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  • DNS question and Google PageRank from domains

    - by Beck
    I'm not so good at dns at all :) Just basics. A while ago i have noticed, that my blog have different Page Ranks, PR 3 for domain www.example.com and PR 1 for domain example.com. In dns records i have this setup: A - IP - www.example.com A - same IP - example.com Should i replace this record "A - same IP - example.com" with row with CNAME instead of A? Like that: CNAME - same IP - example.com - alias www.example.com Will this combine Page Rank value of both domains? Or i can just create 302 redirection inside .htaccess file, verify example.com(without www) inside Google Webmaster Tools as my domain and inside www.example.com options set as main domain? Thanks ;)

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  • What is the typical example of old school website design ?

    - by Pierre 303
    I want to build a website for a retro thing that was popular in the mid 90s (beginning of the commercial internet). So I want use old designs that was very popular at that time. The first thing that comes to my mind was those "under construction" animated gifs. People often put animated gifs everywhere. But also those awful repeating backgrounds. So yes, I want my website to look exactly like in the mid nineties ;) (please suggest practical and usable features, I guess an Java Applet menu would not work today, or saying on the bottom that this website is optimized for Netscape 3) EDIT: for those that wants to see the result: Retrology

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  • SQL SERVER – Curious Case of Disappearing Rows – ON UPDATE CASCADE and ON DELETE CASCADE – T-SQL Example – Part 2 of 2

    - by pinaldave
    Yesterday I wrote a real world story of how a friend who thought they have an issue with intrusion or virus whereas the issue was really in the code. I strongly suggest you read my earlier blog post Curious Case of Disappearing Rows – ON UPDATE CASCADE and ON DELETE CASCADE – Part 1 of 2 before continuing this blog post as this is second part of the first blog post. Let me reproduce the simple scenario in T-SQL. Building Sample Data USE [TestDB] GO -- Creating Table Products CREATE TABLE [dbo].[Products]( [ProductID] [int] NOT NULL, [ProductDesc] [varchar](50) NOT NULL, CONSTRAINT [PK_Products] PRIMARY KEY CLUSTERED ( [ProductID] ASC )) ON [PRIMARY] GO -- Creating Table ProductDetails CREATE TABLE [dbo].[ProductDetails]( [ProductDetailID] [int] NOT NULL, [ProductID] [int] NOT NULL, [Total] [int] NOT NULL, CONSTRAINT [PK_ProductDetails] PRIMARY KEY CLUSTERED ( [ProductDetailID] ASC )) ON [PRIMARY] GO ALTER TABLE [dbo].[ProductDetails] WITH CHECK ADD CONSTRAINT [FK_ProductDetails_Products] FOREIGN KEY([ProductID]) REFERENCES [dbo].[Products] ([ProductID]) ON UPDATE CASCADE ON DELETE CASCADE GO -- Insert Data into Table USE TestDB GO INSERT INTO Products (ProductID, ProductDesc) SELECT 1, 'Bike' UNION ALL SELECT 2, 'Car' UNION ALL SELECT 3, 'Books' GO INSERT INTO ProductDetails ([ProductDetailID],[ProductID],[Total]) SELECT 1, 1, 200 UNION ALL SELECT 2, 1, 100 UNION ALL SELECT 3, 1, 111 UNION ALL SELECT 4, 2, 200 UNION ALL SELECT 5, 3, 100 UNION ALL SELECT 6, 3, 100 UNION ALL SELECT 7, 3, 200 GO Select Data from Tables -- Selecting Data SELECT * FROM Products SELECT * FROM ProductDetails GO Delete Data from Products Table -- Deleting Data DELETE FROM Products WHERE ProductID = 1 GO Select Data from Tables Again -- Selecting Data SELECT * FROM Products SELECT * FROM ProductDetails GO Clean up Data -- Clean up DROP TABLE ProductDetails DROP TABLE Products GO My friend was confused as there was no delete was firing over ProductsDetails Table still there was a delete happening. The reason was because there is a foreign key created between Products and ProductsDetails Table with the keywords ON DELETE CASCADE. Due to ON DELETE CASCADE whenever is specified when the data from Table A is deleted and if it is referenced in another table using foreign key it will be deleted as well. Workaround 1: Design Changes – 3 Tables Change the design to have more than two tables. Create One Product Mater Table with all the products. It should historically store all the products list in it. No products should be ever removed from it. Add another table called Current Product and it should contain only the table which should be visible in the product catalogue. Another table should be called as ProductHistory table. There should be no use of CASCADE keyword among them. Workaround 2: Design Changes - Column IsVisible You can keep the same two tables. 1) Products and 2) ProductsDetails. Add a column with BIT datatype to it and name it as a IsVisible. Now change your application code to display the catalogue based on this column. There should be no need to delete anything. Workaround 3: Bad Advices (Bad advises begins here) The reason I have said bad advices because these are going to be bad advices for sure. You should make necessary design changes and not use poor workarounds which can damage the system and database integrity further. Here are the examples 1) Do not delete the data – well, this is not a real solution but can give time to implement design changes. 2) Do not have ON CASCADE DELETE – in this case, you will have entry in productsdetails which will have no corresponding product id and later on there will be lots of confusion. 3) Duplicate Data – you can have all the data of the product table move to the product details table and repeat them at each row. Now remove CASCADE code. This will let you delete the product table rows without any issue. There are so many things wrong this suggestion, that I will not even start here. (Bad advises ends here)  Well, did I miss anything? Please help me with your suggestions. Reference: Pinal Dave (http://blog.sqlauthority.com) Filed under: PostADay, SQL, SQL Authority, SQL Query, SQL Server, SQL Tips and Tricks, T SQL, Technology

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  • What is the typical example of old school website design?

    - by Pierre 303
    I want to build a website for a retro thing that was popular in the mid 90s (beginning of the commercial internet). So I want use old designs that was very popular at that time. The first thing that comes to my mind was those "under construction" animated gifs. People often put animated gifs everywhere. But also those awful repeating backgrounds. So yes, I want my website to look exactly like in the mid nineties ;) (please suggest practical and usable features, I guess an Java Applet menu would not work today, or saying on the bottom that this website is optimized for Netscape 3) EDIT: for those that wants to see the result: Retrology

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  • Is there a good example of the difference between practice and theory?

