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  • Java Executor: Small tasks or big ones?

    - by Arash Shahkar
    Consider one big task which could be broken into hundreds of small, independently-runnable tasks. To be more specific, each small task is to send a light network request and decide upon the answer received from the server. These small tasks are not expected to take longer than a second, and involve a few servers in total. I have in mind two approaches to implement this using the Executor framework, and I want to know which one's better and why. Create a few, say 5 to 10 tasks each involving doing a bunch of send and receives. Create a single task (Callable or Runnable) for each send & receive and schedule all of them (hundreds) to be run by the executor. I'm sorry if my question shows that I'm lazy to test these and see for myself what's better (at least performance-wise). My question, while looking after an answer to this specific case, has a more general aspect. In situations like these when you want to use an executor to do all the scheduling and other stuff, is it better to create lots of small tasks or to group those into a less number of bigger tasks?

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  • Reducing a normalized table to one value

    - by Dio
    Hello, I'm sure this has been asked but I'm not quite sure how to properly search for this question, my apologies. I have two tables, Foo and Bar. For has one row per Food, bar has many rows per food matching descriptors. Foo name id Apple 1 Orange 2 Bar id description 1 Tasty 1 Ripe 2 Sweet etc (sorry for the somewhat contrived example). I'm trying to return a query where if, for each row in Foo, Bar contains a descriptor in ('Tasty', 'Juicy') return true ex: Output Apple True Orange False I had been solving this somewhat trivially with a case when I only had one item to match select Foo.name, case bar.description when 'Tasty' then True else 'False' end from Foo left join Bar on foo.id = bar.id where bar.description = 'Tasty' But with multiple items, I keep ending up with extra rows: Output Apple True Apple False etc etc Can someone point me in the right direction on how to think about this problem or what I should be doing? Thank you.

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  • Best way to identify and dispose locked thread in java.

    - by Bala R
    I have to call a function 3rd party module on a new thread. From what I've seen, the call either completes quickly if everything went well or it just hangs for ever locking up the thread. What's a good way to start the thread and make the call and wait for a few secs and if the thread is still alive, then assuming it's locked up, kill (or stop or abandon) the thread without using any deprecated methods. I have something like this for now, but I'm not sure if this is the best way to do it and I want to avoid calling Thread.stop() as it's deprecated. Thanks. private void foo() throws Exception { Runnable runnable = new Runnable() { @Override public void run() { // stuff that could potentially lock up the thread. } }; Thread thread; thread = new Thread(runnable); thread.start(); thread.join(3500); if (thread.isAlive()) { thread.stop(); throw new Exception(); } }

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  • How to keep Hibernate mapping use under control as requirements grow

    - by David Plumpton
    I've worked on a number of Java web apps where persistence is via Hibernate, and we start off with some central class (e.g. an insurance application) without any time being spent considering how to break things up into manageable chunks. Over time as features are added we add more mappings (rates, clients, addresses, etc.) and then amount of time spent saving and loading an insurance object and everything it connects to grows. In particular you get close to a go-live date and performance testing with larger amounts of data in each table is starting to demonstrate that it's all too slow. Obviously there are a number of ways that we could attempt to partition things up, e.g. map only the client classes for the client CRUD screens, etc., which would have been better to get in place earlier rather than trying to work it in at the end of the dev cycle. I'm just wondering if there are recommendations about ways to handle/mitigate this.

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  • What's wrong in my JavaScript code?

    - by DarkLightA
    I can't figure out what's wrong. var CarObj = function(passengers, maxLoad, wheels, doors, maxSpeed) { this.passengers = passengers; this.maxLoad = maxLoad; this.wheels = wheels; this.doors = doors; this.maxSpeed = maxSpeed; }; var ferrari = new CarObj(4, "700kg", 4, 2, "360km/h"); var output = new Array(); for (var i = 0; i < ferrari.length; i++) { for (var a in ferrari) { output[i] = a; } } document.getElementById('ELEMENTHERE').innerHTML = (output.join(" "));

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  • SQL help - find the table that has 'somefieldId' as the primary key?

