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• Working for free?

  - by Jonny

  I came across this article Work for Free that got me thinking. The goal of every employer is to gain more value from workers than the firm pays out in wages; otherwise, there is no growth, no advance, and no advantage for the employer. Conversely, the goal of every employee should be to contribute more to the firm than he or she receives in wages, and thereby provide a solid rationale for receiving raises and advancement in the firm. I don't need to tell you that the refusenik didn't last long in this job. In contrast, here is a story from last week. My phone rang. It was the employment division of a major university. The man on the phone was inquiring about the performance of a person who did some site work on Mises.org last year. I was able to tell him about a remarkable young man who swung into action during a crisis, and how he worked three 19-hour days, three days in a row, how he learned new software with diligence, how he kept his cool, how he navigated his way with grace and expertise amidst some 80 different third-party plug-ins and databases, how he saw his way around the inevitable problems, how he assumed responsibility for the results, and much more. What I didn't tell the interviewer was that this person did all this without asking for any payment. Did that fact influence my report on his performance? I'm not entirely sure, but the interviewer probably sensed in my voice my sense of awe toward what this person had done for the Mises Institute. The interviewer told me that he had written down 15 different questions to ask me but that I had answered them all already in the course of my monologue, and that he was thrilled to hear all these specifics. The person was offered the job. He had done a very wise thing; he had earned a devotee for life. The harder the economic times, the more employers need to know what they are getting when they hire someone. The job applications pour in by the buckets, all padded with degrees and made to look as impressive as possible. It's all just paper. What matters today is what a person can do for a firm. The resume becomes pro forma but not decisive under these conditions. But for a former boss or manager to rave about you to a potential employer? That's worth everything. What do you think? Has anyone here worked for free? If so, has it benefited you in any way? Why should(nt) you work for free (presuming you have the money from other means to keep you going)? Can you share your experience? Me, I am taking a year out of college and haven't gotten a degree yet so that's probably why most of my job applications are getting ignored. So im thinking about working for free for the experience?

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• Any tips on getting hired as a software project manager straight out of college?

  - by MHarrison

  I graduated with a BS in compsci last September, and I've been trying (unsuccessfully) to find a job as a project manager ever since. I fell in love with software engineering (the formal practice behind it all, not just coding) in school, and I've dedicated the last 3-4 years of my life to learning everything I can about project management and gaining experience. I've managed several projects (with teams around 12 people) while in school, and I worked with my university's software engineering research lab. My résumé is also decent - I worked as a programmer before I went to school (I'm 27 now), and I did Google Summer of Code for 3 summers. I also have general "people management" experience via working as the photo editor for my university's newspaper for 2 years. My first problem with the job hunt is not getting enough interviews. I use careers.stackoverflow.com, which is awesome because I usually get contacted by non-HR people who know what they're talking about, but there's just not enough companies using it for me to get interviews on a regular basis. I've also tried sites like monster.com, and in a fit of desperation, I sent out no less than 60 applications to project management positions. I've gotten 3 automated rejection letters and that's it. At least careers.stackoverflow gets me a phone interview with 8/10 places I apply to. But the main (and extremely frustrating) problem is the matter of experience. I've successfully managed projects from start to finish (in my software engineering classes we had real customers come in with a real software need and we built it for them), but I've never had to deal with budgets and money (I know this is why HR people immediately turn me away). Most of these positions require 5+ years PM experience, and I've seen absurd things like 12+ years required. Interviews are also maddening. I've had so many places who absolutely loved me and I made it to the final round of interviews, and I left thinking things went extremely well and they'd consider me. However, when I check in with them a week later, they tell me "We really liked you and your qualifications are excellent, but we're hoping to find someone with more experience." The bad interviews I can understand - like the PM position that would have had me managing developers both locally and overseas - I had 3 interviews with them and the ENTIRE interview process was them asking me CS brainteasers and having me waste time on things like writing quicksort on paper or writing binary search trees. Even when I tried steering the discussion towards more relevant PM stuff, they gave me some vague generic replies and went back to the "We want to be Google/MS" crap. But when I have a GOOD interview, they say my "qualifications are excellent" but they want "more experience"...that makes me want to tear my hair out. What else can I DO? While I'm aiming for technically-involved PM positions (not just crunching budget numbers), I really don't want a straight development job because I like creating software from the very high-level vs. spending a lot of time debugging memory leaks. In fact, I can't even GET development positions that I'm qualified for because I make the mistake of telling them that my future career goals are as PM (which usually results in them saying something like "Well we already have PMs and this position isn't really set up to get you there." - which I take to mean "No, that's my job, stay away.") My apologies on the long rant, but I'm seriously hellbent on getting hired as a PM since it's both my career goal and the passion that keeps me awake at night. Any suggestions on what the heck else I can do? I'm currently writing a blog where I talk about my philosophies about software engineering, and I'm writing up specs for an iOS app which I will design, code, and show employers, but this takes an awful lot of time that I don't have.

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• I am not satisfied with my career and accomplished nothing in my life. what should I do now [on hold]

  - by user2906155

  After my complete my College education I got chance to work on software programming. I work on few software and now nothing make me feel good. I don't like web-programming. Can't have too much mind to play with other people in team a designer or a senior. it's totally time wasting for me. We do integration without any source code control. copy through pen drive. I write in too many language for web-programming but know nothing about any language specially. I don't like to have a BOSS. I would like to do something on my own. From last 3 year I thing I will got a better job but I am unable to get it. I am not good at Programming nor my English is native. I have a big list for pay then my salary. I have problem with nothing. my atmosphere is about illiterate people. they abuse 24 hours a day. this thing make me sick. people watch CRIME patrol my home (watching rape in TV because it's happen to someone). I do my work from home. I don't like to live in my state. All state is one of the biggest illiterate state of my country. Once I apply for a Job in China and it's look like I can get thing Job but I don't get it. My family doesn't want me to settle anywhere else. I told my family 4 time a day that I can't live in this worst situation. Everyone (including the person who I work for) tell me that you can do it only you have money. Now I really don't know how to make money. My job not allow me to work for anyone. My productivity going down since I don't learn anything new. I thing if this happen to me for next 2 year I don't have any knowledge more then a peon. I hate it. When I was in other city then I see that if I spent 7 days their all my 7 days going better. even I go for travelling in green places then I like it. but all I hate it where I work for. When I work on other city then I see my productivity are improved and I don't hate my work. I listen a song "If you don't your love what are you doing it for". I seriously don' t know what I still live here because this place gave me nothing but depression and trouble. for people I clear that I don't belong to RICH or middle class family. All I got is doing something on my own or help of someone. affording a rental place make my run on footpath. All I save in one month is just 10$ (approximately) (actually I afford some guys's education now). Can a programmer live worst life like this. I really not happy. Today is a festival in India and I don't celebrate it because I really hate myself. I want to do suicide. someone guide me how to start solving this headache

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• [OffTopic] PhD is it worth it?

  - by Zenzen

  So I'll be graduating next year (hopefully) and lately I started thinking about getting a PhD in computer science (to be more precise I was thinking about something related to "distributed systems", don't have any specific topics yet in mind), but is it really worth it? A PhD course here lasts 4 years and is free IF you're doing the "normal one" (which means you have class from monday to friday) OR you have to pay if you want to study on the weekends. So I've been thinking about getting a normal full time job (as a JEE programmer) and doing my PhD during the weekends OR doing the normal PhD course (mon-fri) and getting a part time job as a software dev (the main reason I want a job is simple - I need to eat). That would give me practical working experience and theoretical knowledge+a PhD, but it would also mean working 7days a week from 9 to 5 for 4 years straight (sounds like an overkill). Is it, job wise, really worth getting a PhD? As an employer do you prefer people with PhDs or MScs? This might be kinda important - I'm not from the US or western europe, how are PhDs from other countries (I am graduating one of the best, if not the best, school in my country but it's still a central european country...) seen? Are they useless? I won't hide it - after graduation I am thinking about moving abroad.