    - by a_person
    There has been a lot of posters advising that the best way to retain knowledge is to apply it practically. After ignoring said advice for several years in a futile attempt to accumulate enough theoretical knowledge to be prepared for every possible case scenario, the process which lead me to assembling a library that's easily worth ~6K, I finally get it. I would like to share my story in the hopes that others will avoid taking the same route that was taken by me. I've selected graphical format (photos with caption to be exact) as my media. Help me with your ideas, maybe a fragment of code, or other imagery that would convey a message of the inherent difference between practice and theory.

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  • A more concise example that illustrates that type inference can be very costly?

    - by mrrusof
    It was brought to my attention that the cost of type inference in a functional language like OCaml can be very high. The claim is that there is a sequence of expressions such that for each expression the length of the corresponding type is exponential on the length of the expression. I devised the sequence below. My question is: do you know of a sequence with more concise expressions that achieves the same types? # fun a -> a;; - : 'a -> 'a = <fun> # fun b a -> b a;; - : ('a -> 'b) -> 'a -> 'b = <fun> # fun c b a -> c b (b a);; - : (('a -> 'b) -> 'b -> 'c) -> ('a -> 'b) -> 'a -> 'c = <fun> # fun d c b a -> d c b (c b (b a));; - : ((('a -> 'b) -> 'b -> 'c) -> ('a -> 'b) -> 'c -> 'd) -> (('a -> 'b) -> 'b -> 'c) -> ('a -> 'b) -> 'a -> 'd = <fun> # fun e d c b a -> e d c b (d c b (c b (b a)));; - : (((('a -> 'b) -> 'b -> 'c) -> ('a -> 'b) -> 'c -> 'd) -> (('a -> 'b) -> 'b -> 'c) -> ('a -> 'b) -> 'd -> 'e) -> ((('a -> 'b) -> 'b -> 'c) -> ('a -> 'b) -> 'c -> 'd) -> (('a -> 'b) -> 'b -> 'c) -> ('a -> 'b) -> 'a -> 'e = <fun> # fun f e d c b a -> f e d c b (e d c b (d c b (c b (b a))));; - : ((((('a -> 'b) -> 'b -> 'c) -> ('a -> 'b) -> 'c -> 'd) -> (('a -> 'b) -> 'b -> 'c) -> ('a -> 'b) -> 'd -> 'e) -> ((('a -> 'b) -> 'b -> 'c) -> ('a -> 'b) -> 'c -> 'd) -> (('a -> 'b) -> 'b -> 'c) -> ('a -> 'b) -> 'e -> 'f) -> (((('a -> 'b) -> 'b -> 'c) -> ('a -> 'b) -> 'c -> 'd) -> (('a -> 'b) -> 'b -> 'c) -> ('a -> 'b) -> 'd -> 'e) -> ((('a -> 'b) -> 'b -> 'c) -> ('a -> 'b) -> 'c -> 'd) -> (('a -> 'b) -> 'b -> 'c) -> ('a -> 'b) -> 'a -> 'f = <fun>

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  • Subdomain Is Redirected and Causing an Error Because www. is Added

    - by user532493
    On my site, say example.com, if I try to access test.example.com, Firefox automatically adds www. to test.example.com, making it www.test.example.com, which causes an error. However, if I visit a site like my.ebay.com, no www. is added so no error occurs. What's going on? Just in case, my .htaccess file is as follows: Options -Multiviews RewriteEngine On RewriteCond %{HTTP_HOST} ^example.com RewriteRule ^(.*)$ http://www.example.com/$1 [R=301,L] RewriteCond %{REQUEST_FILENAME} !-f RewriteCond %{REQUEST_FILENAME} !-d RewriteRule ^(.*)$ $1.php I looked through Firebug and it seems like Firefox doesn't even make an attempt to reach test.example.com before reverting to www.test.example.com. One nuance I didn't realize until now. If I try to access the site using test.example.com/, the www. is added. If however that trailing slash is not there, then I am sent to the subdomain properly.

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  • Is there a better way to handle data abstraction in this example?

    - by sigil
    I'm building an application that retrieves Sharepoint list data via a web service SPlists.Lists. To create an instance of the web service, I have the following class: class SharepointServiceCreator { public SPlists.Lists createService() { listsService.Url = "http://wss/sites/SPLists/_vti_bin/lists.asmx"; listsService.Credentials = System.Net.CredentialCache.DefaultCredentials; SPlists.Lists listsService=new SPlists.Lists(); } } I'm concerned that this isn't good OOP abstraction, though, because in order to create this service elsewhere in my application, I would need the following code: class someClass { public void someMethod() { SharepointServiceCreator s=new SharepointServiceCreator() SPlists.Lists listService=s.createService() } } Having to use declare the instance of listService in someMethod as type SPlists.Lists seems wrong, because it means that someClass needs to know about how SharepointServiceCreator is implemented. Or is this ok?

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  • Does anyone have a specific example of using the Flyweight Pattern?

    - by Jeremy E
    I have been studying design patterns and came accross the fly weight pattern. I have been trying to see opportunities to use the pattern in my applications but I am having trouble seeing how to use it. Also, what are some signs that a fly weight pattern is being used when I read other peoples code? According to the definition it says: Use sharing to support large numbers of fine-grained objects efficiently. If I read it right Dictionaries and Hashtables could be instances of fly weights is this correct? Thanks in advance.

