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• SQL Server script commands to check if object exists and drop it

  - by deadlydog

  Over the past couple years I’ve been keeping track of common SQL Server script commands that I use so I don’t have to constantly Google them.  Most of them are how to check if a SQL object exists before dropping it.  I thought others might find these useful to have them all in one place, so here you go: 1: --=============================== 2: -- Create a new table and add keys and constraints 3: --=============================== 4: IF NOT EXISTS (SELECT * FROM INFORMATION_SCHEMA.TABLES WHERE TABLE_NAME = 'TableName' AND TABLE_SCHEMA='dbo') 5: BEGIN 6: CREATE TABLE [dbo].[TableName] 7: ( 8: [ColumnName1] INT NOT NULL, -- To have a field auto-increment add IDENTITY(1,1) 9: [ColumnName2] INT NULL, 10: [ColumnName3] VARCHAR(30) NOT NULL DEFAULT('') 11: ) 12: 13: -- Add the table's primary key 14: ALTER TABLE [dbo].[TableName] ADD CONSTRAINT [PK_TableName] PRIMARY KEY NONCLUSTERED 15: ( 16: [ColumnName1], 17: [ColumnName2] 18: ) 19: 20: -- Add a foreign key constraint 21: ALTER TABLE [dbo].[TableName] WITH CHECK ADD CONSTRAINT [FK_Name] FOREIGN KEY 22: ( 23: [ColumnName1], 24: [ColumnName2] 25: ) 26: REFERENCES [dbo].[Table2Name] 27: ( 28: [OtherColumnName1], 29: [OtherColumnName2] 30: ) 31: 32: -- Add indexes on columns that are often used for retrieval 33: CREATE INDEX IN_ColumnNames ON [dbo].[TableName] 34: ( 35: [ColumnName2], 36: [ColumnName3] 37: ) 38: 39: -- Add a check constraint 40: ALTER TABLE [dbo].[TableName] WITH CHECK ADD CONSTRAINT [CH_Name] CHECK (([ColumnName] >= 0.0000)) 41: END 42: 43: --=============================== 44: -- Add a new column to an existing table 45: --=============================== 46: IF NOT EXISTS (SELECT * FROM INFORMATION_SCHEMA.COLUMNS where TABLE_SCHEMA='dbo' 47: AND TABLE_NAME = 'TableName' AND COLUMN_NAME = 'ColumnName') 48: BEGIN 49: ALTER TABLE [dbo].[TableName] ADD [ColumnName] INT NOT NULL DEFAULT(0) 50: 51: -- Add a description extended property to the column to specify what its purpose is. 52: EXEC sys.sp_addextendedproperty @name=N'MS_Description', 53: @value = N'Add column comments here, describing what this column is for.' , 54: @level0type=N'SCHEMA',@level0name=N'dbo', @level1type=N'TABLE', 55: @level1name = N'TableName', @level2type=N'COLUMN', 56: @level2name = N'ColumnName' 57: END 58: 59: --=============================== 60: -- Drop a table 61: --=============================== 62: IF EXISTS (SELECT * FROM INFORMATION_SCHEMA.TABLES WHERE TABLE_NAME = 'TableName' AND TABLE_SCHEMA='dbo') 63: BEGIN 64: DROP TABLE [dbo].[TableName] 65: END 66: 67: --=============================== 68: -- Drop a view 69: --=============================== 70: IF EXISTS (SELECT * FROM INFORMATION_SCHEMA.VIEWS WHERE TABLE_NAME = 'ViewName' AND TABLE_SCHEMA='dbo') 71: BEGIN 72: DROP VIEW [dbo].[ViewName] 73: END 74: 75: --=============================== 76: -- Drop a column 77: --=============================== 78: IF EXISTS (SELECT * FROM INFORMATION_SCHEMA.COLUMNS where TABLE_SCHEMA='dbo' 79: AND TABLE_NAME = 'TableName' AND COLUMN_NAME = 'ColumnName') 80: BEGIN 81: 82: -- If the column has an extended property, drop it first. 83: IF EXISTS (SELECT * FROM sys.fn_listExtendedProperty(N'MS_Description', N'SCHEMA', N'dbo', N'Table', 84: N'TableName', N'COLUMN', N'ColumnName') 85: BEGIN 86: EXEC sys.sp_dropextendedproperty @name=N'MS_Description', 87: @level0type=N'SCHEMA',@level0name=N'dbo', @level1type=N'TABLE', 88: @level1name = N'TableName', @level2type=N'COLUMN', 89: @level2name = N'ColumnName' 90: END 91: 92: ALTER TABLE [dbo].[TableName] DROP COLUMN [ColumnName] 93: END 94: 95: --=============================== 96: -- Drop Primary key constraint 97: --=============================== 98: IF EXISTS (SELECT * FROM INFORMATION_SCHEMA.TABLE_CONSTRAINTS WHERE CONSTRAINT_TYPE='PRIMARY KEY' AND TABLE_SCHEMA='dbo' 99: AND TABLE_NAME = 'TableName' AND CONSTRAINT_NAME = 'PK_Name') 100: BEGIN 101: ALTER TABLE [dbo].[TableName] DROP CONSTRAINT [PK_Name] 102: END 103: 104: --=============================== 105: -- Drop Foreign key constraint 106: --=============================== 107: IF EXISTS (SELECT * FROM INFORMATION_SCHEMA.TABLE_CONSTRAINTS WHERE CONSTRAINT_TYPE='FOREIGN KEY' AND TABLE_SCHEMA='dbo' 108: AND TABLE_NAME = 'TableName' AND CONSTRAINT_NAME = 'FK_Name') 109: BEGIN 110: ALTER TABLE [dbo].[TableName] DROP CONSTRAINT [FK_Name] 111: END 112: 113: --=============================== 114: -- Drop Unique key constraint 115: --=============================== 116: IF EXISTS (SELECT * FROM INFORMATION_SCHEMA.TABLE_CONSTRAINTS WHERE CONSTRAINT_TYPE='UNIQUE' AND TABLE_SCHEMA='dbo' 117: AND TABLE_NAME = 'TableName' AND CONSTRAINT_NAME = 'UNI_Name') 118: BEGIN 119: ALTER TABLE [dbo].