Search Results

Search found 23347 results on 934 pages for 'key storage'.

Page 153/934 | < Previous Page | 149 150 151 152 153 154 155 156 157 158 159 160  | Next Page >

• Loading any MVC page fails with the error "An item with the same key has already been added."

  - by MajorRefactoring

  I am having an intermittent issue that is appearing on one server only, and is causing all MVC pages to fail to load with the error "An item with the same key has already been added." Restarting the application pool fixes the issue, but until then, loading any mvc page throws the following exception: Event code: 3005 Event message: An unhandled exception has occurred. Event time: 10/11/2012 08:09:24 Event time (UTC): 10/11/2012 08:09:24 Event ID: d76264aedc4241d4bce9247692510466 Event sequence: 6407 Event occurrence: 30 Event detail code: 0 Application information: Application domain: /LM/W3SVC/21/ROOT-2-129969647741292058 Trust level: Full Application Virtual Path: / Application Path: d:\websites\SiteAndAppPoolName\ Machine name: UKSERVER Process information: Process ID: 6156 Process name: w3wp.exe Account name: IIS APPPOOL\SiteAndAppPoolName Exception information: Exception type: ArgumentException Exception message: An item with the same key has already been added. Server stack trace: at System.Collections.Generic.Dictionary`2.Insert(TKey key, TValue value, Boolean add) at System.Linq.Enumerable.ToDictionary[TSource,TKey,TElement](IEnumerable`1 source, Func`2 keySelector, Func`2 elementSelector, IEqualityComparer`1 comparer) at System.Web.WebPages.Scope.WebConfigScopeDictionary.<>c__DisplayClass4.<.ctor>b__0() at System.Lazy`1.CreateValue() Exception rethrown at [0]: at System.Lazy`1.get_Value() at System.Web.WebPages.Scope.WebConfigScopeDictionary.TryGetValue(Object key, Object& value) at System.Web.Mvc.ViewContext.ScopeGet[TValue](IDictionary`2 scope, String name, TValue defaultValue) at System.Web.Mvc.ViewContext.ScopeCache.Get(IDictionary`2 scope, HttpContextBase httpContext) at System.Web.Mvc.ViewContext.GetClientValidationEnabled(IDictionary`2 scope, HttpContextBase httpContext) at System.Web.Mvc.Html.FormExtensions.FormHelper(HtmlHelper htmlHelper, String formAction, FormMethod method, IDictionary`2 htmlAttributes) at System.Web.Mvc.Html.FormExtensions.BeginForm(HtmlHelper htmlHelper, String actionName, String controllerName) at ASP._Page_Views_Dashboard_Functions_BookingQuickLookup_cshtml.Execute() in d:\Websites\SiteAndAppPoolName\Views\Dashboard\Functions\BookingQuickLookup.cshtml:line 3 at System.Web.WebPages.WebPageBase.ExecutePageHierarchy() at System.Web.Mvc.WebViewPage.ExecutePageHierarchy() at System.Web.WebPages.WebPageBase.ExecutePageHierarchy(WebPageContext pageContext, TextWriter writer, WebPageRenderingBase startPage) at System.Web.Mvc.Html.PartialExtensions.Partial(HtmlHelper htmlHelper, String partialViewName, Object model, ViewDataDictionary viewData) at ASP._Page_Views_Dashboard_Functions_cshtml.Execute() in d:\Websites\SiteAndAppPoolName\Views\Dashboard\Functions.cshtml:line 5 at System.Web.WebPages.WebPageBase.ExecutePageHierarchy() at