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• Hadoop safemode recovery - taking lot of time

  - by Algorist

  Hi, We are running our cluster on Amazon EC2. we are using cloudera scripts to setup hadoop. On the master node, we start below services. 609 $AS_HADOOP '"$HADOOP_HOME"/bin/hadoop-daemon.sh start namenode' 610 $AS_HADOOP '"$HADOOP_HOME"/bin/hadoop-daemon.sh start secondarynamenode' 611 $AS_HADOOP '"$HADOOP_HOME"/bin/hadoop-daemon.sh start jobtracker' 612 613 $AS_HADOOP '"$HADOOP_HOME"/bin/hadoop dfsadmin -safemode wait' On the slave machine, we run the below services. 625 $AS_HADOOP '"$HADOOP_HOME"/bin/hadoop-daemon.sh start datanode' 626 $AS_HADOOP '"$HADOOP_HOME"/bin/hadoop-daemon.sh start tasktracker' The main problem we are facing is, hdfs safemode recovery is taking more than an hour and this is causing delays in our job completion. Below are the main log messages. 1. domU-12-31-39-0A-34-61.compute-1.internal 10/05/05 20:44:19 INFO ipc.Client: Retrying connect to server: ec2-184-73-64-64.compute-1.amazonaws.com/10.192.11.240:8020. Already tried 21 time(s). 2. The reported blocks 283634 needs additional 322258 blocks to reach the threshold 0.9990 of total blocks 606499. Safe mode will be turned off automatically. The first message is thrown in task trackers log because, job tracker is not started. job tracker didn't start because of hdfs safemode recovery. The second message is thrown during the recovery process. Is there something I am doing wrong? How much time does normal hdfs safemode recovery takes? Will there be any speedup, by not starting task trackers till job tracker is started? Are there any known hadoop problems on amazon cluster? Thanks for your help. Regards Bala Mudiam

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• local variable 'sresult' referenced before assignment

  - by user288558

  I have had multiple problems trying to use PP. I am running python2.6 and pp 1.6.0 rc3. Using the following test code: import pp nodes=('mosura02','mosura03','mosura04','mosura05','mosura06', 'mosura09','mosura10','mosura11','mosura12') def pptester(): js=pp.Server(ppservers=nodes) tmp=[] for i in range(200): tmp.append(js.submit(ppworktest,(),(),('os',))) return tmp def ppworktest(): return os.system("uname -a") gives me the following result: In [10]: Exception in thread run_local: Traceback (most recent call last): File "/usr/lib64/python2.6/threading.py", line 525, in __bootstrap_inner self.run() File "/usr/lib64/python2.6/threading.py", line 477, in run self.__target(*self.__args, **self.__kwargs) File "/home/wkerzend/python_coala/lib/python2.6/site-packages/pp.py", line 751, in _run_local job.finalize(sresult) UnboundLocalError: local variable 'sresult' referenced before assignment Exception in thread run_local: Traceback (most recent call last): File "/usr/lib64/python2.6/threading.py", line 525, in __bootstrap_inner self.run() File "/usr/lib64/python2.6/threading.py", line 477, in run self.__target(*self.__args, **self.__kwargs) File "/home/wkerzend/python_coala/lib/python2.6/site-packages/pp.py", line 751, in _run_local job.finalize(sresult) UnboundLocalError: local variable 'sresult' referenced before assignment Exception in thread run_local: Traceback (most recent call last): File "/usr/lib64/python2.6/threading.py", line 525, in __bootstrap_inner self.run() File "/usr/lib64/python2.6/threading.py", line 477, in run self.__target(*self.__args, **self.__kwargs) File "/home/wkerzend/python_coala/lib/python2.6/site-packages/pp.py", line 751, in _run_local job.finalize(sresult) UnboundLocalError: local variable 'sresult' referenced before assignment Exception in thread run_local: Traceback (most recent call last): File "/usr/lib64/python2.6/threading.py", line 525, in __bootstrap_inner self.run() File "/usr/lib64/python2.6/threading.py", line 477, in run self.__target(*self.__args, **self.__kwargs) File "/home/wkerzend/python_coala/lib/python2.6/site-packages/pp.py", line 751, in _run_local job.finalize(sresult) UnboundLocalError: local variable 'sresult' referenced before assignment any help greatly appreciated

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• using ghostscript in server mode to convert pdfs to pngs

  - by emh

  while i am able to convert a specific page of a PDF to a PNG like so: gs -dSAFER -dBATCH -dNOPAUSE -sDEVICE=png16m -dGraphicsAlphaBits=4 -sOutputFile=gymnastics-20.png -dFirstPage=20 -dLastPage=20 gymnastics.pdf i am wondering if i can somehow use ghostscript's JOBSERVER mode to process several conversions without having to incur the cost of starting up ghostscript each time. from: http://pages.cs.wisc.edu/~ghost/doc/svn/Use.htm -dJOBSERVER Define \004 (^D) to start a new encapsulated job used for compatibility with Adobe PS Interpreters that ordinarily run under a job server. The -dNOOUTERSAVE switch is ignored if -dJOBSERVER is specified since job servers always execute the input PostScript under a save level, although the exitserver operator can be used to escape from the encapsulated job and execute as if the -dNOOUTERSAVE was specified. This also requires that the input be from stdin, otherwise an error will result (Error: /invalidrestore in --restore--). Example usage is: gs ... -dJOBSERVER - < inputfile.ps -or- cat inputfile.ps | gs ... -dJOBSERVER - Note: The ^D does not result in an end-of-file action on stdin as it may on some PostScript printers that rely on TBCP (Tagged Binary Communication Protocol) to cause an out-of-band ^D to signal EOF in a stream input data. This means that direct file actions on stdin such as flushfile and closefile will affect processing of data beyond the ^D in the stream. the idea is to run ghostscript in-process. the script would receive a request for a particular page of a pdf and would use ghostscript to generate the specified image. i'd rather not start up a new ghostscript process every time.

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• SQL Agent Logon - What is going on?

  - by James Wiseman

  I have a DTSX package that is called from a SQL Agent Job. The DTSX package references a file at a fixed location (e.g. e:\mssql\myfile.txt). On most machines, this location exists, but on some I have to manually map this (which is not a problem - I know a better solution would be to use package conifgurations to dynamically pull the file location, but this is not an option here - and anyway I'd like to understand what is going on) I have set up the agent service to run as a specific user (e.g. myuser) When I log on as this user and map the directory, then run the dtsx package directly, then all goes well. When I run the package through a SQL Agent Job, the file cannot be found. If I add a command line job step to the agent job to map the drive: net use e: \\svr\location Then all works file also. So what is going on in the backgound? How come the SQL Agent user requries the drive mapping even when I am logged in as this user.