[TableNames] DROP CONSTRAINT [UNI_Name] 120: END 121: 122: --=============================== 123: -- Drop Check constraint 124: --=============================== 125: IF EXISTS (SELECT * FROM INFORMATION_SCHEMA.TABLE_CONSTRAINTS WHERE CONSTRAINT_TYPE='CHECK' AND TABLE_SCHEMA='dbo' 126: AND TABLE_NAME = 'TableName' AND CONSTRAINT_NAME = 'CH_Name') 127: BEGIN 128: ALTER TABLE [dbo].[TableName] DROP CONSTRAINT [CH_Name] 129: END 130: 131: --=============================== 132: -- Drop a column's Default value constraint 133: --=============================== 134: DECLARE @ConstraintName VARCHAR(100) 135: SET @ConstraintName = (SELECT TOP 1 s.name FROM sys.sysobjects s JOIN sys.syscolumns c ON s.parent_obj=c.id 136: WHERE s.xtype='d' AND c.cdefault=s.id 137: AND parent_obj = OBJECT_ID('TableName') AND c.name ='ColumnName') 138: 139: IF @ConstraintName IS NOT NULL 140: BEGIN 141: EXEC ('ALTER TABLE [dbo].[TableName] DROP CONSTRAINT ' + @ConstraintName) 142: END 143: 144: --=============================== 145: -- Example of how to drop dynamically named Unique constraint 146: --=============================== 147: DECLARE @ConstraintName VARCHAR(100) 148: SET @ConstraintName = (SELECT TOP 1 CONSTRAINT_NAME FROM INFORMATION_SCHEMA.TABLE_CONSTRAINTS 149: WHERE CONSTRAINT_TYPE='UNIQUE' AND TABLE_SCHEMA='dbo' 150: AND TABLE_NAME = 'TableName' AND CONSTRAINT_NAME LIKE 'FirstPartOfConstraintName%') 151: 152: IF EXISTS (SELECT * FROM INFORMATION_SCHEMA.TABLE_CONSTRAINTS WHERE CONSTRAINT_TYPE='UNIQUE' AND TABLE_SCHEMA='dbo' 153: AND TABLE_NAME = 'TableName' AND CONSTRAINT_NAME = @ConstraintName) 154: BEGIN 155: EXEC ('ALTER TABLE [dbo].[TableName] DROP CONSTRAINT ' + @ConstraintName) 156: END 157: 158: --=============================== 159: -- Check for and drop a temp table 160: --=============================== 161: IF OBJECT_ID('tempdb..#TableName') IS NOT NULL DROP TABLE #TableName 162: 163: --=============================== 164: -- Drop a stored procedure 165: --=============================== 166: IF EXISTS (SELECT * FROM INFORMATION_SCHEMA.ROUTINES WHERE ROUTINE_TYPE='PROCEDURE' AND ROUTINE_SCHEMA='dbo' AND 167: ROUTINE_NAME = 'StoredProcedureName') 168: BEGIN 169: DROP PROCEDURE [dbo].[StoredProcedureName] 170: END 171: 172: --=============================== 173: -- Drop a UDF 174: --=============================== 175: IF EXISTS (SELECT * FROM INFORMATION_SCHEMA.ROUTINES WHERE ROUTINE_TYPE='FUNCTION' AND ROUTINE_SCHEMA='dbo' AND 176: ROUTINE_NAME = 'UDFName') 177: BEGIN 178: DROP FUNCTION [dbo].[UDFName] 179: END 180: 181: --=============================== 182: -- Drop an Index 183: --=============================== 184: IF EXISTS (SELECT * FROM SYS.INDEXES WHERE name = 'IndexName') 185: BEGIN 186: DROP INDEX TableName.IndexName 187: END 188: 189: --=============================== 190: -- Drop a Schema 191: --=============================== 192: IF EXISTS (SELECT * FROM INFORMATION_SCHEMA.SCHEMATA WHERE SCHEMA_NAME = 'SchemaName') 193: BEGIN 194: EXEC('DROP SCHEMA SchemaName') 195: END And here’s the same code, just not in the little code view window so that you don’t have to scroll it.--=============================== -- Create a new table and add keys and constraints --=============================== IF NOT EXISTS (SELECT * FROM INFORMATION_SCHEMA.TABLES WHERE TABLE_NAME = 'TableName' AND TABLE_SCHEMA='dbo') BEGIN CREATE TABLE [dbo].[TableName]  ( [ColumnName1] INT NOT NULL, -- To have a field auto-increment add IDENTITY(1,1) [ColumnName2] INT NULL, [ColumnName3] VARCHAR(30) NOT NULL DEFAULT('') ) -- Add the table's primary key ALTER TABLE [dbo].[TableName] ADD CONSTRAINT [PK_TableName] PRIMARY KEY NONCLUSTERED ( [ColumnName1],  [ColumnName2] ) -- Add a foreign key constraint ALTER TABLE [dbo].[TableName] WITH CHECK ADD CONSTRAINT [FK_Name] FOREIGN KEY ( [ColumnName1],  [ColumnName2] ) REFERENCES [dbo].[Table2Name]  ( [OtherColumnName1],  [OtherColumnName2] ) -- Add indexes on columns that are often used for retrieval CREATE INDEX IN_ColumnNames ON [dbo].[TableName] ( [ColumnName2], [ColumnName3] ) -- Add a check constraint ALTER TABLE [dbo].[TableName] WITH CHECK ADD CONSTRAINT [CH_Name] CHECK (([ColumnName] >= 0.0000)) END --=============================== -- Add a new column to an existing table --=============================== IF NOT EXISTS (SELECT * FROM INFORMATION_SCHEMA.COLUMNS where TABLE_SCHEMA='dbo' AND TABLE_NAME = 'TableName' AND COLUMN_NAME = 'ColumnName') BEGIN ALTER TABLE [dbo].[TableName] ADD [ColumnName] INT NOT NULL DEFAULT(0) -- Add a description extended property to the column to specify what its purpose is. EXEC sys.sp_addextendedproperty @name=N'MS_Description',  @value = N'Add column comments here, describing what this column is for.' ,  @level0type=N'SCHEMA',@level0name=N'dbo', @level1type=N'TABLE', @level1name = N'TableName', @level2type=N'COLUMN', @level2name = N'ColumnName' END --=============================== -- Drop a table --=============================== IF EXISTS (SELECT * FROM INFORMATION_SCHEMA.TABLES WHERE TABLE_NAME = 'TableName' AND TABLE_SCHEMA='dbo') BEGIN DROP TABLE [dbo].