

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• SQL SERVER – Identify Most Resource Intensive Queries – SQL in Sixty Seconds #028 – Video

  - by pinaldave

  During performance tuning conversation the very first question people often ask is what are the queries offending the server or in another word let us identify the queries which are the most resource intensive. The resources are often described as either Memory, CPU or IO. When we talk about the queries the same is applicable for them as well. The query which is doing lots of reads or writes are for sure resource intensive as well query which are taking maximum CPU time. Performance tuning is a very deep subject and we all have our own preference regarding what should be the first step to tuning and what should be looked with the salt of grain. Though there is no denying that a query which uses more resources than what it should be using for sure require tuning. There are many ways to do identify query using intense resources (e.g. Extended events etc) but in this one we will go by simple DMV. There is a small gotcha we all have to remember about usage of DMV is that it only brings back results from existing cache. So if you have a query which is very resource intensive but is not cached or if you have explicitly removed the query from the cache it will be not part of the result returned by this DMV. It is quite possible that a query is aged and removed from the cache if your cache is not huge. If your cache is large you may want to be careful in running this query during business hours as this query itself can be resource intensive. Get Script to identify resource intensive query from Here Related Tips in SQL in Sixty Seconds: SQL SERVER – Find Most Expensive Queries Using DMV Simple Example to Configure Resource Governor – Introduction to Resource Governor SQL SERVER – DMV – sys.dm_exec_query_optimizer_info – Statistics of Optimizer SQL SERVER – Wait Stats – Wait Types – Wait Queues – Day 0 of 28 Reference: Pinal Dave (http://blog.sqlauthority.com) Filed under: Database, Pinal Dave, PostADay, SQL, SQL Authority, SQL in Sixty Seconds, SQL Query, SQL Scripts, SQL Server, SQL Server Management Studio, SQL Tips and Tricks, T SQL, Technology, Video Tagged: Excel

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• First round playing with Memcached

  - by Shaun

  To be honest I have not been very interested in the caching before I’m going to a project which would be using the multi-site deployment and high connection and concurrency and very sensitive to the user experience. That means we must cache the output data for better performance. After looked for the Internet I finally focused on the Memcached. What’s the Memcached? I think the description on its main site gives us a very good and simple explanation. Free & open source, high-performance, distributed memory object caching system, generic in nature, but intended for use in speeding up dynamic web applications by alleviating database load. Memcached is an in-memory key-value store for small chunks of arbitrary data (strings, objects) from results of database calls, API calls, or page rendering. Memcached is simple yet powerful. Its simple design promotes quick deployment, ease of development, and solves many problems facing large data caches. Its API is available for most popular languages. The original Memcached was built on *nix system are is being widely used in the PHP world. Although it’s not a problem to use the Memcached installed on *nix system there are some windows version available fortunately. Since we are WISC (Windows – IIS – SQL Server – C#, which on the opposite of LAMP) it would be much easier for us to use the Memcached on Windows rather than *nix. I’m using the Memcached Win X64 version provided by NorthScale. There are also the x86 version and other operation system version.   Install Memcached Unpack the Memcached file to a folder on the machine you want it to be installed, we can see that there are only 3 files and the main file should be the “memcached.exe”. Memcached would be run on the server as a service. To install the service just open a command windows and navigate to the folder which contains the “memcached.exe”, let’s say “C:\Memcached\”, and then type “memcached.exe -d install”. If you are using Windows Vista and Windows 7 system please be execute the command through the administrator role. Right-click the command item in the start menu and use “Run as Administrator”, otherwise the Memcached would not be able to be installed successfully. Once installed successful we can type “memcached.exe -d start” to launch the service. Now it’s ready to be used. The default port of Memcached is 11211 but you can change it through the command argument. You can find the help by typing “memcached -h”.   Using Memcached Memcahed has many good and ready-to-use providers for vary program language. After compared and reviewed I chose the Memcached Providers. It’s built based on another 3rd party Memcached client named enyim.com Memcached Client. The Memcached Providers is very simple to set/get the cached objects through the Memcached servers and easy to be configured through the application configuration file (aka web.config and app.config). Let’s create a console application for the demonstration and add the 3 DLL files from the package of the Memcached Providers to the project reference. Then we need to add the configuration for the Memcached server. Create an App.config file and firstly add the section on top of it. Here we need three sections: the section for Memcached Providers, for enyim.com Memcached client and the log4net. 1: <configSections> 2: <section name="cacheProvider" 3: type="MemcachedProviders.Cache.CacheProviderSection, MemcachedProviders" 4: allowDefinition="MachineToApplication" 5: restartOnExternalChanges="true"/> 6: <sectionGroup name="enyim.com"> 7: <section name="memcached" 8: type="Enyim.Caching.Configuration.MemcachedClientSection, Enyim.Caching"/> 9: </sectionGroup> 10: <section name="log4net" 11: type="log4net.Config.Log4NetConfigurationSectionHandler,log4net"/> 12: </configSections> Then we will add the configuration for 3 of them in the App.config file. The Memcached server information would be defined under the enyim.com section since it will be responsible for connect to the Memcached server. Assuming I installed the Memcached on two servers with the default port, the configuration would be like this. 1: <enyim.com> 2: <memcached> 3: <servers> 4: <!-- put your own server(s) here--> 5: <add address="192.168.0.149" port="11211"/> 6: <add address="10.10.20.67" port="11211"/> 7: </servers> 8: <socketPool minPoolSize="10" maxPoolSize="100" connectionTimeout="00:00:10" deadTimeout="00:02:00"/> 9: </memcached> 10: </enyim.com> Memcached supports the multi-deployment which means you can install the Memcached on the servers as many as you need. The protocol of the Memcached responsible for routing the cached objects into the proper server. So it’s very easy to scale-out your system by Memcached. And then define the Memcached Providers configuration. The defaultExpireTime indicates how long the objected cached in the Memcached would be expired, the default value is 2000 ms. 1: <cacheProvider defaultProvider="MemcachedCacheProvider"> 2: <providers> 3: <add name="MemcachedCacheProvider" 4: type="MemcachedProviders.Cache.MemcachedCacheProvider, MemcachedProviders" 5: keySuffix="_MySuffix_" 6: defaultExpireTime="2000"/> 7: </providers> 8: </cacheProvider> The last configuration would be the log4net. 1: <log4net> 2: <!-- Define some output appenders --> 3: <appender name="ConsoleAppender" type="log4net.Appender.ConsoleAppender"> 4: <layout type="log4net.Layout.PatternLayout"> 5: <conversionPattern value="%date [%thread] %-5level %logger [%property{NDC}] - %message%newline"/> 6: </layout> 7: </appender> 8: <!--<threshold value="OFF" />--> 9: <!-- Setup the root category, add the appenders and set the default priority --> 10: <root> 11: <priority value="WARN"/> 12: <appender-ref ref="ConsoleAppender"> 13: <filter type="log4net.Filter.LevelRangeFilter"> 14: <levelMin value="WARN"/> 15: <levelMax value="FATAL"/> 16: </filter> 17: </appender-ref> 18: </root> 19: </log4net>   Get, Set and Remove the Cached Objects Once we finished the configuration it would be very simple to consume the Memcached servers. The Memcached Providers gives us a static class named DistCache that can be used to operate the Memcached servers. Get<T>: Retrieve the cached object from the Memcached servers. If failed it will return null or the default value. Add: Add an object with a unique key into the Memcached servers. Assuming that we have an operation that retrieve the email from the name which is time consuming. This is the operation that should be cached. The method would be like this. I utilized Thread.Sleep to simulate the long-time operation. 1: static string GetEmailByNameSlowly(string name) 2: { 3: Thread.Sleep(2000); 4: return name + "@ethos.com.cn"; 5: } Then in the real retrieving method we will firstly check whether the name, email information had been searched previously and cached. If yes we will just return them from the Memcached, otherwise we will invoke the slowly method to retrieve it and then cached. 1: static string GetEmailByName(string name) 2: { 3: var email = DistCache.Get<string>(name); 4: if (string.IsNullOrEmpty(email)) 5: { 6: Console.WriteLine("==> The name/email not be in memcached so need slow loading. (name = {0})==>", name); 7: email = GetEmailByNameSlowly(name); 8: DistCache.Add(name, email); 9: } 10: else 11: { 12: Console.WriteLine("==> The name/email had been in memcached. (name = {0})==>", name); 13: } 14: return email; 15: } Finally let’s finished the calling method and execute. 1: static void Main(string[] args) 2: { 3: var name = string.Empty; 4: while (name != "q") 5: { 6: Console.Write("==> Please enter the name to find the email: "); 7: name = Console.ReadLine(); 8:  9: var email = GetEmailByName(name); 10: Console.WriteLine("==> The email of {0} is {1}.", name, email); 11: } 12: } The first time I entered “ziyanxu” it takes about 2 seconds to get the email since there’s nothing cached. But the next time I entered “ziyanxu” it returned very quickly from the Memcached.   Summary In this post I explained a bit on why we need cache, what’s Memcached and how to use it through the C# application. The example is fairly simple but hopefully demonstrated on how to use it. Memcached is very easy and simple to be used since it gives you the full opportunity to consider what, when and how to cache the objects. And when using Memcached you don’t need to consider the cache servers. The Memcached would be like a huge object pool in front of you. The next step I’m thinking now are: What kind of data should be cached? And how to determined the key? How to implement the cache as a layer on top of the business layer so that the application will not notice that the cache is there. How to implement the cache by AOP so that the business logic no need to consider the cache. I will investigate on them in the future and will share my thoughts and results.   Hope this helps, Shaun All documents and related graphics, codes are provided "AS IS" without warranty of any kind. Copyright © Shaun Ziyan Xu. This work is licensed under the Creative Commons License.

