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• When is a SQL function not a function?

  - by Rob Farley

  Should SQL Server even have functions? (Oh yeah – this is a T-SQL Tuesday post, hosted this month by Brad Schulz) Functions serve an important part of programming, in almost any language. A function is a piece of code that is designed to return something, as opposed to a piece of code which isn’t designed to return anything (which is known as a procedure). SQL Server is no different. You can call stored procedures, even from within other stored procedures, and you can call functions and use these in other queries. Stored procedures might query something, and therefore ‘return data’, but a function in SQL is considered to have the type of the thing returned, and can be used accordingly in queries. Consider the internal GETDATE() function. SELECT GETDATE(), SomeDatetimeColumn FROM dbo.SomeTable; There’s no logical difference between the field that is being returned by the function and the field that’s being returned by the table column. Both are the datetime field – if you didn’t have inside knowledge, you wouldn’t necessarily be able to tell which was which. And so as developers, we find ourselves wanting to create functions that return all kinds of things – functions which look up values based on codes, functions which do string manipulation, and so on. But it’s rubbish. Ok, it’s not all rubbish, but it mostly is. And this isn’t even considering the SARGability impact. It’s far more significant than that. (When I say the SARGability aspect, I mean “because you’re unlikely to have an index on the result of some function that’s applied to a column, so try to invert the function and query the column in an unchanged manner”) I’m going to consider the three main types of user-defined functions in SQL Server: Scalar Inline Table-Valued Multi-statement Table-Valued I could also look at user-defined CLR functions, including aggregate functions, but not today. I figure that most people don’t tend to get around to doing CLR functions, and I’m going to focus on the T-SQL-based user-defined functions. Most people split these types of function up into two types. So do I. Except that most people pick them based on ‘scalar or table-valued’. I’d rather go with ‘inline or not’. If it’s not inline, it’s rubbish. It really is. Let’s start by considering the two kinds of table-valued function, and compare them. These functions are going to return the sales for a particular salesperson in a particular year, from the AdventureWorks database. CREATE FUNCTION dbo.FetchSales_inline(@salespersonid int, @orderyear int) RETURNS TABLE AS  RETURN (     SELECT e.LoginID as EmployeeLogin, o.OrderDate, o.SalesOrderID     FROM Sales.SalesOrderHeader AS o     LEFT JOIN HumanResources.Employee AS e     ON e.EmployeeID = o.SalesPersonID     WHERE o.SalesPersonID = @salespersonid     AND o.OrderDate >= DATEADD(year,@orderyear-2000,'20000101')     AND o.OrderDate < DATEADD(year,@orderyear-2000+1,'20000101') ) ; GO CREATE FUNCTION dbo.FetchSales_multi(@salespersonid int, @orderyear int) RETURNS @results TABLE (     EmployeeLogin nvarchar(512),     OrderDate datetime,     SalesOrderID int     ) AS BEGIN     INSERT @results (EmployeeLogin, OrderDate, SalesOrderID)     SELECT e.LoginID, o.OrderDate, o.SalesOrderID     FROM Sales.SalesOrderHeader AS o     LEFT JOIN HumanResources.Employee AS e     ON e.EmployeeID = o.SalesPersonID     WHERE o.SalesPersonID = @salespersonid     AND o.OrderDate >= DATEADD(year,@orderyear-2000,'20000101')     AND o.OrderDate < DATEADD(year,@orderyear-2000+1,'20000101')     ;     RETURN END ; GO You’ll notice that I’m being nice and responsible with the use of the DATEADD function, so that I have SARGability on the OrderDate filter. Regular readers will be hoping I’ll show what’s going on in the execution plans here. Here I’ve run two SELECT * queries with the “Show Actual Execution Plan” option turned on. Notice that the ‘Query cost’ of the multi-statement version is just 2% of the ‘Batch cost’. But also notice there’s trickery going on. And it’s nothing to do with that extra index that I have on the OrderDate column. Trickery. Look at it – clearly, the first plan is showing us what’s going on inside the function, but the second one isn’t. The second one is blindly running the function, and then scanning the results. There’s a Sequence operator which is calling the TVF operator, and then calling a Table Scan to get the results of that function for the SELECT operator. But surely it still has to do all the work that the first one is doing... To see what’s actually going on, let’s look at the Estimated plan. Now, we see the same plans (almost) that we saw in the Actuals, but we have an extra one – the one that was used for the TVF. Here’s where we see the inner workings of it. You’ll probably recognise the right-hand side of the TVF’s plan as looking very similar to the first plan – but it’s now being called by a stack of other operators, including an INSERT statement to be able to populate the table variable that the multi-statement TVF requires. And the cost of the TVF is 57% of the batch! But it gets worse. Let’s consider what happens if we don’t need all the columns. We’ll leave out the EmployeeLogin column. Here, we see that the inline function call has been simplified down. It doesn’t need the Employee table. The join is redundant and has been eliminated from the plan, making it even cheaper. But the multi-statement plan runs the whole thing as before, only removing the extra column when the Table Scan is performed. A multi-statement function is a lot more powerful than an inline one. An inline function can only be the result of a single sub-query. It’s essentially the same as a parameterised view, because views demonstrate this same behaviour of extracting the definition of the view and using it in the outer query. A multi-statement function is clearly more powerful because it can contain far more complex logic. But a multi-statement function isn’t really a function at all. It’s a stored procedure. It’s wrapped up like a function, but behaves like a stored procedure. It would be completely unreasonable to expect that a