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• Bypassing confirmation prompt of an external process

  - by Alidad

  How can I convert this Perl code to Groovy? How to bypass confirmation prompts of an external process? I am trying to convert a Perl script to Groovy. The program is loading/delete maestro (job scheduling) jobs automatically. The problem is the delete command will prompt for confirmation (Y/N) on every single job that it finds. I tried the process execute in groovy but will stop at the prompts. The Perl script is writing bunch of Ys to the stream and print it to the handler( if I understood it correctly) to avoid stopping. I am wondering how to do the same thing in Groovy ? Or any other approach to execute a command and somehow write Y on every confirmation prompt. Perl Script: $maestrostring=""; while ($x < 1500) { $maestrostring .= "y\n"; $x++; } # delete the jobs open(MAESTRO_CMD, "|ssh mserver /bin/composer delete job=pserver#APPA@") print MAESTRO_CMD $maestrostring; close(MAESTRO_CMD); This is my groovy code so far: def deleteMaestroJobs (){ ... def commandSched ="ssh $maestro_server /bin/composer delete sched=$primary_server#$app_acronym$app_level@" def commandJobs ="ssh $maestro_server /bin/composer delete job=$primary_server#$app_acronym$app_level@" try { executeCommand commandJobs } catch (Exception ex ){ throw new Exception("Error executing the Maestro Composer [DELETE]") } try { executeCommand commandSched } catch (Exception ex ){ throw new Exception("Error executing the Maestro Composer [DELETE]") } } def executeCommand(command){ def process = command.execute() process.withWriter { writer -> 1500.times {writer.println 'Y' } } process.consumeProcessOutput(System.out, System.err) process.waitFor() }

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• How can I get a distinct list of elements in a hierarchical query?

  - by RenderIn

  I have a database table, with people identified by a name, a job and a city. I have a second table that contains a hierarchical representation of every job in the company in every city. Suppose I have 3 people in the people table: [name(PK),title,city] Jim, Salesman, Houston Jane, Associate Marketer, Chicago Bill, Cashier, New York And I have thousands of job type/location combinations in the job table, a sample of which follow. You can see the hierarchical relationship since parent_title is a foreign key to title: [title,city,pay,parent_title] Salesman, Houston, $50000, CEO Cashier, Houston, $25000 CEO, USA, $1000000 Associate Marketer, Chicago, $75000 Senior Marketer, Chicago, $125000 ..... The problem I'm having is that my Person table is a composite key, so I don't know how to structure the start with part of my query so that it starts with each of the three jobs in the cities I specified. I can execute three separate queries to get what I want, but this doesn't scale well. e.g.: select * from jobs start with city = (select city from people where name = 'Bill') and title = (select title from people where name = 'Bill') connect by prior parent_title = title UNION select * from jobs start with city = (select city from people where name = 'Jim') and title = (select title from people where name = 'Jim') connect by prior parent_title = title UNION select * from jobs start with city = (select city from people where name = 'Jane') and title = (select title from people where name = 'Jane') connect by prior parent_title = title How else can I get a distinct list (or I could wrap it with a distinct if not possible) of all the jobs which are above the three people I specified?

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• Minimum privileges to read SQL Jobs using SQL SMO

  - by Gustavo Cavalcanti

  I wrote an application to use SQL SMO to find all SQL Servers, databases, jobs and job outcomes. This application is executed through a scheduled task using a local service account. This service account is local to the application server only and is not present in any SQL Server to be inspected. I am having problems getting information on job and job outcomes when connecting to the servers using a user with dbReader rights on system tables. If we set the user to be sysadmin on the server it all works fine. My question to you is: What are the minimum privileges a local SQL Server user needs to have in order to connect to the server and inspect jobs/job outcomes using the SQL SMO API? I connect to each SQL Server by doing the following: var conn = new ServerConnection { LoginSecure = false, ApplicationName = "SQL Inspector", ServerInstance = serverInstanceName, ConnectAsUser = false, Login = user, Password = password }; var smoServer = new Server (conn); I read the jobs by reading smoServer.JobServer.Jobs and read the JobSteps property on each of these jobs. The variable server is of type Microsoft.SqlServer.Management.Smo.Server. user/password are of the user found in each SQL Server to be inspected. If "user" is SysAdmin on the SQL Server to be inspected all works ok, as well as if we set ConnectAsUser to true and execute the scheduled task using my own credentials, which grants me SysAdmin privileges on SQL Server per my Active Directory membership. Thanks!

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• SQL Query with multiple values in one column

  - by lp1

  I've been beating my head on the desk tring to figure this one out. I have a table that stores job information, and reasons for a job not being completed. The reasons are numeric,01,02,03,etc. You can have two reason for a pending job. If you select two reasons, they are stored in the same column, seperated by a comma. This is anExample from the JOBID table: Job_Number User_Assigned PendingInfo 1 user1 01,02 Now, there is another table named Pending, that stores what those values actually represent. 01=Not enough info, 02=Not enough time, 03=Waiting Review. Example: Pending_Num PendingWord 01 Not Enough Info 02 Not Enough Time What I'm trying to do is query the database to give me all the job numbers, users, pendinginfo, and pending reason. I can break out the first value, but can't figure out how to do the second. What my limited skills have so far: *select Job_number,user_assigned,SUBSTRING(pendinginfo,0,3),pendingword from jobid,pending where SUBSTRING(pendinginfo,0,3)=pending.pending_num and pendinginfo!='00,00' and pendinginfo!='NULL'* What I would like to see for this example would be: Job_Number User_Assigned PendingInfo PendingWord PendingInfo PendingWord 1 User1 01 Not Enough Info 02 Not Enough Time Thanks in advance

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• Should I write more SQL to be more efficient, or less SQL to be less buggy?

  - by RenderIn

  I've been writing a lot of one-off SQL queries to return exactly what a certain page needs and no more. I could reuse existing queries and issue a number of SQL requests linear to the number of records on the page. As an example, I have a query to return People and a query to return Job Details for a person. To return a list of people with their job details I could query once for people and then once for each person to retrieve their job details. I've found that in most cases that solution returns things in a reasonable amount of time, but I don't know how well it will scale in my environment. Instead I've been writing queries to join people + job details, or people + salary history, etc. I'm looking at my models and I see how I could shave off maybe 30% of my code if I were to re-use existing queries. This is a big temptation. Is it a bad thing to go for reuse over efficiency in general or does it all come down to the specific situation? Should I first do it the easy way and then optimize later, or is it best to get the code knocked out while everything is fresh in my mind? Thoughts, experiences?

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• activemessaging with stomp and activemq.prefetchSize=1

  - by Clint Miller

  I have a situation where I have a single activemq broker with 2 queues, Q1 and Q2. I have two ruby-based consumers using activemessaging. Let's call them C1 and C2. Both consumers subscribe to each queue. I'm setting activemq.prefetchSize=1 when subscribing to each queue. I'm also setting ack=client. Consider the following sequence of events: 1) A message that triggers a long-running job is published to queue Q1. Call this M1. 2) M1 is dispatched to consumer C1, kicking off a long operation. 3) Two messages that trigger short jobs are published to queue Q2. Call these M2 and M3. 4) M2 is dispatched to C2 which quickly runs the short job. 5) M3 is dispatched to C1, even though C1 is still running M1. It's able to dispatch to C1 because prefetchSize=1 is set on the queue subscription, not on the connection. So the fact that a Q1 message has already been dispatched doesn't stop one Q2 message from being dispatched. Since activemessaging consumers are single-threaded, the net result is that M3 sits and waits on C1 for a long time until C1 finishes processing M1. So, M3 is not processed for a long time, despite the fact that consumer C2 is sitting idle (since it quickly finishes with message M2). Essentially, whenever a long Q1 job is run and then a whole bunch of short Q2 jobs are created, exactly one of the short Q2 jobs gets stuck on a consumer waiting for the long Q1 job to finish. Is there a way to set prefetchSize at the connection level rather than at the subscription level? I really don't want any messages dispatched to C1 while it is processing M1. The other alternative is that I could create a consumer dedicated to processing Q1 and then have other consumers dedicated to processing Q2. But, I'd rather not do that since Q1 messages are infrequent--Q1's dedicated consumers would sit idle most of the day tying up memory.

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• How can I "pack()" a printable Java Swing component?