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• E: Sub-process /usr/bin/dpkg returned an error code (1) seems to be choking on kde-runtime-data version issue

  - by BMT

  12.04 LTS, on a dell mini 10. Install stable until about a week ago. Updated about 1x a week, sometimes more often. Several days ago, I booted up and the system was no longer working correctly. All these symptoms occurred simultaneously: Cannot run (exit on opening, every time): Update manager, software center, ubuntuOne, libreOffice. Vinagre autostarts on boot, no explanation, not set to startup with Ubuntu. Using apt-get to fix install results in the following: maura@pandora:~$ sudo apt-get -f install Reading package lists... Done Building dependency tree Reading state information... Done Correcting dependencies... Done The following package was automatically installed and is no longer required: libtelepathy-farstream2 Use 'apt-get autoremove' to remove them. The following extra packages will be installed: gwibber gwibber-service kde-runtime-data software-center Suggested packages: gwibber-service-flickr gwibber-service-digg gwibber-service-statusnet gwibber-service-foursquare gwibber-service-friendfeed gwibber-service-pingfm gwibber-service-qaiku unity-lens-gwibber The following packages will be upgraded: gwibber gwibber-service kde-runtime-data software-center 4 upgraded, 0 newly installed, 0 to remove and 39 not upgraded. 20 not fully installed or removed. Need to get 0 B/5,682 kB of archives. After this operation, 177 kB of additional disk space will be used. Do you want to continue [Y/n]? debconf: Perl may be unconfigured (Can't locate Scalar/Util.pm in @INC (@INC contains: /etc/perl /usr/local/lib/perl/5.14.2 /usr/local/share/perl/5.14.2 /usr/lib/perl5 /usr/share/perl5 /usr/lib/perl/5.14 /usr/share/perl/5.14 /usr/local/lib/site_perl .) at /usr/lib/perl/5.14/Hash/Util.pm line 9. BEGIN failed--compilation aborted at /usr/lib/perl/5.14/Hash/Util.pm line 9. Compilation failed in require at /usr/share/perl/5.14/fields.pm line 122. Compilation failed in require at /usr/share/perl5/Debconf/Log.pm line 10. Compilation failed in require at (eval 1) line 4. BEGIN failed--compilation aborted at (eval 1) line 4. ) -- aborting (Reading database ... 242672 files and directories currently installed.) Preparing to replace gwibber 3.4.1-0ubuntu1 (using .../gwibber_3.4.2-0ubuntu1_i386.deb) ... Could not find platform dependent libraries <exec_prefix> Consider setting $PYTHONHOME to <prefix>[:<exec_prefix>] Traceback (most recent call last): File "/usr/bin/pyclean", line 25, in <module> import logging ImportError: No module named logging Error in sys.excepthook: Traceback (most recent call last): File "/usr/lib/python2.7/dist-packages/apport_python_hook.py", line 64, in apport_excepthook from apport.fileutils import likely_packaged, get_recent_crashes File "/usr/lib/python2.7/dist-packages/apport/__init__.py", line 1, in <module> from apport.report import Report File "/usr/lib/python2.7/dist-packages/apport/report.py", line 16, in <module> from xml.parsers.expat import ExpatError File "/usr/lib/python2.7/xml/parsers/expat.py", line 4, in <module> from pyexpat import * ImportError: No module named pyexpat Original exception was: Traceback (most recent call last): File "/usr/bin/pyclean", line 25, in <module> import logging ImportError: No module named logging dpkg: warning: subprocess old pre-removal script returned error exit status 1 dpkg - trying script from the new package instead ... Could not find platform dependent libraries <exec_prefix> Consider setting $PYTHONHOME to <prefix>[:<exec_prefix>] Traceback (most recent call last): File "/usr/bin/pyclean", line 25, in <module> import logging ImportError: No module named logging Error in sys.excepthook: Traceback (most recent call last): File "/usr/lib/python2.7/dist-packages/apport_python_hook.py", line 64, in apport_excepthook from apport.fileutils import likely_packaged, get_recent_crashes File "/usr/lib/python2.7/dist-packages/apport/__init__.py", line 1, in <module> from apport.report import Report File "/usr/lib/python2.7/dist-packages/apport/report.py", line 16, in <module> from xml.parsers.expat import ExpatError File "/usr/lib/python2.7/xml/parsers/expat.py", line 4, in <module> from pyexpat import * ImportError: No module named pyexpat Original exception was: Traceback (most recent call last): File "/usr/bin/pyclean", line 25, in <module> import logging ImportError: No module named logging dpkg: error processing /var/cache/apt/archives/gwibber_3.4.2-0ubuntu1_i386.deb (--unpack): subprocess new pre-removal script returned error exit status 1 Could not find platform dependent libraries <exec_prefix> Consider setting $PYTHONHOME to <prefix>[:<exec_prefix>] Traceback (most recent call last): File "/usr/bin/pycompile", line 27, in <module> import logging ImportError: No module named logging Error in sys.excepthook: Traceback (most recent call last): File "/usr/lib/python2.7/dist-packages/apport_python_hook.py", line 64, in apport_excepthook from apport.fileutils import likely_packaged, get_recent_crashes File "/usr/lib/python2.7/dist-packages/apport/__init__.py", line 1, in <module> from apport.report import Report File "/usr/lib/python2.7/dist-packages/apport/report.py", line 16, in <module> from xml.parsers.expat import ExpatError File "/usr/lib/python2.7/xml/parsers/expat.py", line 4, in <module> from pyexpat import * ImportError: No module named pyexpat Original exception was: Traceback (most recent call last): File "/usr/bin/pycompile", line 27, in <module> import logging ImportError: No module named logging dpkg: error while cleaning up: subprocess installed post-installation script returned error exit status 1 Preparing to replace gwibber-service 3.4.1-0ubuntu1 (using .../gwibber-service_3.4.2-0ubuntu1_all.deb) ... Could not find platform dependent libraries <exec_prefix> Consider setting $PYTHONHOME to <prefix>[:<exec_prefix>] Traceback (most recent call last): File "/usr/bin/pyclean", line 25, in <module> import logging ImportError: No module named logging Error in sys.excepthook: Traceback (most recent call last): File "/usr/lib/python2.7/dist-packages/apport_python_hook.py", line 64, in apport_excepthook from apport.fileutils import likely_packaged, get_recent_crashes File "/usr/lib/python2.7/dist-packages/apport/__init__.py", line 1, in <module> from apport.report import Report File "/usr/lib/python2.7/dist-packages/apport/report.py", line 16, in <module> from xml.parsers.expat import ExpatError File "/usr/lib/python2.7/xml/parsers/expat.py", line 4, in <module> from pyexpat import * ImportError: No module named pyexpat Original exception was: Traceback (most recent call last): File "/usr/bin/pyclean", line 25, in <module> import logging ImportError: No module named logging dpkg: warning: subprocess old pre-removal script returned error exit status 1 dpkg - trying script from the new package instead ... Could not find platform dependent libraries <exec_prefix> Consider setting $PYTHONHOME to <prefix>[:<exec_prefix>] Traceback (most recent call last): File "/usr/bin/pyclean", line 25, in <module> import logging ImportError: No module named logging Error in sys.excepthook: Traceback (most recent call last): File "/usr/lib/python2.7/dist-packages/apport_python_hook.py", line 64, in apport_excepthook from apport.fileutils import likely_packaged, get_recent_crashes File "/usr/lib/python2.7/dist-packages/apport/__init__.py", line 1, in <module> from apport.report import Report File "/usr/lib/python2.7/dist-packages/apport/report.py", line 16, in <module> from xml.parsers.expat import ExpatError File "/usr/lib/python2.7/xml/parsers/expat.py", line 4, in <module> from pyexpat import * ImportError: No module named pyexpat Original exception was: Traceback (most recent call last): File "/usr/bin/pyclean", line 25, in <module> import logging ImportError: No module named logging dpkg: error processing /var/cache/apt/archives/gwibber-service_3.4.2-0ubuntu1_all.deb (--unpack): subprocess new pre-removal script returned error exit status 1 Could not find platform dependent libraries <exec_prefix> Consider setting $PYTHONHOME to <prefix>[:<exec_prefix>] Traceback (most recent call last): File "/usr/bin/pycompile", line 27, in <module> import logging ImportError: No module named logging Error in sys.excepthook: Traceback (most recent call last): File "/usr/lib/python2.7/dist-packages/apport_python_hook.py", line 64, in apport_excepthook from apport.fileutils import likely_packaged, get_recent_crashes File "/usr/lib/python2.7/dist-packages/apport/__init__.py", line 1, in <module> from apport.report import Report File "/usr/lib/python2.7/dist-packages/apport/report.py", line 16, in <module> from xml.parsers.expat import ExpatError File "/usr/lib/python2.7/xml/parsers/expat.py", line 4, in <module> from pyexpat import * ImportError: No module named pyexpat Original exception was: Traceback (most recent call last): File "/usr/bin/pycompile", line 27, in <module> import logging ImportError: No module named logging dpkg: error while cleaning up: subprocess installed post-installation script returned error exit status 1 Preparing to replace kde-runtime-data 4:4.8.3-0ubuntu0.1 (using .../kde-runtime-data_4%3a4.8.4-0ubuntu0.1_all.deb) ... Unpacking replacement kde-runtime-data ... dpkg: error processing /var/cache/apt/archives/kde-runtime-data_4%3a4.8.4-0ubuntu0.1_all.deb (--unpack): trying to overwrite '/usr/share/sounds', which is also in package sound-theme-freedesktop 0.7.pristine-2 dpkg-deb (subprocess): subprocess data was killed by signal (Broken pipe) dpkg-deb: error: subprocess <decompress> returned error exit status 2 Preparing to replace python-crypto 2.4.1-1 (using .../python-crypto_2.4.1-1_i386.deb) ... Could not find platform dependent libraries <exec_prefix> Consider setting $PYTHONHOME to <prefix>[:<exec_prefix>] Traceback (most recent call last): File "/usr/bin/pyclean", line 25, in <module> import logging ImportError: No module named logging Error in sys.excepthook: Traceback (most recent call last): File "/usr/lib/python2.7/dist-packages/apport_python_hook.py", line 64, in apport_excepthook from apport.fileutils import likely_packaged, get_recent_crashes File "/usr/lib/python2.7/dist-packages/apport/__init__.py", line 