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  • Information I need to know as a Java Developer [on hold]

    - by Woy
    I'm a java developer. I'm trying to get more knowledge to become a better programmer. I've listed a number of technologies to learn. Instead of what I've listed, what technologies would you suggest to learn as well for a Junior Java Developer? I realize, there's a lot of things to study. Java: - how a garbage collector works - resource management - network programming - TCP/IP HTTP - transactions, - consistency: interfaces, classes collections, hash codes, algorithms, comp. complexity concurrent programming: synchronizing, semafores steam management metability: thread-safety byte code manipulations, reflections, Aspect-Oriented Programming as base to understand frameworks such as Spring etc. Web stack: servlets, filters, socket programming Libraries: JDK, GWT, Apache Commons, Joda-Time, Dependency Injections: Spring, Nano Tools: IDE: very good knowledge - debugger - profiler - web analyzers: Wireshark, firebugs - unit testing SQL/Databases: Basics SELECTing columns from a table Aggregates Part 1: COUNT, SUM, MAX/MIN Aggregates Part 2: DISTINCT, GROUP BY, HAVING + Intermediate JOINs, ANSI-89 and ANSI-92 syntax + UNION vs UNION ALL x NULL handling: COALESCE & Native NULL handling Subqueries: IN, EXISTS, and inline views Subqueries: Correlated ITH syntax: Subquery Factoring/CTE Views Advanced Topics Functions, Stored Procedures, Packages Pivoting data: CASE & PIVOT syntax Hierarchical Queries Cursors: Implicit and Explicit Triggers Dynamic SQL Materialized Views Query Optimization: Indexes Query Optimization: Explain Plans Query Optimization: Profiling Data Modelling: Normal Forms, 1 through 3 Data Modelling: Primary & Foreign Keys Data Modelling: Table Constraints Data Modelling: Link/Corrollary Tables Full Text Searching XML Isolation Levels Entity Relationship Diagrams (ERDs), Logical and Physical Transactions: COMMIT, ROLLBACK, Error Handling

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  • Facebook contest policy no-no?

    - by Fred
    I would like to post a link on a Facebook page where it will exit Facebook entirely and go to a client's website, where people will be on a page (client's) where they can enter their e-mail address to be entered in a temporary database file with rules and disclosures etc., for a draw once the number of entries reaches 100 for instance. Once the number of entries reaches 100, a random winner is picked and notified via E-mail. The functionality is as follows: A link is place on a Facebook page leading to an external page The page is a form to merely enter their email address for a contest The email is placed in a temporary file An automatic E-mail is sent to the address used for confirmation using SHAH-256 hash The person receives the Email saying something to the affect "Please confirm your Email address etc. - If you did not authorize this, simply ignore this message and no further action will be taken". If the person clicks on the confirmation link, the Email is then stored in the database and the person is again notified saying "Thank you for signing up etc." Once others do the same process and the database reaches a certain number, the form is no longer accessible and automatically picks a random Email. Once picked, an Email is automatically sent to the winner stating the instructions, and notifying me also. Once that person clicks yet another confirmation link, the database is then automatically deleted. I have built this myself and have no intentions of breaking any rules, nor jeopardize the work/time/energy I have put into this project. Is this allowed?

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  • How to setup users for desktop app with SQL Azure as backend?

    - by Manuel
    I'm considering SQL Azure as DB for a new application I'm developing. The reason I want to go with Azure is because I don't want to have to maintain yet another database(s) and I want my users to be able to access the data from anywhere. The problem is that I'm not clear regarding how to users will connect. The application is a basic CRUD type of windows app. I've read that you need to add your IP to SQL Azure's firewall to connect to it, but I don't know if it's only for administration purposes only. Can anyone clarify if anyone (anywhere) can access the data with the proper credentials? Which of the following scenarios would work best (if at all)? A) Add each user to SQL Azure and have the app connect directly to Azure as if it was connecting to SQL Server B) Add an anonymous user SQL Azure and pass the real user's password/hash with every call so the Azure database can service the requests accordingly. C) Put a WCF service in between so that it handles the authentication stuff. The service will only serve the appropriate information to the user given his/her authentication and SQL Azure would be open to the service exclusively. D) - ideas are welcomed - This is confusing because all Azure examples I see are for websites. I have a hard time believing SQL Azure wouldn't handle the case of desktop apps connecting to it. So what's the best practice?

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  • Solutions for "Maintenance Mode"

    - by Ka Lyse
    Given a web application running across 10+ servers, what techniques have you put in place for doing things like altering the state of your website so that you can implement certain features. For instance, you might want to: Restrict Logins/Disable Certain Features Turn Site to "Read Only" Turn Site to Single "Maintenance Mode" page. Doing any of the above is pretty trivial. You can throw a particular "flag" in an .ini file, or add a row/value to a site_options table in your database and just read that value and do the appropriate thing. But these solutions have their problems. Disadvantages/Problems For instance, if you use a file for your application, and you want to switch off a certain feature temporarily, then you need to update this file on all servers. So then you might want to look at running something like ZooKeeper, but you are probably overcomplicating things. So then, you might decide that you want to store these "feature" flags in a database. But then you are obviously adding unncessary queries to each page request. So you think to yourself, that you will throw memcached in to the mix and just cache the query. Then you just retrieve all of your "Features" from memcached and add a 2ms~ latency to your application on every page. So to get around this, you decide to use a two tier-cache system, whereby you use an inmemory cache on each machine, (like Apc/Redis etc). This would work, but then it gets complicated, because you would have to set the key/hash life to perhaps 60 seconds, so that when you purge/invalidate the memcached object storing your "Features" result, your on machine cache is prompt enough to get the the new states. What suggestions might you have? Keeping in mind that optimization/efficiency is the priority here.

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  • How to match responses from a server with their corresponding requests? [closed]

    - by Deele
    There is a server that responds to requests on a socket. The client has functions to emit requests and functions to handle responses from the server. The problem is that the request sending function and the response handling function are two unrelated functions. Given a server response X, how can I know whether it's a response to request X or some other request Y? I would like to make a construct that would ensure that response X is definitely the answer to request X and also to make a function requestX() that returns response X and not some other response Y. This question is mostly about the general programming approach and not about any specific language construct. Preferably, though, the answer would involve Ruby, TCP sockets, and PHP. My code so far: require 'socket' class TheConnection def initialize(config) @config = config end def send(s) toConsole("--> #{s}") @conn.send "#{s}\n", 0 end def connect() # Connect to the server begin @conn = TCPSocket.open(@config['server'], @config['port']) rescue Interrupt rescue Exception => detail toConsole('Exception: ' + detail.message()) print detail.backtrace.join('\n') retry end end def getSpecificAnswer(input) send "GET #{input}" end def handle_server_input(s) case s.strip when /^Hello. (.*)$/i toConsole "[ Server says hello ]" send "Hello to you too! #{$1}" else toConsole(s) end end def main_loop() while true ready = select([@conn, $stdin], nil, nil, nil) next if !ready for s in ready[0] if s == $stdin then return if $stdin.eof s = $stdin.gets send s elsif s == @conn then return if @conn.eof s = @conn.gets handle_server_input(s) end end end end def toConsole(msg) t = Time.new puts t.strftime("[%H:%M:%S]") + ' ' + msg end end @config = Hash[ 'server'=>'test.server.com', 'port'=>'2020' ] $conn = TheConnection.new(@config) $conn.connect() $conn.getSpecificAnswer('itemsX') begin $conn.main_loop() rescue Interrupt rescue Exception => detail $conn.toConsole('Exception: ' + detail.message()) print detail.backtrace.join('\n') retry end

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  • Model View Controller² [closed]

    - by user694971
    I am working on a quite complex web application in Go and I tried to stay in an MVC pattern. However, I ended up having a structure isomorphic to this: /boilerplate The usual boilerplate an application needs to survive in the wilderness /db Layer talking to an SQL DB /helpers Helpers /logic Backend logic, not directly affiliated with any routes, sessions etc. /templates View /web Glue between /logic and /templates. In more dynamic languages the size of /web would be next to zero. But Go doesn't exactly have a RoR integrated so I need a lot of helper structures to feed the templates with data, to process GET/POST parameters and session information. I remember once reading about patterns similar to MVC with one extra letter but Wiki-searching I couldn't find it right now. (BTW currently /logic also contains data retrieval from API services to fill some hash maps; this is no simple task, but that probably belongs into the model, right?) So question: is this structure considered sane? Or does it need some bending to be tagged MVC app?

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  • Disable Opera Thumbnail Previews on Windows 7 Taskbar

    - by Asian Angel
    If you are one of the people who does not care for the Taskbar Thumbnail Previews in Windows 7 then we have a quick and easy way for you to turn them off in Opera Browser. Before Here is our Opera Browser with four tabs full of HTG Network goodness… Hovering the mouse over the Taskbar Icon gives a nice preview of each tabs content. Looking closer you can see the fanned edge on the Taskbar Icon indicating that there are multiple tabs open. This is all good but what if you just want something simpler? Disabling the Previews If you want to disable the Taskbar Thumbnail Previews in Opera you will need to type opera:config in the Address Bar and press Enter. Once you have done that, you will see a condensed listing for all of Opera’s preferences. There is one Preference Category that we need to look for…User Prefs. Note: While a Quick Find Search could be conducted for the entry that needs to be modified, we have chosen to show the full method here. After scrolling down and finding the User Prefs category you will need to expand the section. Notice the size of the scrollbar in comparison with the screenshot above…there is quite a lot that you can look at and finesse in Opera if desired. Scroll down until you find the Use Windows 7 Taskbar Thumbnails entry. Uncheck the box but do not close the opera:config Tab yet…or your changes will not take effect. Scroll down once more until you reach the end of the User Prefs category and click Save. With this particular modification you will need to restart Opera after clicking OK. After restarting Opera the Taskbar Icon and Taskbar Thumbnail Preview will revert to the minimal Windows 7 default as shown here. You can see Opera’s Tab Bar in the thumbnail and the Taskbar Icon no longer has a “fanned edge”. Conclusion If you want to disable Opera’s Taskbar Thumbnail Previews on your Windows 7 system, then this quick modification will help get it sorted out in just a few moments. Similar Articles Productive Geek Tips Disable IE 8 Thumbnail Previews on Windows 7 TaskbarIncrease the size of Taskbar Preview Thumbnails in Windows 7Vista Style Popup Previews for Firefox TabsEnable Thumbnail Previews for Firefox in Windows 7 TaskbarWorkaround for Vista Taskbar Thumbnail Previews Not Showing Correctly TouchFreeze Alternative in AutoHotkey The Icy Undertow Desktop Windows Home Server – Backup to LAN The Clear & Clean Desktop Use This Bookmarklet to Easily Get Albums Use AutoHotkey to Assign a Hotkey to a Specific Window Latest Software Reviews Tinyhacker Random Tips All My Movies 5.9 CloudBerry Online Backup 1.5 for Windows Home Server Snagit 10 VMware Workstation 7 10 Superb Firefox Wallpapers OpenDNS Guide Google TV The iPod Revolution Ultimate Boot CD can help when disaster strikes Windows Firewall with Advanced Security – How To Guides

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  • Preview of MSDN Library Changes

