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  • What are the reasons *not* to use a GUID for a primary key?

    - by Yarin
    Whenever I design a database I automatically start with an auto-generating GUID primary key for each of my tables (excepting look-up tables) I know I'll never lose sleep over duplicate keys, merging tables, etc. To me it just makes sense philosophically that any given record should be unique across all domains, and that that uniqueness should be represented in a consistent way from table to table. I realize it will never be the most performant option, but putting performance aside, I'd like to know if there are philosophical arguments against this practice?

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  • How to pick a chunksize for python multiprocessing with large datasets

    - by Sandro
    I am attempting to to use python to gain some performance on a task that can be highly parallelized using http://docs.python.org/library/multiprocessing. When looking at their library they say to use chunk size for very long iterables. Now, my iterable is not long, one of the dicts that it contains is huge: ~100000 entries, with tuples as keys and numpy arrays for values. How would I set the chunksize to handle this and how can I transfer this data quickly? Thank you.

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  • Foreign key pointing to different tables

    - by Álvaro G. Vicario
    I'm implementing a table per subclass design I discussed in a previous question. It's a product database where products can have very different attributes depending on their type, but attributes are fixed for each type and types are not manageable at all. I have a master table that holds common attributes: product_type ============ product_type_id INT product_type_name VARCHAR E.g.: 1 'Magazine' 2 'Web site' product ======= product_id INT product_name VARCHAR product_type_id INT -> Foreign key to product_type.product_type_id valid_since DATETIME valid_to DATETIME E.g. 1 'Foo Magazine' 1 '1998-12-01' NULL 2 'Bar Weekly Review' 1 '2005-01-01' NULL 3 'E-commerce App' 2 '2009-10-15' NULL 4 'CMS' 2 '2010-02-01' NULL ... and one subtable for each product type: item_magazine ============= item_magazine_id INT title VARCHAR product_id INT -> Foreign key to product.product_id issue_number INT pages INT copies INT close_date DATETIME release_date DATETIME E.g. 1 'Foo Magazine Regular Issue' 1 89 52 150000 '2010-06-25' '2010-06-31' 2 'Foo Magazine Summer Special' 1 90 60 175000 '2010-07-25' '2010-07-31' 3 'Bar Weekly Review Regular Issue' 2 12 16 20000 '2010-06-01' '2010-06-02' item_web_site ============= item_web_site_id INT name VARCHAR product_id INT -> Foreign key to product.product_id bandwidth INT hits INT date_from DATETIME date_to DATETIME E.g. 1 'The Carpet Store' 3 10 90000 '2010-06-01' NULL 2 'Penauts R Us' 3 20 180000 '2010-08-01' NULL 3 'Springfield Cattle Fair' 4 15 150000 '2010-05-01' '2010-10-31' Now I want to add some fees that relate to one specific item. Since there are very little subtypes, it's feasible to do this: fee === fee_id INT fee_description VARCHAR item_magazine_id INT -> Foreign key to item_magazine.item_magazine_id item_web_site_id INT -> Foreign key to item_web_site.item_web_site_id net_price DECIMAL E.g.: 1 'Front cover' 2 NULL 1999.99 2 'Half page' 2 NULL 500.00 3 'Square banner' NULL 3 790.50 4 'Animation' NULL 3 2000.00 I have tight foreign keys to handle cascaded editions and I presume I can add a constraint so only one of the IDs is NOT NULL. However, my intuition suggests that it would be cleaner to get rid of the item_WHATEVER_id columns and keep a separate table: fee_to_item =========== fee_id INT -> Foreign key to fee.fee_id product_id INT -> Foreign key to product.product_id item_id INT -> ??? But I can't figure out how to create foreign keys on item_id since the source table varies depending on product_id. Should I stick to my original idea?

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  • How to get right values from Views touch event

    - by Pinker
    I have a problem with implementing touch events on GLSurfaceView. Views size is 1280x696, because of android (tablet) status bar at bottom with soft keys, time etc.., (screen resolution is 1280x800), but OnTouchListener is receiving touch events with coords [646.0,739.0], and thus my gluunproject method fails to return correct values is there any way to return events that respect these boundaries? or how should I recalculate the position?

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  • Key Event Handling in Windows Services C#

    - by Yakov
    Hi! I want to create a windows service that may log pressed keys into files. For handling global key events I use hooks, hooks works great for desktop apps. But it doesn't work for the services. Is it possible to develop a windows service with key event handling? Developing on C#... Thanks for your time.