1, in <module> from apport.report import Report File "/usr/lib/python2.7/dist-packages/apport/report.py", line 16, in <module> from xml.parsers.expat import ExpatError File "/usr/lib/python2.7/xml/parsers/expat.py", line 4, in <module> from pyexpat import * ImportError: No module named pyexpat Original exception was: Traceback (most recent call last): File "/usr/bin/pyclean", line 25, in <module> import logging ImportError: No module named logging dpkg: warning: subprocess old pre-removal script returned error exit status 1 dpkg - trying script from the new package instead ... Could not find platform dependent libraries <exec_prefix> Consider setting $PYTHONHOME to <prefix>[:<exec_prefix>] Traceback (most recent call last): File "/usr/bin/pyclean", line 25, in <module> import logging ImportError: No module named logging Error in sys.excepthook: Traceback (most recent call last): File "/usr/lib/python2.7/dist-packages/apport_python_hook.py", line 64, in apport_excepthook from apport.fileutils import likely_packaged, get_recent_crashes File "/usr/lib/python2.7/dist-packages/apport/__init__.py", line 1, in <module> from apport.report import Report File "/usr/lib/python2.7/dist-packages/apport/report.py", line 16, in <module> from xml.parsers.expat import ExpatError File "/usr/lib/python2.7/xml/parsers/expat.py", line 4, in <module> from pyexpat import * ImportError: No module named pyexpat Original exception was: Traceback (most recent call last): File "/usr/bin/pyclean", line 25, in <module> import logging ImportError: No module named logging dpkg: error processing /var/cache/apt/archives/python-crypto_2.4.1-1_i386.deb (--unpack): subprocess new pre-removal script returned error exit status 1 No apport report written because MaxReports is reached already Could not find platform dependent libraries <exec_prefix> Consider setting $PYTHONHOME to <prefix>[:<exec_prefix>] Traceback (most recent call last): File "/usr/bin/pycompile", line 27, in <module> import logging ImportError: No module named logging Error in sys.excepthook: Traceback (most recent call last): File "/usr/lib/python2.7/dist-packages/apport_python_hook.py", line 64, in apport_excepthook from apport.fileutils import likely_packaged, get_recent_crashes File "/usr/lib/python2.7/dist-packages/apport/__init__.py", line 1, in <module> from apport.report import Report File "/usr/lib/python2.7/dist-packages/apport/report.py", line 16, in <module> from xml.parsers.expat import ExpatError File "/usr/lib/python2.7/xml/parsers/expat.py", line 4, in <module> from pyexpat import * ImportError: No module named pyexpat Original exception was: Traceback (most recent call last): File "/usr/bin/pycompile", line 27, in <module> import logging ImportError: No module named logging dpkg: error while cleaning up: subprocess installed post-installation script returned error exit status 1 Preparing to replace software-center 5.2.2.2 (using .../software-center_5.2.4_all.deb) ... Could not find platform dependent libraries <exec_prefix> Consider setting $PYTHONHOME to <prefix>[:<exec_prefix>] Traceback (most recent call last): File "/usr/bin/pyclean", line 25, in <module> import logging ImportError: No module named logging Error in sys.excepthook: Traceback (most recent call last): File "/usr/lib/python2.7/dist-packages/apport_python_hook.py", line 64, in apport_excepthook from apport.fileutils import likely_packaged, get_recent_crashes File "/usr/lib/python2.7/dist-packages/apport/__init__.py", line 1, in <module> from apport.report import Report File "/usr/lib/python2.7/dist-packages/apport/report.py", line 16, in <module> from xml.parsers.expat import ExpatError File "/usr/lib/python2.7/xml/parsers/expat.py", line 4, in <module> from pyexpat import * ImportError: No module named pyexpat Original exception was: Traceback (most recent call last): File "/usr/bin/pyclean", line 25, in <module> import logging ImportError: No module named logging dpkg: warning: subprocess old pre-removal script returned error exit status 1 dpkg - trying script from the new package instead ... Could not find platform dependent libraries <exec_prefix> Consider setting $PYTHONHOME to <prefix>[:<exec_prefix>] Traceback (most recent call last): File "/usr/bin/pyclean", line 25, in <module> import logging ImportError: No module named logging Error in sys.excepthook: Traceback (most recent call last): File "/usr/lib/python2.7/dist-packages/apport_python_hook.py", line 64, in apport_excepthook from apport.fileutils import likely_packaged, get_recent_crashes File "/usr/lib/python2.7/dist-packages/apport/__init__.py", line 1, in <module> from apport.report import Report File "/usr/lib/python2.7/dist-packages/apport/report.py", line 16, in <module> from xml.parsers.expat import ExpatError File "/usr/lib/python2.7/xml/parsers/expat.py", line 4, in <module> from pyexpat import * ImportError: No module named pyexpat Original exception was: Traceback (most recent call last): File "/usr/bin/pyclean", line 25, in <module> import logging ImportError: No module named logging dpkg: error processing /var/cache/apt/archives/software-center_5.2.4_all.deb (--unpack): subprocess new pre-removal script returned error exit status 1 No apport report written because MaxReports is reached already Could not find platform dependent libraries <exec_prefix> Consider setting $PYTHONHOME to <prefix>[:<exec_prefix>] Traceback (most recent call last): File "/usr/bin/pycompile", line 27, in <module> import logging ImportError: No module named logging Error in sys.excepthook: Traceback (most recent call last): File "/usr/lib/python2.7/dist-packages/apport_python_hook.py", line 64, in apport_excepthook from apport.fileutils import likely_packaged, get_recent_crashes File "/usr/lib/python2.7/dist-packages/apport/__init__.py", line 1, in <module> from apport.report import Report File "/usr/lib/python2.7/dist-packages/apport/report.py", line 16, in <module> from xml.parsers.expat import ExpatError File "/usr/lib/python2.7/xml/parsers/expat.py", line 4, in <module> from pyexpat import * ImportError: No module named pyexpat Original exception was: Traceback (most recent call last): File "/usr/bin/pycompile", line 27, in <module> import logging ImportError: No module named logging dpkg: error while cleaning up: subprocess installed post-installation script returned error exit status 1 Preparing to replace xdiagnose 2.5 (using .../archives/xdiagnose_2.5_all.deb) ... Could not find platform dependent libraries <exec_prefix> Consider setting $PYTHONHOME to <prefix>[:<exec_prefix>] Traceback (most recent call last): File "/usr/bin/pyclean", line 25, in <module> import logging ImportError: No module named logging Error in sys.excepthook: Traceback (most recent call last): File "/usr/lib/python2.7/dist-packages/apport_python_hook.py", line 64, in apport_excepthook from apport.fileutils import likely_packaged, get_recent_crashes File "/usr/lib/python2.7/dist-packages/apport/__init__.py", line 1, in <module> from apport.report import Report File "/usr/lib/python2.7/dist-packages/apport/report.py", line 16, in <module> from xml.parsers.expat import ExpatError File "/usr/lib/python2.7/xml/parsers/expat.py", line 4, in <module> from pyexpat import * ImportError: No module named pyexpat Original exception was: Traceback (most recent call last): File "/usr/bin/pyclean", line 25, in <module> import logging ImportError: No module named logging dpkg: warning: subprocess old pre-removal script returned error exit status 1 dpkg - trying script from the new package instead ... Could not find platform dependent libraries <exec_prefix> Consider setting $PYTHONHOME to <prefix>[:<exec_prefix>] Traceback (most recent call last): File "/usr/bin/pyclean", line 25, in <module> import logging ImportError: No module named logging Error in sys.excepthook: Traceback (most recent call last): File "/usr/lib/python2.7/dist-packages/apport_python_hook.py", line 64, in apport_excepthook from apport.fileutils import likely_packaged, get_recent_crashes File "/usr/lib/python2.7/dist-packages/apport/__init__.py", line 1, in <module> from apport.report import Report File "/usr/lib/python2.7/dist-packages/apport/report.py", line 16, in <module> from xml.parsers.expat import ExpatError File "/usr/lib/python2.7/xml/parsers/expat.py", line 4, in <module> from pyexpat import * ImportError: No module named pyexpat Original exception was: Traceback (most recent call last): File "/usr/bin/pyclean", line 25, in <module> import logging ImportError: No module named logging dpkg: error processing /var/cache/apt/archives/xdiagnose_2.5_all.deb (--unpack): subprocess new pre-removal script returned error exit status 1 No apport report written because MaxReports is reached already Could not find platform dependent libraries <exec_prefix> Consider setting $PYTHONHOME to <prefix>[:<exec_prefix>] Traceback (most recent call last): File "/usr/bin/pycompile", line 27, in <module> import logging ImportError: No module named logging Error in sys.excepthook: Traceback (most recent call last): File "/usr/lib/python2.7/dist-packages/apport_python_hook.py", line 64, in apport_excepthook from apport.fileutils import likely_packaged, get_recent_crashes File "/usr/lib/python2.7/dist-packages/apport/__init__.py", line 1, in <module> from apport.report import Report File "/usr/lib/python2.7/dist-packages/apport/report.py", line 16, in <module> from xml.parsers.expat import ExpatError File "/usr/lib/python2.7/xml/parsers/expat.py", line 4, in <module> from pyexpat import * ImportError: No module named pyexpat Original exception was: Traceback (most recent call last): File "/usr/bin/pycompile", line 27, in <module> import logging ImportError: No module named logging dpkg: error while cleaning up: subprocess installed post-installation script returned error exit status 1 Errors were encountered while processing: /var/cache/apt/archives/gwibber_3.4.2-0ubuntu1_i386.deb /var/cache/apt/archives/gwibber-service_3.4.2-0ubuntu1_all.deb /var/cache/apt/archives/kde-runtime-data_4%3a4.8.4-0ubuntu0.1_all.deb /var/cache/apt/archives/python-crypto_2.4.1-1_i386.deb /var/cache/apt/archives/software-center_5.2.4_all.deb /var/cache/apt/archives/xdiagnose_2.5_all.deb E: Sub-process /usr/bin/dpkg returned an error code (1) maura@pandora:~$ ^C maura@pandora:~$