System.Web.Mvc.WebViewPage.ExecutePageHierarchy() at System.Web.WebPages.WebPageBase.ExecutePageHierarchy(WebPageContext pageContext, TextWriter writer, WebPageRenderingBase startPage) at System.Web.Mvc.Html.RenderPartialExtensions.RenderPartial(HtmlHelper htmlHelper, String partialViewName, Object model) at ASP._Page_Views_Dashboard_Index_cshtml.Execute() in d:\Websites\SiteAndAppPoolName\Views\Dashboard\Index.cshtml:line 9 at System.Web.WebPages.WebPageBase.ExecutePageHierarchy() at System.Web.Mvc.WebViewPage.ExecutePageHierarchy() at System.Web.WebPages.WebPageBase.ExecutePageHierarchy(WebPageContext pageContext, TextWriter writer, WebPageRenderingBase startPage) at System.Web.Mvc.ViewResultBase.ExecuteResult(ControllerContext context) at System.Web.Mvc.ControllerActionInvoker.<>c__DisplayClass1c.<InvokeActionResultWithFilters>b__19() at System.Web.Mvc.ControllerActionInvoker.InvokeActionResultFilter(IResultFilter filter, ResultExecutingContext preContext, Func`1 continuation) at System.Web.Mvc.ControllerActionInvoker.InvokeActionResultFilter(IResultFilter filter, ResultExecutingContext preContext, Func`1 continuation) at System.Web.Mvc.ControllerActionInvoker.InvokeActionResultWithFilters(ControllerContext controllerContext, IList`1 filters, ActionResult actionResult) at System.Web.Mvc.ControllerActionInvoker.InvokeAction(ControllerContext controllerContext, String actionName) at System.Web.Mvc.Controller.ExecuteCore() at System.Web.Mvc.ControllerBase.Execute(RequestContext requestContext) at System.Web.Mvc.MvcHandler.<>c__DisplayClass6.<>c__DisplayClassb.<BeginProcessRequest>b__5() at System.Web.Mvc.Async.AsyncResultWrapper.<>c__DisplayClass1.<MakeVoidDelegate>b__0() at System.Web.Mvc.MvcHandler.<>c__DisplayClasse.<EndProcessRequest>b__d() at System.Web.HttpApplication.CallHandlerExecutionStep.System.Web.HttpApplication.IExecutionStep.Execute() at System.Web.HttpApplication.ExecuteStep(IExecutionStep step, Boolean& completedSynchronously) Request information: Request URL: http://SiteAndAppPoolName.spawtz.com/Dashboard Request path: /Dashboard User host address: 86.164.135.41 User: Is authenticated: False Authentication Type: Thread account name: IIS APPPOOL\SiteAndAppPoolName Thread information: Thread ID: 17 Thread account name: IIS APPPOOL\SiteAndAppPoolName Is impersonating: False Stack trace: at System.Lazy`1.get_Value() at System.Web.WebPages.Scope.WebConfigScopeDictionary.TryGetValue(Object key, Object& value) at System.Web.Mvc.ViewContext.ScopeGet[TValue](IDictionary`2 scope, String name, TValue defaultValue) at System.Web.Mvc.ViewContext.ScopeCache.Get(IDictionary`2 scope, HttpContextBase httpContext) at System.Web.Mvc.ViewContext.GetClientValidationEnabled(IDictionary`2 scope, HttpContextBase httpContext) at System.Web.Mvc.Html.FormExtensions.FormHelper(HtmlHelper htmlHelper, String formAction, FormMethod method, IDictionary`2 htmlAttributes) at System.Web.Mvc.Html.FormExtensions.BeginForm(HtmlHelper htmlHelper, String actionName, String controllerName) at ASP._Page_Views_Dashboard_Functions_BookingQuickLookup_cshtml.Execute() in