  - by Jonas

  I have implemented a Java Swing component that implements Printable. If I add the component to a JFrame, and do this.pack(); on the JFrame, it prints perfect. But if I don't add the component to a JFrame, just a blank page is printed. This code gives a great printout: final PrintablePanel p = new PrintablePanel(pageFormat); new JFrame() {{ getContentPane().add(p); this.pack(); }}; job.setPrintable(p, pageFormat); try { job.print(); } catch (PrinterException ex) { System.out.println("Fail"); } But this code gives a blank page: final PrintablePanel p = new PrintablePanel(pageFormat); // new JFrame() {{ getContentPane().add(p); this.pack(); }}; job.setPrintable(p, pageFormat); try { job.print(); } catch (PrinterException ex) { System.out.println("Fail"); } I think that this.pack(); is the big difference. How can I do pack() on my printable component so it prints fine, without adding it to a JFrame? The panel is using several LayoutManagers. I have tried with p.validate(); and p.revalidate(); but it's not working. Any suggestions? Or do I have to add it to a hidden JFrame before I print the component?

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• How to change the date/time in Python for all modules?

  - by Felix Schwarz

  When I write with business logic, my code often depends on the current time. For example the algorithm which looks at each unfinished order and checks if an invoice should be sent (which depends on the no of days since the job was ended). In these cases creating an invoice is not triggered by an explicit user action but by a background job. Now this creates a problem for me when it comes to testing: I can test invoice creation itself easily However it is hard to create an order in a test and check that the background job identifies the correct orders at the correct time. So far I found two solutions: In the test setup, calculate the job dates relative to the current date. Downside: The code becomes quite complicated as there are no explicit dates written anymore. Sometimes the business logic is pretty complex for edge cases so it becomes hard to debug due to all these relative dates. I have my own date/time accessor functions which I use throughout my code. In the test I just set a current date and all modules get this date. So I can simulate an order creation in February and check that the invoice is created in April easily. Downside: 3rd party modules do not use this mechanism so it's really hard to integrate+test these. The second approach was way more successful to me after all. Therefore I'm looking for a way to set the time Python's datetime+time modules return. Setting the date is usually enough, I don't need to set the current hour or second (even though this would be nice). Is there such a utility? Is there an (internal) Python API that I can use?

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• How do you work on Strategic Development initiatives when Tactical work takes priority?

  - by Shaun F

  My day-to-day job consists of maintaining large volume websites and this has given me exposure to developing better methods to develop and maintain the code. This has also given me a large body of knowledge in the code base in terms of troubleshooting that is beneficial to the company. I'm also the maintainer of an IDE plug in I created to help navigate and generate code that is used. Operationally though, my job is to handle any client requests that come in of that are emergencies and make any enhancements and additions to the code base required. This work, along with the daily managing and feeding of the the project managers will take up my entire day. How does one manage the time between the tactical day job and the strategic initiatives? How does one get and ask for recognition for taking strategic initiatives? Is the 8-9 hour day just not going to cut it? Is there even a job out there for programmers to develop strategic initiatives and solutions for a company? I want to also point out that this isn't a problem with the company at all. I think this is more of a personal-improvement decision. Nobody will say no to the improvements at all. I believe in making the things happen but I don't think I'm going to get time from the company to do it...

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• wpf progress bar slows 10x times serial port communications... how could be possible that?

  - by D_Guidi

  I know that this could look a dumb question, but here's my problem. I have a worker dialog that "hides" a backgroundworker, so in a worker thread I do my job, I report the progress in a standard way and then I show the results in my WPF program. The dialog contains a simply animated gif and a standard wpf progress bar, and when a progress is notified I set Value property. All lokks as usual and works well for any kind of job, like web service calls, db queries, background elaboration and so on. For my job we use also many "couplers", card readers that reads data from smart card, that are managed with native C code that access to serial port (so, I don't use .NET SerialPort object). I have some nunit tests and I read a sample card in 10 seconds, but using my actual program, under the backgroundworker and showing my worker dialog, I need 1.30 minutes to do the SAME job. I struggled into problem for days until I decide to remove the worker dialog, and without dialog I obtain the same performances of the tests! So I investigated, and It's not the dialog, not the animated gif, but the wpf progress bar! Simply the fact that a progress bar is shown (so, no animation, no Value set called, nothing of nothing) slows serialport communicatitons. Looks incredible? I've tested this behavior and it's exactly what happens.

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• What choices do I have for a future in software development?

  - by user354892

  After graduating from college with a degree in mathematics and a minor in computer science, I took over a year to find my first programming job. I very much enjoy my work environment, but sometimes I feel like I'm not developing professionally as quickly as I am capable of. My company does mostly web programming. The project that I work on is basically a front-end for a SQL database. The entire project is (AFAIK) coded is VB.NET. I've been working on the back-end logic of the program. After some time on the job, we decided that designing web pages is not my cup of tea. It seems like the thing that I spend more time on than anything else is searching the web and SO for information about poorly documented .net and web APIs. This does not make me happy; is this normal for a programming job; I don't think it is. It really hit me the other day when i saw a question about math asked here and I didn't know the answer; I feel like my knowledge is going stale! I was previously almost hired by another company where they design graphic-intensive battle simulations for the military. I sometimes wonder what my life might be like if I had that job. I feel like my math and problem solving skills might have been a better fit at this other company. Within the wide field of software development, there are a number of directions in which to go as evidenced by the huge variety of topics discussed here on StackOverflow. I would like to feel like I'm going in the direction where I will make the most of my skills and have a satisfying career. Let me word this question as clearly as possible: given the wide breadth of the field of software development, how does it break down into sub-fields and what are the considerations for developing a software development career. I do not want to manage my career by default.

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• What are your suggestions for best practises for regular data updates in a website database?

  - by bboyle1234

  My shared-hosting asp.net website must automatically run data update routines at regular times of day. Once it has finished running certain update routines, it can run update routines that are dependent on the previous updates. I have done this type of work before, using quite complicated setups. Some features of the framework I created are: A cron job from another server makes a request which starts a data update routine on the main server Each updater is loaded from web.config Each updater overrides a "canRunUpdate" method that determines whether its dependencies have finished updating Each updater overrides a "hasFinishedUpdate" method Each updater overrides a "runUpdate" method Updaters start and run in parallel threads The initial request from the cron job server started each updater in its own thread and then ended. As a result, the threads containing the updaters would be terminated before the updaters were finished. Therefore I had to give the updaters the ability to save partial results and continue the update job next time they are started up. As a result, the cron server had to call the updater many times to ensure the job is done. Sometimes the cron server would continue making update requests long after all the updates were completed. Sometimes the cron server would finish calling the update requests and leave some updates uncompleted. It's not the best system. I'm looking for inspiration. Any ideas please? Thank you :)

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• Career development as a Software Developer without becoming a manager.