    - by ScottGu
    The MSDN team has been working some potential changes to the online MSDN Library designed to help streamline the navigation experience and make it easier to find the .NET Framework information you need. To solicit feedback on the proposed changes while they are still in development, they’ve posted a preview version of some proposed changes to a new MSDN Library Preview site which you can check out.  They’ve also created a survey that leads you through the ideas and asks for your opinions on some of the changes.  We’d very much like to have as many people as possible people take the survey and give us feedback. Quick Preview of Some of the Changes Below are some examples of a few of the changes being proposed: Streamlined .NET Namespaces Navigation The current MSDN Class Library lists all .NET namespaces in a flat-namespace (sorted alphabetically): Two downsides of the above approach are: Some of the least-used namespaces are listed first (like Microsoft.Aspnet.Snapin and Microsoft.Build.BuildEngine) All sub-namespaces are listed, which makes the list a little overwhelming, and page-load times to be slow The new MSDN Library Preview Site now lists “System” namespaces first (since those are the most used), and the home-page lists just top-level namespace groups – which makes it easier to find things, and enables the page to load faster:   Class overview and members pages merged into a single topic about each class Previously you had to navigate to several different pages to find member information about types: Links to these are still available in the MSDN Library Preview Site TOC – but the members are also now listed on the overview page, which makes it easy to quickly find everything in one place: Commonly used things are nearer the top of the page One of the other usability improvements with the new MSDN Library Preview Site is that common elements like “Code Examples” and “Inheritance Hierarchy” (for classes) are now listed near the top of the help page – making them easy to quickly find: Give Us Feedback with a Survey Above are just a few of the changes made with the new MSDN preview site – there are many other changes also rolled into it.  The MSDN team is doing usability studies on the new layout and navigation right now, and would very much like feedback on it. If you have 15 minutes and want to help vote on which of these ideas makes it into the production MSDN site, please visit this survey before June 30, play with the changes a bit, and let the MSDN team know what you think. Important Note: the MSDN preview site is not a fully functional version of MSDN – it’s really only there to preview the new ideas themselves, so please don’t expect it to be integrated with the rest of MSDN, with search, etc.  Once the MSDN team gets feedback on some of the changes being proposed they will roll them into the live site for everyone to use. Hope this helps, Scott

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  • Advanced TSQL Tuning: Why Internals Knowledge Matters