d:\Websites\SiteAndAppPoolName\Views\Dashboard\Functions\BookingQuickLookup.cshtml:line 3 at System.Web.WebPages.WebPageBase.ExecutePageHierarchy() at System.Web.Mvc.WebViewPage.ExecutePageHierarchy() at System.Web.WebPages.WebPageBase.ExecutePageHierarchy(WebPageContext pageContext, TextWriter writer, WebPageRenderingBase startPage) at System.Web.Mvc.Html.PartialExtensions.Partial(HtmlHelper htmlHelper, String partialViewName, Object model, ViewDataDictionary viewData) at ASP._Page_Views_Dashboard_Functions_cshtml.Execute() in d:\Websites\SiteAndAppPoolName\Views\Dashboard\Functions.cshtml:line 5 at System.Web.WebPages.WebPageBase.ExecutePageHierarchy() at System.Web.Mvc.WebViewPage.ExecutePageHierarchy() at System.Web.WebPages.WebPageBase.ExecutePageHierarchy(WebPageContext pageContext, TextWriter writer, WebPageRenderingBase startPage) at System.Web.Mvc.Html.RenderPartialExtensions.RenderPartial(HtmlHelper htmlHelper, String partialViewName, Object model) at ASP._Page_Views_Dashboard_Index_cshtml.Execute() in d:\Websites\SiteAndAppPoolName\Views\Dashboard\Index.cshtml:line 9 at System.Web.WebPages.WebPageBase.ExecutePageHierarchy() at System.Web.Mvc.WebViewPage.ExecutePageHierarchy() at System.Web.WebPages.WebPageBase.ExecutePageHierarchy(WebPageContext pageContext, TextWriter writer, WebPageRenderingBase startPage) at System.Web.Mvc.ViewResultBase.ExecuteResult(ControllerContext context) at System.Web.Mvc.ControllerActionInvoker.<>c__DisplayClass1c.<InvokeActionResultWithFilters>b__19() at System.Web.Mvc.ControllerActionInvoker.InvokeActionResultFilter(IResultFilter filter, ResultExecutingContext preContext, Func`1 continuation) at System.Web.Mvc.ControllerActionInvoker.InvokeActionResultFilter(IResultFilter filter, ResultExecutingContext preContext, Func`1 continuation) at System.Web.Mvc.ControllerActionInvoker.InvokeActionResultWithFilters(ControllerContext controllerContext, IList`1 filters, ActionResult actionResult) at System.Web.Mvc.ControllerActionInvoker.InvokeAction(ControllerContext controllerContext, String actionName) at System.Web.Mvc.Controller.ExecuteCore() at System.Web.Mvc.ControllerBase.Execute(RequestContext requestContext) at System.Web.Mvc.MvcHandler.<>c__DisplayClass6.<>c__DisplayClassb.<BeginProcessRequest>b__5() at System.Web.Mvc.Async.AsyncResultWrapper.<>c__DisplayClass1.<MakeVoidDelegate>b__0() at System.Web.Mvc.MvcHandler.<>c__DisplayClasse.<EndProcessRequest>b__d() at System.Web.HttpApplication.CallHandlerExecutionStep.System.Web.HttpApplication.IExecutionStep.Execute() at System.Web.HttpApplication.ExecuteStep(IExecutionStep step, Boolean& completedSynchronously) Custom event details: As mentioned, it's every MVC action that throws this error until the app pool is restarted, and the error seems to be occurring in System.Web.WebPages.Scope.WebConfigScopeDictionary.TryGetValue(Object key, Object& value) Has anyone seen this issue before? It's only happening on this server, on any of the app pools on the server (not confined to this one) and an app pool restart sorts it. Any help much appreciated. Cheers, Matthew