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• Beware Sneaky Reads with Unique Indexes

  - by Paul White NZ

  A few days ago, Sandra Mueller (twitter | blog) asked a question using twitter’s #sqlhelp hash tag: “Might SQL Server retrieve (out-of-row) LOB data from a table, even if the column isn’t referenced in the query?” Leaving aside trivial cases (like selecting a computed column that does reference the LOB data), one might be tempted to say that no, SQL Server does not read data you haven’t asked for.  In general, that’s quite correct; however there are cases where SQL Server might sneakily retrieve a LOB column… Example Table Here’s a T-SQL script to create that table and populate it with 1,000 rows: CREATE TABLE dbo.LOBtest ( pk INTEGER IDENTITY NOT NULL, some_value INTEGER NULL, lob_data VARCHAR(MAX) NULL, another_column CHAR(5) NULL, CONSTRAINT [PK dbo.LOBtest pk] PRIMARY KEY CLUSTERED (pk ASC) ); GO DECLARE @Data VARCHAR(MAX); SET @Data = REPLICATE(CONVERT(VARCHAR(MAX), 'x'), 65540);   WITH Numbers (n) AS ( SELECT ROW_NUMBER() OVER (ORDER BY (SELECT 0)) FROM master.sys.columns C1, master.sys.columns C2 ) INSERT LOBtest WITH (TABLOCKX) ( some_value, lob_data ) SELECT TOP (1000) N.n, @Data FROM Numbers N WHERE N.n <= 1000; Test 1: A Simple Update Let’s run a query to subtract one from every value in the some_value column: UPDATE dbo.LOBtest WITH (TABLOCKX) SET some_value = some_value - 1; As you might expect, modifying this integer column in 1,000 rows doesn’t take very long, or use many resources.  The STATITICS IO and TIME output shows a total of 9 logical reads, and 25ms elapsed time.  The query plan is also very simple: Looking at the Clustered Index Scan, we can see that SQL Server only retrieves the pk and some_value columns during the scan: The pk column is needed by the Clustered Index Update operator to uniquely identify the row that is being changed.  The some_value column is used by the Compute Scalar to calculate the new value.  (In case you are wondering what the Top operator is for, it is used to enforce SET ROWCOUNT). Test 2: Simple Update with an Index Now let’s create a nonclustered index keyed on the some_value column, with lob_data as an included column: CREATE NONCLUSTERED INDEX [IX dbo.LOBtest some_value (lob_data)] ON dbo.LOBtest (some_value) INCLUDE ( lob_data ) WITH ( FILLFACTOR = 100, MAXDOP = 1, SORT_IN_TEMPDB = ON ); This is not a useful index for our simple update query; imagine that someone else created it for a different purpose.  Let’s run our update query again: UPDATE dbo.LOBtest WITH (TABLOCKX) SET some_value = some_value - 1; We find that it now requires 4,014 logical reads and the elapsed query time has increased to around 100ms.  The extra logical reads (4 per row) are an expected consequence of maintaining the nonclustered index. The query plan is very similar to before (click to enlarge): The Clustered Index Update operator picks up the extra work of maintaining the nonclustered index. The new Compute Scalar operators detect whether the value in the some_value column has actually been changed by the update.  SQL Server may be able to skip maintaining the nonclustered index if the value hasn’t changed (see my previous post on non-updating updates for details).  Our simple query does change the value of some_data in every row, so this optimization doesn’t add any value in this specific case. The output list of columns from the Clustered Index Scan hasn’t changed from the one shown previously: SQL Server still just reads the pk and some_data columns.  Cool. Overall then, adding the nonclustered index hasn’t had any startling effects, and the LOB column data still isn’t being read from the table.  Let’s see what happens if we make the nonclustered index unique. Test 3: Simple Update with a Unique Index Here’s the script to create a new unique index, and drop the old one: CREATE UNIQUE NONCLUSTERED INDEX [UQ dbo.LOBtest some_value (lob_data)] ON dbo.LOBtest (some_value) INCLUDE ( lob_data ) WITH ( FILLFACTOR = 100, MAXDOP = 1, SORT_IN_TEMPDB = ON ); GO DROP INDEX [IX dbo.LOBtest some_value (lob_data)] ON dbo.LOBtest; Remember that SQL Server only enforces uniqueness on index keys (the some_data column).  The lob_data column is simply stored at the leaf-level of the non-clustered index.  With that in mind, we might expect this change to make very little difference.  Let’s see: UPDATE dbo.LOBtest WITH (TABLOCKX) SET some_value = some_value - 1; Whoa!  Now look at the elapsed time and logical reads: Scan count 1, logical reads 2016, physical reads 0, read-ahead reads 0, lob logical reads 36015, lob physical reads 0, lob read-ahead reads 15992.   CPU time = 172 ms, elapsed time = 16172 ms. Even with all the data and index pages in memory, the query took over 16 seconds to update just 1,000 rows, performing over 52,000 LOB logical reads (nearly 16,000 of those using read-ahead). Why on earth is SQL Server reading LOB data in a query that only updates a single integer column? The Query Plan The query plan for test 3 looks a bit more complex than before: In fact, the bottom level is exactly the same as we saw with the non-unique index.  The top level has heaps of new stuff though, which I’ll come to in a moment. You might be expecting to find that the Clustered Index Scan is now reading the lob_data column (for some reason).  After all, we need to explain where all the LOB logical reads are coming from.  Sadly, when we look at the properties of the Clustered Index Scan, we see exactly the same as before: SQL Server is still only reading the pk and some_value columns – so what’s doing the LOB reads? Updates that Sneakily Read Data We have to go as far as the Clustered Index Update operator before we see LOB data in the output list: [Expr1020] is a bit flag added by an earlier Compute Scalar.  It is set true if the some_value column has not been changed (part of the non-updating updates optimization I mentioned earlier). The Clustered Index Update operator adds two new columns: the lob_data column, and some_value_OLD.  The some_value_OLD column, as the name suggests, is the pre-update value of the some_value column.  At this point, the clustered index has already been updated with the new value, but we haven’t touched the nonclustered index yet. An interesting observation here is that the Clustered Index Update operator can read a column into the data flow as part of its update operation.  SQL Server could have read the LOB data as part of the initial Clustered Index Scan, but that would mean carrying the data through all the operations that occur prior to the Clustered Index Update.  The server knows it will have to go back to the clustered index row to update it, so it delays reading the LOB data until then.  Sneaky! Why the LOB Data Is Needed This is all very interesting (I hope), but why is SQL Server reading the LOB data?  For that matter, why does it need to pass the pre-update value of the some_value column out of the Clustered Index Update? The answer relates to the top row of the query plan for test 3.  I’ll reproduce it here for convenience: Notice that this is a wide (per-index) update plan.  SQL Server used a narrow (per-row) update plan in test 2, where the Clustered Index Update took care of maintaining the nonclustered index too.  I’ll talk more about this difference shortly. The Split/Sort/Collapse combination is an optimization, which aims to make per-index update plans more efficient.  It does this by breaking each update into a delete/insert pair, reordering the operations, removing any redundant operations, and finally applying the net effect of all the changes to the nonclustered index. Imagine we had a unique index which currently holds three rows with the values 1, 2, and 3.  If we run a query that adds 1 to each row value, we would end up with values 2, 3, and 4.  The net effect of all the changes is the same as if we simply deleted the value 1, and added a new value 4. By applying net changes, SQL Server can also avoid false unique-key violations.  If we tried to immediately update the value 1 to a 2, it would conflict with the existing value 2 (which would soon be updated to 3 of course) and the query would fail.  You might argue that SQL Server could avoid the uniqueness violation by starting with the highest value (3) and working down.  That’s fine, but it’s not possible to generalize this logic to work with every possible update query. SQL Server has to use a wide update plan if it sees any risk of false uniqueness violations.  It’s worth noting that the logic SQL Server uses to detect whether these violations are possible has definite limits.  As a result, you will often receive a wide update plan, even when you can see that no violations are possible. Another benefit of this optimization is that it includes a sort on the index key as part of its work.  Processing the index changes in index key order promotes sequential I/O against the nonclustered index. A side-effect of all this is that the net changes might include one or more inserts.  In order to insert a new row in the index, SQL Server obviously needs all the columns – the key column and the included LOB column.  This is the reason SQL Server reads the LOB data as part of the Clustered Index Update. In addition, the some_value_OLD column is required by the Split operator (it turns updates into delete/insert pairs).  In order to generate the correct index key delete operation, it needs the old key value. The irony is that in this case the Split/Sort/Collapse optimization is anything but.  Reading all that LOB data is extremely expensive, so it is sad that the current version of SQL Server has no way to avoid it. Finally, for completeness, I should mention that the Filter operator is there to filter out the non-updating updates. Beating the Set-Based Update with a Cursor One situation where SQL Server can see that false unique-key violations aren’t possible is where it can guarantee that only one row is being updated.  Armed with this knowledge, we can write a cursor (or the WHILE-loop equivalent) that updates one row at a time, and so avoids reading the LOB data: SET NOCOUNT ON; SET STATISTICS XML, IO, TIME OFF;   DECLARE @PK INTEGER, @StartTime DATETIME; SET @StartTime = GETUTCDATE();   DECLARE curUpdate CURSOR LOCAL FORWARD_ONLY KEYSET SCROLL_LOCKS FOR SELECT L.pk FROM LOBtest L ORDER BY L.pk ASC;   OPEN curUpdate;   WHILE (1 = 1) BEGIN FETCH NEXT FROM curUpdate INTO @PK;   IF @@FETCH_STATUS = -1 BREAK; IF @@FETCH_STATUS = -2 CONTINUE;   UPDATE dbo.LOBtest SET some_value = some_value - 1 WHERE CURRENT OF curUpdate; END;   CLOSE curUpdate; DEALLOCATE curUpdate;   SELECT DATEDIFF(MILLISECOND, @StartTime, GETUTCDATE()); That completes the update in 1280 milliseconds (remember test 3 took over 16 seconds!) I used the WHERE CURRENT OF syntax there and a KEYSET cursor, just for the fun of it.  One could just as well use a WHERE clause that specified the primary key value instead. Clustered Indexes A clustered index is the ultimate index with included columns: all non-key columns are included columns in a clustered index.  Let’s re-create the test table and data with an updatable primary key, and without any non-clustered indexes: IF OBJECT_ID(N'dbo.LOBtest', N'U') IS NOT NULL DROP TABLE dbo.LOBtest; GO CREATE TABLE dbo.LOBtest ( pk INTEGER NOT NULL, some_value INTEGER NULL, lob_data VARCHAR(MAX) NULL, another_column CHAR(5) NULL, CONSTRAINT [PK dbo.LOBtest pk] PRIMARY KEY CLUSTERED (pk ASC) ); GO DECLARE @Data VARCHAR(MAX); SET @Data = REPLICATE(CONVERT(VARCHAR(MAX), 'x'), 65540);   WITH Numbers (n) AS ( SELECT ROW_NUMBER() OVER (ORDER BY (SELECT 0)) FROM master.sys.columns C1, master.sys.columns C2 ) INSERT LOBtest WITH (TABLOCKX) ( pk, some_value, lob_data ) SELECT TOP (1000) N.n, N.n, @Data FROM Numbers N WHERE N.n <= 1000; Now here’s a query to modify the cluster keys: UPDATE dbo.LOBtest SET pk = pk + 1; The query plan is: As you can see, the Split/Sort/Collapse optimization is present, and we also gain an Eager Table Spool, for Halloween protection.  In addition, SQL Server now has no choice but to read the LOB data in the Clustered Index Scan: The performance is not great, as you might expect (even though there is no non-clustered index to maintain): Table 'LOBtest'. Scan count 1, logical reads 2011, physical reads 0, read-ahead reads 0, lob logical reads 36015, lob physical reads 0, lob read-ahead reads 15992.   Table 'Worktable'. Scan count 1, logical reads 2040, physical reads 0, read-ahead reads 0, lob logical reads 34000, lob physical reads 0, lob read-ahead reads 8000.   SQL Server Execution Times: CPU time = 483 ms, elapsed time = 17884 ms. Notice how the LOB data is read twice: once from the Clustered Index Scan, and again from the work table in tempdb used by the Eager Spool. If you try the same test with a non-unique clustered index (rather than a primary key), you’ll get a much more efficient plan that just passes the cluster key (including uniqueifier) around (no LOB data or other non-key columns): A unique non-clustered index (on a heap) works well too: Both those queries complete in a few tens of milliseconds, with no LOB reads, and just a few thousand logical reads.  (In fact the heap is rather more efficient). There are lots more fun combinations to try that I don’t have space for here. Final Thoughts The behaviour shown in this post is not limited to LOB data by any means.  If the conditions are met, any unique index that has included columns can produce similar behaviour – something to bear in mind when adding large INCLUDE columns to achieve covering queries, perhaps. Paul White Email: [email protected] Twitter: @PaulWhiteNZ