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  • How can I get HTTPD to serve the html/php files and not list/index them when they are in folder for virtual host. Using Centos 6.0

    - by LaserBeak
    My virtual hosts are configured as below, initally I could not even get to the /public_html/ directory when typing example.com and apache would just serve me up the default welcome page, I would also get the error: Directory index forbidden by Options directive: /var/www/html/example.com/public_html/ in the log . After editing the welcome.conf page (- Index) so it does not show again when I now type example.com the/public_html/ contents (Index.php) are indexed in the browser. Where as I want it to actually execute and diplay the index.php page. vhost.conf , located in etc/httpd/vhost.d/ NameVirtualHost *:80 <VirtualHost *:80> ServerAdmin [email protected] ServerName localhost ServerAlias localhost.example.com DocumentRoot /var/www/html/example.com/public_html/ ErrorLog /var/www/html/example.com/logs/error.log CustomLog /var/www/html/example.com/logs/access.log combined </VirtualHost> <VirtualHost *:80> ServerAdmin [email protected] ServerName example.org ServerAlias www.example.org DocumentRoot /var/www/html/example.org/public_html/ ErrorLog /var/www/html/example.org/logs/error.log CustomLog /var/www/html/example.org/logs/access.log combined </VirtualHost> httpd.conf, settings on default, added onto end: Include /etc/httpd/vhosts.d/*.conf Root directories: DocumentRoot "/var/www/html"

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  • Trouble serving vhosts when trying to set up wildcard subdomains with dnsmasq in local development e

    - by Jeremy Kendall
    I'm trying to get wildcard DNS enabled on my laptop using dnsmasq. I realize that this has been asked and answered more than once on this forum, but I can't get the solution to work for me. Steps taken so far: Installed dnsmasq Set address=/example.dev/127.0.0.1 in dnsmasq.conf Set listen-address=127.0.0.1 in dnsmasq.conf Ensured nameserver 127.0.0.1 is in /etc/resolv.conf Set prepend domain-name-servers 127.0.0.1; in /etc/dhcp3/dhclient.conf Created a vhost for example.dev Restarted apache and dnsmasq Note: example.dev is not set in /etc/hosts My vhost for example.dev <VirtualHost *:80> ServerName example.dev DocumentRoot /home/jkendall/public_html/example/public ServerAlias *.example.dev # This should be omitted in the production environment SetEnv APPLICATION_ENV development <Directory /home/jkendall/public_html/example/public> DirectoryIndex index.php AllowOverride All Order allow,deny Allow from all </Directory> </VirtualHost> The setup above will server example.dev locally without any problem. It will also serve test.example.dev, but test.example.dev returns the default apache "It works!" index.html from /var/www rather than my index.php in /home/jkendall/public_html/example/public. The solution in this Server Fault thread suggests that address=/.example.dev/127.0.0.1 would resolve my problem, but when I try to use that solution, restarting dnsmasq results in a failure with the error message dnsmasq: error at line 62 of /etc/dnsmasq.conf For grins, I moved my project over to /var/www/example and modified the vhost appropriately. I got the same result as described above. At this point I'm not sure what other steps I can take to resolve the issue. Thoughts?

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  • Specific DNS sometimes resolves to wildcard, incorrectly

    - by Mojo
    I have an intermittent problem, and I'm not sure where to start trying to troubleshoot it. In our dev environment, we have two visible IP addresses on load balancers, one to the front-end, and one to a number of back-end service machines. The front-end is configured to take a wildcard DNS name to support generic "portals." dev.example.com A 10.1.1.1 *.dev.example.com CNAME dev.example.com The back-end servers are all specific names within the same space: core.dev.example.com A 10.1.1.2 cms.dev.example.com CNAME core.dev.example.com search.dev.example.com CNAME core.dev.example.com Here's the problem. Periodically a developer or a program trying to reach, say, cms.dev.example.com will get a result that points to the front-end, instead of the back-end load balancer: cms.dev.example.com is an alias to core.dev.example.com core.dev.example.com is an alias to dev.example.com (WRONG!) dev.example.com 10.1.1.1 The developers are all on Mac OS X machines, though I've seen the problem occur on an Ubuntu machine as well, using a local cloud host DNS resolver. Sometimes the developer is using a VPN, which directs the DNS to its own resolver, and sometimes he's on the local net using a DNS resolver assigned by the NAT router. Sometimes clearing the Mac OS X DNS cache, logging into the VPN, then logging out of the VPN, will make the problem go away. The origin authoritative server is on zerigo, and a dig directly to their name servers always seems to give the correct answer. The published DNS cache time for these records is 15 minutes, but the problem has been intermittent for about a week. Any troubleshooting suggestions?

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  • My DNS works! But, what is the simplest way to add something to it?

    - by Alex
    This is my current DNS example.com.db zone file. I followed a tutorial. It works, because when I point to this DNS from another server via resolve.conf, it will actually forward me to the right IP when I do "ping example.com". ; ; BIND data file for example.com ; $TTL 604800 @ IN SOA example.com. info.example.com. ( 2007011501 ; Serial 7200 ; Refresh 120 ; Retry 2419200 ; Expire 604800) ; Default TTL ; @ IN NS ns1.example.com. @ IN NS ns2.example.com. example.com. IN MX 10 mail.example.com. example.com. IN A 192.168.254.1 www IN CNAME example.com. mail IN A 192.168.254.1 ftp IN CNAME example.com. example.com. IN TXT "v=spf1 ip4:192.168.254.1 a mx ~all" mail IN TXT "v=spf1 a -all" Right now, ping example.com....goes to 192.168.254.1. That's great!!! it works! My question is--how can I add something do this file so that when my other servers: ping dbserver1....goes to 44.245.66.222 ping cacheserver1 ....goes to 38.221.44.555 I want to use it like a universal hosts file for my machines.

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  • Can't get DNS Alias work on Ubuntu 10.04 with Apache 2

    - by Johnny
    I want to use the DNS Alias to configure one of my domain pointing to a specific directory on the server. Here is what I've done: Change the IP address in domain setting, and it works $ ping www.example.com PING example.com (124.205.62.xxx): 56 data bytes 64 bytes from 124.205.62.xxx: icmp_seq=0 ttl=48 time=53.088 ms 64 bytes from 124.205.62.xxx: icmp_seq=1 ttl=48 time=52.125 ms ^C --- example.com ping statistics --- 2 packets transmitted, 2 packets received, 0.0% packet loss round-trip min/avg/max/stddev = 52.125/52.606/53.088/0.482 ms Add sites-available and sites-enabled $ ls -l /etc/apache2/sites-available/ total 16 -rw-r--r-- 1 root root 948 2010-04-14 03:27 default -rw-r--r-- 1 root root 7467 2010-04-14 03:27 default-ssl -rw-r--r-- 1 root root 365 2010-06-09 18:27 example.com $ ls -l /etc/apache2/sites-enabled/ total 0 lrwxrwxrwx 1 root root 26 2010-06-09 15:46 000-default -> ../sites-available/default lrwxrwxrwx 1 root root 33 2010-06-09 18:17 001-example.com -> ../sites-available/example.com But it doesn't work and when I open the browser for www.example.com, it shows an 111 error: The following error was encountered: Connection to 124.205.62.48 Failed The system returned: (111) Connection refused Here is how example.com's config: $ cat /etc/apache2/sites-enabled/001-example.com <virtualhost *:80> DocumentRoot "/vhosts/example.com/htdocs/" ServerName www.example.com ServerAlias example.com <Location /> Order Deny,Allow Deny from None Allow from all </Location> #Include /etc/phpmyadmin/apache.conf ErrorLog /vhosts/example.com/logs/error.log CustomLog /vhosts/example.com/logs/access.log combined Could you please tell me how to solve this?