    - by Paul White
    There is much more to query tuning than reducing logical reads and adding covering nonclustered indexes.  Query tuning is not complete as soon as the query returns results quickly in the development or test environments.  In production, your query will compete for memory, CPU, locks, I/O and other resources on the server.  Today’s entry looks at some tuning considerations that are often overlooked, and shows how deep internals knowledge can help you write better TSQL. As always, we’ll need some example data.  In fact, we are going to use three tables today, each of which is structured like this: Each table has 50,000 rows made up of an INTEGER id column and a padding column containing 3,999 characters in every row.  The only difference between the three tables is in the type of the padding column: the first table uses CHAR(3999), the second uses VARCHAR(MAX), and the third uses the deprecated TEXT type.  A script to create a database with the three tables and load the sample data follows: USE master; GO IF DB_ID('SortTest') IS NOT NULL DROP DATABASE SortTest; GO CREATE DATABASE SortTest COLLATE LATIN1_GENERAL_BIN; GO ALTER DATABASE SortTest MODIFY FILE ( NAME = 'SortTest', SIZE = 3GB, MAXSIZE = 3GB ); GO ALTER DATABASE SortTest MODIFY FILE ( NAME = 'SortTest_log', SIZE = 256MB, MAXSIZE = 1GB, FILEGROWTH = 128MB ); GO ALTER DATABASE SortTest SET ALLOW_SNAPSHOT_ISOLATION OFF ; ALTER DATABASE SortTest SET AUTO_CLOSE OFF ; ALTER DATABASE SortTest SET AUTO_CREATE_STATISTICS ON ; ALTER DATABASE SortTest SET AUTO_SHRINK OFF ; ALTER DATABASE SortTest SET AUTO_UPDATE_STATISTICS ON ; ALTER DATABASE SortTest SET AUTO_UPDATE_STATISTICS_ASYNC ON ; ALTER DATABASE SortTest SET PARAMETERIZATION SIMPLE ; ALTER DATABASE SortTest SET READ_COMMITTED_SNAPSHOT OFF ; ALTER DATABASE SortTest SET MULTI_USER ; ALTER DATABASE SortTest SET RECOVERY SIMPLE ; USE SortTest; GO CREATE TABLE dbo.TestCHAR ( id INTEGER IDENTITY (1,1) NOT NULL, padding CHAR(3999) NOT NULL,   CONSTRAINT [PK dbo.TestCHAR (id)] PRIMARY KEY CLUSTERED (id), ) ; CREATE TABLE dbo.TestMAX ( id INTEGER IDENTITY (1,1) NOT NULL, padding VARCHAR(MAX) NOT NULL,   CONSTRAINT [PK dbo.TestMAX (id)] PRIMARY KEY CLUSTERED (id), ) ; CREATE TABLE dbo.TestTEXT ( id INTEGER IDENTITY (1,1) NOT NULL, padding TEXT NOT NULL,   CONSTRAINT [PK dbo.TestTEXT (id)] PRIMARY KEY CLUSTERED (id), ) ; -- ============= -- Load TestCHAR (about 3s) -- ============= INSERT INTO dbo.TestCHAR WITH (TABLOCKX) ( padding ) SELECT padding = REPLICATE(CHAR(65 + (Data.n % 26)), 3999) FROM ( SELECT TOP (50000) n = ROW_NUMBER() OVER (ORDER BY (SELECT 0)) - 1 FROM master.sys.columns C1, master.sys.columns C2, master.sys.columns C3 ORDER BY n ASC ) AS Data ORDER BY Data.n ASC ; -- ============ -- Load TestMAX (about 3s) -- ============ INSERT INTO dbo.TestMAX WITH (TABLOCKX) ( padding ) SELECT CONVERT(VARCHAR(MAX), padding) FROM dbo.TestCHAR ORDER BY id ; -- ============= -- Load TestTEXT (about 5s) -- ============= INSERT INTO dbo.TestTEXT WITH (TABLOCKX) ( padding ) SELECT CONVERT(TEXT, padding) FROM dbo.TestCHAR ORDER BY id ; -- ========== -- Space used -- ========== -- EXECUTE sys.sp_spaceused @objname = 'dbo.TestCHAR'; EXECUTE sys.sp_spaceused @objname = 'dbo.TestMAX'; EXECUTE sys.sp_spaceused @objname = 'dbo.TestTEXT'; ; CHECKPOINT ; That takes around 15 seconds to run, and shows the space allocated to each table in its output: To illustrate the points I want to make today, the example task we are going to set ourselves is to return a random set of 150 rows from each table.  The basic shape of the test query is the same for each of the three test tables: SELECT TOP (150) T.id, T.padding FROM dbo.Test AS T ORDER BY NEWID() OPTION (MAXDOP 1) ; Test 1 – CHAR(3999) Running the template query shown above using the TestCHAR table as the target, we find that the query takes around 5 seconds to return its results.  This seems slow, considering that the table only has 50,000 rows.  Working on the assumption that generating a GUID for each row is a CPU-intensive operation, we might try enabling parallelism to see if that speeds up the response time.  Running the query again (but without the MAXDOP 1 hint) on a machine with eight logical processors, the query now takes 10 seconds to execute – twice as long as when run serially. Rather than attempting further guesses at the cause of the slowness, let’s go back to serial execution and add some monitoring.  The script below monitors STATISTICS IO output and the amount of tempdb used by the test query.  We will also run a Profiler trace to capture any warnings generated during query execution. DECLARE @read BIGINT, @write BIGINT ; SELECT @read = SUM(num_of_bytes_read), @write = SUM(num_of_bytes_written) FROM tempdb.sys.database_files AS DBF JOIN sys.dm_io_virtual_file_stats(2, NULL) AS FS ON FS.file_id = DBF.file_id WHERE DBF.type_desc = 'ROWS' ; SET STATISTICS IO ON ; SELECT TOP (150) TC.id, TC.padding FROM dbo.TestCHAR AS TC ORDER BY NEWID() OPTION (MAXDOP 1) ; SET STATISTICS IO OFF ; SELECT tempdb_read_MB = (SUM(num_of_bytes_read) - @read) / 1024. / 1024., tempdb_write_MB = (SUM(num_of_bytes_written) - @write) / 1024. / 1024., internal_use_MB = ( SELECT internal_objects_alloc_page_count / 128.0 FROM sys.dm_db_task_space_usage WHERE session_id = @@SPID ) FROM tempdb.sys.database_files AS DBF JOIN sys.dm_io_virtual_file_stats(2, NULL) AS FS ON FS.file_id = DBF.file_id WHERE DBF.type_desc = 'ROWS' ; Let’s take a closer look at the statistics and query plan generated from this: Following the flow of the data from right to left, we see the expected 50,000 rows emerging from the Clustered Index Scan, with a total estimated size of around 191MB.  The Compute Scalar adds a column containing a random GUID (generated from the NEWID() function call) for each row.  With this extra column in place, the size of the data arriving at the Sort operator is estimated to be 192MB. Sort is a blocking operator – it has to examine all of the rows on its input before it can produce its first row of output (the last row received might sort first).  This characteristic means that Sort requires a memory grant – memory allocated for the query’s use by SQL Server just before execution starts.  In this case, the Sort is the only memory-consuming operator in the plan, so it has access to the full 243MB (248,696KB) of memory reserved by SQL Server for this query execution. Notice that the memory grant is significantly larger than the expected size of the data to be sorted.  SQL Server uses a number of techniques to speed up sorting, some of which sacrifice size for comparison speed.  Sorts typically require a very large number of comparisons, so this is usually a very effective optimization.  One of the drawbacks is that it is not possible to exactly predict the sort space needed, as it depends on the data itself.  SQL Server takes an educated guess based on data types, sizes, and the number of rows expected, but the algorithm is not perfect. In spite of the large memory grant, the Profiler trace shows a Sort Warning event (indicating that the sort ran out of memory), and the tempdb usage monitor shows that 195MB of tempdb space was used – all of that for system use.  The 195MB represents physical write activity on tempdb, because SQL Server strictly enforces memory grants – a query cannot ‘cheat’ and effectively gain extra memory by spilling to tempdb pages that reside in memory.  Anyway, the key point here is that it takes a while to write 195MB to disk, and this is the main reason that the query takes 5 seconds overall. If you are wondering why using parallelism made the problem worse, consider that eight threads of execution result in eight concurrent partial sorts, each receiving one eighth of the memory grant.  The eight sorts all spilled to tempdb, resulting in inefficiencies as the spilled sorts competed for disk resources.  More importantly, there are specific problems at the point where the eight partial results are combined, but I’ll cover that in a future post. CHAR(3999) Performance Summary: 5 seconds elapsed time 243MB memory grant 195MB tempdb usage 192MB estimated sort set 25,043 logical reads Sort Warning Test 2 – VARCHAR(MAX) We’ll now run exactly the same test (with the additional monitoring) on the table using a VARCHAR(MAX) padding column: DECLARE @read BIGINT, @write BIGINT ; SELECT @read = SUM(num_of_bytes_read), @write = SUM(num_of_bytes_written) FROM tempdb.sys.database_files AS DBF JOIN sys.dm_io_virtual_file_stats(2, NULL) AS FS ON FS.file_id = DBF.file_id WHERE DBF.type_desc = 'ROWS' ; SET STATISTICS IO ON ; SELECT TOP (150) TM.id, TM.padding FROM dbo.TestMAX AS TM ORDER BY NEWID() OPTION (MAXDOP 1) ; SET STATISTICS IO OFF ; SELECT tempdb_read_MB = (SUM(num_of_bytes_read) - @read) / 1024. / 1024., tempdb_write_MB = (SUM(num_of_bytes_written) - @write) / 1024. / 1024., internal_use_MB = ( SELECT internal_objects_alloc_page_count / 128.0 FROM sys.dm_db_task_space_usage WHERE session_id = @@SPID ) FROM tempdb.sys.database_files AS DBF JOIN sys.dm_io_virtual_file_stats(2, NULL) AS FS ON FS.file_id = DBF.file_id WHERE DBF.type_desc = 'ROWS' ; This time the query takes around 8 seconds to complete (3 seconds longer than Test 1).  Notice that the estimated row and data sizes are very slightly larger, and the overall memory grant has also increased very slightly to 245MB.  The most marked difference is in the amount of tempdb space used – this query wrote almost 391MB of sort run data to the physical tempdb file.  Don’t draw any general conclusions about VARCHAR(MAX) versus CHAR from this – I chose the length of the data specifically to expose this edge case.  In most cases, VARCHAR(MAX) performs very similarly to CHAR – I just wanted to make test 2 a bit more exciting. MAX Performance Summary: 8 seconds elapsed time 245MB memory grant 391MB tempdb usage 193MB estimated sort set 25,043 logical reads Sort warning Test 3 – TEXT The same test again, but using the deprecated TEXT data type for the padding column: DECLARE @read BIGINT, @write BIGINT ; SELECT @read = SUM(num_of_bytes_read), @write = SUM(num_of_bytes_written) FROM tempdb.sys.database_files AS DBF JOIN sys.dm_io_virtual_file_stats(2, NULL) AS FS ON FS.file_id = DBF.file_id WHERE DBF.type_desc = 'ROWS' ; SET STATISTICS IO ON ; SELECT TOP (150) TT.id, TT.padding FROM dbo.TestTEXT AS TT ORDER BY NEWID() OPTION (MAXDOP 1, RECOMPILE) ; SET STATISTICS IO OFF ; SELECT tempdb_read_MB = (SUM(num_of_bytes_read) - @read) / 1024. / 1024., tempdb_write_MB = (SUM(num_of_bytes_written) - @write) / 1024. / 1024., internal_use_MB = ( SELECT internal_objects_alloc_page_count / 128.0 FROM sys.dm_db_task_space_usage WHERE session_id = @@SPID ) FROM tempdb.sys.database_files AS DBF JOIN sys.dm_io_virtual_file_stats(2, NULL) AS FS ON FS.file_id = DBF.file_id WHERE DBF.type_desc = 'ROWS' ; This time the query runs in 500ms.  If you look at the metrics we have been checking so far, it’s not hard to understand why: TEXT Performance Summary: 0.5 seconds elapsed time 9MB memory grant 5MB tempdb usage 5MB estimated sort set 207 logical reads 596 LOB logical reads Sort warning SQL Server’s memory grant algorithm still underestimates the memory needed to perform the sorting operation, but the size of the data to sort is so much smaller (5MB versus 193MB previously) that the spilled sort doesn’t matter very much.  Why is the data size so much smaller?  The query still produces the correct results – including the large amount of data held in the padding column – so what magic is being performed here? TEXT versus MAX Storage The answer lies in how columns of the TEXT data type are stored.  By default, TEXT data is stored off-row in separate LOB pages – which explains why this is the first query we have seen that records LOB logical reads in its STATISTICS IO output.  You may recall from my last post that LOB data leaves an in-row pointer to the separate storage structure holding the LOB data. SQL Server can see that the full LOB value is not required by the query plan until results are returned, so instead of passing the full LOB value down the plan from the Clustered Index Scan, it passes the small in-row structure instead.  SQL Server estimates that each row coming from the scan will be 79 bytes long – 11 bytes for row overhead, 4 bytes for the integer id column, and 64 bytes for the LOB pointer (in fact the pointer is rather smaller – usually 16 bytes – but the details of that don’t really matter right now). OK, so this query is much more efficient because it is sorting a very much smaller data set – SQL Server delays retrieving the LOB data itself until after the Sort starts producing its 150 rows.  The question that normally arises at this point is: Why doesn’t SQL Server use the same trick when the padding column is defined as VARCHAR(MAX)? The answer is connected with the fact that if the actual size of the VARCHAR(MAX) data is 8000 bytes or less, it is usually stored in-row in exactly the same way as for a VARCHAR(8000) column – MAX data only moves off-row into LOB storage when it exceeds 8000 bytes.  The default behaviour of the TEXT type is to be stored off-row by default, unless the ‘text in row’ table option is set suitably and there is room on the page.  There is an analogous (but opposite) setting to control the storage of MAX data – the ‘large value types out of row’ table option.  By enabling this option for a table, MAX data will be stored off-row (in a LOB structure) instead of in-row.  SQL Server Books Online has good coverage of both options in the topic In Row Data. The MAXOOR Table The essential difference, then, is that MAX defaults to in-row storage, and TEXT defaults to off-row (LOB) storage.  You might be thinking that we could get the same benefits seen for the TEXT data type by storing the VARCHAR(MAX) values off row – so let’s look at that option now.  This script creates a fourth table, with the VARCHAR(MAX) data stored off-row in LOB pages: CREATE TABLE dbo.TestMAXOOR ( id INTEGER IDENTITY (1,1) NOT NULL, padding VARCHAR(MAX) NOT NULL,   CONSTRAINT [PK dbo.TestMAXOOR (id)] PRIMARY KEY CLUSTERED (id), ) ; EXECUTE sys.sp_tableoption @TableNamePattern = N'dbo.TestMAXOOR', @OptionName = 'large value types out of row', @OptionValue = 'true' ; SELECT large_value_types_out_of_row FROM sys.tables WHERE [schema_id] = SCHEMA_ID(N'dbo') AND name = N'TestMAXOOR' ; INSERT INTO dbo.TestMAXOOR WITH (TABLOCKX) ( padding ) SELECT SPACE(0) FROM dbo.TestCHAR ORDER BY id ; UPDATE TM WITH (TABLOCK) SET padding.WRITE (TC.padding, NULL, NULL) FROM dbo.TestMAXOOR AS TM JOIN dbo.TestCHAR AS TC ON TC.id = TM.id ; EXECUTE sys.sp_spaceused @objname = 'dbo.TestMAXOOR' ; CHECKPOINT ; Test 4 – MAXOOR We can now re-run our test on the MAXOOR (MAX out of row) table: DECLARE @read BIGINT, @write BIGINT ; SELECT @read = SUM(num_of_bytes_read), @write = SUM(num_of_bytes_written) FROM tempdb.sys.database_files AS DBF JOIN sys.dm_io_virtual_file_stats(2, NULL) AS FS ON FS.file_id = DBF.file_id WHERE DBF.type_desc = 'ROWS' ; SET STATISTICS IO ON ; SELECT TOP (150) MO.id, MO.padding FROM dbo.TestMAXOOR AS MO ORDER BY NEWID() OPTION (MAXDOP 1, RECOMPILE) ; SET STATISTICS IO OFF ; SELECT tempdb_read_MB = (SUM(num_of_bytes_read) - @read) / 1024. / 1024., tempdb_write_MB = (SUM(num_of_bytes_written) - @write) / 1024. / 1024., internal_use_MB = ( SELECT internal_objects_alloc_page_count / 128.0 FROM sys.dm_db_task_space_usage WHERE session_id = @@SPID ) FROM tempdb.sys.database_files AS DBF JOIN sys.dm_io_virtual_file_stats(2, NULL) AS FS ON FS.file_id = DBF.file_id WHERE DBF.type_desc = 'ROWS' ; TEXT Performance Summary: 0.3 seconds elapsed time 245MB memory grant 0MB tempdb usage 193MB estimated sort set 207 logical reads 446 LOB logical reads No sort warning The query runs very quickly – slightly faster than Test 3, and without spilling the sort to tempdb (there is no sort warning in the trace, and the monitoring query shows zero tempdb usage by this query).  SQL Server is passing the in-row pointer structure down the plan and only looking up the LOB value on the output side of the sort. The Hidden Problem There is still a huge problem with this query though – it requires a 245MB memory grant.  No wonder the sort doesn’t spill to tempdb now – 245MB is about 20 times more memory than this query actually requires to sort 50,000 records containing LOB data pointers.  Notice that the estimated row and data sizes in the plan are the same as in test 2 (where the MAX data was stored in-row). The optimizer assumes that MAX data is stored in-row, regardless of the sp_tableoption setting ‘large value types out of row’.  Why?  Because this option is dynamic – changing it does not immediately force all MAX data in the table in-row or off-row, only when data is added or actually changed.  SQL Server does not keep statistics to show how much MAX or TEXT data is currently in-row, and how much is stored in LOB pages.  This is an annoying limitation, and one which I hope will be addressed in a future version of the product. So why should we worry about this?  Excessive memory grants reduce concurrency and may result in queries waiting on the RESOURCE_SEMAPHORE wait type while they wait for memory they do not need.  245MB is an awful lot of memory, especially on 32-bit versions where memory grants cannot use AWE-mapped memory.  Even on a 64-bit server with plenty of memory, do you really want a single query to consume 0.25GB of memory unnecessarily?  That’s 32,000 8KB pages that might be put to much better use. The Solution The answer is not to use the TEXT data type for the padding column.  That solution happens to have better performance characteristics for this specific query, but it still results in a spilled sort, and it is hard to recommend the use of a data type which is scheduled for removal.  I hope it is clear to you that the fundamental problem here is that SQL Server sorts the whole set arriving at a Sort operator.  Clearly, it is not efficient to sort the whole table in memory just to return 150 rows in a random order. The TEXT example was more efficient because it dramatically reduced the size of the set that needed to be sorted.  We can do the same thing by selecting 150 unique keys from the table at random (sorting by NEWID() for example) and only then retrieving the large padding column values for just the 150 rows we need.  The following script implements that idea for all four tables: SET STATISTICS IO ON ; WITH TestTable AS ( SELECT * FROM dbo.TestCHAR ), TopKeys AS ( SELECT TOP (150) id FROM TestTable ORDER BY NEWID() ) SELECT T1.id, T1.padding FROM TestTable AS T1 WHERE T1.id = ANY (SELECT id FROM TopKeys) OPTION (MAXDOP 1) ; WITH TestTable AS ( SELECT * FROM dbo.TestMAX ), TopKeys AS ( SELECT TOP (150) id FROM TestTable ORDER BY NEWID() ) SELECT T1.id, T1.padding FROM TestTable AS T1 WHERE T1.id IN (SELECT id FROM TopKeys) OPTION (MAXDOP 1) ; WITH TestTable AS ( SELECT * FROM dbo.TestTEXT ), TopKeys AS ( SELECT TOP (150) id FROM TestTable ORDER BY NEWID() ) SELECT T1.id, T1.padding FROM TestTable AS T1 WHERE T1.id IN (SELECT id FROM TopKeys) OPTION (MAXDOP 1) ; WITH TestTable AS ( SELECT * FROM dbo.TestMAXOOR ), TopKeys AS ( SELECT TOP (150) id FROM TestTable ORDER BY NEWID() ) SELECT T1.id, T1.padding FROM TestTable AS T1 WHERE T1.id IN (SELECT id FROM TopKeys) OPTION (MAXDOP 1) ; SET STATISTICS IO OFF ; All four queries now return results in much less than a second, with memory grants between 6 and 12MB, and without spilling to tempdb.  The small remaining inefficiency is in reading the id column values from the clustered primary key index.  As a clustered index, it contains all the in-row data at its leaf.  The CHAR and VARCHAR(MAX) tables store the padding column in-row, so id values are separated by a 3999-character column, plus row overhead.  The TEXT and MAXOOR tables store the padding values off-row, so id values in the clustered index leaf are separated by the much-smaller off-row pointer structure.  This difference is reflected in the number of logical page reads performed by the four queries: Table 'TestCHAR' logical reads 25511 lob logical reads 000 Table 'TestMAX'. logical reads 25511 lob logical reads 000 Table 'TestTEXT' logical reads 00412 lob logical reads 597 Table 'TestMAXOOR' logical reads 00413 lob logical reads 446 We can increase the density of the id values by creating a separate nonclustered index on the id column only.  This is the same key as the clustered index, of course, but the nonclustered index will not include the rest of the in-row column data. CREATE UNIQUE NONCLUSTERED INDEX uq1 ON dbo.TestCHAR (id); CREATE UNIQUE NONCLUSTERED INDEX uq1 ON dbo.TestMAX (id); CREATE UNIQUE NONCLUSTERED INDEX uq1 ON dbo.TestTEXT (id); CREATE UNIQUE NONCLUSTERED INDEX uq1 ON dbo.TestMAXOOR (id); The four queries can now use the very dense nonclustered index to quickly scan the id values, sort them by NEWID(), select the 150 ids we want, and then look up the padding data.  The logical reads with the new indexes in place are: Table 'TestCHAR' logical reads 835 lob logical reads 0 Table 'TestMAX' logical reads 835 lob logical reads 0 Table 'TestTEXT' logical reads 686 lob logical reads 597 Table 'TestMAXOOR' logical reads 686 lob logical reads 448 With the new index, all four queries use the same query plan (click to enlarge): Performance Summary: 0.3 seconds elapsed time 6MB memory grant 0MB tempdb usage 1MB sort set 835 logical reads (CHAR, MAX) 686 logical reads (TEXT, MAXOOR) 597 LOB logical reads (TEXT) 448 LOB logical reads (MAXOOR) No sort warning I’ll leave it as an exercise for the reader to work out why trying to eliminate the Key Lookup by adding the padding column to the new nonclustered indexes would be a daft idea Conclusion This post is not about tuning queries that access columns containing big strings.  It isn’t about the internal differences between TEXT and MAX data types either.  It isn’t even about the cool use of UPDATE .WRITE used in the MAXOOR table load.  No, this post is about something else: Many developers might not have tuned our starting example query at all – 5 seconds isn’t that bad, and the original query plan looks reasonable at first glance.  Perhaps the NEWID() function would have been blamed for ‘just being slow’ – who knows.  5 seconds isn’t awful – unless your users expect sub-second responses – but using 250MB of memory and writing 200MB to tempdb certainly is!  If ten sessions ran that query at the same time in production that’s 2.5GB of memory usage and 2GB hitting tempdb.  Of course, not all queries can be rewritten to avoid large memory grants and sort spills using the key-lookup technique in this post, but that’s not the point either. The point of this post is that a basic understanding of execution plans is not enough.  Tuning for logical reads and adding covering indexes is not enough.  If you want to produce high-quality, scalable TSQL that won’t get you paged as soon as it hits production, you need a deep understanding of execution plans, and as much accurate, deep knowledge about SQL Server as you can lay your hands on.  The advanced database developer has a wide range of tools to use in writing queries that perform well in a range of circumstances. By the way, the examples in this post were written for SQL Server 2008.  They will run on 2005 and demonstrate the same principles, but you won’t get the same figures I did because 2005 had a rather nasty bug in the Top N Sort operator.  Fair warning: if you do decide to run the scripts on a 2005 instance (particularly the parallel query) do it before you head out for lunch… This post is dedicated to the people of Christchurch, New Zealand. © 2011 Paul White email: @[email protected] twitter: @SQL_Kiwi