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• When is a SQL function not a function?

  - by Rob Farley

  Should SQL Server even have functions? (Oh yeah – this is a T-SQL Tuesday post, hosted this month by Brad Schulz) Functions serve an important part of programming, in almost any language. A function is a piece of code that is designed to return something, as opposed to a piece of code which isn’t designed to return anything (which is known as a procedure). SQL Server is no different. You can call stored procedures, even from within other stored procedures, and you can call functions and use these in other queries. Stored procedures might query something, and therefore ‘return data’, but a function in SQL is considered to have the type of the thing returned, and can be used accordingly in queries. Consider the internal GETDATE() function. SELECT GETDATE(), SomeDatetimeColumn FROM dbo.SomeTable; There’s no logical difference between the field that is being returned by the function and the field that’s being returned by the table column. Both are the datetime field – if you didn’t have inside knowledge, you wouldn’t necessarily be able to tell which was which. And so as developers, we find ourselves wanting to create functions that return all kinds of things – functions which look up values based on codes, functions which do string manipulation, and so on. But it’s rubbish. Ok, it’s not all rubbish, but it mostly is. And this isn’t even considering the SARGability impact. It’s far more significant than that. (When I say the SARGability aspect, I mean “because you’re unlikely to have an index on the result of some function that’s applied to a column, so try to invert the function and query the column in an unchanged manner”) I’m going to consider the three main types of user-defined functions in SQL Server: Scalar Inline Table-Valued Multi-statement Table-Valued I could also look at user-defined CLR functions, including aggregate functions, but not today. I figure that most people don’t tend to get around to doing CLR functions, and I’m going to focus on the T-SQL-based user-defined functions. Most people split these types of function up into two types. So do I. Except that most people pick them based on ‘scalar or table-valued’. I’d rather go with ‘inline or not’. If it’s not inline, it’s rubbish. It really is. Let’s start by considering the two kinds of table-valued function, and compare them. These functions are going to return the sales for a particular salesperson in a particular year, from the AdventureWorks database. CREATE FUNCTION dbo.FetchSales_inline(@salespersonid int, @orderyear int) RETURNS TABLE AS  RETURN (     SELECT e.LoginID as EmployeeLogin, o.OrderDate, o.SalesOrderID     FROM Sales.SalesOrderHeader AS o     LEFT JOIN HumanResources.Employee AS e     ON e.EmployeeID = o.SalesPersonID     WHERE o.SalesPersonID = @salespersonid     AND o.OrderDate >= DATEADD(year,@orderyear-2000,'20000101')     AND o.OrderDate < DATEADD(year,@orderyear-2000+1,'20000101') ) ; GO CREATE FUNCTION dbo.FetchSales_multi(@salespersonid int, @orderyear int) RETURNS @results TABLE (     EmployeeLogin nvarchar(512),     OrderDate datetime,     SalesOrderID int     ) AS BEGIN     INSERT @results (EmployeeLogin, OrderDate, SalesOrderID)     SELECT e.LoginID, o.OrderDate, o.SalesOrderID     FROM Sales.SalesOrderHeader AS o     LEFT JOIN HumanResources.Employee AS e     ON e.EmployeeID = o.SalesPersonID     WHERE o.SalesPersonID = @salespersonid     AND o.OrderDate >= DATEADD(year,@orderyear-2000,'20000101')     AND o.OrderDate < DATEADD(year,@orderyear-2000+1,'20000101')     ;     RETURN END ; GO You’ll notice that I’m being nice and responsible with the use of the DATEADD function, so that I have SARGability on the OrderDate filter. Regular readers will be hoping I’ll show what’s going on in the execution plans here. Here I’ve run two SELECT * queries with the “Show Actual Execution Plan” option turned on. Notice that the ‘Query cost’ of the multi-statement version is just 2% of the ‘Batch cost’. But also notice there’s trickery going on. And it’s nothing to do with that extra index that I have on the OrderDate column. Trickery. Look at it – clearly, the first plan is showing us what’s going on inside the function, but the second one isn’t. The second one is blindly running the function, and then scanning the results. There’s a Sequence operator which is calling the TVF operator, and then calling a Table Scan to get the results of that function for the SELECT operator. But surely it still has to do all the work that the first one is doing... To see what’s actually going on, let’s look at the Estimated plan. Now, we see the same plans (almost) that we saw in the Actuals, but we have an extra one – the one that was used for the TVF. Here’s where we see the inner workings of it. You’ll probably recognise the right-hand side of the TVF’s plan as looking very similar to the first plan – but it’s now being called by a stack of other operators, including an INSERT statement to be able to populate the table variable that the multi-statement TVF requires. And the cost of the TVF is 57% of the batch! But it gets worse. Let’s consider what happens if we don’t need all the columns. We’ll leave out the EmployeeLogin column. Here, we see that the inline function call has been simplified down. It doesn’t need the Employee table. The join is redundant and has been eliminated from the plan, making it even cheaper. But the multi-statement plan runs the whole thing as before, only removing the extra column when the Table Scan is performed. A multi-statement function is a lot more powerful than an inline one. An inline function can only be the result of a single sub-query. It’s essentially the same as a parameterised view, because views demonstrate this same behaviour of extracting the definition of the view and using it in the outer query. A multi-statement function is clearly more powerful because it can contain far more complex logic. But a multi-statement function isn’t really a function at all. It’s a stored procedure. It’s wrapped up like a function, but behaves like a stored procedure. It would be completely unreasonable to expect that a stored procedure could be simplified down to recognise that not all the columns might be needed, but yet this is part of the pain associated with this procedural function situation. The biggest clue that a multi-statement function is more like a stored procedure than a function is the “BEGIN” and “END” statements that surround the code. If you try to create a multi-statement function without these statements, you’ll get an error – they are very much required. When I used to present on this kind of thing, I even used to call it “The Dangers of BEGIN and END”, and yes, I’ve written about this type of thing before in a similarly-named post over at my old blog. Now how about scalar functions... Suppose we wanted a scalar function to return the count of these. CREATE FUNCTION dbo.FetchSales_scalar(@salespersonid int, @orderyear int) RETURNS int AS BEGIN     RETURN (         SELECT COUNT(*)         FROM Sales.SalesOrderHeader AS o         LEFT JOIN HumanResources.Employee AS e         ON e.EmployeeID = o.SalesPersonID         WHERE o.SalesPersonID = @salespersonid         AND o.OrderDate >= DATEADD(year,@orderyear-2000,'20000101')         AND o.OrderDate < DATEADD(year,@orderyear-2000+1,'20000101')     ); END ; GO Notice the evil words? They’re required. Try to remove them, you just get an error. That’s right – any scalar function is procedural, despite the fact that