  - by albertpascual

  I’m a developer, I like to write new exciting code everyday, my perfect day at work is a day that when I wake up, I know that I have to write some code that I haven’t done before or to use a new framework/language/platform that is unknown to me. The best days in the office is when a project is waiting for me to architect or write. In my 15 years in the development field, I had to in order to get a better salary to manage people, not just to lead developers, to actually manage people. Something that I found out when I get into a management position is that I’m not that good at managing people, and not afraid to say it. I do not enjoy that part of the job, the worse one, takes time away from what I really like. Leading developers and managing people are very different things. I do like teaching and leading developers in a project. Yet most people believe, and is true in most companies, the way to get a better salary is to be promoted to a manager position. In order to advance in your career you need to let go of the everyday writing code and become a supervisor or manager. This is the path for developers after they become senior developers. As you get older and your family grows, the only way to hit your salary requirements is to advance your career to become a manager and get that manager salary. That path is the common in most companies, the most intelligent companies out there, have learned that promoting good developers mean getting a crappy manager and losing a good resource. Now scratch everything I said, because as I previously stated, I don’t see myself going to the office everyday and just managing people until is time to go home. I like to spend hours working in some code to accomplish a task, learning new platforms and languages or patterns to existing languages. Being interrupted every 15 minutes by emails or people stopping by my office to resolve their problems, is not something I could enjoy. All the sudden riding my motorcycle to work one cold morning over the Redlands Canyon and listening to .NET Rocks podcast, Michael “Doc” Norton explaining how to take control of your development career without necessary going to the manager’s track. I know, I should not have headphones under my helmet when riding a motorcycle in California. His conversation with Carl Franklin and Richard Campbell was just confirming everything I have ever did with actually more details and assuring that there are other paths. His method was simple yet most of us, already do many of those steps, Mr. Michael “Doc” Norton believe that it pays off on the long run, that finally companies prefer to pay higher salaries to those developers, yet I would actually think that many companies do not see developers that way, this is not true for bigger companies. However I do believe the value of those developers increase and most of the time, changing companies could increase their salary instead of staying in the same one. In short without even trying to get into the shadow of Mr. Norton and without following the steps in the order; you should love to learn new technologies, and then teach them to other geeks. I personally have learn many technologies and I haven’t stop doing that, I am a professor at UCR where I teach ASP.NET and Silverlight. Mr Norton continues that after than, you want to be involve in the development community, user groups, online forums, open source projects. I personally talk to user groups, I’m very active in forums asking and answering questions as well as for those I got awarded the Microsoft MVP for ASP.NET. After you accomplish all those, you should also expose yourself for what you know and what you do not know, learning a new language will make you humble again as well as extremely happy. There is no better feeling that learning a new language or pattern in your daily job. If you love your job everyday and what you do, I really recommend you to follow Michael’s presentation that he kindly share it on the link below. His confirmation is a refreshing, knowing that my future is not behind a desk where the computer screen is on my right hand side instead of in front of me. Where I don’t have to spent the days filling up performance forms for people and the new platforms that I haven’t been using yet are just at my fingertips. Presentation here. http://www.slideshare.net/LeanDog/take-control-of-your-development-career-michael-doc-norton?from=share_email_logout3 Take Control of Your Development Career Welcome! Michael “Doc” Norton @DocOnDev http://docondev.blogspot.com/ [email protected] Recovering Post Technical I love to learn I love to teach I love to work in teams I love to write code I really love to write code What about YOU? Do you love your job? Do you love your Employer? Do you love your Boss? What do you love? What do you really love? Take Control Take Control • Get Noticed • Get Together • Get Your Mojo • Get Naked • Get Schooled Get Noticed Get Noticed Know Your Business Get Noticed Get Noticed Understand Management Get Noticed Get Noticed Do Your Existing Job Get Noticed Get Noticed Make Yourself Expendable Get Together Get Together Join a User Group Get Together Help Run a User Group Get Together Start a User Group Get Your Mojo Get Your Mojo Kata Get Your Mojo Koans Get Your Mojo Breakable Toys Get Your Mojo Open Source Get Naked Get Naked Run with Group A Get Naked Do Something Different Get Naked Own Your Mistakes Get Naked Admit You Don’t Know Get Schooled Get Schooled Choose a Mentor Get Schooled Attend Conferences Get Schooled Teach a New Subject Get Started Read These (Again) Take Control of Your Development Career Thank You! Michael “Doc” Norton @DocOnDev http://docondev.blogspot.com/ [email protected] In a short summary, I recommend any developer to check his blog and more important his presentation, I haven’t been lucky enough to watch him live, I’m looking forward the day I have the opportunity. He is giving us hope in the future of developers, when I see some of my geek friends moving to position that in short years they begin to regret, I get more unsure of my future doing what I love. I would say that now is looking at the spectrum of companies that understand and appreciate developers. There are a few there, hopefully with time code sweat shops will start disappearing and being a developer will feed a family of 4. Cheers Al tweetmeme_url = 'http://weblogs.asp.net/albertpascual/archive/2010/12/07/career-development-as-a-software-developer-without-becoming-a-manager.aspx'; tweetmeme_source = 'alpascual';

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• Oracle Enterprise Manager Ops Center : Using Operational Profiles to Install Packages and other Content

  - by LeonShaner

  Oracle Enterprise Manager Ops Center provides numerous ways to deploy content, such as through OS Update Profiles, or as part of an OS Provisioning plan or combinations of those and other "Install Software" capabilities of Deployment Plans.  This short "how-to" blog will highlight an alternative way to deploy content using Operational Profiles. Usually we think of Operational Profiles as a way to execute a simple "one-time" script to perform a basic system administration function, which can optionally be based on user input; however, Operational Profiles can be much more powerful than that.  There is often more to performing an action than merely running a script -- sometimes configuration files, packages, binaries, and other scripts, etc. are needed to perform the action, and sometimes the user would like to leave such content on the system for later use. For shell scripts and other content written to be generic enough to work on any flavor of UNIX, converting the same scripts and configuration files into Solaris 10 SVR4 package, Solaris 11 IPS package, and/or a Linux RPM's might be seen as three times the work, for little appreciable gain.   That is where using an Operational Profile to deploy simple scripts and other generic content can be very helpful.  The approach is so powerful, that pretty much any kind of content can be deployed using an Operational Profile, provided the files involved are not overly large, and it is not necessary to convert the content into UNIX variant-specific formats. The basic formula for deploying content with an Operational Profile is as follows: Begin with a traditional script header, which is a UNIX shell script that will be responsible for decoding and extracting content, copying files into the right places, and executing any other scripts and commands needed to install and configure that content. Include steps to make the script platform-aware, to do the right thing for a given UNIX variant, or a "sorry" message if the operator has somehow tried to run the Operational Profile on a system where the script is not designed to run.  Ops Center can constrain execution by target type, so such checks at this level are an added safeguard, but also useful with the generic target type of "Operating System" where the admin wants the script to "do the right thing," whatever the UNIX variant. Include helpful output to show script progress, and any other informational messages that can help the admin determine what has gone wrong in the case of a problem in script execution.  Such messages will be shown in the job execution log. Include necessary "clean up" steps for normal and error exit conditions Set non-zero exit codes when appropriate -- a non-zero exit code will cause an Operational Profile job to be marked failed, which is the admin's cue to look into the job details for diagnostic messages in the output from the script. That first bullet deserves some explanation.  If Operational Profiles are usually simple "one-time" scripts and binary content is not allowed, then how does the actual content, packages, binaries, and other scripts get delivered along with the script?  More specifically, how does one include such content without needing to first create some kind of traditional package?   All that is required is to simply encode the content and append it to the end of the Operational Profile.  The header portion of the Operational Profile will need to contain the commands to decode the embedded content that has been appended to the bottom of the script.  The header code can do whatever else is needed, and finally clean up any intermediate files that were created during the decoding and extraction of the content. One way to encode binary and other content for inclusion in a script is to use the "uuencode" utility to convert the content into simple base64 ASCII text -- a form that is suitable to be appended to an Operational Profile.   The behavior of the "uudecode" utility is such that it will skip over any parts of the input that do not fit the uuencoded "begin" and "end" clauses.  For that reason, your header script will be skipped over, and uudecode will find your embedded content, that you will uuencode and paste at the end of the Operational Profile.  You can have as many "begin" / "end" clauses as you need -- just separate each embedded file by an empty line between "begin" and "end" clauses. Example:  Install SUNWsneep and set the system serial number Script:  deploySUNWsneep.sh ( <- right-click / save to download) Highlights: #!/bin/sh # Required variables: OC_SERIAL="$OC_SERIAL" # The user-supplied serial number for the asset ... Above is a good practice, showing right up front what kind of input the Operational Profile will require.   The right-hand side where $OC_SERIAL appears in this example will be filled in by Ops Center based on the user input at deployment time. The script goes on to restrict the use of the program to the intended OS type (Solaris 10 or older, in this example, but other content might be suitable for Solaris 11, or Linux -- it depends on the content and the script that will handle it). A temporary working directory is created, and then we have the command that decodes the embedded content from "self" which in scripting terms is $0 (a variable that expands to the name of the currently executing script): # Pass myself through uudecode, which will extract content to the current dir uudecode $0 At that point, whatever content was appended in uuencoded form at the end of the script has been written out to the current directory.  In this example that yields a file, SUNWsneep.7.0.zip, which the rest of the script proceeds to unzip, and pkgadd, followed by running "/opt/SUNWsneep/bin/sneep -s $OC_SERIAL" which is the command that stores the system serial for future use by other programs such as Explorer.   Don't get hung up on the example having used a pkgadd command.  The content started as a zip file and it could have been a tar.gz, or any other file.  This approach simply decodes the file.  The header portion of the script has to make sense of the file and do the right thing (e.g. it's up to you). The script goes on to clean up after itself, whether or not the above was successful.  Errors are echo'd by the script and a non-zero exit code is set where appropriate. Second to last, we have: # just in case, exit explicitly, so that uuencoded content will not cause error OPCleanUP exit # The rest of the script is ignored, except by uudecode # # UUencoded content follows # # e.g. for each file needed, #  $ uuencode -m {source} {source} > {target}.uu5 # then paste the {target}.uu5 files below # they will be extracted into the workding dir at $TDIR # The commentary above also describes how to encode the content. Finally we have the uuencoded content: begin-base64 444 SUNWsneep.7.0.zip UEsDBBQAAAAIAPsRy0Di3vnukAAAAMcAAAAKABUAcmVhZG1lLnR4dFVUCQADOqnVT7up ... VXgAAFBLBQYAAAAAAgACAJEAAADTNwEAAAA= ==== That last line of "====" is the base64 uuencode equivalent of a blank line, followed by "end" and as mentioned you can have as many begin/end clauses as you need.  Just separate each embedded file by a blank line after each ==== and before each begin-base64. Deploying the example Operational Profile looks like this (where I have pasted the system serial number into the required field): The job succeeded, but here is an example of the kind of diagnostic messages that the example script produces, and how Ops Center displays them in the job details: This same general approach could be used to deploy Explorer, and other useful utilities and scripts. Please let us know what you think?  Until next time...\Leon-- Leon Shaner | Senior IT/Product ArchitectSystems Management | Ops Center Engineering @ Oracle The views expressed on this [blog; Web site] are my own and do not necessarily reflect the views of Oracle. For more information, please go to Oracle Enterprise Manager  web page or  follow us at :  Twitter | Facebook | YouTube | Linkedin | Newsletter