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  • Missing parameter error after running MySql query

    - by annelie
    Hello, I'm completely new to MySql and haven't used SqlDataSource with UpdateParameters before, so I'm probably missing something very obvious. When trying to update a record, the update does happen but then throws an error saying "'id' parameter is missing at the statement". So the query works and the database gets updated as it should, but an error is thrown afterwards. These are the update parameters: <UpdateParameters> <asp:Parameter Name="business_name" Type="string" Size="256" /> <asp:Parameter Name="addr_line_1" Type="string" Size="256" /> <asp:Parameter Name="addr_line_2" Type="string" Size="256" /> <asp:Parameter Name="addr_line_3" Type="string" Size="256" /> <asp:Parameter Name="postcode" Type="string" Size="32" /> <asp:Parameter Name="county" Type="string" Size="128" /> <asp:Parameter Name="town_city" Type="string" Size="256" /> <asp:Parameter Name="tl_url" Type="string" Size="256" /> <asp:Parameter Name="customer_id" Type="string" Size="16" /> <asp:Parameter Name="region_id" Type="Int16" /> <asp:Parameter Name="description" Type="string" Size="1024" /> <asp:Parameter Name="approval_status" Type="string" Size="1" /> <asp:Parameter Name="tl_user_name" Type="string" Size="256" /> <asp:Parameter Name="phone" Type="string" Size="50" /> <asp:Parameter Name="uploaders_own" Type="Int16" /> </UpdateParameters> Here's the update statement: UPDATE myTable SET business_name = ?, addr_line_1 = ?, addr_line_2 = ?, addr_line_3 = ?, postcode = ?, county = ?, town_city = ?, tl_url = ?, customer_id = ?, region_id = ?, description = ?, approval_status = ?, tl_user_name = ?, phone = ?, uploaders_own = ? WHERE id = " + id Here's the stack trace: [InvalidOperationException: 'id' parameter is missing at the statement] CoreLab.MySql.r.a() +775 CoreLab.MySql.r.a(Int32& A_0, ArrayList& A_1) +448 CoreLab.MySql.x.e() +398 CoreLab.MySql.x.o() +89 CoreLab.MySql.MySqlCommand.a(CommandBehavior A_0, IDisposable A_1, Int32 A_2, Int32 A_3) +1306 CoreLab.Common.DbCommandBase.ExecuteDbDataReader(CommandBehavior behavior) +310 System.Data.Common.DbCommand.ExecuteReader() +12 CoreLab.Common.DbCommandBase.ExecuteNonQuery() +64 System.Web.UI.WebControls.SqlDataSourceView.ExecuteDbCommand(DbCommand command, DataSourceOperation operation) +386 System.Web.UI.WebControls.SqlDataSourceView.ExecuteUpdate(IDictionary keys, IDictionary values, IDictionary oldValues) +325 System.Web.UI.DataSourceView.Update(IDictionary keys, IDictionary values, IDictionary oldValues, DataSourceViewOperationCallback callback) +92 System.Web.UI.WebControls.DetailsView.HandleUpdate(String commandArg, Boolean causesValidation) +837 System.Web.UI.WebControls.DetailsView.HandleEvent(EventArgs e, Boolean causesValidation, String validationGroup) +509 System.Web.UI.WebControls.DetailsView.OnBubbleEvent(Object source, EventArgs e) +95 System.Web.UI.Control.RaiseBubbleEvent(Object source, EventArgs args) +37 System.Web.UI.WebControls.DetailsViewRow.OnBubbleEvent(Object source, EventArgs e) +113 System.Web.UI.Control.RaiseBubbleEvent(Object source, EventArgs args) +37 System.Web.UI.WebControls.LinkButton.OnCommand(CommandEventArgs e) +118 System.Web.UI.WebControls.LinkButton.RaisePostBackEvent(String eventArgument) +135 System.Web.UI.WebControls.LinkButton.System.Web.UI.IPostBackEventHandler.RaisePostBackEvent(String eventArgument) +10 System.Web.UI.Page.RaisePostBackEvent(IPostBackEventHandler sourceControl, String eventArgument) +13 System.Web.UI.Page.RaisePostBackEvent(NameValueCollection postData) +175 System.Web.UI.Page.ProcessRequestMain(Boolean includeStagesBeforeAsyncPoint, Boolean includeStagesAfterAsyncPoint) +1565 Does anyone know what I'm doing wrong? Thanks, Annelie

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  • errors when trying to delete a key in the registry

    - by NightsEVil
    i'm trying to delete a registry from the Local_Machine\Software in the registry i made a key titles "DeleteMe" as a test to try it out but i cant get it to work iv tried multiple options and they all say that the "subkey" "subkeytree" and "value" do not exist BUT IT DOES! and i hope i'm using the right terminology here to its HKEY_LOCAL_MACHINE\SOFTWARE\DeleteMe i want it and all the sub keys/values deleted.. (i hope key is the right terminology they look just like folders but when right clicked on they have the option "copy key name")

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  • How do I perform 'WHERE' on groups of rows?