[TableName] END --=============================== -- Drop a view --=============================== IF EXISTS (SELECT * FROM INFORMATION_SCHEMA.VIEWS WHERE TABLE_NAME = 'ViewName' AND TABLE_SCHEMA='dbo') BEGIN DROP VIEW [dbo].[ViewName] END --=============================== -- Drop a column --=============================== IF EXISTS (SELECT * FROM INFORMATION_SCHEMA.COLUMNS where TABLE_SCHEMA='dbo' AND TABLE_NAME = 'TableName' AND COLUMN_NAME = 'ColumnName') BEGIN -- If the column has an extended property, drop it first. IF EXISTS (SELECT * FROM sys.fn_listExtendedProperty(N'MS_Description', N'SCHEMA', N'dbo', N'Table', N'TableName', N'COLUMN', N'ColumnName') BEGIN EXEC sys.sp_dropextendedproperty @name=N'MS_Description',  @level0type=N'SCHEMA',@level0name=N'dbo', @level1type=N'TABLE', @level1name = N'TableName', @level2type=N'COLUMN', @level2name = N'ColumnName' END ALTER TABLE [dbo].[TableName] DROP COLUMN [ColumnName] END --=============================== -- Drop Primary key constraint --=============================== IF EXISTS (SELECT * FROM INFORMATION_SCHEMA.TABLE_CONSTRAINTS WHERE CONSTRAINT_TYPE='PRIMARY KEY' AND TABLE_SCHEMA='dbo' AND TABLE_NAME = 'TableName' AND CONSTRAINT_NAME = 'PK_Name') BEGIN ALTER TABLE [dbo].[TableName] DROP CONSTRAINT [PK_Name] END --=============================== -- Drop Foreign key constraint --=============================== IF EXISTS (SELECT * FROM INFORMATION_SCHEMA.TABLE_CONSTRAINTS WHERE CONSTRAINT_TYPE='FOREIGN KEY' AND TABLE_SCHEMA='dbo' AND TABLE_NAME = 'TableName' AND CONSTRAINT_NAME = 'FK_Name') BEGIN ALTER TABLE [dbo].[TableName] DROP CONSTRAINT [FK_Name] END --=============================== -- Drop Unique key constraint --=============================== IF EXISTS (SELECT * FROM INFORMATION_SCHEMA.TABLE_CONSTRAINTS WHERE CONSTRAINT_TYPE='UNIQUE' AND TABLE_SCHEMA='dbo' AND TABLE_NAME = 'TableName' AND CONSTRAINT_NAME = 'UNI_Name') BEGIN ALTER TABLE [dbo].[TableNames] DROP CONSTRAINT [UNI_Name] END --=============================== -- Drop Check constraint --=============================== IF EXISTS (SELECT * FROM INFORMATION_SCHEMA.TABLE_CONSTRAINTS WHERE CONSTRAINT_TYPE='CHECK' AND TABLE_SCHEMA='dbo' AND TABLE_NAME = 'TableName' AND CONSTRAINT_NAME = 'CH_Name') BEGIN ALTER TABLE [dbo].[TableName] DROP CONSTRAINT [CH_Name] END --=============================== -- Drop a column's Default value constraint --=============================== DECLARE @ConstraintName VARCHAR(100) SET @ConstraintName = (SELECT TOP 1 s.name FROM sys.sysobjects s JOIN sys.syscolumns c ON s.parent_obj=c.id WHERE s.xtype='d' AND c.cdefault=s.id  AND parent_obj = OBJECT_ID('TableName') AND c.name ='ColumnName') IF @ConstraintName IS NOT NULL BEGIN EXEC ('ALTER TABLE [dbo].[TableName] DROP CONSTRAINT ' + @ConstraintName) END --=============================== -- Example of how to drop dynamically named Unique constraint --=============================== DECLARE @ConstraintName VARCHAR(100) SET @ConstraintName = (SELECT TOP 1 CONSTRAINT_NAME FROM INFORMATION_SCHEMA.TABLE_CONSTRAINTS  WHERE CONSTRAINT_TYPE='UNIQUE' AND TABLE_SCHEMA='dbo' AND TABLE_NAME = 'TableName' AND CONSTRAINT_NAME LIKE 'FirstPartOfConstraintName%') IF EXISTS (SELECT * FROM INFORMATION_SCHEMA.TABLE_CONSTRAINTS WHERE CONSTRAINT_TYPE='UNIQUE' AND TABLE_SCHEMA='dbo' AND TABLE_NAME = 'TableName' AND CONSTRAINT_NAME = @ConstraintName) BEGIN EXEC ('ALTER TABLE [dbo].[TableName] DROP CONSTRAINT ' + @ConstraintName) END --=============================== -- Check for and drop a temp table --=============================== IF OBJECT_ID('tempdb..#TableName') IS NOT NULL DROP TABLE #TableName --=============================== -- Drop a stored procedure --=============================== IF EXISTS (SELECT * FROM INFORMATION_SCHEMA.ROUTINES WHERE ROUTINE_TYPE='PROCEDURE' AND ROUTINE_SCHEMA='dbo' AND ROUTINE_NAME = 'StoredProcedureName') BEGIN DROP PROCEDURE [dbo].[StoredProcedureName] END --=============================== -- Drop a UDF --=============================== IF EXISTS (SELECT * FROM INFORMATION_SCHEMA.ROUTINES WHERE ROUTINE_TYPE='FUNCTION' AND ROUTINE_SCHEMA='dbo' AND  ROUTINE_NAME = 'UDFName') BEGIN DROP FUNCTION [dbo].[UDFName] END --=============================== -- Drop an Index --=============================== IF EXISTS (SELECT * FROM SYS.INDEXES WHERE name = 'IndexName') BEGIN DROP INDEX TableName.IndexName END --=============================== -- Drop a Schema --=============================== IF EXISTS (SELECT * FROM INFORMATION_SCHEMA.SCHEMATA WHERE SCHEMA_NAME = 'SchemaName') BEGIN EXEC('DROP SCHEMA SchemaName') END