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• Inheritance Mapping Strategies with Entity Framework Code First CTP5: Part 3 – Table per Concrete Type (TPC) and Choosing Strategy Guidelines

  - by mortezam

  This is the third (and last) post in a series that explains different approaches to map an inheritance hierarchy with EF Code First. I've described these strategies in previous posts: Part 1 – Table per Hierarchy (TPH) Part 2 – Table per Type (TPT)In today’s blog post I am going to discuss Table per Concrete Type (TPC) which completes the inheritance mapping strategies supported by EF Code First. At the end of this post I will provide some guidelines to choose an inheritance strategy mainly based on what we've learned in this series. TPC and Entity Framework in the Past Table per Concrete type is somehow the simplest approach suggested, yet using TPC with EF is one of those concepts that has not been covered very well so far and I've seen in some resources that it was even discouraged. The reason for that is just because Entity Data Model Designer in VS2010 doesn't support TPC (even though the EF runtime does). That basically means if you are following EF's Database-First or Model-First approaches then configuring TPC requires manually writing XML in the EDMX file which is not considered to be a fun practice. Well, no more. You'll see that with Code First, creating TPC is perfectly possible with fluent API just like other strategies and you don't need to avoid TPC due to the lack of designer support as you would probably do in other EF approaches. Table per Concrete Type (TPC)In Table per Concrete type (aka Table per Concrete class) we use exactly one table for each (nonabstract) class. All properties of a class, including inherited properties, can be mapped to columns of this table, as shown in the following figure: As you can see, the SQL schema is not aware of the inheritance; effectively, we’ve mapped two unrelated tables to a more expressive class structure. If the base class was concrete, then an additional table would be needed to hold instances of that class. I have to emphasize that there is no relationship between the database tables, except for the fact that they share some similar columns. TPC Implementation in Code First Just like the TPT implementation, we need to specify a separate table for each of the subclasses. We also need to tell Code First that we want all of the inherited properties to be mapped as part of this table. In CTP5, there is a new helper method on EntityMappingConfiguration class called MapInheritedProperties that exactly does this for us. Here is the complete object model as well as the fluent API to create a TPC mapping: public abstract class BillingDetail {     public int BillingDetailId { get; set; }     public string Owner { get; set; }     public string Number { get; set; } }          public class BankAccount : BillingDetail {     public string BankName { get; set; }     public string Swift { get; set; } }          public class CreditCard : BillingDetail {     public int CardType { get; set; }     public string ExpiryMonth { get; set; }     public string ExpiryYear { get; set; } }      public class InheritanceMappingContext : DbContext {     public DbSet<BillingDetail> BillingDetails { get; set; }              protected override void OnModelCreating(ModelBuilder modelBuilder)     {         modelBuilder.Entity<BankAccount>().Map(m =>         {             m.MapInheritedProperties();             m.ToTable("BankAccounts");         });         modelBuilder.Entity<CreditCard>().Map(m =>         {             m.MapInheritedProperties();             m.ToTable("CreditCards");         });                 } } The Importance of EntityMappingConfiguration ClassAs a side note, it worth mentioning that EntityMappingConfiguration class turns out to be a key type for inheritance mapping in Code First. Here is an snapshot of this class: namespace System.Data.Entity.ModelConfiguration.Configuration.Mapping {     public class EntityMappingConfiguration<TEntityType> where TEntityType : class     {         public ValueConditionConfiguration Requires(string discriminator);         public void ToTable(string tableName);         public void MapInheritedProperties();     } } As you have seen so far, we used its Requires method to customize TPH. We also used its ToTable method to create a TPT and now we are using its MapInheritedProperties along with ToTable method to create our TPC mapping. TPC Configuration is Not Done Yet!We are not quite done with our TPC configuration and there is more into this story even though the fluent API we saw perfectly created a TPC mapping for us in the database. To see why, let's start working with our object model. For example, the following code creates two new objects of BankAccount and CreditCard types and tries to add them to the database: using (var context = new InheritanceMappingContext()) {     BankAccount bankAccount = new BankAccount();     CreditCard creditCard = new CreditCard() { CardType = 1 };                      context.BillingDetails.Add(bankAccount);     context.BillingDetails.Add(creditCard);     context.SaveChanges(); } Running this code throws an InvalidOperationException with this message: The changes to the database were committed successfully, but an error occurred while updating the object context. The ObjectContext might be in an inconsistent state. Inner exception message: AcceptChanges cannot continue because the object's key values conflict with another object in the ObjectStateManager. Make sure that the key values are unique before calling AcceptChanges. The reason we got this exception is because DbContext.SaveChanges() internally invokes SaveChanges method of its internal ObjectContext. ObjectContext's SaveChanges method on its turn by default calls AcceptAllChanges after it has performed the database modifications. AcceptAllChanges method merely iterates over all entries in ObjectStateManager and invokes AcceptChanges on each of them. Since the entities are in Added state, AcceptChanges method replaces their temporary EntityKey with a regular EntityKey based on the primary key values (i.e. BillingDetailId) that come back from the database and that's where the problem occurs since both the entities have been assigned the same value for their primary key by the database (i.e. on both BillingDetailId = 1) and the problem is that ObjectStateManager cannot track objects of the same type (i.e. BillingDetail) with the same EntityKey value hence it throws. If you take a closer look at the TPC's SQL schema above, you'll see why the database generated the same values for the primary keys: the BillingDetailId column in both BankAccounts and CreditCards table has been marked as identity. How to Solve The Identity Problem in TPC As you saw, using SQL Server’s int identity columns doesn't work very well together with TPC since there will be duplicate entity keys when inserting in subclasses tables with all having the same identity seed. Therefore, to solve this, either a spread seed (where each table has its own initial seed value) will be needed, or a mechanism other than SQL Server’s int identity should be used. Some other RDBMSes have other mechanisms allowing a sequence (identity) to be shared by multiple tables, and something similar can be achieved with GUID keys in SQL Server. While using GUID keys, or int identity keys with different starting seeds will solve the problem but yet another solution would be to completely switch off