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  • How do browser cookie domains work?

    - by Vilx-
    Due to weird domain/subdomain cookie issues that I'm getting, I'd like to know how browsers handle cookies. If they do it in different ways, it would also be nice to know the differences. In other words - when a browser receives a cookie, that cookie MAY have a domain and a path attached to it. Or not, in which case the browser probably substitutes some defaults for them. Question 1: what are they? Later, when the browser is about to make a request, it checks its cookies and filters out the ones it should send for that request. It does so by matching them against the requests path and domain. Question 2: what are the matching rules? Added: The reason I'm asking this is because I'm interested in some edge cases. Like: Will a cookie for .example.com be available for www.example.com? Will a cookie for .example.com be available for example.com? Will a cookie for example.com be available for www.example.com? Will a cookie for example.com be available for anotherexample.com? Will www.example.com be able to set cookie for example.com? Will www.example.com be able to set cookie for www2.example.com? Will www.example.com be able to set cookie for .com? Etc. Added 2: Also, could someone suggest how I should set a cookie so that: It can be set by either www.example.com or example.com; It is accessible by both www.example.com and example.com.

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  • BIND - zone not loaded du to errors

    - by Johan Barelds
    After upgrading from Ubuntu 8.04 to 10.04 my DNS isn't working properly anymore. I keep getting this error when I run named-checkzone example.com /var/cache/bind/example.com.zone.db zone example.com/IN: NS 'mx002a.example.com' has no address records (A or AAAA) zone example.com/IN: not loaded due to errors. in /var/cached/bind/example.com.db $TTL 3D @ IN SOA mx002a.example.com. chantra.example.com. ( 200608081 ; serial, todays date + todays serial # 8H ; refresh, seconds 2H ; retry, seconds 4W ; expire, seconds 1D ) ; minimum, seconds ; ; mx002a.example.com IN A 192.168.85.19 example.com. IN NS mx002a.example.com. mx001 60 IN A 192.168.85.17 mx001 60 IN A 192.168.85.18

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  • MX records and CNAMEs

    - by sly
    I realize similar questions were asked/answered on this, but I have a subtle detail to which I can not find answers anywhere. Let's exemplify with the following DNS entries: foo.example.com A 1.1.1.1 bar.example.com A 1.1.1.2 wee.example.com CNAME foo.example.com foo.example.com MX foo.example.com.s9a1.psmtp.com bar.example.com MX bar.example.com.s9a1.psmtp.com Note the last line. My institution has that kind of MX records, where for each MX record the value has the label prepended. Question 1 is, what is the motivation for this (why not just s9a1.psmtp.com)? Question 2 is more subtle and follows.. My understanding is that an MX record should not contain any aliases for neither label nor the value, i.e. the following would be bad practice: wee.example.com MX wee.example.com.s9a1.psmtp.com Then, how should the RRs look for the alias wee.example.com? Thanks!

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  • So…is it a Seek or a Scan?