  Read the article

• For a primary key of an integral type, why is it important to avoid gaps ?

  - by Jacques René Mesrine

  I am generating a surrogate key for a table & due to my hi/lo algorithm, everytime you reboot/restart the machine, gaps may appear. T1: current hi = 10000000 (sequence being dished out .. 1 to 100) Assume that current sequence is 10000050 T2: restart system. T3: System gives out the next_hi as 10000100 (sequence being dished out now ranges from 101 to 200) T4: Next request for a key returns 100001001 From a primary key or indexing internals perspective, why is it important that there be no gaps in the sequences ? I'm asking this for a deeper understanding of mysql specifically. Thanks

  Read the article

• How to intercept capture TAB key in WinForms application?

  - by Axarydax

  Hi, could you please help me with this one? I'm trying to capture Tab key in Windows Forms application and do a custom action on it. I have a Form with several listViews and buttons, I've set Form's KeyPreview property to true and when I press any other key than tab, my KeyDown event handler does get called. But that's not true with the Tab key - I don't receive WM_KEYDOWN message even in WndProc. Do I need to set each control inside my form - its TabStop property - to false? There must be a more ellegant way that that. Thanks.

  Read the article

• How to get the last key pressed on Mac ?

  - by Dheeraj

  Hi All, I'm writing a plugin for an application. I cannot derive from NSApplication as it is a third party application. I can get the callback in my plugin when any key is pressed. But I will not know what key is pressed. So is there any call in Cocoa to find the last key pressed when I get the callback? I only have NSView object. Any ideas will help me a lot. Thanks, Dheeraj.

  Read the article

• Where do I find API key and API secret for Facebook?

  - by Sara

  Trying to connect to Facebook to make a statusupdate through my Android application. Got the whole thing running but I need API key + secret. Where can I create/get a hold of these? private static final String apiKey = "<YOUR API KEY>"; private static final String apiSecret = "<YOUR SECRET KEY>"; Tried the same thing with Twitter and then I just "created" an application and recieved "ConsumerKEY" and "ConsumerSECRET", but what is the deal with Facebook?

  Read the article

• Can I allow a write access to a particular registry key without elevation?

  - by 280Z28

  I develop an extension for Visual Studio 2005, 2008, and 2010. The Visual Studio 2005 SDK requires write access to the following registry key during builds. The normal way to handle this run Visual Studio with elevated privileges. The entire issue can be avoided if there's some way I can set permissions to allow access to this particular registry key without elevation: HKLM\SOFTWARE\Microsoft\VisualStudio\8.0Exp Side note: This key is only used for testing Visual Studio 2005 extensions. The issue does not occur on client machines so this is just a workaround for my own development machine.

  Read the article

• Where should the partitioning column go in the primary key on SQL Server?

  - by Bialecki

  Using SQL Server 2005 and 2008. I've got a potentially very large table (potentially hundreds of millions of rows) consisting of the following columns: CREATE TABLE ( date SMALLDATETIME, id BIGINT, value FLOAT ) which is being partitioned on column date in daily partitions. The question then is should the primary key be on date, id or value, id? I can imagine that SQL Server is smart enough to know that it's already partitioning on date and therefore, if I'm always querying for whole chunks of days, then I can have it second in the primary key. Or I can imagine that SQL Server will need that column to be first in the primary key to get the benefit of partitioning. Can anyone lend some insight into which way the table should be keyed?

  Read the article

• What kind of storage with two-way replication for multi site C# application?

  - by twk

  Hi I have a web-based system written using asp.net backed by mssql. A synchronized replica of this system is to be run on mobile locations and must be available regardless of the state of the connection to the main system (few hours long interruptions happens). For now I am using a copy of the main web application and a copy of the mssql server with merge replication to the main system. This works unreliably, and setting the replication is a pain. The amount of data the system contains is not huge, so I can migrate to different storage type. For the new version of this system I would like to implement a new replication system. I am considering migration to db4o for storage with it's replication support. I am thinking about other possible solutions like couchdb which had native replication support. I would like to stay with C#. Could you recommend a way to go for such a distributed environment? PS. Master-Slave replication is not an option: any side must be allowed to add/update data.

  Read the article

• Linq to Entities, checking for specific foreign key id?

  - by AaronLS

  I am trying to get rows where the foreign key ParentID == 0, and this is what I am trying but I get a NotSupportedException because it can't translate the ArrayIndex [0]: IQueryable<ApplicationSectionNode> topLevelNodeQuery = from n in uacEntitiesContext.ApplicationSectionNodeSet where (int)n.Parent.EntityKey.EntityKeyValues[0].Value == 0 orderby n.Sequence select n; So I need to pull that ArrayIndex out of the query so that the runtime can successfully translate the query. I'm not sure how to do that though. How does one query a specific object via it's primary key or set of objects via foreign key? Edit: Note that there is not actually a row in the table with NodeId == 0, the 0 is a magic value(not my idea) to indicate top level nodes. So I can't do n.Parent.NodeId == 0

  Read the article

• [Django] How to find out whether a model's column is a foreign key?