identity on the primary key property. As a result, we need to take the responsibility of providing unique keys when inserting records to the database. We will go with this solution since it works regardless of which database engine is used. Switching Off Identity in Code First We can switch off identity simply by placing DatabaseGenerated attribute on the primary key property and pass DatabaseGenerationOption.None to its constructor. DatabaseGenerated attribute is a new data annotation which has been added to System.ComponentModel.DataAnnotations namespace in CTP5: public abstract class BillingDetail {     [DatabaseGenerated(DatabaseGenerationOption.None)]     public int BillingDetailId { get; set; }     public string Owner { get; set; }     public string Number { get; set; } } As always, we can achieve the same result by using fluent API, if you prefer that: modelBuilder.Entity<BillingDetail>()             .Property(p => p.BillingDetailId)             .HasDatabaseGenerationOption(DatabaseGenerationOption.None); Working With The Object Model Our TPC mapping is ready and we can try adding new records to the database. But, like I said, now we need to take care of providing unique keys when creating new objects: using (var context = new InheritanceMappingContext()) {     BankAccount bankAccount = new BankAccount()      {          BillingDetailId = 1                          };     CreditCard creditCard = new CreditCard()      {          BillingDetailId = 2,         CardType = 1     };                      context.BillingDetails.Add(bankAccount);     context.BillingDetails.Add(creditCard);     context.SaveChanges(); } Polymorphic Associations with TPC is Problematic The main problem with this approach is that it doesn’t support Polymorphic Associations very well. After all, in the database, associations are represented as foreign key relationships and in TPC, the subclasses are all mapped to different tables so a polymorphic association to their base class (abstract BillingDetail in our example) cannot be represented as a simple foreign key relationship. For example, consider the the domain model we introduced here where User has a polymorphic association with BillingDetail. This would be problematic in our TPC Schema, because if User has a many-to-one relationship with BillingDetail, the Users table would need a single foreign key column, which would have to refer both concrete subclass tables. This isn’t possible with regular foreign key constraints. Schema Evolution with TPC is Complex A further conceptual problem with this mapping strategy is that several different columns, of different tables, share exactly the same semantics. This makes schema evolution more complex. For example, a change to a base class property results in changes to multiple columns. It also makes it much more difficult to implement database integrity constraints that apply to all subclasses. Generated SQLLet's examine SQL output for polymorphic queries in TPC mapping. For example, consider this polymorphic query for all BillingDetails and the resulting SQL statements that being executed in the database: var query = from b in context.BillingDetails select b; Just like the SQL query generated by TPT mapping, the CASE statements that you see in the beginning of the query is merely to ensure columns that are irrelevant for a particular row have NULL values in the returning flattened table. (e.g. BankName for a row that represents a CreditCard type). TPC's SQL Queries are Union Based As you can see in the above screenshot, the first SELECT uses a FROM-clause subquery (which is selected with a red rectangle) to retrieve all instances of BillingDetails from all concrete class tables. The tables are combined with a UNION operator, and a literal (in this case, 0 and 1) is inserted into the intermediate result; (look at the lines highlighted in yellow.) EF reads this to instantiate the correct class given the data from a particular row. A union requires that the queries that are combined, project over the same columns; hence, EF has to pad and fill up nonexistent columns with NULL. This query will really perform well since here we can let the database optimizer find the best execution plan to combine rows from several tables. There is also no Joins involved so it has a better performance than the SQL queries generated by TPT where a Join is required between the base and subclasses tables. Choosing Strategy GuidelinesBefore we get into this discussion, I want to emphasize that there is no one single "best strategy fits all scenarios" exists. As you saw, each of the approaches have their own advantages and drawbacks. Here are some rules of thumb to identify the best strategy in a particular scenario: If you don’t require polymorphic associations or queries, lean toward TPC—in other words, if you never or rarely query for BillingDetails and you have no class that has an association to BillingDetail base class. I recommend TPC (only) for the top level of your class hierarchy, where polymorphism isn’t usually required, and when modification of the base class in the future is unlikely. If you do require polymorphic associations or queries, and subclasses declare relatively few properties (particularly if the main difference between subclasses is in their behavior), lean toward TPH. Your goal is to minimize the number of nullable columns and to convince yourself (and your DBA) that a denormalized schema won’t create problems in the long run. If you do require polymorphic associations or queries, and subclasses declare many properties (subclasses differ mainly by the data they hold), lean toward TPT. Or, depending on the width and depth of your inheritance hierarchy and the possible cost of joins versus unions, use TPC. By default, choose TPH only for simple problems. For more complex cases (or when you’re overruled by a data modeler insisting on the importance of nullability constraints and normalization), you should consider the TPT strategy. But at that point, ask yourself whether it may not be better to remodel inheritance as delegation in the object model (delegation is a way of making composition as powerful for reuse as inheritance). Complex inheritance is often best avoided for all sorts of reasons unrelated to persistence or ORM. EF acts as a buffer between the domain and relational models, but that doesn’t mean you can ignore persistence concerns when designing your classes. SummaryIn this series, we focused on one of the main structural aspect of the object/relational paradigm mismatch which is inheritance and discussed how EF solve this problem as an ORM solution. We learned about the three well-known inheritance mapping strategies and their implementations in EF Code First. Hopefully it gives you a better insight about the mapping of inheritance hierarchies as well as choosing the best strategy for your particular scenario. Happy New Year and Happy Code-Firsting! References ADO.NET team blog Java Persistence with Hibernate book a { color: #5A99FF; } a:visited { color: #5A99FF; } .title { padding-bottom: 5px; font-family: Segoe UI; font-size: 11pt; font-weight: bold; padding-top: 15px; } .code, .typeName { font-family: consolas; } .typeName { color: #2b91af; } .padTop5 { padding-top: 5px; } .padTop10 { padding-top: 10px; } .exception { background-color: #f0f0f0; font-style: italic; padding-bottom: 5px; padding-left: 5px; padding-top: 5px; padding-right: 5px; }

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• Silverlight Tree View with Multiple Levels