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  • What was missing from the Content Strategy Forum?

    - by Roger Hart
    In April, Paris hosted the first ever Content Strategy Forum. The event's website proudly proclaims: 170 attendees, 18 nationalities, 17 speakers, 1 volcano... Content Strategy Forum 2010 rocked the world! The volcano was in Iceland, and the closest we came to rocking the world was a cursory mention in the Huffington Post, but I'll grant the event was awesome. One thing missing from that list, however, is "94 companies" (Plus a couple of universities and freelancers, and what have you). A glance through the attendees directory reveals a fairly wide organisational turnout - 24 students from two Parisian universities, countless design and marketing agencies, a series of tech firms, small and large. Two delegates from IBM, two from ARM, an appearance from RIM, Skype, and Facebook; twelve from the various bits of eBay. Oh, and, err, nobody from Google, Microsoft, Yahoo, Amazon, Play, Twitter, LinkedIn, Craigslist, the BBC, no banks I noticed, and I didn't spot a newspaper. You get the idea. Facebook notwithstanding, you have to scroll through a few pages to Alexa rankings to find company names from the attendee list. I find this interesting, and I'm not wholly sure what to make of it. Of the large, web-centric, content-rich organizations conspicuously absent, at least one of two things is true: They didn't know about the event They didn't care about the event Maybe these guys all have content strategy completely sorted, and it's an utterly naturalised part of their business process. Maybe nobody at say, Apple or Play.com ever publishes a single piece of content that isn't neatly tailored to their (clearly defined, of course) user and business goals. Wouldn't that be lovely? The thing is, in that rosy and beatific world, there's still a case for those folks to join the community. There are bound to be other perspectives, and things to learn. You see, the other thing achingly conspicuous by its absence was case studies. In her keynote address, Kristina Halvorson made the point that what content strategy really needs is some big, loud success stories. A point I'd firmly second as a content strategist working within an organisation. Sarah Cancilla's presentation on content strategy at Facebook included some very neat, specific examples, and was richer for it. It didn't hurt that the example was Facebook - you're getting impressively big numbers off base. What about the other big boys? Is there anybody out there with a perspective? Do we all just look very silly to you, fretting away over text and images and users and purposes? Is content validation and maintenance so accustomed a part of your business that calling attention to it is like sniffing the air and saying "Hmm, a lot of nitrogen about today."? And if it is, do you have any wisdom to share?

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  • Manage Your Twitter Account from the Sidebar in Firefox

    - by Asian Angel
    Are you a Twitter addict and need an easy way to manage your account in Firefox? Now you can access Twitter in your Sidebar or as a separate window with the TwitKit+ extension for Firefox. Accessing TwitKit+ There are three ways that you can access TwitKit+ after installing the extension. The first is by adding the “Toolbar Button” to your browser’s UI. The second and third methods are through the “View & Tools Menus”.   TwitKit+ in Action When you open TwitKit+ for the first time you will see Twitter’s “Public Tweet Stream”. To get started login into your account. Note: If you do not care for the “brown theme” you can select a different one in “Preferences”. Here is a closer look at the top area and the commands available. Notice the “blue arrow symbol” in the upper left corner…very useful if you want to separate TwitKit+ from your main browser window for a bit. Secure Mode, Undock, Preferences, Login/Logout Google Search, Twitter Search, Copy Selection To Status Box, Shorten Selected URL Public, User, Friends, Followers, @ Messages, Direct Messages, Profile Note: To use Google or Twitter search enter your term in the “Status Area” and click on the appropriate service icon. Here is the regular timeline for our account…the “clickable tab buttons” make everything easy to view and work with. You can perform actions such as replying, retweeting, marking as a favorite, etc. using the set of “management buttons” at the bottom of each tweet. To add a new tweet to your timeline enter your text and press “Enter”. A look at the “Following List” for our account. Having a more defined and separate “view categories” set makes this better than directly accessing the Twitter website. Preferences The preferences can be quickly sorted out…choose how often the timeline is updated, name display, favorite URL shortening service, theme, and font size. Note: The default connection setting is for “Secure Access”. Conclusion TwitKit+ makes a nice addition to Firefox for anyone who loves keeping up with Twitter throughout the day. There when you want it and out of your way the rest of the time. Links Download the TwitKit+ extension (Mozilla Add-ons) Similar Articles Productive Geek Tips Move Add-on Management to the Sidebar in FirefoxPreview and Manage Multiple Tabs in Firefox with Tab SidebarDisable Windows Sidebar in VistaQuick Tip: Use Google Talk Sidebar in FirefoxRun Windows Sidebar Gadgets Without the Sidebar TouchFreeze Alternative in AutoHotkey The Icy Undertow Desktop Windows Home Server – Backup to LAN The Clear & Clean Desktop Use This Bookmarklet to Easily Get Albums Use AutoHotkey to Assign a Hotkey to a Specific Window Latest Software Reviews Tinyhacker Random Tips Revo Uninstaller Pro Registry Mechanic 9 for Windows PC Tools Internet Security Suite 2010 PCmover Professional Enable Check Box Selection in Windows 7 OnlineOCR – Free OCR Service Betting on the Blind Side, a Vanity Fair article 30 Minimal Logo Designs that Say More with Less LEGO Digital Designer – Free Create a Personal Website Quickly using Flavors.me

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  • Manage Your Twitter Account from the Sidebar in Firefox

    - by Asian Angel
    Are you a Twitter addict and need an easy way to manage your account in Firefox? Now you can access Twitter in your Sidebar or as a separate window with the TwitKit+ extension for Firefox. Accessing TwitKit+ There are three ways that you can access TwitKit+ after installing the extension. The first is by adding the “Toolbar Button” to your browser’s UI. The second and third methods are through the “View & Tools Menus”.   TwitKit+ in Action When you open TwitKit+ for the first time you will see Twitter’s “Public Tweet Stream”. To get started login into your account. Note: If you do not care for the “brown theme” you can select a different one in “Preferences”. Here is a closer look at the top area and the commands available. Notice the “blue arrow symbol” in the upper left corner…very useful if you want to separate TwitKit+ from your main browser window for a bit. Secure Mode, Undock, Preferences, Login/Logout Google Search, Twitter Search, Copy Selection To Status Box, Shorten Selected URL Public, User, Friends, Followers, @ Messages, Direct Messages, Profile Note: To use Google or Twitter search enter your term in the “Status Area” and click on the appropriate service icon. Here is the regular timeline for our account…the “clickable tab buttons” make everything easy to view and work with. You can perform actions such as replying, retweeting, marking as a favorite, etc. using the set of “management buttons” at the bottom of each tweet. To add a new tweet to your timeline enter your text and press “Enter”. A look at the “Following List” for our account. Having a more defined and separate “view categories” set makes this better than directly accessing the Twitter website. Preferences The preferences can be quickly sorted out…choose how often the timeline is updated, name display, favorite URL shortening service, theme, and font size. Note: The default connection setting is for “Secure Access”. Conclusion TwitKit+ makes a nice addition to Firefox for anyone who loves keeping up with Twitter throughout the day. There when you want it and out of your way the rest of the time. Links Download the TwitKit+ extension (Mozilla Add-ons) Similar Articles Productive Geek Tips Move Add-on Management to the Sidebar in FirefoxPreview and Manage Multiple Tabs in Firefox with Tab SidebarDisable Windows Sidebar in VistaQuick Tip: Use Google Talk Sidebar in FirefoxRun Windows Sidebar Gadgets Without the Sidebar TouchFreeze Alternative in AutoHotkey The Icy Undertow Desktop Windows Home Server – Backup to LAN The Clear & Clean Desktop Use This Bookmarklet to Easily Get Albums Use AutoHotkey to Assign a Hotkey to a Specific Window Latest Software Reviews Tinyhacker Random Tips Revo Uninstaller Pro Registry Mechanic 9 for Windows PC Tools Internet Security Suite 2010 PCmover Professional Enable Check Box Selection in Windows 7 OnlineOCR – Free OCR Service Betting on the Blind Side, a Vanity Fair article 30 Minimal Logo Designs that Say More with Less LEGO Digital Designer – Free Create a Personal Website Quickly using Flavors.me