you wrap up a sub-query inside that RETURN statement. It’s as ugly as anything. Hopefully this will change in future versions. Let’s have a look at how this is reflected in an execution plan. Here’s a query, its Actual plan, and its Estimated plan: SELECT e.LoginID, y.year, dbo.FetchSales_scalar(p.SalesPersonID, y.year) AS NumSales FROM (VALUES (2001),(2002),(2003),(2004)) AS y (year) CROSS JOIN Sales.SalesPerson AS p LEFT JOIN HumanResources.Employee AS e ON e.EmployeeID = p.SalesPersonID; We see here that the cost of the scalar function is about twice that of the outer query. Nicely, the query optimizer has worked out that it doesn’t need the Employee table, but that’s a bit of a red herring here. There’s actually something way more significant going on. If I look at the properties of that UDF operator, it tells me that the Estimated Subtree Cost is 0.337999. If I just run the query SELECT dbo.FetchSales_scalar(281,2003); we see that the UDF cost is still unchanged. You see, this 0.0337999 is the cost of running the scalar function ONCE. But when we ran that query with the CROSS JOIN in it, we returned quite a few rows. 68 in fact. Could’ve been a lot more, if we’d had more salespeople or more years. And so we come to the biggest problem. This procedure (I don’t want to call it a function) is getting called 68 times – each one between twice as expensive as the outer query. And because it’s calling it in a separate context, there is even more overhead that I haven’t considered here. The cheek of it, to say that the Compute Scalar operator here costs 0%! I know a number of IT projects that could’ve used that kind of costing method, but that’s another story that I’m not going to go into here. Let’s look at a better way. Suppose our scalar function had been implemented as an inline one. Then it could have been expanded out like a sub-query. It could’ve run something like this: SELECT e.LoginID, y.year, (SELECT COUNT(*)     FROM Sales.SalesOrderHeader AS o     LEFT JOIN HumanResources.Employee AS e     ON e.EmployeeID = o.SalesPersonID     WHERE o.SalesPersonID = p.SalesPersonID     AND o.OrderDate >= DATEADD(year,y.year-2000,'20000101')     AND o.OrderDate < DATEADD(year,y.year-2000+1,'20000101')     ) AS NumSales FROM (VALUES (2001),(2002),(2003),(2004)) AS y (year) CROSS JOIN Sales.SalesPerson AS p LEFT JOIN HumanResources.Employee AS e ON e.EmployeeID = p.SalesPersonID; Don’t worry too much about the Scan of the SalesOrderHeader underneath a Nested Loop. If you remember from plenty of other posts on the matter, execution plans don’t push the data through. That Scan only runs once. The Index Spool sucks the data out of it and populates a structure that is used to feed the Stream Aggregate. The Index Spool operator gets called 68 times, but the Scan only once (the Number of Executions property demonstrates this). Here, the Query Optimizer has a full picture of what’s being asked, and can make the appropriate decision about how it accesses the data. It can simplify it down properly. To get this kind of behaviour from a function, we need it to be inline. But without inline scalar functions, we need to make our function be table-valued. Luckily, that’s ok. CREATE FUNCTION dbo.FetchSales_inline2(@salespersonid int, @orderyear int) RETURNS table AS RETURN (SELECT COUNT(*) as NumSales     FROM Sales.SalesOrderHeader AS o     LEFT JOIN HumanResources.Employee AS e     ON e.EmployeeID = o.SalesPersonID     WHERE o.SalesPersonID = @salespersonid     AND o.OrderDate >= DATEADD(year,@orderyear-2000,'20000101')     AND o.OrderDate < DATEADD(year,@orderyear-2000+1,'20000101') ); GO But we can’t use this as a scalar. Instead, we need to use it with the APPLY operator. SELECT e.LoginID, y.year, n.NumSales FROM (VALUES (2001),(2002),(2003),(2004)) AS y (year) CROSS JOIN Sales.SalesPerson AS p LEFT JOIN HumanResources.Employee AS e ON e.EmployeeID = p.SalesPersonID OUTER APPLY dbo.FetchSales_inline2(p.SalesPersonID, y.year) AS n; And now, we get the plan that we want for this query. All we’ve done is tell the function that it’s returning a table instead of a single value, and removed the BEGIN and END statements. We’ve had to name the column being returned, but what we’ve gained is an actual inline simplifiable function. And if we wanted it to return multiple columns, it could do that too. I really consider this function to be superior to the scalar function in every way. It does need to be handled differently in the outer query, but in many ways it’s a more elegant method there too. The function calls can be put amongst the FROM clause, where they can then be used in the WHERE or GROUP BY clauses without fear of calling the function multiple times (another horrible side effect of functions). So please. If you see BEGIN and END in a function, remember it’s not really a function, it’s a procedure. And then fix it. @rob_farley

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• How to recover dpkg from corrupted downloads?

  - by rocker9455

  I just upgraded to the 10.10 RC earlier and had a few problems with graphic drivers (x didnt start) But i have remedied that now. When i run 'sudo apt-get install -f' i get this: will@UbuntuBox:/mnt/slax$ sudo apt-get install -f [sudo] password for will: Reading package lists... Done Building dependency tree Reading state information... Done Correcting dependencies... Done The following extra packages will be installed: libmono-wcf3.0-cil openoffice.org-calc openoffice.org-core The following NEW packages will be installed: libmono-wcf3.0-cil The following packages will be upgraded: openoffice.org-calc openoffice.org-core 2 upgraded, 1 newly installed, 0 to remove and 0 not upgraded. 16 not fully installed or removed. Need to get 0B/32.5MB of archives. After this operation, 1,929kB disk space will be freed. Do you want to continue [Y/n]? Y (Reading database ... 201565 files and directories currently installed.) Preparing to replace openoffice.org-calc 1:3.2.1-6ubuntu2~10.04.1 (using .../openoffice.org-calc_1%3a3.2.1-7ubuntu1_i386.deb) ... Unpacking replacement openoffice.org-calc ... xz: (stdin): Compressed data is corrupt dpkg-deb: subprocess <decompress> returned error exit status 1 dpkg: error processing /var/cache/apt/archives/openoffice.org-calc_1%3a3.2.1-7ubuntu1_i386.deb (--unpack): short read on buffer copy for backend dpkg-deb during `./usr/lib/openoffice/basis3.2/program/libscfiltli.so' dpkg: regarding .../openoffice.org-core_1%3a3.2.1-7ubuntu1_i386.deb containing openoffice.org-core: openoffice.org-core conflicts with openoffice.org-calc (<< 1:3.2.1-7ubuntu1) openoffice.org-calc (version 1:3.2.1-6ubuntu2~10.04.1) is present and installed. dpkg: error processing /var/cache/apt/archives/openoffice.org-core_1%3a3.2.1-7ubuntu1_i386.deb (--unpack): conflicting packages - not installing openoffice.org-core Unpacking libmono-wcf3.0-cil (from .../libmono-wcf3.0-cil_2.6.7-3ubuntu1_all.deb) ... dpkg-deb (subprocess): data: internal gzip read error: '<fd:0>: data error' dpkg-deb: subprocess <decompress> returned error exit status 2 dpkg: error processing /var/cache/apt/archives/libmono-wcf3.0-cil_2.6.7-3ubuntu1_all.deb (--unpack): subprocess dpkg-deb --fsys-tarfile returned error exit status 2 Errors were encountered while processing: /var/cache/apt/archives/openoffice.org-calc_1%3a3.2.1-7ubuntu1_i386.deb /var/cache/apt/archives/openoffice.org-core_1%3a3.2.1-7ubuntu1_i386.deb /var/cache/apt/archives/libmono-wcf3.0-cil_2.6.7-3ubuntu1_all.deb E: Sub-process /usr/bin/dpkg returned an error code (1) Any idea how i can get the broken packages fixed? Cheers, Will