    - by Drew
    I have a table, which looks like: +-----------+----------+ + person_id + group_id + +-----------+----------+ + 1 + 10 + + 1 + 20 + + 1 + 30 + + 2 + 10 + + 2 + 20 + + 3 + 10 + +-----------+----------+ I need a query such that only person_ids with groups 10 AND 20 AND 30 are returned (only person_id: 1). I am not sure how to do this, as from what I can see it would require me to group the rows by person_id and then select the rows which contain all group_ids. I'm looking for something which will preserve the use of keys without resorting to string operations on group_concat() or such.

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  • Why is my Android emulator keyboard in Japanese character mode?

    - by mckoss
    I'm debugging my Android application using the AVD (Android Virtual Device). When I try to enter text in a text field, my characters are being interpreted as Japanese (or Chinese?) in the IME. I don't know how I got into this mode or how to get out of it (I just want to enter alphabetic keys)? Here's a screen shot: http://u.go2.me/3cn

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  • A Couple Android Soft Keyboard Questions

    - by Rich
    This is kind of a repost, and I apologize for any broken rules, but I have a couple of questions about the soft keyboard on Android phones: 1) I have an Android app with a couple different views (that the user switches between). How can I determine which is the current view?? I need to get the current view to execute the code that hides the virtual keyboard. 2) How can I check whether the virtual keyboard is currently being displayed (so I can filter the actions of my various hard keys)?? Thanks, R.

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  • SQL Server unique constraint problem

    - by b0x0rz
    How to create a unique constraint on a varchar(max) field in visual studio, visually. the problem is when i try it: manage indexes and keys add columns I can only chose the bigint columns, but not any of the varchar(max) ones. Do I maybe have to use check constraints? If yes, what to put in the expression? Thnx for the info

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  • RSA Encryption C#

    - by Ryan
    Hi guys, I have a class which in C# doing RSA encryption where I used the default RSACryptoServiceProvider class. But I have a concern regarding the following; If you have the word hello for an input and the encrypted string is returned as ABCDE, if you perform another encrypt operation on the input hello, using the same keys (public and private) for the RSA will the output be again ABCDE? Thanks in advance

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  • Catching multiple keystrokes simultaneously in Cocoa

    - by Vinod Kumar
    I have used 4 NSButtons and assigned them to the 4 arrow keys separately to move in four different directions. Now I want to use two keystrokes, left arrow and up arrow together simultaneously, for north east movement, how can I do it? I am only able to use one keystroke at a time , I need to catch two key strokes simultaneously, I need it for my game project.

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  • SQL inserting value of a specific column under multple case

    - by Lo Wai Lun
    Suppose I have got a table which I have to insert the description of the contract under different keys of contract. But when executing, there is a n error near then Is there any limitation of using syntax set ? The below is my SQL declare @i int, @j v nvarchar(MAX) set @i = 1 while (@i<=8) begin set @j = case when @i = 1 then 'CR' when @i = 2 then 'Facebook' else 'N/A' end INSERT INTO CostNature (CNKey, CNNDescription) VALUES (@i , @j ); set @i = @i + 1 end

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  • The explain tells that the query is awful (it doesn't use a single key) but I'm using LIMIT 1. Is th

    - by Ricardo
    The explain command with the query: explain SELECT * FROM leituras WHERE categorias_id=75 AND textos_id=190304 AND cookie='3f203349ce5ad3c67770ebc882927646' AND endereco_ip='127.0.0.1' LIMIT 1 The result: id select_type table type possible_keys key key_len ref rows Extra 1 SIMPLE leituras ALL (null) (null) (null) (null) 1022597 Using where Will it make any difference adding some keys on the table? Even that the query will always return only one row.

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  • SQL Server unique contraint problem

    - by b0x0rz
    How to create a unique constraint on a varchar(max) field in visual studio, visually. the problem is when i try it: manage indexes and keys add columns i can only chose the bigint columns, but not any of the varchar(max) ones. do i maybe have to use check constraints? if yes, what to put in the expression? thnx for the info

    Read the article

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