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  • dpkg stuck downloading font files

    - by Bob Bowles
    I have been reinstalling Ubuntu 12.04. The install from USB works fine, and I could update everything OK, but when I got to re-installing my application software I hit a snag. One of the packages I tried to re-install was ttf-mscorefonts-installer. dpkg stalled during this setup, downloading a font file (it had tried to download it all night). I stopped dpkg, and attempted to re-start downloading something else, but it would not let me. The commands I typed are as follows: bob@bobStudio:~$ sudo rm /var/lib/dpkg/lock This unlocks dpkg, but if I try to do something I get the following message (eg): bob@bobStudio:~$ sudo apt-get install synaptic E: dpgk was interrupted, you must manually run 'sudo dpkg --configure -a' to correct the problem So, I did just that: bob@bobStudio:~$ sudo dpkg --configure -a whereupon it started the previously failed download all over again. I went round the loop here a few times and each time after the configure command it re-started the failing download, but then I got this: bob@bobStudio:~$ sudo dpkg --configure -a Setting up update-notifier-common (0.119ubuntu8.4) ... ttf-mscorefonts-installer: downloading http://downloads.sourceforge.net/corefonts/andale32.exe Traceback (most recent call last): File "/usr/lib/update-notifier/package-data-downloader", line 234, in process_download_requests dest_file = urllib.urlretrieve(files[i])[0] File "/usr/lib/python2.7/urllib.py", line 93, in urlretrieve return _urlopener.retrieve(url, filename, reporthook, data) File "/usr/lib/python2.7/urllib.py", line 239, in retrieve fp = self.open(url, data) File "/usr/lib/python2.7/urllib.py", line 207, in open return getattr(self, name)(url) File "/usr/lib/python2.7/urllib.py", line 344, in open_http h.endheaders(data) File "/usr/lib/python2.7/httplib.py", line 954, in endheaders self._send_output(message_body) File "/usr/lib/python2.7/httplib.py", line 814, in _send_output self.send(msg) File "/usr/lib/python2.7/httplib.py", line 776, in send self.connect() File "/usr/lib/python2.7/httplib.py", line 757, in connect self.timeout, self.source_address) File "/usr/lib/python2.7/socket.py", line 553, in create_connection for res in getaddrinfo(host, port, 0, SOCK_STREAM): IOError: [Errno socket error] [Errno -2] Name or service not known Setting up ttf-mscorefonts-installer (3.4ubuntu3) ... bob@bobStudio:~$ sudo apt-get update E: Could not get lock /var/lib/apt/lists/lock - open (11: Resource temporarily unavailable) E: Unable to lock directory /var/lib/apt/lists/ bob@bobStudio:~$ sudo rm /var/lib/dpkg/lock bob@bobStudio:~$ sudo apt-get update E: Could not get lock /var/lib/apt/lists/lock - open (11: Resource temporarily unavailable) E: Unable to lock directory /var/lib/apt/lists/ The good news is that, once I sorted out the file locks, this seems to have permanently aborted the setup of the font package, so at least I can do something else with dpkg. That leaves two questions: 1) How could I have broken the loop without actually crashing out of dpkg? 2) How can I set up the ttf-mscorefonts-installer package in the future? Is this download really broken, or is it 'just' a bad Internet connection?

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  • SQL SERVER – Introduction to PERCENTILE_DISC() – Analytic Functions Introduced in SQL Server 2012

    - by pinaldave
    SQL Server 2012 introduces new analytical function PERCENTILE_DISC(). The book online gives following definition of this function: Computes a specific percentile for sorted values in an entire rowset or within distinct partitions of a rowset in Microsoft SQL Server 2012 Release Candidate 0 (RC 0). For a given percentile value P, PERCENTILE_DISC sorts the values of the expression in the ORDER BY clause and returns the value with the smallest CUME_DIST value (with respect to the same sort specification) that is greater than or equal to P. If you are clear with understanding of the function – no need to read further. If you got lost here is the same in simple words – find value of the column which is equal or more than CUME_DIST. Before you continue reading this blog I strongly suggest you read about CUME_DIST function over here Introduction to CUME_DIST – Analytic Functions Introduced in SQL Server 2012. Now let’s have fun following query: USE AdventureWorks GO SELECT SalesOrderID, OrderQty, ProductID, CUME_DIST() OVER(PARTITION BY SalesOrderID ORDER BY ProductID ) AS CDist, PERCENTILE_DISC(0.5) WITHIN GROUP (ORDER BY ProductID) OVER (PARTITION BY SalesOrderID) AS PercentileDisc FROM Sales.SalesOrderDetail WHERE SalesOrderID IN (43670, 43669, 43667, 43663) ORDER BY SalesOrderID DESC GO The above query will give us the following result: You can see that I have used PERCENTILE_DISC(0.5) in query, which is similar to finding median but not exactly. PERCENTILE_DISC() function takes a percentile as a passing parameters. It returns the value as answer which value is equal or great to the percentile value which is passed into the example. For example in above example we are passing 0.5 into the PERCENTILE_DISC() function. It will go through the resultset and identify which rows has values which are equal to or great than 0.5. In first example it found two rows which are equal to 0.5 and the value of ProductID of that row is the answer of PERCENTILE_DISC(). In some third windowed resultset there is only single row with the CUME_DIST() value as 1 and that is for sure higher than 0.5 making it as a answer. To make sure that we are clear with this example properly. Here is one more example where I am passing 0.6 as a percentile. Now let’s have fun following query: USE AdventureWorks GO SELECT SalesOrderID, OrderQty, ProductID, CUME_DIST() OVER(PARTITION BY SalesOrderID ORDER BY ProductID ) AS CDist, PERCENTILE_DISC(0.6) WITHIN GROUP (ORDER BY ProductID) OVER (PARTITION BY SalesOrderID) AS PercentileDisc FROM Sales.SalesOrderDetail WHERE SalesOrderID IN (43670, 43669, 43667, 43663) ORDER BY SalesOrderID DESC GO The above query will give us the following result: The result of the PERCENTILE_DISC(0.6) is ProductID of which CUME_DIST() is more than 0.6. This means for SalesOrderID 43670 has row with CUME_DIST() 0.75 is the qualified row, resulting answer 773 for ProductID. I hope this explanation makes it further clear. Reference: Pinal Dave (http://blog.SQLAuthority.com) Filed under: Pinal Dave, PostADay, SQL, SQL Authority, SQL Function, SQL Query, SQL Scripts, SQL Server, SQL Tips and Tricks, T SQL, Technology

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  • C#/.NET Little Wonders: The ConcurrentDictionary