  - by codethief

  I'm dynamically storing information in the database depending on the request: // table, id and column are provided by the request table_obj = getattr(models, table) record = table_obj.objects.get(pk=id) setattr(record, column, request.POST['value']) The problem is that request.POST['value'] sometimes contains a foreign record's primary key (i.e. an integer) whereas Django expects the column's value to be an object of type ForeignModel: Cannot assign "u'122'": "ModelA.b" must be a "ModelB" instance. Now, is there an elegant way to dynamically check whether b is a column containing foreign keys and what model these keys are linked to? (So that I can load the foreign record by it's primary key and assign it to ModelA?) Or doesn't Django provide information like this to the programmer so I really have to get my hands dirty and use isinstance() on the foreign-key column?

  Read the article

• how to search values in a dictionary that is assigned to a key for a PFObject without downloading all PFObjects of that class (iOS/Parse)

  - by mkc842

  Suppose I have a set of PFObjects (essentially dictionaries) of class "myObject". Objects of this class contain for key "myDictionary" a dictionary. "myDictionary", in turn, has a key "myKey" that I want to access and search for matches against "mySearchTerm". I don't want to download all myObject objects and then iterate through them to check myKey in each, because that would be very inefficient. I want to use a findObjects message to return just the matches. Is such a query possible? In other words, how can I search the values in a dictionary that is assigned to a key for a PFObject without downloading all PFObjects of that class? Here's what it might look like if there were a simple method for it, but I made up the containsKey part to clarify what I am contemplating: PFQuery *objectQuery = [PFQuery queryWithClassName:@"myObject"]; [objectQuery whereKey:@"myDictionary" ~containsKey~:@"myKey" equalTo:"mySearchTerm"];

  Read the article

• M2Crypto: Is PKey a reference to a Public or a Private key?

  - by Andrea Zilio

  In the PKey class documentation of the M2Crypto python package (an OpenSSL wrapper for Python) it is said that PKey is a reference to a Public key. My opinion is instead that it's a reference to a Private Key because the init method of the PKey class calls the evp_pkey_new openssl function that, from this link: http://linux.die.net/man/3/evp_pkey_new , should allocate a new reference to a private key structure! There are two only possible explaination: The M2Crypto documentation is wrong or the link I've reported has wrong informations. Can someone help me to find the truth?

  Read the article

• What's a good icon to represent a legend or a key for a diagram?

  - by Bears will eat you

  I'm implementing a small web app widget that shows a legend/key for a diagram (or chart/map/graph/whatever), but only during mouseover of the widget. It's basically just going to be a div with a background image. What would be a good icon that communicates "I show the legend" or "I am the legend" to the unfamiliar users? I'm looking for something in the 10x10 to 20x20 pixel range. Assuming that a legend is the same thing as a key (is it?) then I could use a small icon of a key (like you'd unlock a door with) but that seems cheesy or unclear at worst. I'm not sure that's really the clearest way to do it. Is there an icon that should instantly remind users of a legend?

  Read the article

• How do I close a form when the ESC key was hit, but only if no Control handled it?

  - by Gabriel

  I have a Form that closes itself when the ESC key is pressed, thanks to KeyPreview, ProcessKeyEventArgs, ProcessCmdKey or whatever. But I have a Control on that form that does very relevant things when ESC is pressed (it hides itself) and the Form should not be closed when that happens. The control uses the KeyDown event and sets the SuppressKeyPress flag to true, but that happens after the aforementioned form key preview, thus having no effect. Is there some sort KeyPostview ? How do I not close the form when a Control has a relevant use of a key hit ? Edit: The control handling ESC is a textbox embedded in a hand-maid ListView. The textbox appears when the user clicks a cell, enabling edition. To validate the new text, ENTER would be nice (that already works, as giving the focus to anything else). To cancel edition, ESC seems most natural.

  Read the article

• How to design data storage for partitioned tagging system?