  - by psheriff

  There are many examples of the Silverlight Tree View that you will find on the web, however, most of them only show you how to go to two levels. What if you have more than two levels? This is where understanding exactly how the Hierarchical Data Templates works is vital. In this blog post, I am going to break down how these templates work so you can really understand what is going on underneath the hood. To start, let’s look at the typical two-level Silverlight Tree View that has been hard coded with the values shown below: <sdk:TreeView>  <sdk:TreeViewItem Header="Managers">    <TextBlock Text="Michael" />    <TextBlock Text="Paul" />  </sdk:TreeViewItem>  <sdk:TreeViewItem Header="Supervisors">    <TextBlock Text="John" />    <TextBlock Text="Tim" />    <TextBlock Text="David" />  </sdk:TreeViewItem></sdk:TreeView> Figure 1 shows you how this tree view looks when you run the Silverlight application. Figure 1: A hard-coded, two level Tree View. Next, let’s create three classes to mimic the hard-coded Tree View shown above. First, you need an Employee class and an EmployeeType class. The Employee class simply has one property called Name. The constructor is created to accept a “name” argument that you can use to set the Name property when you create an Employee object. public class Employee{  public Employee(string name)  {    Name = name;  }   public string Name { get; set; }} Finally you create an EmployeeType class. This class has one property called EmpType and contains a generic List<> collection of Employee objects. The property that holds the collection is called Employees. public class EmployeeType{  public EmployeeType(string empType)  {    EmpType = empType;    Employees = new List<Employee>();  }   public string EmpType { get; set; }  public List<Employee> Employees { get; set; }} Finally we have a collection class called EmployeeTypes created using the generic List<> class. It is in the constructor for this class where you will build the collection of EmployeeTypes and fill it with Employee objects: public class EmployeeTypes : List<EmployeeType>{  public EmployeeTypes()  {    EmployeeType type;            type = new EmployeeType("Manager");    type.Employees.Add(new Employee("Michael"));    type.Employees.Add(new Employee("Paul"));    this.Add(type);     type = new EmployeeType("Project Managers");    type.Employees.Add(new Employee("Tim"));    type.Employees.Add(new Employee("John"));    type.Employees.Add(new Employee("David"));    this.Add(type);  }} You now have a data hierarchy in memory (Figure 2) which is what the Tree View control expects to receive as its data source. Figure 2: A hierachial data structure of Employee Types containing a collection of Employee objects. To connect up this hierarchy of data to your Tree View you create an instance of the EmployeeTypes class in XAML as shown in line 13 of Figure 3. The key assigned to this object is “empTypes”. This key is used as the source of data to the entire Tree View by setting the ItemsSource property as shown in Figure 3, Callout #1. Figure 3: You need to start from the bottom up when laying out your templates for a Tree View. The ItemsSource property of the Tree View control is used as the data source in the Hierarchical Data Template with the key of employeeTypeTemplate. In this case there is only one Hierarchical Data Template, so any data you wish to display within that template comes from the collection of Employee Types. The TextBlock control in line 20 uses the EmpType property of the EmployeeType class. You specify the name of the Hierarchical Data Template to use in the ItemTemplate property of the Tree View (Callout #2). For the second (and last) level of the Tree View control you use a normal <DataTemplate> with the name of employeeTemplate (line 14). The Hierarchical Data Template in lines 17-21 sets its ItemTemplate property to the key name of employeeTemplate (Line 19 connects to Line 14). The source of the data for the <DataTemplate> needs to be a property of the EmployeeTypes collection used in the Hierarchical Data Template. In this case that is the Employees property. In the Employees property there is a “Name” property of the Employee class that is used to display the employee name in the second level of the Tree View (Line 15). What is important here is that your lowest level in your Tree View is expressed in a <DataTemplate> and should be listed first in your Resources section. The next level up in your Tree View should be a <HierarchicalDataTemplate> which has its ItemTemplate property set to the key name of the <DataTemplate> and the ItemsSource property set to the data you wish to display in the <DataTemplate>. The Tree View control should have its ItemsSource property set to the data you wish to display in the <HierarchicalDataTemplate> and its ItemTemplate property set to the key name of the <HierarchicalDataTemplate> object. It is in this way that you get the Tree View to display all levels of your hierarchical data structure. Three Levels in a Tree View Now let’s expand upon this concept and use three levels in our Tree View (Figure 4). This Tree View shows that you now have EmployeeTypes at the top of the tree, followed by a small set of employees that themselves manage employees. This means that the EmployeeType class has a collection of Employee objects. Each Employee class has a collection of Employee objects as well. Figure 4: When using 3 levels in your TreeView you will have 2 Hierarchical Data Templates and 1 Data Template. The EmployeeType class has not changed at all from our previous example. However, the Employee class now has one additional property as shown below: public class Employee{  public Employee(string name)  {    Name = name;    ManagedEmployees = new List<Employee>();  }   public string Name { get; set; }  public List<Employee> ManagedEmployees { get; set; }} The next thing that changes in our code is the EmployeeTypes class. The constructor now needs additional code to create a list of managed employees. Below is the new code. public class EmployeeTypes : List<EmployeeType>{  public EmployeeTypes()  {    EmployeeType type;    Employee emp;    Employee managed;     type = new EmployeeType("Manager");    emp = new Employee("Michael");    managed = new Employee("John");    emp.ManagedEmployees.Add(managed);    managed = new Employee("Tim");    emp.ManagedEmployees.Add(managed);    type.Employees.Add(emp);     emp = new Employee("Paul");    managed = new Employee("Michael");    emp.ManagedEmployees.Add(managed);    managed = new Employee("Sara");    emp.ManagedEmployees.Add(managed);    type.Employees.Add(emp);    this.Add(type);     type = new EmployeeType("Project Managers");    type.Employees.Add(new Employee("Tim"));    type.Employees.Add(new Employee("John"));    type.Employees.Add(new Employee("David"));    this.Add(type);  }} Now that you have all of the data built in your classes, you are now ready to hook up this three-level structure to your Tree View. Figure 5 shows the complete XAML needed to hook up your three-level Tree View. You can see in the XAML that there are now two Hierarchical Data Templates and one Data Template. Again you list the Data Template first since that is the lowest level in your Tree View. The next Hierarchical Data Template listed is the next level up from the lowest level, and finally you have a Hierarchical Data Template for the first level in your tree. You need to work your way from the bottom up when creating your Tree View hierarchy. XAML is processed from the top down, so if you attempt to reference a XAML key name that is below where you are referencing it from, you will get a runtime error. Figure 5: For three levels in a Tree View you will need two Hierarchical Data Templates and one Data Template. Each Hierarchical Data Template uses the previous template as its ItemTemplate. The ItemsSource of each Hierarchical Data Template is used to feed the data to the previous template. This is probably the most confusing part about working with the Tree View control. You are expecting the content of the current Hierarchical Data Template to use the properties set in the ItemsSource property of that template. But you need to look to the template lower down in the XAML to see the source of the data as shown in Figure 6. Figure 6: The properties you use within the Content of a template come from the ItemsSource of the next template in the resources section. Summary Understanding how to put together your hierarchy in a Tree View is simple once you understand that you need to work from the bottom up. Start with the bottom node in your Tree View and determine what that will look like and where the data will come from. You then build the next Hierarchical Data Template to feed the data to the previous template you created. You keep doing this for each level in your Tree View until you get to the last level. The data for that last Hierarchical Data Template comes from the ItemsSource in the Tree View itself. NOTE: You can download the sample code for this article by visiting my website at http://www.pdsa.com/downloads. Select “Tips & Tricks”, then select “Silverlight TreeView with Multiple Levels” from the drop down list.

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• Amazon EC2 master node hanging

  - by Algorist

  Hi, I am using cloudera setup to launch a cluster with hadoop on Amazon. Sometimes, the master hadoop node hangs and we have to restart the job from the job. Did anyone face similar problem and resolve the issue. Thank you.

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