    - by James Michael Hare
    Once again we consider some of the lesser known classes and keywords of C#.  In this series of posts, we will discuss how the concurrent collections have been developed to help alleviate these multi-threading concerns.  Last week’s post began with a general introduction and discussed the ConcurrentStack<T> and ConcurrentQueue<T>.  Today's post discusses the ConcurrentDictionary<T> (originally I had intended to discuss ConcurrentBag this week as well, but ConcurrentDictionary had enough information to create a very full post on its own!).  Finally next week, we shall close with a discussion of the ConcurrentBag<T> and BlockingCollection<T>. For more of the "Little Wonders" posts, see the index here. Recap As you'll recall from the previous post, the original collections were object-based containers that accomplished synchronization through a Synchronized member.  While these were convenient because you didn't have to worry about writing your own synchronization logic, they were a bit too finely grained and if you needed to perform multiple operations under one lock, the automatic synchronization didn't buy much. With the advent of .NET 2.0, the original collections were succeeded by the generic collections which are fully type-safe, but eschew automatic synchronization.  This cuts both ways in that you have a lot more control as a developer over when and how fine-grained you want to synchronize, but on the other hand if you just want simple synchronization it creates more work. With .NET 4.0, we get the best of both worlds in generic collections.  A new breed of collections was born called the concurrent collections in the System.Collections.Concurrent namespace.  These amazing collections are fine-tuned to have best overall performance for situations requiring concurrent access.  They are not meant to replace the generic collections, but to simply be an alternative to creating your own locking mechanisms. Among those concurrent collections were the ConcurrentStack<T> and ConcurrentQueue<T> which provide classic LIFO and FIFO collections with a concurrent twist.  As we saw, some of the traditional methods that required calls to be made in a certain order (like checking for not IsEmpty before calling Pop()) were replaced in favor of an umbrella operation that combined both under one lock (like TryPop()). Now, let's take a look at the next in our series of concurrent collections!For some excellent information on the performance of the concurrent collections and how they perform compared to a traditional brute-force locking strategy, see this wonderful whitepaper by the Microsoft Parallel Computing Platform team here. ConcurrentDictionary – the fully thread-safe dictionary The ConcurrentDictionary<TKey,TValue> is the thread-safe counterpart to the generic Dictionary<TKey, TValue> collection.  Obviously, both are designed for quick – O(1) – lookups of data based on a key.  If you think of algorithms where you need lightning fast lookups of data and don’t care whether the data is maintained in any particular ordering or not, the unsorted dictionaries are generally the best way to go. Note: as a side note, there are sorted implementations of IDictionary, namely SortedDictionary and SortedList which are stored as an ordered tree and a ordered list respectively.  While these are not as fast as the non-sorted dictionaries – they are O(log2 n) – they are a great combination of both speed and ordering -- and still greatly outperform a linear search. Now, once again keep in mind that if all you need to do is load a collection once and then allow multi-threaded reading you do not need any locking.  Examples of this tend to be situations where you load a lookup or translation table once at program start, then keep it in memory for read-only reference.  In such cases locking is completely non-productive. However, most of the time when we need a concurrent dictionary we are interleaving both reads and updates.  This is where the ConcurrentDictionary really shines!  It achieves its thread-safety with no common lock to improve efficiency.  It actually uses a series of locks to provide concurrent updates, and has lockless reads!  This means that the ConcurrentDictionary gets even more efficient the higher the ratio of reads-to-writes you have. ConcurrentDictionary and Dictionary differences For the most part, the ConcurrentDictionary<TKey,TValue> behaves like it’s Dictionary<TKey,TValue> counterpart with a few differences.  Some notable examples of which are: Add() does not exist in the concurrent dictionary. This means you must use TryAdd(), AddOrUpdate(), or GetOrAdd().  It also means that you can’t use a collection initializer with the concurrent dictionary. TryAdd() replaced Add() to attempt atomic, safe adds. Because Add() only succeeds if the item doesn’t already exist, we need an atomic operation to check if the item exists, and if not add it while still under an atomic lock. TryUpdate() was added to attempt atomic, safe updates. If we want to update an item, we must make sure it exists first and that the original value is what we expected it to be.  If all these are true, we can update the item under one atomic step. TryRemove() was added to attempt atomic, safe removes. To safely attempt to remove a value we need to see if the key exists first, this checks for existence and removes under an atomic lock. AddOrUpdate() was added to attempt an thread-safe “upsert”. There are many times where you want to insert into a dictionary if the key doesn’t exist, or update the value if it does.  This allows you to make a thread-safe add-or-update. GetOrAdd() was added to attempt an thread-safe query/insert. Sometimes, you want to query for whether an item exists in the cache, and if it doesn’t insert a starting value for it.  This allows you to get the value if it exists and insert if not. Count, Keys, Values properties take a snapshot of the dictionary. Accessing these properties may interfere with add and update performance and should be used with caution. ToArray() returns a static snapshot of the dictionary. That is, the dictionary is locked, and then copied to an array as a O(n) operation.  GetEnumerator() is thread-safe and efficient, but allows dirty reads. Because reads require no locking, you can safely iterate over the contents of the dictionary.  The only downside is that, depending on timing, you may get dirty reads. Dirty reads during iteration The last point on GetEnumerator() bears some explanation.  Picture a scenario in which you call GetEnumerator() (or iterate using a foreach, etc.) and then, during that iteration the dictionary gets updated.  This may not sound like a big deal, but it can lead to inconsistent results if used incorrectly.  The problem is that items you already iterated over that are updated a split second after don’t show the update, but items that you iterate over that were updated a split second before do show the update.  Thus you may get a combination of items that are “stale” because you iterated before the update, and “fresh” because they were updated after GetEnumerator() but before the iteration reached them. Let’s illustrate with an example, let’s say you load up a concurrent dictionary like this: 1: // load up a dictionary. 2: var dictionary = new ConcurrentDictionary<string, int>(); 3:  4: dictionary["A"] = 1; 5: dictionary["B"] = 2; 6: dictionary["C"] = 3; 7: dictionary["D"] = 4; 8: dictionary["E"] = 5; 9: dictionary["F"] = 6; Then you have one task (using the wonderful TPL!) to iterate using dirty reads: 1: // attempt iteration in a separate thread 2: var iterationTask = new Task(() => 3: { 4: // iterates using a dirty read 5: foreach (var pair in dictionary) 6: { 7: Console.WriteLine(pair.Key + ":" + pair.Value); 8: } 9: }); And one task to attempt updates in a separate thread (probably): 1: // attempt updates in a separate thread 2: var updateTask = new Task(() => 3: { 4: // iterates, and updates the value by one 5: foreach (var pair in dictionary) 6: { 7: dictionary[pair.Key] = pair.Value + 1; 8: } 9: }); Now that we’ve done this, we can fire up both tasks and wait for them to complete: 1: // start both tasks 2: updateTask.Start(); 3: iterationTask.Start(); 4:  5: // wait for both to complete. 6: Task.WaitAll(updateTask, iterationTask); Now, if I you didn’t know about the dirty reads, you may have expected to see the iteration before the updates (such as A:1, B:2, C:3, D:4, E:5, F:6).  However, because the reads are dirty, we will quite possibly get a combination of some updated, some original.  My own run netted this result: 1: F:6 2: E:6 3: D:5 4: C:4 5: B:3 6: A:2 Note that, of course, iteration is not in order because ConcurrentDictionary, like Dictionary, is unordered.  Also note that both E and F show the value 6.  This is because the output task reached F before the update, but the updates for the rest of the items occurred before their output (probably because console output is very slow, comparatively). If we want to always guarantee that we will get a consistent snapshot to iterate over (that is, at the point we ask for it we see precisely what is in the dictionary and no subsequent updates during iteration), we should iterate over a call to ToArray() instead: 1: // attempt iteration in a separate thread 2: var iterationTask = new Task(() => 3: { 4: // iterates using a dirty read 5: foreach (var pair in dictionary.ToArray()) 6: { 7: Console.WriteLine(pair.Key + ":" + pair.Value); 8: } 9: }); The atomic Try…() methods As you can imagine TryAdd() and TryRemove() have few surprises.  Both first check the existence of the item to determine if it can be added or removed based on whether or not the key currently exists in the dictionary: 1: // try add attempts an add and returns false if it already exists 2: if (dictionary.TryAdd("G", 7)) 3: Console.WriteLine("G did not exist, now inserted with 7"); 4: else 5: Console.WriteLine("G already existed, insert failed."); TryRemove() also has the virtue of returning the value portion of the removed entry matching the given key: 1: // attempt to remove the value, if it exists it is removed and the original is returned 2: int removedValue; 3: if (dictionary.TryRemove("C", out removedValue)) 4: Console.WriteLine("Removed C and its value was " + removedValue); 5: else 6: Console.WriteLine("C did not exist, remove failed."); Now TryUpdate() is an interesting creature.  You might think from it’s name that TryUpdate() first checks for an item’s existence, and then updates if the item exists, otherwise it returns false.  Well, note quite... It turns out when you call TryUpdate() on a concurrent dictionary, you pass it not only the new value you want it to have, but also the value you expected it to have before the update.  If the item exists in the dictionary, and it has the value you expected, it will update it to the new value atomically and return true.  If the item is not in the dictionary or does not have the value you expected, it is not modified and false is returned. 1: // attempt to update the value, if it exists and if it has the expected original value 2: if (dictionary.TryUpdate("G", 42, 7)) 3: Console.WriteLine("G existed and was 7, now it's 42."); 4: else 5: Console.WriteLine("G either didn't exist, or wasn't 7."); The composite Add methods The ConcurrentDictionary also has composite add methods that can be used to perform updates and gets, with an add if the item is not existing at the time of the update or get. The first of these, AddOrUpdate(), allows you to add a new item to the dictionary if it doesn’t exist, or update the existing item if it does.  For example, let’s say you are creating a dictionary of counts of stock ticker symbols you’ve subscribed to from a market data feed: 1: public sealed class SubscriptionManager 2: { 3: private readonly ConcurrentDictionary<string, int> _subscriptions = new ConcurrentDictionary<string, int>(); 4:  5: // adds a new subscription, or increments the count of the existing one. 6: public void AddSubscription(string tickerKey) 7: { 8: // add a new subscription with count of 1, or update existing count by 1 if exists 9: var resultCount = _subscriptions.AddOrUpdate(tickerKey, 1, (symbol, count) => count + 1); 10:  11: // now check the result to see if we just incremented the count, or inserted first count 12: if (resultCount == 1) 13: { 14: // subscribe to symbol... 15: } 16: } 17: } Notice the update value factory Func delegate.  If the key does not exist in the dictionary, the add value is used (in this case 1 representing the first subscription for this symbol), but if the key already exists, it passes the key and current value to the update delegate which computes the new value to be stored in the dictionary.  The return result of this operation is the value used (in our case: 1 if added, existing value + 1 if updated). Likewise, the GetOrAdd() allows you to attempt to retrieve a value from the dictionary, and if the value does not currently exist in the dictionary it will insert a value.  This can be handy in cases where perhaps you wish to cache data, and thus you would query the cache to see if the item exists, and if it doesn’t you would put the item into the cache for the first time: 1: public sealed class PriceCache 2: { 3: private readonly ConcurrentDictionary<string, double> _cache = new ConcurrentDictionary<string, double>(); 4:  5: // adds a new subscription, or increments the count of the existing one. 6: public double QueryPrice(string tickerKey) 7: { 8: // check for the price in the cache, if it doesn't exist it will call the delegate to create value. 9: return _cache.GetOrAdd(tickerKey, symbol => GetCurrentPrice(symbol)); 10: } 11:  12: private double GetCurrentPrice(string tickerKey) 13: { 14: // do code to calculate actual true price. 15: } 16: } There are other variations of these two methods which vary whether a value is provided or a factory delegate, but otherwise they work much the same. Oddities with the composite Add methods The AddOrUpdate() and GetOrAdd() methods are totally thread-safe, on this you may rely, but they are not atomic.  It is important to note that the methods that use delegates execute those delegates outside of the lock.  This was done intentionally so that a user delegate (of which the ConcurrentDictionary has no control of course) does not take too long and lock out other threads. This is not necessarily an issue, per se, but it is something you must consider in your design.  The main thing to consider is that your delegate may get called to generate an item, but that item may not be the one returned!  Consider this scenario: A calls GetOrAdd and sees that the key does not currently exist, so it calls the delegate.  Now thread B also calls GetOrAdd and also sees that the key does not currently exist, and for whatever reason in this race condition it’s delegate completes first and it adds its new value to the dictionary.  Now A is done and goes to get the lock, and now sees that the item now exists.  In this case even though it called the delegate to create the item, it will pitch it because an item arrived between the time it attempted to create one and it attempted to add it. Let’s illustrate, assume this totally contrived example program which has a dictionary of char to int.  And in this dictionary we want to store a char and it’s ordinal (that is, A = 1, B = 2, etc).  So for our value generator, we will simply increment the previous value in a thread-safe way (perhaps using Interlocked): 1: public static class Program 2: { 3: private static int _nextNumber = 0; 4:  5: // the holder of the char to ordinal 6: private static ConcurrentDictionary<char, int> _dictionary 7: = new ConcurrentDictionary<char, int>(); 8:  9: // get the next id value 10: public static int NextId 11: { 12: get { return Interlocked.Increment(ref _nextNumber); } 13: } Then, we add a method that will perform our insert: 1: public static void Inserter() 2: { 3: for (int i = 0; i < 26; i++) 4: { 5: _dictionary.GetOrAdd((char)('A' + i), key => NextId); 6: } 7: } Finally, we run our test by starting two tasks to do this work and get the results… 1: public static void Main() 2: { 3: // 3 tasks attempting to get/insert 4: var tasks = new List<Task> 5: { 6: new Task(Inserter), 7: new Task(Inserter) 8: }; 9:  10: tasks.ForEach(t => t.Start()); 11: Task.WaitAll(tasks.ToArray()); 12:  13: foreach (var pair in _dictionary.OrderBy(p => p.Key)) 14: { 15: Console.WriteLine(pair.Key + ":" + pair.Value); 16: } 17: } If you run this with only one task, you get the expected A:1, B:2, ..., Z:26.  But running this in parallel you will get something a bit more complex.  My run netted these results: 1: A:1 2: B:3 3: C:4 4: D:5 5: E:6 6: F:7 7: G:8 8: H:9 9: I:10 10: J:11 11: K:12 12: L:13 13: M:14 14: N:15 15: O:16 16: P:17 17: Q:18 18: R:19 19: S:20 20: T:21 21: U:22 22: V:23 23: W:24 24: X:25 25: Y:26 26: Z:27 Notice that B is 3?  This is most likely because both threads attempted to call GetOrAdd() at roughly the same time and both saw that B did not exist, thus they both called the generator and one thread got back 2 and the other got back 3.  However, only one of those threads can get the lock at a time for the actual insert, and thus the one that generated the 3 won and the 3 was inserted and the 2 got discarded.  This is why on these methods your factory delegates should be careful not to have any logic that would be unsafe if the value they generate will be pitched in favor of another item generated at roughly the same time.  As such, it is probably a good idea to keep those generators as stateless as possible. Summary The ConcurrentDictionary is a very efficient and thread-safe version of the Dictionary generic collection.  It has all the benefits of type-safety that it’s generic collection counterpart does, and in addition is extremely efficient especially when there are more reads than writes concurrently. Tweet Technorati Tags: C#, .NET, Concurrent Collections, Collections, Little Wonders, Black Rabbit Coder,James Michael Hare