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• Does having multiple URIs mapping to the same resource help SEO?

  - by Brian Wheeler

  Let's say I have a site with products that have tags, if each resource is available at GET '/products/tagged/:tag_list/:product_permalink' Could that be better for SEO than just one permalink? For example a product tagged "tea" and "coffee" would be available at GET '/products/tagged/tea/:product_permalink' GET '/products/tagged/coffee/:product_permalink' GET '/products/tagged/tea/coffee/:product_permalink' GET '/products/tagged/coffee/tea/:product_permalink' I would imagine that google would appreciate this because it gives multiple URIs with different levels of detail about the product, but I cant really be certain. Anyone have any direct knowledge on the topic? --EDIT-- As John Conde points, this is a horrible idea. What about having the links on my site link to a route such as GET '/products/tagged/:full_tag_list/:product_permalink', and then any time a user changes tags just have a HTTP moved permanently status to the new URL. Therefore duplicate URLs would be highly unlikely and mitigated by the proper response. Would this be better?

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• In an Entity/Component system, can component data be implemented as a simple array of key-value pairs? [on hold]

  - by 010110110101

  I'm trying to wrap my head around how to organize components in an Entity Component Systems once everything in the current scene/level is loaded in memory. (I'm a hobbyist BTW) Some people seem to implement the Entity as an object that contains a list of of "Component" objects. Components contain data organized as an array of key-value pairs. Where the value is serialized "somehow". (pseudocode is loosely in C# for brevity) class Entity { Guid _id; List<Component> _components; } class Component { List<ComponentAttributeValue> _attributes; } class ComponentAttributeValue { string AttributeName; object AttributeValue; } Others describe Components as an in-memory "table". An entity acquires the component by having its key placed in a table. The attributes of the component-entity instance are like the columns in a table class Renderable_Component { List<RenderableComponentAttributeValue> _entities; } class RenderableComponentAttributeValue { Guid entityId; matrix4 transformation; // other stuff for rendering // everything is strongly typed } Others describe this actually as a table. (and such tables sound like an EAV database schema BTW) (and the value is serialized "somehow") Render_Component_Table ---------------- Entity Id Attribute Name Attribute Value and when brought into running code: class Entity { Guid _id; Dictionary<string, object> _attributes; } My specific question is: Given various components, (Renderable, Positionable, Explodeable, Hideable, etc) and given that each component has an attribute with a particular name, (TRANSLATION_MATRIX, PARTICLE_EMISSION_VELOCITY, CAN_HIDE, FAVORITE_COLOR, etc) should: an entity contain a list of components where each component, in turn, has their own array of named attributes with values serialized somehow or should components exist as in-memory tables of entity references and associated with each "row" there are "columns" representing the attribute with values that are specific to each entity instance and are strongly typed or all attributes be stored in an entity as a singular array of named attributes with values serialized somehow (could have name collisions) or something else???

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• Setup shortcut keys not working

  - by Tim

  In my Ubuntu 12.04, in keyboard settings, I didn't find a shortcut key for restarting X, so in "Customer Shorcut", I set up Ctrl+Alt+Backspace for command sudo restart lightdm. But after that the shortcut doesn't work. Is it because it requires root privilege? Also I have a SysRq key on my keyboard, which I think to be the "Magic SysReq Key". My SysRq key is shared with PrtSc key (for screen shoot), and is in blue which means I have to press Fn key at the same time to invoke SysRq instead of PrtSC. But every time I press Fn+SysRq, it always shoots a photo of the screen, same as just hitting PrtSc i.e. without hitting Fn. I wonder how to use the Magic SysReq Key? Does it mean the shortcut has not been linked to any command that is supposed for Magic SysReq Key yet? PS: My laptop is Lenovo T400 and OS is Ubuntu 12.04. Thanks!

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• When mapping the surface of a sphere with tiles, how might you deal with polar distortion?

  - by clweeks

  It's easy to deal with the way locations interact on a clean Cartesian grid. It's just vanilla math. And you can kind of ignore the geometry of the sphere's surface for a bunch of it if you want to just truncate the poles or something. But I keep coming up with ideas for games where the polar space matters. Geo-coded ARGs and global roguelikes and stuff. I want square(ish?) locations -- reasonably representable by square tiles of the same size across the globe, anyway. This has to be a solved problem, right? What are the solutions? ETA: At the equator -- and assuming that your square locations are reasonably small, it's close enough to true that you can get away with having one square in the rows north and south of the most equatorial row. And you could probably get away with that by just hand-waving the difference up to like 45-degrees or so. But eventually, you need to have fewer squares in a pole-ward circumferential row. If I reduce the length of the row by one and offset the squares by 1/2 then they're just like hexes and it's relatively easy to do the coding to keep track of the connections. But as you get pole-ward, it gets more and more extreme. Projecting the surface of the world onto the surface of a cube is tempting. But I figured there must be more elegant solutions already in use. If I did the cube thing (not dissecting it further through geodesy) Are there any pros and cons related to placing the pole at the center of a face or at the vertex of three sides?