    - by Paul White
    You’re probably most familiar with the terms ‘Seek’ and ‘Scan’ from the graphical plans produced by SQL Server Management Studio (SSMS).  The image to the left shows the most common ones, with the three types of scan at the top, followed by four types of seek.  You might look to the SSMS tool-tip descriptions to explain the differences between them: Not hugely helpful are they?  Both mention scans and ranges (nothing about seeks) and the Index Seek description implies that it will not scan the index entirely (which isn’t necessarily true). Recall also yesterday’s post where we saw two Clustered Index Seek operations doing very different things.  The first Seek performed 63 single-row seeking operations; and the second performed a ‘Range Scan’ (more on those later in this post).  I hope you agree that those were two very different operations, and perhaps you are wondering why there aren’t different graphical plan icons for Range Scans and Seeks?  I have often wondered about that, and the first person to mention it after yesterday’s post was Erin Stellato (twitter | blog): Before we go on to make sense of all this, let’s look at another example of how SQL Server confusingly mixes the terms ‘Scan’ and ‘Seek’ in different contexts.  The diagram below shows a very simple heap table with two columns, one of which is the non-clustered Primary Key, and the other has a non-unique non-clustered index defined on it.  The right hand side of the diagram shows a simple query, it’s associated query plan, and a couple of extracts from the SSMS tool-tip and Properties windows. Notice the ‘scan direction’ entry in the Properties window snippet.  Is this a seek or a scan?  The different references to Scans and Seeks are even more pronounced in the XML plan output that the graphical plan is based on.  This fragment is what lies behind the single Index Seek icon shown above: You’ll find the same confusing references to Seeks and Scans throughout the product and its documentation. Making Sense of Seeks Let’s forget all about scans for a moment, and think purely about seeks.  Loosely speaking, a seek is the process of navigating an index B-tree to find a particular index record, most often at the leaf level.  A seek starts at the root and navigates down through the levels of the index to find the point of interest: Singleton Lookups The simplest sort of seek predicate performs this traversal to find (at most) a single record.  This is the case when we search for a single value using a unique index and an equality predicate.  It should be readily apparent that this type of search will either find one record, or none at all.  This operation is known as a singleton lookup.  Given the example table from before, the following query is an example of a singleton lookup seek: Sadly, there’s nothing in the graphical plan or XML output to show that this is a singleton lookup – you have to infer it from the fact that this is a single-value equality seek on a unique index.  The other common examples of a singleton lookup are bookmark lookups – both the RID and Key Lookup forms are singleton lookups (an RID lookup finds a single record in a heap from the unique row locator, and a Key Lookup does much the same thing on a clustered table).  If you happen to run your query with STATISTICS IO ON, you will notice that ‘Scan Count’ is always zero for a singleton lookup. Range Scans The other type of seek predicate is a ‘seek plus range scan’, which I will refer to simply as a range scan.  The seek operation makes an initial descent into the index structure to find the first leaf row that qualifies, and then performs a range scan (either backwards or forwards in the index) until it reaches the end of the scan range. The ability of a range scan to proceed in either direction comes about because index pages at the same level are connected by a doubly-linked list – each page has a pointer to the previous page (in logical key order) as well as a pointer to the following page.  The doubly-linked list is represented by the green and red dotted arrows in the index diagram presented earlier.  One subtle (but important) point is that the notion of a ‘forward’ or ‘backward’ scan applies to the logical key order defined when the index was built.  In the present case, the non-clustered primary key index was created as follows: CREATE TABLE dbo.Example ( key_col INTEGER NOT NULL, data INTEGER NOT NULL, CONSTRAINT [PK dbo.Example key_col] PRIMARY KEY NONCLUSTERED (key_col ASC) ) ; Notice that the primary key index specifies an ascending sort order for the single key column.  This means that a forward scan of the index will retrieve keys in ascending order, while a backward scan would retrieve keys in descending key order.  If the index had been created instead on key_col DESC, a forward scan would retrieve keys in descending order, and a backward scan would return keys in ascending order. A range scan seek predicate may have a Start condition, an End condition, or both.  Where one is missing, the scan starts (or ends) at one extreme end of the index, depending on the scan direction.  Some examples might help clarify that: the following diagram shows four queries, each of which performs a single seek against a column holding every integer from 1 to 100 inclusive.  The results from each query are shown in the blue columns, and relevant attributes from the Properties window appear on the right: Query 1 specifies that all key_col values less than 5 should be returned in ascending order.  The query plan achieves this by seeking to the start of the index leaf (there is no explicit starting value) and scanning forward until the End condition (key_col < 5) is no longer satisfied (SQL Server knows it can stop looking as soon as it finds a key_col value that isn’t less than 5 because all later index entries are guaranteed to sort higher). Query 2 asks for key_col values greater than 95, in descending order.  SQL Server returns these results by seeking to the end of the index, and scanning backwards (in descending key order) until it comes across a row that isn’t greater than 95.  Sharp-eyed readers may notice that the end-of-scan condition is shown as a Start range value.  This is a bug in the XML show plan which bubbles up to the Properties window – when a backward scan is performed, the roles of the Start and End values are reversed, but the plan does not reflect that.  Oh well. Query 3 looks for key_col values that are greater than or equal to 10, and less than 15, in ascending order.  This time, SQL Server seeks to the first index record that matches the Start condition (key_col >= 10) and then scans forward through the leaf pages until the End condition (key_col < 15) is no longer met. Query 4 performs much the same sort of operation as Query 3, but requests the output in descending order.  Again, we have to mentally reverse the Start and End conditions because of the bug, but otherwise the process is the same as always: SQL Server finds the highest-sorting record that meets the condition ‘key_col < 25’ and scans backward until ‘key_col >= 20’ is no longer true. One final point to note: seek operations always have the Ordered: True attribute.  This means that the operator always produces rows in a sorted order, either ascending or descending depending on how the index was defined, and whether the scan part of the operation is forward or backward.  You cannot rely on this sort order in your queries of course (you must always specify an ORDER BY clause if order is important) but SQL Server can make use of the sort order internally.  In the four queries above, the query optimizer was able to avoid an explicit Sort operator to honour the ORDER BY clause, for example. Multiple Seek Predicates As we saw yesterday, a single index seek plan operator can contain one or more seek predicates.  These seek predicates can either be all singleton seeks or all range scans – SQL Server does not mix them.  For example, you might expect the following query to contain two seek predicates, a singleton seek to find the single record in the unique index where key_col = 10, and a range scan to find the key_col values between 15 and 20: SELECT key_col FROM dbo.Example WHERE key_col = 10 OR key_col BETWEEN 15 AND 20 ORDER BY key_col ASC ; In fact, SQL Server transforms the singleton seek (key_col = 10) to the equivalent range scan, Start:[key_col >= 10], End:[key_col <= 10].  This allows both range scans to be evaluated by a single seek operator.  To be clear, this query results in two range scans: one from 10 to 10, and one from 15 to 20. Final Thoughts That’s it for today – tomorrow we’ll look at monitoring singleton lookups and range scans, and I’ll show you a seek on a heap table. Yes, a seek.  On a heap.  Not an index! If you would like to run the queries in this post for yourself, there’s a script below.  Thanks for reading! IF OBJECT_ID(N'dbo.Example', N'U') IS NOT NULL BEGIN DROP TABLE dbo.Example; END ; -- Test table is a heap -- Non-clustered primary key on 'key_col' CREATE TABLE dbo.Example ( key_col INTEGER NOT NULL, data INTEGER NOT NULL, CONSTRAINT [PK dbo.Example key_col] PRIMARY KEY NONCLUSTERED (key_col) ) ; -- Non-unique non-clustered index on the 'data' column CREATE NONCLUSTERED INDEX [IX dbo.Example data] ON dbo.Example (data) ; -- Add 100 rows INSERT dbo.Example WITH (TABLOCKX) ( key_col, data ) SELECT key_col = V.number, data = V.number FROM master.dbo.spt_values AS V WHERE V.[type] = N'P' AND V.number BETWEEN 1 AND 100 ; -- ================ -- Singleton lookup -- ================ ; -- Single value equality seek in a unique index -- Scan count = 0 when STATISTIS IO is ON -- Check the XML SHOWPLAN SELECT E.key_col FROM dbo.Example AS E WHERE E.key_col = 32 ; -- =========== -- Range Scans -- =========== ; -- Query 1 SELECT E.key_col FROM dbo.Example AS E WHERE E.key_col <= 5 ORDER BY E.key_col ASC ; -- Query 2 SELECT E.key_col FROM dbo.Example AS E WHERE E.key_col > 95 ORDER BY E.key_col DESC ; -- Query 3 SELECT E.key_col FROM dbo.Example AS E WHERE E.key_col >= 10 AND E.key_col < 15 ORDER BY E.key_col ASC ; -- Query 4 SELECT E.key_col FROM dbo.Example AS E WHERE E.key_col >= 20 AND E.key_col < 25 ORDER BY E.key_col DESC ; -- Final query (singleton + range = 2 range scans) SELECT E.key_col FROM dbo.Example AS E WHERE E.key_col = 10 OR E.key_col BETWEEN 15 AND 20 ORDER BY E.key_col ASC ; -- === TIDY UP === DROP TABLE dbo.Example; © 2011 Paul White email: [email protected] twitter: @SQL_Kiwi