  - by Morgan Cheng

  How to design data storage for huge tagging system (like digg or delicious)? There is already discussion about it, but it is about centralized database. Since the data is supposed to grow, we'll need to partition the data into multiple shards soon or later. So, the question turns to be: How to design data storage for partitioned tagging system? The tagging system basically has 3 tables: Item (item_id, item_content) Tag (tag_id, tag_title) TagMapping(map_id, tag_id, item_id) That works fine for finding all items for given tag and finding all tags for given item, if the table is stored in one database instance. If we need to partition the data into multiple database instances, it is not that easy. For table Item, we can partition its content with its key item_id. For table Tag, we can partition its content with its key tag_id. For example, we want to partition table Tag into K databases. We can simply choose number (tag_id % K) database to store given tag. But, how to partition table TagMapping? The TagMapping table represents the many-to-many relationship. I can only image to have duplication. That is, same content of TagMappping has two copies. One is partitioned with tag_id and the other is partitioned with item_id. In scenario to find tags for given item, we use partition with tag_id. If scenario to find items for given tag, we use partition with item_id. As a result, there is data redundancy. And, the application level should keep the consistency of all tables. It looks hard. Is there any better solution to solve this many-to-many partition problem?

  Read the article

• Are C++ exceptions sufficient to implement thread-local storage?

  - by Potatoswatter

  I was commenting on an answer that thread-local storage is nice and recalled another informative discussion about exceptions where I supposed The only special thing about the execution environment within the throw block is that the exception object is referenced by rethrow. Putting two and two together, wouldn't executing an entire thread inside a function-catch-block of its main function imbue it with thread-local storage? It seems to work fine: #include <iostream> #include <pthread.h> using namespace std; struct thlocal { string name; thlocal( string const &n ) : name(n) {} }; thlocal &get_thread() { try { throw; } catch( thlocal &local ) { return local; } } void print_thread() { cerr << get_thread().name << endl; } void *kid( void *local_v ) try { thlocal &local = * static_cast< thlocal * >( local_v ); throw local; } catch( thlocal & ) { print_thread(); return NULL; } int main() try { thlocal local( "main" ); throw local; } catch( thlocal & ) { print_thread(); pthread_t th; thlocal kid_local( "kid" ); pthread_create( &th, NULL, &kid, &kid_local ); pthread_join( th, NULL ); print_thread(); return 0; } Is this novel or well-characterized? Was my initial premise correct? What kind of overhead does get_thread incur in, say, GCC and VC++? It would require throwing only exceptions derived from struct thlocal, but altogether this doesn't feel like an unproductive insomnia-ridden Sunday morning…

  Read the article

• Whats the API Key for in Google Maps API V3?

  - by Brandon

  In the older version of the API, I'd have to insert the javascript into the page using something like this for just basic functionality to work: http://maps.google.com/maps?file=api&v=2&key=GoogleMapsAPIKey Where I had to configure the API key for each individual site. Looking at the documentation, it says to get a basic map working I just need this: http://maps.google.com/maps/api/js?sensor=true/false Where does the API key fit in? Do I need to worry about it if I just plan on using a basic map and marker and none of the more advanced functions?

  Read the article

• How do I drop a foerign key in mssql?

  - by mmattax

  I have created a foreign key (in mssql / tsql) by: alter table company add CountryID varchar(3); alter table company add constraint Company_CountryID_FK foreign key(CountryID) references Country; I then run this query: alter table company drop column CountryID; and I get this error: Msg 5074, Level 16, State 4, Line 2 The object 'Company_CountryID_FK' is dependent on column 'CountryID'. Msg 4922, Level 16, State 9, Line 2 ALTER TABLE DROP COLUMN CountryID failed because one or more objects access this column. I have tried this, yet it does not seem to work: alter table company drop foreign key Company_CountryID_FK; alter table company drop column CountryID; What do I need to do to drop the CountryID column? Thanks.

  Read the article

• Indexed key vs indexed separate columns, which one is faster ?