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• Here’s a Quick Alternative Way to Download Videos from YouTube

  - by Taylor Gibb

  More than 24 hours of video content are uploaded to the internet per minute. With so many videos being uploaded, there’s no doubt you’ve come across a video you want to keep. Read on to find out how you can download your favorite videos for offline viewing. This method of downloading YouTube videos, is different, in the sense that you are just retrieving a buffered version of the video from your browsers cache. While you could always do this manually, different browsers store the cache in different places, a much easier method would be to head over to the NirSoft site and download a copy of Video Cache View (choose the zipped version), which allows you to view all the videos in your cache and supports all major browsers. Note: The download link is quite far down the page, see screenshot below How To Properly Scan a Photograph (And Get An Even Better Image) The HTG Guide to Hiding Your Data in a TrueCrypt Hidden Volume Make Your Own Windows 8 Start Button with Zero Memory Usage

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• Using bindings to control column order in a DataGrid

  - by DanM

  Problem I have a WPF Toolkit DataGrid, and I'd like to be able to switch among several preset column orders. This is an MVVM project, so the column orders are stored in a ViewModel. The problem is, I can't get bindings to work for the DisplayIndex property. No matter what I try, including the sweet method in this Josh Smith tutorial, I get: The DisplayIndex for the DataGridColumn with Header 'ID' is out of range. DisplayIndex must be greater than or equal to 0 and less than Columns.Count. Parameter name: displayIndex. Actual value was -1. Is there any workaround for this? I'm including my test code below. Please let me know if you see any problems with it. ViewModel code public class MainViewModel { public List<Plan> Plans { get; set; } public int IdDisplayIndex { get; set; } public int NameDisplayIndex { get; set; } public int DescriptionDisplayIndex { get; set; } public MainViewModel() { Initialize(); } private void Initialize() { IdDisplayIndex = 1; NameDisplayIndex = 2; DescriptionDisplayIndex = 0; Plans = new List<Plan> { new Plan { Id = 1, Name = "Primary", Description = "Likely to work." }, new Plan { Id = 2, Name = "Plan B", Description = "Backup plan." }, new Plan { Id = 3, Name = "Plan C", Description = "Last resort." } }; } } Plan Class public class Plan { public int Id { get; set; } public string Name { get; set; } public string Description { get; set; } } Window code - this uses Josh Smith's DataContextSpy <Window x:Class="WpfApplication1.MainWindow" xmlns="http://schemas.microsoft.com/winfx/2006/xaml/presentation" xmlns:x="http://schemas.microsoft.com/winfx/2006/xaml" xmlns:local="clr-namespace:WpfApplication1" xmlns:mwc="http://schemas.microsoft.com/wpf/2008/toolkit" Title="Main Window" Height="300" Width="300"> <Grid> <mwc:DataGrid ItemsSource="{Binding Plans}" AutoGenerateColumns="False"> <mwc:DataGrid.Resources> <local:DataContextSpy x:Key="spy" /> </mwc:DataGrid.Resources> <mwc:DataGrid.Columns> <mwc:DataGridTextColumn Header="ID" Binding="{Binding Id}" DisplayIndex="{Binding Source={StaticResource spy}, Path=DataContext.IdDisplayIndex}" /> <mwc:DataGridTextColumn Header="Name" Binding="{Binding Name}" DisplayIndex="{Binding Source={StaticResource spy}, Path=DataContext.NameDisplayIndex}" /> <mwc:DataGridTextColumn Header="Description" Binding="{Binding Description}" DisplayIndex="{Binding Source={StaticResource spy}, Path=DataContext.DescriptionDisplayIndex}" /> </mwc:DataGrid.Columns> </mwc:DataGrid> </Grid> </Window> Note: If I just use plain numbers for DisplayIndex, everything works fine, so the problem is definitely with the bindings. Update 5/1/2010 I was just doing a little maintenance on my project, and I noticed that when I ran it, the problem I discuss in this post had returned. I knew that it worked last time I ran it, so I eventually narrowed the problem down to the fact that I had installed a newer version of the WPF Toolkit (Feb '10). When I reverted to the June '09 version, everything worked fine again. So, I'm now doing something I should have done in this first place: I'm including the WPFToolkit.dll that works in my solution folder and checking it into version control. It's unfortunate, though, that the newer toolkit has a breaking change.

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• Can't Remove Logical Drive/Array from HP P400

  - by Myles

  This is my first post here. Thank you in advance for any assistance with this matter. I'm trying to remove a logical drive (logical drive 2) and an array (array "B") from my Smart Array P400. The host is a DL580 G5 running 64-bit Red Hat Enterprise Linux Server release 5.7 (Tikanga). I am unable to remove the array using either hpacucli or cpqacuxe. I believe it is because of "OS Status: LOCKED". The file system that lives on this array has been unmounted. I do not want to reboot the host. Is there some way to "release" this logical drive so I can remove the array? Note that I do not need to preserve the data on logical drive 2. I intend to physically remove the drives from the machine and replace them with larger drives. I'm using the cciss kernel module that ships with Red Hat 5.7. Here is some information pertaining to the host and the P400 configuration: [root@gort ~]# cat /etc/redhat-release Red Hat Enterprise Linux Server release 5.7 (Tikanga) [root@gort ~]# uname -a Linux gort 2.6.18-274.el5 #1 SMP Fri Jul 8 17:36:59 EDT 2011 x86_64 x86_64 x86_64 GNU/Linux [root@gort ~]# rpm -qa | egrep '^(hp|cpq)' cpqacuxe-9.30-15.0 hp-health-9.25-1551.7.rhel5 hpsmh-7.1.2-3 hpdiags-9.3.0-466 hponcfg-3.1.0-0 hp-snmp-agents-9.25-2384.8.rhel5 hpacucli-9.30-15.0 [root@gort ~]# hpacucli HP Array Configuration Utility CLI 9.30.15.0 Detecting Controllers...Done. Type "help" for a list of supported commands. Type "exit" to close the console. => ctrl all show config detail Smart Array P400 in Slot 0 (Embedded) Bus Interface: PCI Slot: 0 Cache Serial Number: PA82C0J9SVW34U RAID 6 (ADG) Status: Enabled Controller Status: OK Hardware Revision: D Firmware Version: 7.22 Rebuild Priority: Medium Expand Priority: Medium Surface Scan Delay: 15 secs Surface Scan Mode: Idle Wait for Cache Room: Disabled Surface Analysis Inconsistency Notification: Disabled Post Prompt Timeout: 0 secs Cache Board Present: True Cache Status: OK Cache Ratio: 25% Read / 75% Write Drive Write Cache: Disabled Total Cache Size: 256 MB Total Cache Memory Available: 208 MB No-Battery Write Cache: Disabled Cache Backup Power Source: Batteries Battery/Capacitor Count: 1 Battery/Capacitor Status: OK SATA NCQ Supported: True Logical Drive: 1 Size: 136.7 GB Fault Tolerance: RAID 1 Heads: 255 Sectors Per Track: 32 Cylinders: 35132 Strip Size: 128 KB Full Stripe Size: 128 KB Status: OK Caching: Enabled Unique Identifier: 600508B100184A395356573334550002 Disk Name: /dev/cciss/c0d0 Mount Points: /boot 101 MB, /tmp 7.8 GB, /usr 3.9 GB, /usr/local 2.0 GB, /var 3.9 GB, / 2.0 GB, /local 113.2 GB OS Status: LOCKED Logical Drive Label: A0027AA78DEE Mirror Group 0: physicaldrive 1I:1:2 (port 1I:box 1:bay 2, SAS, 146 GB, OK) Mirror Group 1: physicaldrive 1I:1:1 (port 1I:box 1:bay 1, SAS, 146 GB, OK) Drive Type: Data Array: A Interface Type: SAS Unused Space: 0 MB Status: OK Array Type: Data physicaldrive 1I:1:1 Port: 1I Box: 1 Bay: 1 Status: OK Drive Type: Data Drive Interface Type: SAS Size: 146 GB Rotational Speed: 10000 Firmware Revision: HPDE Serial Number: 3NM57RF40000983878FX Model: HP DG146BB976 Current Temperature (C): 29 Maximum Temperature (C): 35 PHY Count: 2 PHY Transfer Rate: Unknown, Unknown physicaldrive 1I:1:2 Port: 1I Box: 1 Bay: 2 Status: OK Drive Type: Data Drive Interface Type: SAS Size: 146 GB Rotational Speed: 10000 Firmware Revision: HPDE Serial Number: 3NM55VQC000098388524 Model: HP DG146BB976 Current Temperature (C): 29 Maximum Temperature (C): 36 PHY Count: 2 PHY Transfer Rate: Unknown, Unknown Logical Drive: 2 Size: 546.8 GB Fault Tolerance: RAID 5 Heads: 255 Sectors Per Track: 32 Cylinders: 65535 Strip Size: 64 KB Full Stripe Size: 256 KB Status: OK Caching: Enabled Parity Initialization Status: Initialization Completed Unique Identifier: 600508B100184A395356573334550003 Disk Name: /dev/cciss/c0d1 Mount Points: None OS Status: LOCKED Logical Drive Label: A5C9C6F81504 Drive Type: Data Array: B Interface Type: SAS Unused Space: 0 MB Status: OK Array Type: Data physicaldrive 1I:1:3 Port: 1I Box: 1 Bay: 3 Status: OK Drive Type: Data Drive Interface Type: SAS Size: 146 GB Rotational Speed: 10000 Firmware Revision: HPDE Serial Number: 3NM2H5PE00009802NK19 Model: HP DG146ABAB4 Current Temperature (C): 30 Maximum Temperature (C): 37 PHY Count: 1 PHY Transfer Rate: Unknown physicaldrive 1I:1:4 Port: 1I Box: 1 Bay: 4 Status: OK Drive Type: Data Drive Interface Type: SAS Size: 146 GB Rotational Speed: 10000 Firmware Revision: HPDE Serial Number: 3NM28YY400009750MKPJ Model: HP DG146ABAB4 Current Temperature (C): 31 Maximum Temperature (C): 36 PHY Count: 1 PHY Transfer Rate: 3.0Gbps physicaldrive 2I:1:5 Port: 2I Box: 1 Bay: 5 Status: OK Drive Type: Data Drive Interface Type: SAS Size: 146 GB Rotational Speed: 10000 Firmware Revision: HPDE Serial Number: 3NM2FGYV00009802N3GN Model: HP DG146ABAB4 Current Temperature (C): 30 Maximum Temperature (C): 38 PHY Count: 1 PHY Transfer Rate: Unknown physicaldrive 2I:1:6 Port: 2I Box: 1 Bay: 6 Status: OK Drive Type: Data Drive Interface Type: SAS Size: 146 GB Rotational Speed: 10000 Firmware Revision: HPDE Serial Number: 3NM8AFAK00009920MMV1 Model: HP DG146BB976 Current Temperature (C): 31 Maximum Temperature (C): 41 PHY Count: 2 PHY Transfer Rate: Unknown, Unknown physicaldrive 2I:1:7 Port: 2I Box: 1 Bay: 7 Status: OK Drive Type: Data Drive Interface Type: SAS Size: 146 GB Rotational Speed: 10000 Firmware Revision: HPDE Serial Number: 3NM2FJQD00009801MSHQ Model: HP DG146ABAB4 Current Temperature (C): 29 Maximum Temperature (C): 39 PHY Count: 1 PHY Transfer Rate: Unknown