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• Multithreading 2D gravity calculations

  - by Postman

  I'm building a space exploration game and I've currently started working on gravity ( In C# with XNA). The gravity still needs tweaking, but before I can do that, I need to address some performance issues with my physics calculations. This is using 100 objects, normally rendering 1000 of them with no physics calculations gets well over 300 FPS (which is my FPS cap), but any more than 10 or so objects brings the game (and the single thread it runs on) to its knees when doing physics calculations. I checked my thread usage and the first thread was killing itself from all the work, so I figured I just needed to do the physics calculation on another thread. However when I try to run the Gravity.cs class's Update method on another thread, even if Gravity's Update method has nothing in it, the game is still down to 2 FPS. Gravity.cs public void Update() { foreach (KeyValuePair<string, Entity> e in entityEngine.Entities) { Vector2 Force = new Vector2(); foreach (KeyValuePair<string, Entity> e2 in entityEngine.Entities) { if (e2.Key != e.Key) { float distance = Vector2.Distance(entityEngine.Entities[e.Key].Position, entityEngine.Entities[e2.Key].Position); if (distance > (entityEngine.Entities[e.Key].Texture.Width / 2 + entityEngine.Entities[e2.Key].Texture.Width / 2)) { double angle = Math.Atan2(entityEngine.Entities[e2.Key].Position.Y - entityEngine.Entities[e.Key].Position.Y, entityEngine.Entities[e2.Key].Position.X - entityEngine.Entities[e.Key].Position.X); float mult = 0.1f * (entityEngine.Entities[e.Key].Mass * entityEngine.Entities[e2.Key].Mass) / distance * distance; Vector2 VecForce = new Vector2((float)Math.Cos(angle), (float)Math.Sin(angle)); VecForce.Normalize(); Force = Vector2.Add(Force, VecForce * mult); } } } entityEngine.Entities[e.Key].Position += Force; } } Yeah, I know. It's a nested foreach loop, but I don't know how else to do the gravity calculation, and this seems to work, it's just so intensive that it needs its own thread. (Even if someone knows a super efficient way to do these calculations, I'd still like to know how I COULD do it on multiple threads instead) EntityEngine.cs (manages an instance of Gravity.cs) public class EntityEngine { public Dictionary<string, Entity> Entities = new Dictionary<string, Entity>(); public Gravity gravity; private Thread T; public EntityEngine() { gravity = new Gravity(this); } public void Update() { foreach (KeyValuePair<string, Entity> e in Entities) { Entities[e.Key].Update(); } T = new Thread(new ThreadStart(gravity.Update)); T.IsBackground = true; T.Start(); } } EntityEngine is created in Game1.cs, and its Update() method is called within Game1.cs. I need my physics calculation in Gravity.cs to run every time the game updates, in a separate thread so that the calculation doesn't slow the game down to horribly low (0-2) FPS. How would I go about making this threading work? (any suggestions for an improved Planetary Gravity system are welcome if anyone has them) I'm also not looking for a lesson in why I shouldn't use threading or the dangers of using it incorrectly, I'm looking for a straight answer on how to do it. I've already spent an hour googling this very question with little results that I understood or were helpful. I don't mean to come off rude, but it always seems hard as a programming noob to get a straight meaningful answer, I usually rather get an answer so complex I'd easily be able to solve my issue if I understood it, or someone saying why I shouldn't do what I want to do and offering no alternatives (that are helpful). Thank you for the help!

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• Using string[] as a Dictionary key e.g. Dictionary<string[], StringBuilder>

  - by Nick Allen - Tungle139

  The structure I am trying to achieve is a composite Dictionary key which is item name and item displayname and the Dictionary value being the combination of n strings So I came up with var pages = new Dictionary<string[], StringBuilder>() { { new string[] { "food-and-drink", "Food & Drink" }, new StringBuilder() }, { new string[] { "activities-and-entertainment", "Activities & Entertainment" }, new StringBuilder() } }; foreach (var obj in my collection) { switch (obj.Page) { case "Food": case "Drink": pages["KEY"].Append("obj.PageValue"); break; ... } } The part I am having trouble with is accessing the Dictionary Key pages["KEY"] How do I target the Dictionary Key whose value at [0] == some value? Hope that makes sense

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• Oracle - Is there any effects of not having a primary key on a table ?

  - by Sathya

  We use sequence numbers for primary keys on the tables. There are some tables where we dont really use the primary key for any querying purpose. But, we have Indexes on other columns. These are non-unique indexes. The queries use these non-primary key columns in the WHERE conditions. So, I dont really see any benefit of having a primary key on such tables. My experience with SQL 2000 was that, it used to replicate tables which had some primary key. Otherwise it would not. I am using Oracle 10gR2. I would like to know if there are any such side-effects of having tables that dont have primary key.

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• DbMetal chokes on repeated foreign key references in SQLite - any ideas?

  - by DanM

  I've been struggling to get DbMetal to process my SQLite database. I finally isolated the problem. It won't allow a table to have two foreign key references to the same column. For example, a SQLite database with these two tables will fail: CREATE TABLE Person ( Id INTEGER PRIMARY KEY, Name TEXT NOT NULL ); CREATE TABLE Match ( Id INTEGER PRIMARY KEY, WinnerPersonId INTEGER NOT NULL REFERENCES Person(Id), LoserPersonId INTEGER NOT NULL REFERENCES Person(Id) ); I get this error: DbMetal: Sequence contains more than one matching element If I get rid of the second foreign key reference, no error occurs. So, this works: CREATE TABLE Match ( Id INTEGER PRIMARY KEY, WinnerPersonId INTEGER NOT NULL REFERENCES Person(Id), LoserPersonId INTEGER NOT NULL ); But I really need both "person" columns to reference the person table. I submitted a bug report for this, but I could use a workaround in the meantime. Any ideas?

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• Is it a good idea to use only a key to encrypt an entire (small) filesystem?