  - by Jerry

  In MYSQL, from a pure performance perspective, if I have a table with large amount of data with 10/1 read/write ratio. is it faster in read/write performance to have 4 search criteria in separate columns and all indexed or have them combined in to one single string acting as a key and store in one indexed column ? e.g. say this table with 5 columns, first name, last name, sex, country and file where the first four columns will ALWAYS be given as a part of search parameters in a search or have a table with two columns, key and file. where the value of key can be john-smith-male-australia ?? I don't quite get the pros and cons. the point I try to stress is the fact that all parameters will be given.in a search.

  Read the article

• What's quicker and better to determine if an array key exists in PHP?

  - by alex

  Consider these 2 examples $key = 'jim'; // example 1 if (isset($array[$key])) { doWhatIWant(); } // example 2 if (array_key_exists($key, $array)) { doWhatIWant(); } I'm interested in knowing if either of these are better. I've always used the first, but have seen a lot of people use the second example on this site. So, which is better? Faster? Clearer intent? Update Thanks for the quality answers. I now understand the difference between the 2. A benchmark states that isset() alone is quicker than array_key_exists(). However, if you want the isset() to behave like array_key_exists() it is slower.

  Read the article

• Accessing the next 3 element values in a Map knowing the key.

  - by Rachel

  I have java.util.LinkedHashMap with Integer as Key and Character as Value. I know the key of the element i want to access. In addition to the element value for the key, i also want to retrieve the next 3 element values so that i can append all the 4 element values and form a string with 4 chars. I am asking for something like how we will do in a java.util.List. Is this feasible by any means in a Map/ordered map? Please suggest any other data structure that can help me achieve this. I am using Java 6.

  Read the article

• How to find the entity with the greatest primary key?

  - by simpatico

  I've an entity LearningUnit that has an int primary key. Actually, it has nothing more. Entity Concept has the following relationship with it: @ManyToOne @Size(min=1,max=7) private LearningUnit learningUnit; In a constructor of Concept I need to retrieve the LearningUnit with the greatest primary key. If no LearningUnit exists yet I instantiate one. I then set this.learningUnit to the retrieved/instantied. Finally, I call the empty constructor of Concept in a try-catch block, to have the entitymanager do the cardinality check. If an exception is thrown (I expect one in the case that already another 7 Concepts are referring to the same LearningUnit. In that case, I case instantiate a new LearningUnit with a new greater primary key. Please, also point out, if any, clear pitfalls in my outlined algorithm above.

  Read the article

• Can a primary key be equal to a different column?

  - by eric

  I know that a primary key must be unique, but is it okay for a primary key to be equal to a different column in the same table by coincidence? For instance, I have 2 tables. One table is called person that holds information about a person (ID, email, telephone, address, name). The other table is staff (ID, pID(person ID), salary, position). In staff the ID column is the primary key and is used to uniquely identify a staff member. The number is from 1 - 100. However, the pID (person ID) may be equal to the ID. For instance the staff ID may be 1 and the pID that it references to may be equal to 1. Is that okay?

  Read the article

• Way to check for foreign key references before deleting in MySQL?

  - by Chad Johnson

  I'm working with a content management system, and users are prompted with a confirmation screen before deleting records. Some records are foreign key referenced in other tables, and therefore they cannot be deleted. I would like to display a message beside a given record if it has foreign key references. To know whether I should display the message for a record, I could just query the referencing table and see if there are references. But the problem is, there are about a dozen tables with records potentially referencing this record, and a lookup could take a "long" time. Is there an easy way to tell whether the record is delete-ready (ie. has no foreign key references)?

  Read the article

• How do I get the key of an item when doing a FOR loop through a dictionary or list in Python?

  - by Mike Hayes

  Hi I am new to Python. Say I have a list: list = ['A','B','C','D'] The key for each item respectively here is 0,1,2,3 - right? Now I am going to loop through it with a for loop... for item in list: print item That's great, I can print out my list. How do I get the key here? For example being able to do: print key print item on each loop? If this isn't possible with a list, where keys are not declared myself, is it possible with a Dictionary? Thanks

  Read the article

< Previous Page | 149 150 151 152 153 154 155 156 157 158 159 160  | Next Page >