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  • New Process For Receiving Oracle Certification Exam Results

    - by Brandye Barrington
    On November 15, 2012, Oracle Certification exam results will be available directly from Oracle's certification portal, CertView. After completing an exam at a testing center, you will login to CertView to access and print your exam scores by selecting the See My New Exam Results Now link or the Print My New Exam Results Now link from the homepage. This will provide access to all certification and exam history in one place through Oracle, providing tighter integration with other activities at Oracle. This change in policy will also increase security around data privacy. AUTHENTICATE YOUR CERTVIEW ACCOUNT NOW One very important step you must take is to authenticate your CertView account BEFORE taking your exam. This way, if there are any issues with authorization, you have time to get these sorted out before testing. Keep in mind that it can take up to 3 business days for a CertView account to be manually authenticated, so completing this process before testing is key! You will need to create a web account at PearsonVUE prior to registering for your exam and you will need to create an Oracle Web Account prior to authenticating your CertView account. The CertView account will be available for authentication within 30 minutes of creating a Pearson VUE web account at certview.oracle.com. GETTING YOUR EXAM RESULTS FROM ORACLE Before taking the scheduled exam, you should authenticate your account at certview.oracle.com using the email address and Oracle Testing ID in your Pearson VUE profile. You will be required to have an Oracle Web Account to authenticate your CertView account. After taking the exam, you will receive an email from Oracle indicating that your exam results are available at certview.oracle.com If you have previously authenticated your CertView account, you will simply click on the link in the email, which will take you to CertView, login and select See My New Exam Results Now. If you have not authenticated your CertView account before receiving this notification email, you will be required to authenticate your CertView account before accessing your exam results. Authentication requires an Oracle Web Account user name and password and the following information from your Pearson VUE profile: email address and Oracle Testing ID. Click on the link in the email to authenticate your CertView account You will be given the option to create an Oracle Web Account if you do no already have one.  After account authentication, you will be able to login to CertView and select See My New Exam Results Now to view your exam results or Print My New Exam Results Now to print your exam results. As always, if you need assistance with your CertView account, please contact Oracle Certification Support. YOUR QUESTIONS ANSWERED More Information FAQ: Receiving Exam Scores FAQ: How Do I Log Into CertView? FAQ: How To Get Exam Results FAQ: Accessing Exam Results in CertView FAQ: How Will I Know When My Exam Results Are Available? FAQ: What If I Don't Get An Exam Results Email Alert? FAQ: How To Download and Print Exam Score Reports FAQ: What If I Think My Exam Results Are Wrong In CertView? FAQ: Is Oracle Changing The Way That Exams Are Scored?

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  • How to Disable the New Geolocation Feature in Google Chrome

    - by Asian Angel
    The latest release of Google Chrome has geolocation enabled by default, and if you are worried about privacy or just don’t want websites to prompt you for your location, we’ve got the quick details on how to turn it off. Readers should note that the new Geolocation feature doesn’t give out your details by default, so don’t panic. It’s also only active, at the time of this writing, in the Dev channel builds of Chrome—so if you are using the regular stable build this feature won’t arrive for a while anyway. Note: If you’re a Firefox user, be sure to check out our guide to disabling geolocation in Firefox 3.x. What’s this Geolocation Feature About? Geolocation is a way for your browser to tell a website about your physical location, so you can get results tailored to where you actually are—for example, if you visited Google Maps it can ask you for your location to give you an accurate picture of where you are. To use this feature in Google Maps, you would click on the small white icon to activate the feature. As soon as you have clicked on the small white icon, a thin green toolbar will appear at the top of the webpage, asking to Allow or Deny.   How to Turn Chrome’s Geolocation Off If you want to turn geolocation off you will need to open the “Chrome Options Window”, navigate to the third tab, and click on the “Content settings… ” button. When the “Content Settings Window” opens go to the “Location Tab” and select “Do not allow any site to track my physical location”. Once that is done close out the “Content Settings & Chrome Options Windows”. When you go back to Google Maps and try using the small white icon again this is the message that you will see at the top of the page. Now that is much better! If you are unhappy with geolocation being enabled by default in the latest Dev Channel release then this will help get the problem sorted out nicely. Similar Articles Productive Geek Tips Stupid Geek Tricks: Compare Your Browser’s Memory Usage with Google ChromeHow To Disable Individual Plug-ins in Google ChromeStop YouTube Videos from Automatically Playing in ChromeDisable YouTube Comments while using ChromeHow to Make Google Chrome Your Default Browser TouchFreeze Alternative in AutoHotkey The Icy Undertow Desktop Windows Home Server – Backup to LAN The Clear & Clean Desktop Use This Bookmarklet to Easily Get Albums Use AutoHotkey to Assign a Hotkey to a Specific Window Latest Software Reviews Tinyhacker Random Tips DVDFab 6 Revo Uninstaller Pro Registry Mechanic 9 for Windows PC Tools Internet Security Suite 2010 Microsoft’s “How Do I ?” Videos Home Networks – How do they look like & the problems they cause Check Your IMAP Mail Offline In Thunderbird Follow Finder Finds You Twitter Users To Follow Combine MP3 Files Easily QuicklyCode Provides Cheatsheets & Other Programming Stuff

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  • How to sort a ListView control by a column in Visual C#

    - by bconlon
    Microsoft provide an article of the same name (previously published as Q319401) and it shows a nice class 'ListViewColumnSorter ' for sorting a standard ListView when the user clicks the column header. This is very useful for String values, however for Numeric or DateTime data it gives odd results. E.g. 100 would come before 99 in an ascending sort as the string compare sees 1 < 9. So my challenge was to allow other types to be sorted. This turned out to be fairly simple as I just needed to create an inner class in ListViewColumnSorter which extends the .Net CaseInsensitiveComparer class, and then use this as the ObjectCompare member's type. Note: Ideally we would be able to use IComparer as the member's type, but the Compare method is not virtual in CaseInsensitiveComparer , so we have to create an exact type: public class ListViewColumnSorter : IComparer {     private CaseInsensitiveComparer ObjectCompare;     private MyComparer ObjectCompare;     ... rest of Microsofts class implementation... } Here is my private inner comparer class, note the 'new int Compare' as Compare is not virtual, and also note we pass the values to the base compare as the correct type (e.g. Decimal, DateTime) so they compare correctly: private class MyComparer : CaseInsensitiveComparer {     public new int Compare(object x, object y)     {         try         {             string s1 = x.ToString();             string s2 = y.ToString();               // check for a numeric column             decimal n1, n2 = 0;             if (Decimal.TryParse(s1, out n1) && Decimal.TryParse(s2, out n2))                 return base.Compare(n1, n2);             else             {                 // check for a date column                 DateTime d1, d2;                 if (DateTime.TryParse(s1, out d1) && DateTime.TryParse(s2, out d2))                     return base.Compare(d1, d2);             }         }         catch (ArgumentException) { }           // just use base string compare         return base.Compare(x, y);     } } You could extend this for other types, even custom classes as long as they support ICompare. Microsoft also have another article How to: Sort a GridView Column When a Header Is Clicked that shows this for WPF, which looks conceptually very similar. I need to test it out to see if it handles non-string types. #

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  • What is the rationale behind snazzy Window Managers/Composers?

    - by Emanuele
    This is more of a generic question, based on trying out Window Managers like Awesome, Mate and others. To me looks like that other Window Managers like Gnome3 and/or Unity are heavy and pointless. I do understand that having all the composed UIs is more pleasant for the eye, but apart that, what are the other major benefits? To make an example, when I run the game Heroes of Newerth (using nVidia drivers) under: Unity : the FPS drops sharply Gnome3 : FPS is ok, but X and other processes use 15~20% of CPU and quite some additional memory Awesome : FPS is ok, and other processes use very little memory and CPU Below some numbers regarding what I'm saying (please note my system is 64 bit, AMD Phenom II X4, 8 GB RAM, nd nVidia 470 GTX, SSD disk). All data is sorted by mem usage (watch -d -n 10 "ps -e -o pcpu,pmem,pid,user,cmd --sort=-pmem | head -20"); again note that CPU time of ./hon-x86_64 might be different due to the fact I can't take the snapshot of the system during exactly same time. Awesome: %CPU %MEM PID USER CMD 91.8 21.6 3579 ema ./hon-x86_64 2.4 0.9 3223 root /usr/bin/X :0 -auth /var/run/lightdm/root/:0 -nolisten tcp vt7 -novtswitch 1.6 0.4 2600 ema /usr/lib/erlang/erts-5.8.5/bin/beam.smp -Bd -K true -A 4 -- -root /usr/lib/erlang -progname erl -- -home /home/ema -- -noshell -noinp 0.3 0.2 3602 ema gnome-terminal 0.0 0.2 2698 ema /usr/bin/python /usr/lib/desktopcouch/desktopcouch-service Gnome3: %CPU %MEM PID USER CMD 82.7 21.0 5528 ema ./hon-x86_64 17.7 1.7 5315 ema /usr/bin/gnome-shell 5.8 1.2 5062 root /usr/bin/X :0 -auth /var/run/lightdm/root/:0 -nolisten tcp vt7 -novtswitch 1.0 0.4 5657 ema /usr/bin/python /usr/lib/ubuntuone-client/ubuntuone-syncdaemon 0.7 0.3 5331 ema nautilus -n 1.6 0.3 2600 ema /usr/lib/erlang/erts-5.8.5/bin/beam.smp -Bd -K true -A 4 -- -root /usr/lib/erlang -progname erl -- -home /home/ema -- - 0.9 0.2 5451 ema gnome-terminal 0.1 0.2 5400 ema /usr/bin/python /usr/lib/desktopcouch/desktopcouch-service Unity 3D: %CPU %MEM PID USER CMD 87.2 21.1 6554 ema ./hon-x86_64 10.7 2.6 6105 ema compiz 17.8 1.1 5842 root /usr/bin/X :0 -auth /var/run/lightdm/root/:0 -nolisten tcp vt7 -novtswitch 1.3 0.9 6672 root /usr/bin/python /usr/sbin/aptd 0.4 0.4 6606 ema /usr/bin/python /usr/lib/ubuntuone-client/ubuntuone-syncdaemon 0.5 0.3 6115 ema nautilus -n 1.5 0.3 2600 ema /usr/lib/erlang/erts-5.8.5/bin/beam.smp -Bd -K true -A 4 -- -root /usr/lib/erlang -progname erl -- -home /home/ema -- -noshell -noinput -sasl errl 0.3 0.2 6180 ema /usr/lib/unity/unity-panel-service So my point is, what's the rationale behind going towards such heavy WMs/Composers?