  - by Fernando Miguélez

  This question comes as part of my doubts presented on a broader question about ideas implementing a small encrypted filesystem on Java Mobile phones (J2ME, BlackBerry, Android). Provided the litte feedback received, considering the density of the question, I decided to divide those doubts into small questions. So to sum up I plan to "create" an encrypted filesystem for for mobile phones (with the help of BoucyCastle or a subset of JCE), providing an API that let access to them in a transparent way. Encryption would be carried out on a file basis (not blocks). My question is this: Is it a good idea to use only a simmetric key (maybe AES-256) to encrypt all the files (they wouldn't be that many, maybe tens of them) and store this key in a keystore (protected by a pin) or would you rather encrypt each file with an on-the-fly generated key stored alongside each file, encrypting that key with the "master" key stored on the keystore? What are the benefits/drawbacks of each approach?

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• What is the representation of the mac command key in the terminal?

  - by freethinker

  Like control key is represented by a '^' in the terminal, what is the equivalent for the command key (mac)? I am trying to remap my bash shortcuts using stty For eg stty eof ^D But instead of control, I want to use the command key. EDIT: Okay so the issue I was trying to solve was that I wanted to interchange command and control keys because I work on osx and linux and the different key combinations cause me a lot of pain. So I interchanged the modifier keys using osx preferences. But now all the bash shortcuts like Ctrl+C etc had become equivalent of using the key sequences 'cmd+c' - which is not acceptable. Thankfully iTerm2, supports remapping of modifier keys as well, so for iterm2 I reversed them again which means iTerm2 recognizes command as command and control as control. So problem solved for now.

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• Lua : How to check if one of the values associated with the specified key of a table is nil, from ap

  - by felace

  In lua, it's legal to do this : table={} bar if(table[key]==nil) foo However, using C API, I couldn't find way to check if there's a nil value on the specified position. lua_getglobal(L,"table"); lua_gettable(L,key); If there's a nil value stored in table[key], lua_gettable would give me the "unprotected error in call to Lua API (attempt to index a nil value)" message. Is there any way to check if there's actually something associated with that key, before actually pushing the key to do so ?

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• Public key of Android project and keystore created in Eclipse?

  - by user578056

  I created an Android project using Eclipse (under Windows FWIW) and let Eclipse create the keypair during the Export Android Application process. I successfully used Eclipse to make a signed release build that is now on the Market. Now I want to now use ProGuard, which I believe means using Ant instead of Eclipse to build. It was a pain, but Ant building works in both debug and release, until it tries to sign the APK. I get: [signjar] jarsigner: Certificate chain not found for: redacted. redacted must reference a valid KeyStore key entry containing a private key and corresponding public key certificate chain. keytool -list -keystore redacted gives me: Keystore type: JKS Keystore provider: SUN Your keystore contains 1 entry redacted, Jan 16, 2011, PrivateKeyEntry, Certificate fingerprint (MD5): BD:0F:70:C1:39:F5:FE:5B:BC:CD:89:0B:C8:66:95:E0 Which brings me to the actual question: where is my public key? I have some sort of public key on my Android Market profile, but is that the pair for my private key? If so, how do I store that in the keystore so that jarsigner will work?

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• How to do this Unidirectional NHibernate one-to-one mapping?

  - by JMSA

  This is a problem of unidirectional one-to-one mapping in NHibernate. Student.cs public class Student { public int ID { get; set; } public int Roll { get; set; } public int RegNo { get; set; } public string Name { get; set; } public StudentDetail StudentDetail { get; set; } } StudentDetail.cs public class StudentDetail { public int ID { get; set; } public string Father { get; set; } public string Mother { get; set; } } How can I map these classes (how do the hbm mapping files look like) to the following case of one-to-one relationship? Please have a look at the classes very carefully.

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• How to do this NHibernate one-to-one mapping?

  - by JMSA

  This is a problem of unidirectional one-to-one mapping in NHibernate. Student.cs public class Student { public int ID { get; set; } public int Roll { get; set; } public int RegNo { get; set; } public string Name { get; set; } public StudentDetail StudentDetail { get; set; } } StudentDetail.cs public class StudentDetail { public int ID { get; set; } public string Father { get; set; } public string Mother { get; set; } } How can I map these classes (how do the hbm mapping files look like) to the following two distinct cases of one-to-one relationships? 1st case: 2nd case:

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• DSA signature verification input