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  • Using mod_speling with multi-level htaccess and rewriterules

    - by michaelcgorman
    We recently switched formats for managing our 301s. For the most part, everything went well, but it seems to have stopped mod_speling from working properly. Here's what we changed: old /var/www/html/.htaccess: RewriteEngine on RewriteBase / # Change SHTML to HTML RewriteRule ^(.*)\.shtml$ $1.html [R=permanent,L] # Change PCF to HTML ('cause, you know, we probably have CMS users like that...) RewriteRule ^(.*)\.pcf$ $1.html [R=permanent,L] # Force WWW subdomain for all requests RewriteCond %{HTTP_HOST} !^www.example.edu$ [NC] RewriteRule ^(.*)$ http://www.example.edu/$1 [R,L] # User accounts are on sun.example.edu RedirectMatch ^/~(.*)$ http://sun.example.edu/~$1 # Remove index.html at the end of URLs RewriteCond %{REQUEST_URI} ^(.*/)index\.html$ [NC] RewriteRule . %1 [R=301,NE,L] Redirect 301 /academics/calendar2012-13.html http://www.example.edu/academics/calendar.html Redirect 301 /academics/departments/ http://www.example.edu/majors/ Redirect 301 /academics/Pre-Medical.pdf http://www.example.edu/academics/Pre-Medicine.pdf Redirect 301 ... new /var/www/html/.htaccess: RewriteEngine on RewriteBase / # Change SHTML to HTML RewriteRule ^(.*)\.shtml$ $1.html [R=permanent,L] # Change PCF to HTML ('cause, you know, we probably have CMS users like that...) RewriteRule ^(.*)\.pcf$ $1.html [R=permanent,L] # Force WWW subdomain for all requests RewriteCond %{HTTP_HOST} !^www.example.edu$ [NC] RewriteRule ^(.*)$ http://www.example.edu/$1 [R,L] # User accounts are on sun.example.edu RedirectMatch ^/~(.*)$ http://sun.example.edu/~$1 # Remove index.html at the end of URLs RewriteCond %{REQUEST_URI} ^(.*/)index\.html$ [NC] RewriteRule . %1 [R=301,NE,L] RewriteCond %{REQUEST_FILENAME} !-f RewriteCond %{REQUEST_FILENAME} !-d RewriteRule ^(.*) 404/$1 And then we added a new file at /var/www/html/404/.htaccess: RewriteEngine on RewriteBase /404 RewriteRule ^academics/calendar2012-13.html$ /academics/calendar.html [R=302,L] RewriteRule ^academics/departments/$ /majors/ [R=301,L] RewriteRule ^academics/Pre-Medical.pdf$ /academics/Pre-Medicine.pdf[R=301,L] RewriteRule ... I do have (Webmin-based) access to the httpd.conf (though we don't want to store all our 301s there, if possible). We're running Apache 2.2.15 on RHEL 6 on a server in our own data center. Like I said, the only problem we're seeing is that mod_speling isn't doing its magic anymore. The new format has so many advantages over the old that we really don't want to go back, but mod_speling is so nice to have that we'd also really like it to work if possible. Any ideas for how we might be able to fix mod_speling?

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  • Setting up home DNS with Ubuntu Server

    - by Zeophlite
    I have a webserver (with static IP 192.168.1.5), and I want to have my machines on my local network to be able to access it without modifying /etc/hosts (or equivalent for Windows/OSX). My router has Primary DNS server 192.168.1.5 Secondary DNS server 8.8.8.8 (Google's public DNS). Nginx is set up to server websites externally as *.example.com Internally, I want *.example.local to point to the server. My webserver has BIND9 installed, but I'm unsure of the settings. I've been through various contradicting tutorials, and so most of my settings have been clobbered. I've stripped out the lines which I'm confused about. The tutorials I looked at are http://tech.surveypoint.com/blog/installing-a-local-dns-server-behind-a-hardware-router/ and http://ubuntuforums.org/showthread.php?t=236093 . They mostly differ on what should be put in /etc/bind/zones/db.example.local and /etc/bind/zones/db.192, so I've left the conflicting lines out below. Can someone suggest what the correct lines are to give my above behaviour (namely *.example.local pointing to 192.168.1.5)? /etc/network/interfaces auto lo iface lo inet loopback auto eth0 iface eth0 inet static address 192.168.1.5 netmask 255.255.255.0 broadcast 192.168.1.255 gateway 192.168.1.254 /etc/hostname avalon /etc/resolv.conf # Dynamic resolv.conf(5) file for glibc resolver(3) generated by resolvconf(8) # DO NOT EDIT THIS FILE BY HAND -- YOUR CHANGES WILL BE OVERWRITTEN /etc/bind/named.conf.options options { directory "/var/cache/bind"; forwarders { 8.8.8.8; 8.8.4.4; }; dnssec-validation auto; auth-nxdomain no; # conform to RFC1035 listen-on-v6 { any; }; }; /etc/bind/named.conf.local zone "example.local" { type master; file "/etc/bind/zones/db.example.local"; }; zone "1.168.192.in-addr.arpa" { type master; file "/etc/bind/zones/db.192"; }; /etc/bind/zones/db.example.local $TTL 604800 @ IN SOA avalon.example.local. webadmin.example.local. ( 5 ; Serial, increment each edit 604800 ; Refresh 86400 ; Retry 2419200 ; Expire 604800 ) ; Negative Cache TTL /etc/bind/zones/db.192 $TTL 604800 @ IN SOA avalon.example.local. webadmin.example.local. ( 4 ; Serial, increment each edit 604800 ; Refresh 86400 ; Retry 2419200 ; Expire 604800 ) ; Negative Cache TTL ; What do I need to add to the above files so that on a laptop on the internal network, I can type in webapp.example.local, and be served by my webserver? EDIT I made several changes to the above files on the webserver. /etc/network/interfaces (end of file) dns-nameservers 127.0.0.1 dns-search example.local /etc/bind/zones/db.example.local (end of file) @ IN NS avalon.example.local. @ IN A 192.168.1.5 avalon IN A 192.168.1.5 webapp IN A 192.168.1.5 www IN CNAME 192.168.1.5 /etc/bind/zones/db.192 (end of file) IN NS avalon.example.local. 73 IN PTR avalon.example.local. As a side note, my spare Win7 machine was able to connect directly to webapp.example.local, but for a Ubuntu 13.10 machine, I had to make the following changes as well (not on the webserver, but on a separate machine): /etc/nsswitch.conf before hosts: files mdns4_minimal [NOTFOUND=return] dns mdns4 after hosts: files dns /etc/NetworkManager/NetworkManager.conf before dns=dnsmasq after #dns=dnsmasq The issue remains that its not wildcard DNS, and so I have to add entries to /etc/bind/zones/db.example.local for webapp1, webapp2, ...