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  • Why does my int, booleans, doubles does not work?

    - by SystemNetworks
    As you see, my code does not work. When armor1 is true, it would add my life. goldA is another class. public void goldenArmor(GameContainer gc, StateBasedGame sbg, Graphics g) { if(armor1==true) { goldA.life = life; goldA.intelligence = intelligence; goldA.power = power; goldA.lifeLeft = lifeLeft; goldA.head(); goldA.body(); goldA.legs(); } } My other class: package javagame; import org.newdawn.slick.GameContainer; import org.newdawn.slick.Graphics; import org.newdawn.slick.Image; import org.newdawn.slick.Input; import org.newdawn.slick.SlickException; /* Note: Copyright(C)2012 System Networks | Square NET | Julius Bryan Gambe. You cannot copy the style, story of the game and gameplay! To programmers: The int,doubles,strings,booleans are properly sorted out. Please don't mess it up. */ /* NOTE: We have loops but not for programming. The loop is: 1.show the world to user 2.Obtain input from the user 3.Shows the update, repeat step 1 */ import org.newdawn.slick.*; import org.newdawn.slick.state.*; import org.lwjgl.input.Mouse; //contents: // public class GoldenArmor{ //get it from play public int life; public double intelligence; public int lifeLeft; public double power; public GoldenArmor() { // TODO Auto-generated constructor stub } //start here public void head() { life += 10; intelligence +=0.5; } public void body() { lifeLeft += 100; } public void legs() { power += 100; } } /* SYSTEM NETWORKS(C) 2012 NET FRONT */ The life, intelligence, power, lifeLeft are nothing but to use it as just reference to prevent stack overflow. And at my main class, it becomes my real booleans, int, doubles. How do I fix this? It does not add it to my normal int.

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  • How to resolve concurrent ramp collisions in 2d platformer?

    - by Shaun Inman
    A bit about the physics engine: Bodies are all rectangles. Bodies are sorted at the beginning of every update loop based on the body-in-motion's horizontal and vertical velocity (to avoid sticky walls/floors). Solid bodies are resolved by testing the body-in-motion's new X with the old Y and adjusting if necessary before testing the new X with the new Y, again adjusting if necessary. Works great. Ramps (rectangles with a flag set indicating bottom-left, bottom-right, etc) are resolved by calculating the ratio of penetration along the x-axis and setting a new Y accordingly (with some checks to make sure the body-in-motion isn't attacking from the tall or flat side, in which case the ramp is treated as a normal rectangle). This also works great. Side-by-side ramps, eg. \/ and /\, work fine but things get jittery and unpredictable when a top-down ramp is directly above a bottom-up ramp, eg. < or > or when a bottom-up ramp runs right up to the ceiling/top-down ramp runs right down to the floor. I've been able to lock it down somewhat by detecting whether the body-in-motion hadFloor when also colliding with a top-down ramp or hadCeiling when also colliding with a bottom-up ramp then resolving by calculating the ratio of penetration along the y-axis and setting the new X accordingly (the opposite of the normal behavior). But as soon as the body-in-motion jumps the hasFloor flag becomes false, the first ramp resolution pushes the body into collision with the second ramp and collision resolution becomes jittery again for a few frames. I'm sure I'm making this more complicated than it needs to be. Can anyone recommend a good resource that outlines the best way to address this problem? (Please don't recommend I use something like Box2d or Chipmunk. Also, "redesign your levels" isn't an answer; the body-in-motion may at times be riding another body-in-motion, eg. a platform, that pushes it into a ramp so I'd like to be able to resolve this properly.) Thanks!

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  • What is this algorithm for converting strings into numbers called?

    - by CodexArcanum
    I've been doing some work in Parsec recently, and for my toy language I wanted multi-based fractional numbers to be expressible. After digging around in Parsec's source a bit, I found their implementation of a floating-point number parser, and copied it to make the needed modifications. So I understand what this code does, and vaguely why (I haven't worked out the math fully yet, but I think I get the gist). But where did it come from? This seems like a pretty clever way to turn strings into floats and ints, is there a name for this algorithm? Or is it just something basic that's a hole in my knowledge? Did the folks behind Parsec devise it? Here's the code, first for integers: number' :: Integer -> Parser Integer number' base = do { digits <- many1 ( oneOf ( sigilRange base )) ; let n = foldl (\x d -> base * x + toInteger (convertDigit base d)) 0 digits ; seq n (return n) } So the basic idea here is that digits contains the string representing the whole number part, ie "192". The foldl converts each digit individually into a number, then adds that to the running total multiplied by the base, which means that by the end each digit has been multiplied by the correct factor (in aggregate) to position it. The fractional part is even more interesting: fraction' :: Integer -> Parser Double fraction' base = do { digits <- many1 ( oneOf ( sigilRange base )) ; let base' = fromIntegral base ; let f = foldr (\d x -> (x + fromIntegral (convertDigit base d))/base') 0.0 digits ; seq f (return f) Same general idea, but now a foldr and using repeated division. I don't quite understand why you add first and then divide for the fraction, but multiply first then add for the whole. I know it works, just haven't sorted out why. Anyway, I feel dumb not working it out myself, it's very simple and clever looking at it. Is there a name for this algorithm? Maybe the imperative version using a loop would be more familiar?

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  • Data Model Dissonance

    - by Tony Davis
    So often at the start of the development of database applications, there is a premature rush to the keyboard. Unless, before we get there, we’ve mapped out and agreed the three data models, the Conceptual, the Logical and the Physical, then the inevitable refactoring will dog development work. It pays to get the data models sorted out up-front, however ‘agile’ you profess to be. The hardest model to get right, the most misunderstood, and the one most neglected by the various modeling tools, is the conceptual data model, and yet it is critical to all that follows. The conceptual model distils what the business understands about itself, and the way it operates. It represents the business rules that govern the required data, its constraints and its properties. The conceptual model uses the terminology of the business and defines the most important entities and their inter-relationships. Don’t assume that the organization’s understanding of these business rules is consistent or accurate. Too often, one department has a subtly different understanding of what an entity means and what it stores, from another. If our conceptual data model fails to resolve such inconsistencies, it will reduce data quality. If we don’t collect and measure the raw data in a consistent way across the whole business, how can we hope to perform meaningful aggregation? The conceptual data model has more to do with business than technology, and as such, developers often regard it as a worthy but rather arcane ceremony like saluting the flag or only eating fish on Friday. However, the consequences of getting it wrong have a direct and painful impact on many aspects of the project. If you adopt a silo-based (a.k.a. Domain driven) approach to development), you are still likely to suffer by starting with an incomplete knowledge of the domain. Even when you have surmounted these problems so that the data entities accurately reflect the business domain that the application represents, there are likely to be dire consequences from abandoning the goal of a shared, enterprise-wide understanding of the business. In reading this, you may recall experiences of the consequence of getting the conceptual data model wrong. I believe that Phil Factor, for example, witnessed the abandonment of a multi-million dollar banking project due to an inadequate conceptual analysis of how the bank defined a ‘customer’. We’d love to hear of any examples you know of development projects poleaxed by errors in the conceptual data model. Cheers, Tony

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  • External hard drive issue

    - by Blind Fish
    I am running Ubuntu 12.04 and I have a 500GB external hard drive, formatted in ext4, which I have used for about a year to store batches of data that I am sifting through. About once a week I move a chunk of data from the external drive to my internal drive for processing. As I do that I delete the data from the external drive and empty the trash, thereby clearing up space on the external and also preventing myself from grabbing stuff that I've already sorted through. The vast majority of this is text files, but there are a few .jpegs and .mp4s thrown in, if that matters. Anyway, this has been working without a hitch for nearly a year. So today I plug in the drive and I have an odd issue. I was able to move folders from the external over to my internal drive with no problem, but when I tried to delete those files I was unable to do so. I kept getting the "unable to send file to trash, do you wish to delete permanently?" message. I clicked yes / delete all, but no files were actually deleted. It just sat there. Even worse, while the system was trying in vain to delete those files I was unable to move more files over. In short, I was stuck. I canceled the operation, unmounted and remounted the drive, and then I had an even bigger problem. I have a spreadsheet of all the different folders on there ( exactly 818 ) and yet when I opened the drive in Nautilus, it was only finding 512 folders. So I had 306 missing folders, but my free space was unchanged. Immediately I think that the drive may be corrupted. I went into Disk Utility and ran the check disk option. It said that the drive was NOT clean, but offered no remedy or option to repair. I went back into the drive in Nautilus and once again attempted to delete the files I had already moved. Same issue. I clicked on Details and it said that it was unable to create a trashing file I/O error. I've looked, and it's not a permissions issue. The drive and all folders that are in it all belong to me, and they are all read / write. I've started running badblocks on the drive, but it looks like that is going to take several hours to complete. Any ideas?

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  • Why can't I install Microsoft Office 2007 in Ubuntu 11.04?

    - by DK new
    I am very new to Ubuntu and only just getting a hang of it, and my questions might sound stupid especially because I am a learner in terms of techie things as well. So because of the nature of work where everyone uses stupid Windows and Microsoft, I need to have access to MS Office 2007/2010 as documents with too many tables or images open all haywire in Libre Office (which has otherwise been great!). I have been reading up about installing MS Office through WINE/PlayonLinux, but have been unsuccessful so far. I downloaded a MS Office 2007 package from Pirate Bay, which I extracted into a folder. I tried numerous different ways to install through WINE and PlayonLinux, but will discuss the one which seems to be getting me somewhere. http://www.webupd8.org/2011/01/how-to-install-microsoft-office-2007-in.html ..... Initially, when I would click on the install button of MS Office, I get a message saying "The install location you selected does not have 1558MB free space. Free up space from the selected install location or choose a different install location". The install location in this case said "C:\Program Files\Microsoft Office", which confused me as I don't have drives named as C, Z etc. I went to configure WINE and under the drives tab, created a drive named A with the path location /media/cd025f16-433b-4a90-abb6-bb7a025d0450/. Also the space thing is confusing as I have at least 450GB of unused space on my computer. anyways, when I selected the A drive for installation, the installation starts, but soon I get the following error message, "Office cannot find Office.en-us\OfficeLR.Cab. Browse to a valid installation source" .... The part saying "OfficeLR.Cab" have said different things after the Office bit every time I have made an attempt. When I select the Office.en-us sub-folder or any other folder within the folder where MS Office 2007 is saved, it says "invalid source"! I have been trying to get this sorted since 15hrs now (addictive!) and have learnt loads of things in the process, but have not managed to crack it. It might be something stupidly simple I am not aware off that is stopping it. I would really appreciate some help! Thanks a lot.. Also I am still getting used to the language, so might have many questions Also I am using Ubuntu 11.04 (tag 11.04). Also I think I don't have windows -- when my friend installed Ubuntu on my new laptop which had Windows 7, he was trying to keep windows in a separate partition, but something happened and windows was not there! Looking forward to some support! Again thanks a lot

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