  - by calccrypto

  What is the data inputted into DSA when PGP signs a message? From RFC4880, i found A Signature packet describes a binding between some public key and some data. The most common signatures are a signature of a file or a block of text, and a signature that is a certification of a User ID. im not sure if it is the entire public key, just the public key packet, or some other derivative of a pgp key packet. whatever it is, i cannot get the DSA signature to verify here is a sample im testing my program on: -----BEGIN PGP SIGNED MESSAGE----- Hash: SHA1 abcd -----BEGIN PGP SIGNATURE----- Version: BCPG v1.39 iFkEARECABkFAk0z65ESHGFiYyAodGVzdCBrZXkpIDw+AAoJEC3Jkh8+bnkusO0A oKG+HPF2Qrsth2zS9pK+eSCBSypOAKDBgC2Z0vf2EgLiiNMk8Bxpq68NkQ== =gq0e -----END PGP SIGNATURE----- Dumped from pgpdump.net Old: Signature Packet(tag 2)(89 bytes) Ver 4 - new Sig type - Signature of a canonical text document(0x01). Pub alg - DSA Digital Signature Algorithm(pub 17) Hash alg - SHA1(hash 2) Hashed Sub: signature creation time(sub 2)(4 bytes) Time - Mon Jan 17 07:11:13 UTC 2011 Hashed Sub: signer's User ID(sub 28)(17 bytes) User ID - abc (test key) <> Sub: issuer key ID(sub 16)(8 bytes) Key ID - 0x2DC9921F3E6E792E Hash left 2 bytes - b0 ed DSA r(160 bits) - a1 be 1c f1 76 42 bb 2d 87 6c d2 f6 92 be 79 20 81 4b 2a 4e DSA s(160 bits) - c1 80 2d 99 d2 f7 f6 12 02 e2 88 d3 24 f0 1c 69 ab af 0d 91 -> hash(DSA q bits) and the public key for it is: -----BEGIN PGP PUBLIC KEY BLOCK----- Version: BCPG v1.39 mOIETTPqeBECALx+i9PIc4MB2DYXeqsWUav2cUtMU1N0inmFHSF/2x0d9IWEpVzE kRc30PvmEHI1faQit7NepnHkkphrXLAoZukAoNP3PB8NRQ6lRF6/6e8siUgJtmPL Af9IZOv4PI51gg6ICLKzNO9i3bcUx4yeG2vjMOUAvsLkhSTWob0RxWppo6Pn6MOg dMQHIM5sDH0xGN0dOezzt/imAf9St2B0HQXVfAAbveXBeRoO7jj/qcGx6hWmsKUr BVzdQhBk7Sku6C2KlMtkbtzd1fj8DtnrT8XOPKGp7/Y7ASzRtBFhYmMgKHRlc3Qg a2V5KSA8PohGBBMRAgAGBQJNM+p5AAoJEC3Jkh8+bnkuNEoAnj2QnqGtdlTgUXCQ Fyvwk5wiLGPfAJ4jTGTL62nWzsgrCDIMIfEG2shm8bjMBE0z6ngQAgCUlP7AlfO4 XuKGVCs4NvyBpd0KA0m0wjndOHRNSIz44x24vLfTO0GrueWjPMqRRLHO8zLJS/BX O/BHo6ypjN87Af0VPV1hcq20MEW2iujh3hBwthNwBWhtKdPXOndJGZaB7lshLJuW v9z6WyDNXj/SBEiV1gnPm0ELeg8Syhy5pCjMAgCFEc+NkCzcUOJkVpgLpk+VLwrJ /Wi9q+yCihaJ4EEFt/7vzqmrooXWz2vMugD1C+llN6HkCHTnuMH07/E/2dzciEYE GBECAAYFAk0z6nkACgkQLcmSHz5ueS7NTwCdED1P9NhgR2LqwyS+AEyqlQ0d5joA oK9xPUzjg4FlB+1QTHoOhuokxxyN =CTgL -----END PGP PUBLIC KEY BLOCK----- the public key packet of the key is mOIETTPqeBECALx+i9PIc4MB2DYXeqsWUav2cUtMU1N0inmFHSF/2x0d9IWEpVzEkRc30PvmEHI1faQi t7NepnHkkphrXLAoZukAoNP3PB8NRQ6lRF6/6e8siUgJtmPLAf9IZOv4PI51gg6ICLKzNO9i3bcUx4ye G2vjMOUAvsLkhSTWob0RxWppo6Pn6MOgdMQHIM5sDH0xGN0dOezzt/imAf9St2B0HQXVfAAbveXBeRoO 7jj/qcGx6hWmsKUrBVzdQhBk7Sku6C2KlMtkbtzd1fj8DtnrT8XOPKGp7/Y7ASzR in radix 64 i have tried many different combinations of sha1(< some data + 'abcd'),but the calculated value v never equals r, of the signature i know that the pgp implementation i used to create the key and signature is correct. i also know that my DSA implementation and PGP key data extraction program are correct. thus, the only thing left is the data to hash. what is the correct data to be hashed?

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• How can we add IntelliSense to visual studio in time of nhibernate mapping file editing?

  - by masoud ramezani

  How can we add IntelliSense to visual studio in time of nhibernate mapping file editing?

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• java and threads: very strange behaviour

  - by Derk

  private synchronized Map<Team, StandingRow> calculateStanding() { System.out.println("Calculate standing for group " + getName()); Map<Team, StandingRow> standing = new LinkedHashMap<Team, StandingRow>(); for (Team team : teams) { standing.put(team, new StandingRow(team)); } StandingRow homeTeamRow, awayTeamRow; for (Match match : matches.values()) { homeTeamRow = standing.get(match.getHomeTeam()); awayTeamRow = standing.get(match.getAwayTeam()); System.out.println("Contains key for " + match.getHomeTeam() + ": " + standing.containsKey(match.getHomeTeam())); System.out.println("Contains key for " + match.getAwayTeam() + ": " + standing.containsKey(match.getAwayTeam())); } } This is my code. matches contains 6 elements, but the problem is that after two matches no keys are anymore found in the standing map. The output is for example Contains key for Zuid-Afrika: true Contains key for Mexico: true Contains key for Uruguay: true Contains key for Frankrijk: true Contains key for Zuid-Afrika: false Contains key for Uruguay: false Contains key for Frankrijk: false Contains key for Mexico: false Contains key for Mexico: false Contains key for Uruguay: false Contains key for Frankrijk: false Contains key for Zuid-Afrika: false This is in a threaded environment, but the method is synchronized so I thought that this would not give a problem? I have also a simple unit test for this method and that works well.

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• Crashes in Core Data's Inferred Mapping Model Creation (Lightweight Migration). Threading Issue?

  - by enchilada

  I'm getting random crashes when creating an inferred mapping model (with Core Data's lightweight migration) within my application. By the way, I have to do it programmatically in my application while it is running. This is how I create this model (after I have made proper currentModel and newModel objects, of course): NSMappingModel *mappingModel = [NSMappingModel inferredMappingModelForSourceModel:currentModel destinationModel:newModel error:&error]; The problem is this: This method is crashing randomly. When it works, it works just fine without issues. But when it crashes, it crashes my application (instead of returning nil to signify that the method failed, as it should). By randomly, I mean that sometimes it happens and sometimes not. It is unpredictable. Now, here is the deal: I'm running this method in another thread. More precisely, it is located inside a block that is passed via GCD to run on the global main queue. I need to do this for my UI to appear crisp to the user, i.e. so that I can display a progress indicator while the work is underway. The strange thing seems to be that if I remove the GCD stuff and just let it run on the main thread, it seems to be working fine and never crashing. Thus, could it be because I'm running this on a different thread that this is crashing? I somehow find that weird because I don't believe I'm breaking any Core Data rules regarding multi-threading. In particular, I'm not passing any managed objects around, and whenever I need access to the MOC, I create a new MOC, i.e. I'm not relying on any MOC (or for that matter: anything) that has been created earlier on the main thread. Besides the little MOC stuff that occurs, occurs after the mapping model creation method, i.e. after the point at which the app crashes, so it can't possibly be a cause of the crashes under consideration here. All I'm doing is taking two MOMs and asking for a mapping model between them. That can't be wrong even under threading, now can it? Any ideas on what could be going on?