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  • The right way of using index.html

    - by Jeyekomon
    I have quite a lot of issues I'd like to hear your opinion on, so I hope I'll manage to explain it well enough. I should also note that I'm beginner equipped only with the knowledge of HTML and CSS so although I'm almost sure that there is a simple solution using powerful PHP, it won't help me. Let's say that I have my personal blog on the address example.com/blog.html and there are links to several sub-blogs example.com/blog/math.html, example.com/blog/coding.html etc. So my root folder contains blog.html and blog folder, the blog folder itself contains files math.html and coding.html. First of all, I learned (from Google Webmasters Tools) that for SEO and aesthetical purposes it's good to unify example.com.com and example.com/index.html by adding _rel="canonical"_ attribute into the source of the index.html. Using a couple of other tricks (like linking to ../ and ./) I got rid of the ugly index.html appearing in my web addresses. And now I wonder if this trick can be used not only for the root folder but for any folder? I mean, I would move my blog.html into the blog folder, rename it into the index.html and add rel="canonical" to unify example.com/blog/index.html with example.com/blog/. This trick would change the address of my blog from example.com/blog.html into example.com/blog/. Not finished! I'm also experiencing problems with the google robot indexing my folders. So when I type site:example.com/ into the google search, the link to my folder example.com/blog/ with raw files, icons etc. appears among the other results. I guess there are also other ways how to fix it, but IMHO the change mentioned above would do the trick too - the index.html in the blog folder would preserve the user from viewing the actual raw content of that folder, there would appear only the right link example.com/blog/ in the google search and (I hope that) _rel="canonical"_ would make the second, unwanted link example.com/blog/index.html not to appear in the search results. So my questions are: Is it a good practice to have the index.html file in every subfolder or is it intended to be only in the root folder? Are there any disadvantages or problems that may occur when using the second, "index in every folder" method? Which one of the two ways of structuring the website described above would you prefer?

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  • How would you organize a large complex web application (see basic example)?

    - by Anurag
    How do you usually organize complex web applications that are extremely rich on the client side. I have created a contrived example to indicate the kind of mess it's easy to get into if things are not managed well for big apps. Feel free to modify/extend this example as you wish - http://jsfiddle.net/NHyLC/1/ The example basically mirrors part of the comment posting on SO, and follows the following rules: Must have 15 characters minimum, after multiple spaces are trimmed out to one. If Add Comment is clicked, but the size is less than 15 after removing multiple spaces, then show a popup with the error. Indicate amount of characters remaining and summarize with color coding. Gray indicates a small comment, brown indicates a medium comment, orange a large comment, and red a comment overflow. One comment can only be submitted every 15 seconds. If comment is submitted too soon, show a popup with appropriate error message. A couple of issues I noticed with this example. This should ideally be a widget or some sort of packaged functionality. Things like a comment per 15 seconds, and minimum 15 character comment belong to some application wide policies rather than being embedded inside each widget. Too many hard-coded values. No code organization. Model, Views, Controllers are all bundled together. Not that MVC is the only approach for organizing rich client side web applications, but there is none in this example. How would you go about cleaning this up? Applying a little MVC/MVP along the way? Here's some of the relevant functions, but it will make more sense if you saw the entire code on jsfiddle: /** * Handle comment change. * Update character count. * Indicate progress */ function handleCommentUpdate(comment) { var status = $('.comment-status'); status.text(getStatusText(comment)); status.removeClass('mild spicy hot sizzling'); status.addClass(getStatusClass(comment)); } /** * Is the comment valid for submission */ function commentSubmittable(comment) { var notTooSoon = !isTooSoon(); var notEmpty = !isEmpty(comment); var hasEnoughCharacters = !isTooShort(comment); return notTooSoon && notEmpty && hasEnoughCharacters; } // submit comment $('.add-comment').click(function() { var comment = $('.comment-box').val(); // submit comment, fake ajax call if(commentSubmittable(comment)) { .. } // show a popup if comment is mostly spaces if(isTooShort(comment)) { if(comment.length < 15) { // blink status message } else { popup("Comment must be at least 15 characters in length."); } } // show a popup is comment submitted too soon else if(isTooSoon()) { popup("Only 1 comment allowed per 15 seconds."); } });

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  • NetBeans Java Hints: Quick & Dirty Guide