    - by Kettenbach
    Hello All, How can I search my sql database for a table that contains a field 'tiEntityId'. This field is referenced in a stored procedure, but I am unable to identify which table this id is a primary key for? Any suggestions? I currently look through stored procedure definitions for references to text by using something like this Declare @Search varchar(255) SET @Search='[10.10.100.50]' SELECT DISTINCT o.name AS Object_Name,o.type_desc FROM sys.sql_modules m INNER JOIN sys.objects o ON m.object_id=o.object_id WHERE m.definition Like '%'+@Search+'%' ORDER BY 2,1 Any SQL guru's out there know what I need to use to find the table that contains the field, 'preferably the table where that field is the Primary Key. Thanks so much for any tips. Cheers, ~ck in San Diego

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  • VendInvoiceJour.InvoiceAccount <- VendTable.AccountNum relation

    - by vukis
    Hi. I have following situation: I need to join VendInvoiceJour.InvoiceAccount <- VendTable.AccountNum and take VendTable.Vendgroup. In all cases (queries,or even views) Dynamics ax joins tables VendInvoiceJour.OrderAccount<- VendTable.AccountNum not VendInvoiceJour.InvoiceAccount <- VendTable.AccountNum. I`m trying to use this kind of query: qBdSVendJour = element.query().dataSourceTable(tablenum(VendInvoiceJour)); qBdSVendTbl = qBdSVendJour.addDataSource(tablenum(VendTable)); qBdSVendTbl.relations(true); qBdSVendTbl.joinMode(JoinMOde::InnerJoin); qBdSVendTbl.fetchMode(QueryFetchMode::One2One); qBdSVendTbl.addLink(FieldNum(VendInvoiceJour,InvoiceAccount),FieldNum(VendTable,AccountNum));//(Dynamics ax automaticaly corrects InvoiceAccount to orderaccount in reports if trying this link in morphx)

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  • Composite Primary and Cardinality

    - by srini.venigalla
    I have some questions on Composite Primary Keys and the cardinality of the columns. I searched the web, but did not find any definitive answer, so I am trying again. The questions are: Context: Large (50M - 500M rows) OLAP Prep tables, not NOSQL, not Columnar. MySQL and DB2 1) Does the order of keys in a PK matter? 2) If the cardinality of the columns varies heavily, which should be used first. For example, if I have CLIENT/CAMPAIGN/PROGRAM where CLIENT is highly cardinal, CAMPAIGN is moderate, PROGRAM is almost like a bitmap index, what order is the best? 3) What order is the best for Join, if there is a Where clause and when there is no Where Clause (for views) Thanks in advance.

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  • Combine SQL statement

    - by ninumedia
    I have 3 tables (follows, postings, users) follows has 2 fields - profile_id , following_id postings has 3 fields - post_id, profile_id, content users has 3 fields - profile_id, first_name, last_name I have a follows.profile_id value of 1 that I want to match against. When I run the SQL statement below I get the 1st step in obtaining the correct data. However, I now want to match the postings.profile_id of this resulting set against the users table so each of the names (first and last name) are displayed as well for all the listed postings. Thank you for your help! :) Ex: SELECT * FROM follows JOIN postings ON follows.following_id = postings.profile_id WHERE follows.profile_id = 1

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  • How to manually verify a user against the asp.net memberhip database

    - by Ekk
    I would like to know how I can verify a user's credential against an existing asp.net membership database. The short story is that we want provide single sign on access. So what I've done is to connect directly to the membership database and tried to run a sql query against the aspnet_Membership table: private bool CanLogin(string userName, string password) { // Check DB to see if the credential is correct try { string passwordHash = FormsAuthentication.HashPasswordForStoringInConfigFile(password, "SHA1"); string sql = string.Format("select 1 from aspnet_Users a inner join aspnet_Membership b on a.UserId = b.UserId and a.applicationid = b.applicationid where a.username = '{0}' and b.password='{1}'", userName.ToLowerInvariant(), passwordHash); using (SqlConnection sqlConn = new SqlConnection(ConfigurationManager.ConnectionStrings["LocalSqlServer"].ConnectionString)) using (SqlCommand sqlCmd = new SqlCommand(sql, sqlConn)) { sqlConn.Open(); int count = sqlCmd.ExecuteNonQuery(); sqlConn.Close(); return count == 1; } } catch (Exception ex) { return false; } } The problem is the password value, does anyone know how the password it is hashed?