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• Apache 2.4.3 php-fpm mod_fast_cgi and mod_cache

  - by Anjia

  Did anybody successfully configured mod_cache in apache 2.4 with php-fpm and fastcgi? my cgi config: <IfModule mod_fastcgi.c> Alias /php5.fastcgi /var/www/fastcgi/php5.fastcgi AddHandler php-script .php FastCGIExternalServer /var/www/fastcgi/php5.fastcgi -socket /mnt/tmp/fast/php-fpm.sock -idle-timeout 1600 -pass-header Authorization Action php-script /php5.fastcgi virtual My php-fpm config is standard and I am loading mod_cache and mod_disk_cache in Apache. However the Apache does not seems to cache any content. The debug log file: Fri Sep 07 23:22:59.691333 2012] [cache:debug] [pid 35623:tid 123613201929984] mod_cache.c(161): [client 10.0.0.22:21938] AH00750: Adding CACHE_SAVE filter for /index.html [Fri Sep 07 23:22:59.691345 2012] [cache:debug] [pid 35623:tid 123613201929984] mod_cache.c(171): [client 10.0.0.22:21938] AH00751: Adding CACHE_REMOVE_URL filter for /index.html [Fri Sep 07 23:23:01.326598 2012] [cache:debug] [pid 35623:tid 123613185144576] cache_storage.c(626): [client 10.0.0.110:5414] AH00698: cache: Key for entity /index.html?(null) is `http://10.0.1.16:8080/index.html?`

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• Ubuntu software center not opening [closed]

  - by I'll sudeepdino008

  Ubuntu software center is not opening, when I type: software-center in the command line, the following errors are generated: (software-center:8570): Gtk-WARNING **: Theme parsing error: gtk.css:227:31: Failed to import: Error opening file: No such file or directory 2012-09-30 17:00:58,068 - softwarecenter.ui.gtk3.app - INFO - setting up proxy 'http://10.3.100.212:8080/' 2012-09-30 17:00:58,071 - softwarecenter.db.database - INFO - open() database: path=None use_axi=True use_agent=True 2012-09-30 17:00:58,327 - softwarecenter.backend.reviews - WARNING - Could not get usefulness from server, no username in config file 2012-09-30 17:00:58,428 - softwarecenter.ui.gtk3.app - INFO - show_available_packages: search_text is '', app is None. 2012-09-30 17:00:58,433 - softwarecenter.db.pkginfo_impl.aptcache - INFO - aptcache.open() Traceback (most recent call last): File "/usr/share/software-center/softwarecenter/db/pkginfo_impl/aptcache.py", line 243, in open self._cache = apt.Cache(GtkMainIterationProgress()) File "/usr/lib/python2.7/dist-packages/apt/cache.py", line 102, in __init__ self.open(progress) File "/usr/lib/python2.7/dist-packages/apt/cache.py", line 145, in open self._cache = apt_pkg.Cache(progress) SystemError: E:Encountered a section with no Package: header, E:Problem with MergeList /var/lib/apt/lists/ppa.launchpad.net_webupd8team_themes_ubuntu_dists_precise_main_binary-i386_Packages, E:The package lists or status file could not be parsed or opened. 2012-09-30 17:01:00,130 - softwarecenter.db.enquire - ERROR - _get_estimate_nr_apps_and_nr_pkgs failed Traceback (most recent call last): File "/usr/share/software-center/softwarecenter/db/enquire.py", line 115, in _get_estimate_nr_apps_and_nr_pkgs tmp_matches = enquire.get_mset(0, len(self.db), None, xfilter) File "/usr/share/software-center/softwarecenter/db/appfilter.py", line 89, in __call__ if (not pkgname in self.cache and File "/usr/share/software-center/softwarecenter/db/pkginfo_impl/aptcache.py", line 263, in __contains__ return self._cache.__contains__(k) AttributeError: 'NoneType' object has no attribute '__contains__' Traceback (most recent call last): File "/usr/bin/software-center", line 176, in <module> app.run(args) File "/usr/share/software-center/softwarecenter/ui/gtk3/app.py", line 1422, in run self.show_available_packages(args) File "/usr/share/software-center/softwarecenter/ui/gtk3/app.py", line 1352, in show_available_packages self.view_manager.set_active_view(ViewPages.AVAILABLE) File "/usr/share/software-center/softwarecenter/ui/gtk3/session/viewmanager.py", line 154, in set_active_view view_widget.init_view() File "/usr/share/software-center/softwarecenter/ui/gtk3/panes/availablepane.py", line 171, in init_view self.apps_filter) File "/usr/share/software-center/softwarecenter/ui/gtk3/views/catview_gtk.py", line 238, in __init__ self.build(desktopdir) File "/usr/share/software-center/softwarecenter/ui/gtk3/views/catview_gtk.py", line 511, in build self._build_homepage_view() File "/usr/share/software-center/softwarecenter/ui/gtk3/views/catview_gtk.py", line 271, in _build_homepage_view self._append_whats_new() File "/usr/share/software-center/softwarecenter/ui/gtk3/views/catview_gtk.py", line 450, in _append_whats_new whats_new_cat = self._update_whats_new_content() File "/usr/share/software-center/softwarecenter/ui/gtk3/views/catview_gtk.py", line 439, in _update_whats_new_content docs = whats_new_cat.get_documents(self.db) File "/usr/share/software-center/softwarecenter/db/categories.py", line 124, in get_documents nonblocking_load=False) File "/usr/share/software-center/softwarecenter/db/enquire.py", line 317, in set_query self._blocking_perform_search() File "/usr/share/software-center/softwarecenter/db/enquire.py", line 212, in _blocking_perform_search matches = enquire.get_mset(0, self.limit, None, xfilter) File "/usr/share/software-center/softwarecenter/db/appfilter.py", line 89, in __call__ if (not pkgname in self.cache and File "/usr/share/software-center/softwarecenter/db/pkginfo_impl/aptcache.py", line 263, in __contains__ return self._cache.__contains__(k) AttributeError: 'NoneType' object has no attribute '__contains__'

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