    - by Geertjan
    In NetBeans IDE 7.2, a new wizard will be found in the "Module Development" category in the New File dialog, for creating new Java Hints. Select a package in a NetBeans module project. Right click, choose New/Other.../Module Development/Java Hint: You'll then see this: Fill in: Class Name: the name of the class that should be generated. E.g. "Example". Hint Display Name: the display name of the hint itself (as will appear in Tools/Options). E.g. "Example Hint". Warning Message: the warning that should be produced by the hint. E.g. "Something wrong is going on". Hint Description: a longer description of the hint, will appear in Tools/Options and eventually some other places. E.g. "This is an example hint that warns about an example problem." Will also provide an Automatic Fix: whether the hint will provide some kind of transformation. E.g. "yes". Fix Display Name: the display name of such a fix/transformation. E.g. "Fix the problem". Click Finish. Should generate "Example.java", the hint itself: import com.sun.source.util.TreePath; import org.netbeans.api.java.source.CompilationInfo; import org.netbeans.spi.editor.hints.ErrorDescription; import org.netbeans.spi.editor.hints.Fix; import org.netbeans.spi.java.hints.ConstraintVariableType; import org.netbeans.spi.java.hints.ErrorDescriptionFactory; import org.netbeans.spi.java.hints.Hint; import org.netbeans.spi.java.hints.HintContext; import org.netbeans.spi.java.hints.JavaFix; import org.netbeans.spi.java.hints.TriggerPattern; import org.openide.util.NbBundle.Messages; @Hint(displayName = "DN_com.bla.Example", description = "DESC_com.bla.Example", category = "general") //NOI18N @Messages({"DN_com.bla.Example=Example Hint", "DESC_com.bla.Example=This is an example hint that warns about an example problem."}) public class Example { @TriggerPattern(value = "$str.equals(\"\")", //Specify a pattern as needed constraints = @ConstraintVariableType(variable = "$str", type = "java.lang.String")) @Messages("ERR_com.bla.Example=Something wrong is going on") public static ErrorDescription computeWarning(HintContext ctx) { Fix fix = new FixImpl(ctx.getInfo(), ctx.getPath()).toEditorFix(); return ErrorDescriptionFactory.forName(ctx, ctx.getPath(), Bundle.ERR_com.bla_Example(), fix); } private static final class FixImpl extends JavaFix { public FixImpl(CompilationInfo info, TreePath tp) { super(info, tp); } @Override @Messages("FIX_com.bla.Example=Fix the problem") protected String getText() { return Bundle.FIX_com_bla_Example(); } @Override protected void performRewrite(TransformationContext ctx) { //perform the required transformation } } } Should also generate "ExampleTest.java", a test for it. Unfortunately, the wizard infrastructure is not capable of handling changes related to test dependencies. So the ExampleTest.java has a todo list at its begining: /* TODO to make this test work:  - add test dependency on Java Hints Test API (and JUnit 4)  - to ensure that the newest Java language features supported by the IDE are available,   regardless of which JDK you build the module with:  -- for Ant-based modules, add "requires.nb.javac=true" into nbproject/project.properties  -- for Maven-based modules, use dependency:copy in validate phase to create   target/endorsed/org-netbeans-libs-javacapi-*.jar and add to endorseddirs   in maven-compiler-plugin configuration  */Warning: if this is a project for which tests never existed before, you may need to close&reopen the project, so that "Unit Test Libraries" node appears - a bug in apisupport projects, as far as I can tell.  Thanks to Jan Lahoda for the above rough guide.

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  • mod_rewrite to capture subdomain name

    - by Ricky
    I want to write a rewrite scheme such that: user1.example.net will redirect to example.net/user/user1 user2.example.net will redirect to example.net/user/user2 vise versa this is what i have in my .htaccess code. but it always redirects to example.net RewriteCond %{http_host} ^[^.]+.example.net [NC] RewriteRule ^([^.]+).example.net(.*) http://example.net/user/$1 [R=301,L] can someone please tell me what i did wrong? thank you.

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  • Setting up SSL on apache on linux ubuntu

    - by ThomasReggi
    I'm trying to get SSL to run on my apache web server. I do not have the DNS for the domain setup yet is that an issue? How do I setup SSL on my web server? When I start apache it fails. root@vannevar:/etc/apache2/ssl# service apache2 start * Starting web server apache2 Action 'start' failed. The Apache error log may have more information. The log stats that it's unable to read the certificate. [Thu Jun 28 15:01:02 2012] [error] Init: Unable to read server certificate from file /etc/apache2/ssl/www.example.com.csr [Thu Jun 28 15:01:02 2012] [error] SSL Library Error: 218529960 error:0D0680A8:asn1 encoding routines:ASN1_CHECK_TLEN:wrong tag [Thu Jun 28 15:01:02 2012] [error] SSL Library Error: 218595386 error:0D07803A:asn1 encoding routines:ASN1_ITEM_EX_D2I:nested asn1 error The contents of /etc/apache2/httpd.conf ServerName [SERVERIP] The contents of /etc/apache2/ports.conf # If you just change the port or add more ports here, you will likely also # have to change the VirtualHost statement in # /etc/apache2/sites-enabled/000-default # This is also true if you have upgraded from before 2.2.9-3 (i.e. from # Debian etch). See /usr/share/doc/apache2.2-common/NEWS.Debian.gz and # README.Debian.gz NameVirtualHost [SERVERIP]:443 NameVirtualHost *:80 Listen 80 <IfModule mod_ssl.c> # If you add NameVirtualHost *:443 here, you will also have to change # the VirtualHost statement in /etc/apache2/sites-available/default-ssl # to <VirtualHost *:443> # Server Name Indication for SSL named virtual hosts is currently not # supported by MSIE on Windows XP. Listen 443 </IfModule> <IfModule mod_gnutls.c> Listen 443 </IfModule> The contents of /etc/apache2/sites-available/www.example.com <VirtualHost *:80> ServerAdmin [email protected] ServerName example.com ServerAlias www.example.com DocumentRoot /srv/sites/example.com/public/ ErrorLog /srv/sites/example.com/logs/error.log CustomLog /srv/sites/example.com/logs/access.log combined </VirtualHost> <VirtualHost [SERVERIP]:443> SSLEngine On SSLCertificateFile /etc/apache2/ssl/www.example.com.csr SSLCertificateKeyFile /etc/apache2/ssl/www.example.com.key SSLCACertificateFile /etc/apache2/ssl/comodo.crt ServerAdmin [email protected] ServerName example.com ServerAlias www.example.com DocumentRoot /srv/sites/example.com/public/ ErrorLog /srv/sites/example.com/logs/error.log CustomLog /srv/sites/example.com/logs/access.log combined </VirtualHost>

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