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  • Convert SQL to LINQ to SQL

    - by Adam
    Hi I have the SQL query with c as ( select categoryId,parentId, name,0 as [level] from task_Category b where b.parentId is null union all select b.categoryId,b.parentId,b.name,[level] + 1 from task_Category b join c on b.parentId = c.categoryId) select name,[level],categoryId,parentId as item from c and I want to convert it to LINQ to SQL, yet my LINQ skills are not there yet. Could someone please help me convert this. It's the with and union statements that are making this a bit more complex for me. Any help appreciated.

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  • Rails 4.2: "Assets should not be requested directly without their digests"

    - by Nowaker
    On Rails 4.2.0.beta1 I get an error: Assets should not be requested directly without their digests: Use the helpers in ActionView::Helpers to request fonts/source-sans-pro.woff The stylesheet: @font-face { font-family: 'Source Sans Pro'; font-style: normal; font-weight: 400; src: local('Source Sans Pro'), local('SourceSansPro-Regular'), url(/assets/source-sans-pro.woff) format('woff'); } The configuration is: config.serve_static_assets = true config.assets.js_compressor = :uglifier config.assets.compile = true config.assets.digest = true config.assets.version = '1.0' config.assets.paths << Rails.root.join('app', 'assets', 'fonts') config.assets.precompile += %w(.svg .eot .woff .ttf) Sure I can disable digests and it works again, but I'm interested in using them. Therefore, how do I make use of digests when I need to request source-sans-pro.woff? Please note that I place the fonts in assets/fonts directory, not the public/ directory. I don't see a difference between images and fonts, so I want to keep them under the same directory - app/assets.

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  • How to retrieve row count of one-to-many relation while also include original entity?

    - by kaa
    Say I have two entities Foo and Bar where Foo has-many Bar's, class Foo { int ImportantNumber { get; set; } IEnumerable<Bar> Bars { get; set; } } class FooDTO { Foo Foo { get; set; } int BarCount { get; set; } } How can I efficiently sum up the number of Bars per Foo in a DTO using a single query, preferrably only with the Criteria interface. I have tried any number of ways to get the original entity out of a query with ´SetProjection´ but no luck. The current theory is to do something like SELECT Foo.*, BarCounts.counts FROM Foo LEFT JOIN ( SELECT fooId, COUNT(*) as counts FROM Bar GROUP BY fooId ) AS BarCounts ON Foo.id=BarCounts.fooId but with Criterias, and I just can't seem to figure out how.

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  • Gluing tiles together using imagemagick's montage command

    - by AP257
    This seems like it might be a reasonably common question, so I'm going to ask it using as many keywords as I can think of! I have a bunch of (well, nine) tile jpegs, with standard tile filenames. Each jpeg is 220x175 pixels: (top row) tile_1_0_0.jpg tile_1_1_0.jpg tile_1_2_0.jpg (middle row) tile_1_0_1.jpg tile_1_1_1.jpg tile_1_2_1.jpg (bottom row) tile_1_0_2.jpg tile_1_1_2.jpg tile_1_2_2.jpg How can I use imagemagick/montage to 'glue' or join them all together to make a single, coherent image? I don't want to resize them at all, so I guess the final image should be 660x525. That would be montage with no framing, shadowing, bordering, etc - just the nine original images, glued together to make a single jpeg. I know it should be something along these lines, but I'm struggling with getting the order and sizing right: montage +frame +shadow +label -tile 3x3 -geometry <options> *.jpg joined.jpg

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  • Alternative to 'where col in (list)' for MySQL

    - by user210481
    Hi I have the following table T: id 1 2 3 4 col a b a c I want to do a select that returns the id,col when group by(col) having count(col)1 One way of doing it is SELECT id,col FROM T WHERE col IN (SELECT col FROM T GROUP BY(col) HAVING COUNT(col)>1); The intern select (from the right) returns 'a' and main one (left) will return 1,a and 3,a The problem is that the where in statement seems to be extremely slow. In my real case, the results from the internal select has many 'col's, something about 70000 and it's taking hours. Right now it's much faster to do the internal select and the main select getting all ids and upcs and do the intersection locally. MySQL should be able to handle this kind of query efficiently. Can I substitute the where in for a join or something faster? Thanks

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  • How do I do multiple has_and_belongs_to_many associations between the same two classes?