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• What mapping/earth controls are available for iPad app development?

  - by user333639

  What mapping/earth controls are available for iPad app developer? Is MapKit the only one?

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• How do I prevent an ASP.NET MVC deployment on IIS 6.0, using wildcard mapping, from attempting to ha

  - by Rob

  As noted by the title, what is the best way to configure an IIS 6.0 deployment of an ASP.NET MVC application such that connections to hidden shares are ignored? The application in question is using wildcard mapping to allow for clean URLs since we are planning on upgrading to IIS 7.0 in the near future and we are also handling the caching and compression issues with a custom library so we would like to avoid turning wildcard mapping off unless absolutely necessary. Below is a one of the errors from the application to give you an example of what we are seeing. -------------------------------------------------------------------------------- System.Web.HttpException -------------------------------------------------------------------------------- Time Stamp - 03 Mar 2010, 08:11:44 Path - N/A, Internal Server Operation Message - The controller for path '/C$' could not be found or it does not implement IController. Target Site - System.Web.Mvc.IController GetControllerInstance(System.Type) Stack Trace - at System.Web.Mvc.DefaultControllerFactory.GetControllerInstance(Type controllerType) at System.Web.Mvc.DefaultControllerFactory.CreateController(RequestContext requestContext, String controllerName) at System.Web.Mvc.MvcHandler.ProcessRequest(HttpContextBase httpContext) at System.Web.Mvc.MvcHandler.ProcessRequest(HttpContext httpContext) at System.Web.Mvc.MvcHandler.System.Web.IHttpHandler.ProcessRequest(HttpContext httpContext) at System.Web.HttpApplication.CallHandlerExecutionStep.System.Web.HttpApplication.IExecutionStep.Execute() at System.Web.HttpApplication.ExecuteStep(IExecutionStep step, Boolean& completedSynchronously) --------------------------------------------------------------------------------

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• How do you work around memcached's key/value limitations?

  - by mjy

  Memcached has length limitations for keys (250?) and values (roughtly 1MB), as well as some (to my knowledge) not very well defined character restrictions for keys. What is the best way to work around those in your opinion? I use the Perl API Cache::Memcached. What I do currently is store a special string for the main key's value if the original value was too big ("parts:<number") and in that case, I store <number parts with keys named 1+<main key, 2+<main key etc.. This seems "OK" (but messy) for some cases, not so good for others and it has the intrinsic problem that some of the parts might be missing at any time (so space is wasted for keeping the others and time is wasted reading them). As for the key limitations, one could probably implement hashing and store the full key (to work around collisions) in the value, but I haven't needed to do this yet. Has anyone come up with a more elegant way, or even a Perl API that handles arbitrary data sizes (and key values) transparently? Has anyone hacked the memcached server to support arbitrary keys/values?

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• Can I configure AutoMapper to read from custom column names when mapping from IDataReader?

  - by rohancragg

  Psuedo code for mapping configuration (as below) is not possible since the lambda only lets us access Type IDataReader, wheras when actually mapping, AutoMapper will reach into each "cell" of each IDataRecord while IDataReader.Read() == true: var mappingConfig = Mapper.CreateMap<IDataReader, IEnumerable<MyDTO>>(); mappingConfig.ForMember( destination => destination.???, options => options.MapFrom(source => source.???)); Can anyone think of a way to do this using AutoMapper configuration at runtime or just some other dynamic approach that meets the requirement below. The requirement is to support any incoming IDataReader which may have column names that don't match the property names of MyDTO and there is no naming convention I can rely on. Instead we'll ask the user at runtime to cross-reference the expected column names with the actual column names found in the IDataReader via IDataReader.GetSchemaTable().

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• GUID or int entity key with SQL Compact/EF4?

  - by David Veeneman

  This is a follow-up to an earlier question I posted on EF4 entity keys with SQL Compact. SQL Compact doesn't allow server-generated identity keys, so I am left with creating my own keys as objects are added to the ObjectContext. My first choice would be an integer key, and the previous answer linked to a blog post that shows an extension method that uses the Max operator with a selector expression to find the next available key: public static TResult NextId<TSource, TResult>(this ObjectSet<TSource> table, Expression<Func<TSource, TResult>> selector) where TSource : class { TResult lastId = table.Any() ? table.Max(selector) : default(TResult); if (lastId is int) { lastId = (TResult)(object)(((int)(object)lastId) + 1); } return lastId; } Here's my take on the extension method: It will work fine if the ObjectContext that I am working with has an unfiltered entity set. In that case, the ObjectContext will contain all rows from the data table, and I will get an accurate result. But if the entity set is the result of a query filter, the method will return the last entity key in the filtered entity set, which will not necessarily be the last key in the data table. So I think the extension method won't really work. At this point, the obvious solution seems to be to simply use a GUID as the entity key. That way, I only need to call Guid.NewGuid() method to set the ID property before I add a new entity to my ObjectContext. Here is my question: Is there a simple way of getting the last primary key in the data store from EF4 (without having to create a second ObjectContext for that purpose)? Any other reason not to take the easy way out and simply use a GUID? Thanks for your help.

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• Why does "xsd:date" of XML Schema Type mapped "javax.xml.datatype.XMLGregorianCalendar" When Schema-to-Java Mapping of JAXB does.

  - by Take

  I don't know why does "xsd:date" of XML Schema Type mapped "javax.xml.datatype.XMLGregorianCalendar" When Schema-to-Java Mapping of JAXB does. Why does "xsd:date" of XML Schema Type mapped "java.util.Date" ? I guess that JAXB intentionally does its mapping. I want to know that reason if any. And if exists it, how to change "xsd:date" of XML Schema Type to "java.util.Date" of Java class without using annotation(ex.@XmlJavaTypeAdapter). I want to do mashalling and unmarshalling without all annotations.

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