    - by Ermin
    I have the following setup: class Publication < ActiveRecord::Base has_and_belongs_to_many :authors, :class_name=>'Person', :join_table => 'authors_publications' has_and_belongs_to_many :editors, :class_name=>'Person', :join_table => 'editors_publications' end class Person < ActiveRecord::Base has_and_belongs_to_many :publications end With this setup I can do stuff like Publication.first.authors. But if I want to list all publications in which a person is involved Person.first.publications, an error about a missing join table people_publications it thrown. How could I fix that? Should I maybe switch to separate models for authors and editors? It would however introduce some redundancy to the database, since a person can be an author of one publication and an editor of another.

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  • Designing a peer to peer network

    - by Varun
    I am designing a simple peer to peer network. The basic architecture will be as follows: A central server- that keeps track of all the peers. The job of this server is to keep track of all the peers that join the network. Every peer could do things: a. Download a file from it's peer b. Push a file (send a file) to it's peer. Could anybody please tell me what would be the best design for such a system? What would be the problems that i might run into and so on. I am planning to use Java as the programming language to implement. Would it be a good choice? Also, is it necessary that i would need a Linux box to develop the system? or is it fine if i use a Windows machine? Your help will be much appreciated! Thanks!

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  • Resource placement (optimal strategy)

    - by blackened
    I know that this is not exactly the right place to ask this question, but maybe a wise guy comes across and has the solution. I'm trying to write a computer game and I need an algorithm to solve this question: The game is played between 2 players. Each side has 1.000 dollars. There are three "boxes" and each player writes down the amount of money he is going to place into those boxes. Then these amounts are compared. Whoever placed more money in a box scores 1 point (if draw half point each). Whoever scores more points wins his opponents 1.000 dollars. Example game: Player A: [500, 500, 0] Player B: [333, 333, 334] Player A wins because he won Box A and Box B (but lost Box C). Question: What is the optimal strategy to place the money? I have more questions to ask (algorithm related, not math related) but I need to know the answer to this one first. Update (1): After some more research I've learned that these type of problems/games are called Colonel Blotto Games. I did my best and found few (highly technical) documents on the subject. Cutting it short, the problem I have (as described above) is called simple Blotto Game (only three battlefields with symmetric resources). The difficult ones are the ones with, say, 10+ battle fields with non-symmetric resources. All the documents I've read say that the simple Blotto game is easy to solve. The thing is, none of them actually say what that "easy" solution is.

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  • Is my TFS2010 backup/restore hosed?

    - by bwerks
    Hi all, I recently set up a sandbox TFS to test TFS-specific features without interfering with the production TFS. I was happy I did this sooner than I thought--I hadn't been backing up the encryption key from SSRS and upon restoring the reporting databases, they remained inactive, requiring initialization that could only come from applying the encryption key. Said encryption key was lost when I nuked the partition after backing up the TFS databases. The only option I seemed to have is to delete the encrypted data. I'm fine with this, since there wasn't much in there to begin with, however once they're deleted I'm not quite sure how to configure TFS to recognize a new installation of these services while using the restored versions of everything else. Unfortunately, the TFS help file doesn't seem to account for this state though. Is there a way to essentially rebuild the reporting and analysis databases? Or are they gone forever?

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  • running Hadoop software on office computers (when they are idle)

    - by Shahbaz
    Is there a project which helps setup a Hadoop cluster on office desktops, when they are idle? I'd like to experiment with Hadoop/MR/hbase but don't have acces to 5-10 computers. The computers at work are idle after hours and are connected to each other through a very high speed connection. What's more, data on these computers stays within our network so there is no privacy issue. In order for this to work I need a fairly light weight monitor running on each machine. When the computer has been idle for X hours, it will join the cluster. If the user logs on, it has to drop out of the cluster and return all CPU/memory back. Does something like this exist?

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  • Rails Association issue with NoMethodError in event_controller

    - by pmanning
    Kinda a noob trying to understand I think I need to define rsvps but not sure what to put... I'm trying to add a Join/Unjoin button to user created Events, similar to a Follow/Unfollow button for Users. NoMethodError in Events#show undefined method `model_name' for NilClass:Class in line #1 _unjoin.html.erb 1: <%= form_for(current_user.rsvps.find_by_joined_id(@event), 2: html: { method: :delete }) do |f| %> 3: <%= f.submit "Leave", class: "btn btn-large" %> 4: <% end %> events_controller.rb def show @event = Event.find(params[:id]) @user = current_user end Here's the models rsvp.rb class Rsvp < ActiveRecord::Base attr_accessible :joined_id belongs_to :joiner, class_name: "User" belongs_to :joined, class_name: "User" validates :joiner_id, presence: true validates :joined_id, presence: true end user.rb has_many :rsvps, foreign_key: "joiner_id", dependent: :destroy has_many :joined_events, through: :rsvps, source: :joined has_many :reverse_rsvps, foreign_key: "joined_id", class_name: "Rsvp", dependent: :destroy has_many :joiners, through: :reverse_rsvps, source: :joiner event.rb belongs_to :user has_many :rsvps, foreign_key: "joiner_id", dependent: :destroy has_many :joined_events, through: :rsvps, source: :joined has_many :reverse_rsvps, foreign_key: "joined_id", class_name: "Rsvp", dependent: :destroy has_many :joiners, through: :reverse_rsvps, source: :joiner

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  • Casting to specific class in HQL

    - by bungrudi
    My situation is like this.. (note: for those who work with JBPM might already familiar with following data structures and HB mapping) Class LongInstance extends from VariableInstance, with the mapping for field "value" overridden in LongInstance. The mapping for VariableInstance is here and for LongInstance here. VariableInstance is polymorphically mapped to a collection in TokenVariableMap, the mapping is here. The question: how can I query the polymorphic collection using specific/overridden property of the member class? I'm looking for something like this "... from TokenVariableMaps tvm left join fetch tvm.variableInstances tvi where cast(tvi as LongInstance).value in(:vars)"

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  • Add all lines multiplied by another line in another table

    - by russell
    Hi, I hope I can explain this good enough. I have 3 tables. wo_parts, workorders and part2vendor. I am trying to get the cost price of all parts sold in a month. I have this script. $scoreCostQuery = "SELECT SUM(part2vendor.cost*wo_parts.qty) as total_score FROM part2vendor INNER JOIN wo_parts ON (wo_parts.pn=part2vendor.pn) WHERE workorder=$workorder"; What I am trying to do is each part is in wo_parts (under partnumber [pn]). The cost of that item is in part2vendor (under part number[pn]). I need each part price in part2vendor to be multiplied by the quantity sold in wo_parts. The way all 3 tie up is workorders.ident=wo_parts.workorder and part2vendor.pn=wo_parts.pn. I hope someone can assist. The above script does not give me the same total as when added by calculator.

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  • MySQL select two tables at the same time...

    - by Jerry
    Hi all I have two tables and want to make a query. I tried to get team AA and team BB's image base on table A. I used: SELECT tableA.team1, tableA.team2, tableB.team, tableB.image, FROM tableA LEFT JOIN tableB ON tableA.team1=tableB.team The result only display imageA on the column. Are there any ways to select imageA and image B without using the second query? I appreciate any helps! Thanks a lot! My table structure are: table A team1 team2 ------------ AA BB table B team image ------------- AA imagaA BB imageB

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  • Killing a script launched in a Process via os.system()

    - by L.J.
    I have a python script which launches several processes. Each process basically just calls a shell script: from multiprocessing import Process import os import logging def thread_method(n = 4): global logger command = "~/Scripts/run.sh " + str(n) + " >> /var/log/mylog.log" if (debug): logger.debug(command) os.system(command) I launch several of these threads, which are meant to run in the background. I want to have a timeout on these threads, such that if it exceeds the timeout, they are killed: t = [] for x in range(10): try: t.append(Process(target=thread_method, args=(x,) ) ) t[-1].start() except Exception as e: logger.error("Error: unable to start thread") logger.error("Error message: " + str(e)) logger.info("Waiting up to 60 seconds to allow threads to finish") t[0].join(60) for n in range(len(t)): if t[n].is_alive(): logger.info(str(n) + " is still alive after 60 seconds, forcibly terminating") t[n].terminate() The problem is that calling terminate() on the process threads isn't killing the launched run.sh script - it continues running in the background until I either force kill it from the command line, or it finishes internally. Is there a way to have terminate also kill the subshell created by os.system()?

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