stored procedure could be simplified down to recognise that not all the columns might be needed, but yet this is part of the pain associated with this procedural function situation. The biggest clue that a multi-statement function is more like a stored procedure than a function is the “BEGIN” and “END” statements that surround the code. If you try to create a multi-statement function without these statements, you’ll get an error – they are very much required. When I used to present on this kind of thing, I even used to call it “The Dangers of BEGIN and END”, and yes, I’ve written about this type of thing before in a similarly-named post over at my old blog. Now how about scalar functions... Suppose we wanted a scalar function to return the count of these. CREATE FUNCTION dbo.FetchSales_scalar(@salespersonid int, @orderyear int) RETURNS int AS BEGIN     RETURN (         SELECT COUNT(*)         FROM Sales.SalesOrderHeader AS o         LEFT JOIN HumanResources.Employee AS e         ON e.EmployeeID = o.SalesPersonID         WHERE o.SalesPersonID = @salespersonid         AND o.OrderDate >= DATEADD(year,@orderyear-2000,'20000101')         AND o.OrderDate < DATEADD(year,@orderyear-2000+1,'20000101')     ); END ; GO Notice the evil words? They’re required. Try to remove them, you just get an error. That’s right – any scalar function is procedural, despite the fact that you wrap up a sub-query inside that RETURN statement. It’s as ugly as anything. Hopefully this will change in future versions. Let’s have a look at how this is reflected in an execution plan. Here’s a query, its Actual plan, and its Estimated plan: SELECT e.LoginID, y.year, dbo.FetchSales_scalar(p.SalesPersonID, y.year) AS NumSales FROM (VALUES (2001),(2002),(2003),(2004)) AS y (year) CROSS JOIN Sales.SalesPerson AS p LEFT JOIN HumanResources.Employee AS e ON e.EmployeeID = p.SalesPersonID; We see here that the cost of the scalar function is about twice that of the outer query. Nicely, the query optimizer has worked out that it doesn’t need the Employee table, but that’s a bit of a red herring here. There’s actually something way more significant going on. If I look at the properties of that UDF operator, it tells me that the Estimated Subtree Cost is 0.337999. If I just run the query SELECT dbo.FetchSales_scalar(281,2003); we see that the UDF cost is still unchanged. You see, this 0.0337999 is the cost of running the scalar function ONCE. But when we ran that query with the CROSS JOIN in it, we returned quite a few rows. 68 in fact. Could’ve been a lot more, if we’d had more salespeople or more years. And so we come to the biggest problem. This procedure (I don’t want to call it a function) is getting called 68 times – each one between twice as expensive as the outer query. And because it’s calling it in a separate context, there is even more overhead that I haven’t considered here. The cheek of it, to say that the Compute Scalar operator here costs 0%! I know a number of IT projects that could’ve used that kind of costing method, but that’s another story that I’m not going to go into here. Let’s look at a better way. Suppose our scalar function had been implemented as an inline one. Then it could have been expanded out like a sub-query. It could’ve run something like this: SELECT e.LoginID, y.year, (SELECT COUNT(*)     FROM Sales.SalesOrderHeader AS o     LEFT JOIN HumanResources.Employee AS e     ON e.EmployeeID = o.SalesPersonID     WHERE o.SalesPersonID = p.SalesPersonID     AND o.OrderDate >= DATEADD(year,y.year-2000,'20000101')     AND o.OrderDate < DATEADD(year,y.year-2000+1,'20000101')     ) AS NumSales FROM (VALUES (2001),(2002),(2003),(2004)) AS y (year) CROSS JOIN Sales.SalesPerson AS p LEFT JOIN HumanResources.Employee AS e ON e.EmployeeID = p.SalesPersonID; Don’t worry too much about the Scan of the SalesOrderHeader underneath a Nested Loop. If you remember from plenty of other posts on the matter, execution plans don’t push the data through. That Scan only runs once. The Index Spool sucks the data out of it and populates a structure that is used to feed the Stream Aggregate. The Index Spool operator gets called 68 times, but the Scan only once (the Number of Executions property demonstrates this). Here, the Query Optimizer has a full picture of what’s being asked, and can make the appropriate decision about how it accesses the data. It can simplify it down properly. To get this kind of behaviour from a function, we need it to be inline. But without inline scalar functions, we need to make our function be table-valued. Luckily, that’s ok. CREATE FUNCTION dbo.FetchSales_inline2(@salespersonid int, @orderyear int) RETURNS table AS RETURN (SELECT COUNT(*) as NumSales     FROM Sales.SalesOrderHeader AS o     LEFT JOIN HumanResources.Employee AS e     ON e.EmployeeID = o.SalesPersonID     WHERE o.SalesPersonID = @salespersonid     AND o.OrderDate >= DATEADD(year,@orderyear-2000,'20000101')     AND o.OrderDate < DATEADD(year,@orderyear-2000+1,'20000101') ); GO But we can’t use this as a scalar. Instead, we need to use it with the APPLY operator. SELECT e.LoginID, y.year, n.NumSales FROM (VALUES (2001),(2002),(2003),(2004)) AS y (year) CROSS JOIN Sales.SalesPerson AS p LEFT JOIN HumanResources.Employee AS e ON e.EmployeeID = p.SalesPersonID OUTER APPLY dbo.FetchSales_inline2(p.SalesPersonID, y.year) AS n; And now, we get the plan that we want for this query. All we’ve done is tell the function that it’s returning a table instead of a single value, and removed the BEGIN and END statements. We’ve had to name the column being returned, but what we’ve gained is an actual inline simplifiable function. And if we wanted it to return multiple columns, it could do that too. I really consider this function to be superior to the scalar function in every way. It does need to be handled differently in the outer query, but in many ways it’s a more elegant method there too. The function calls can be put amongst the FROM clause, where they can then be used in the WHERE or GROUP BY clauses without fear of calling the function multiple times (another horrible side effect of functions). So please. If you see BEGIN and END in a function, remember it’s not really a function, it’s a procedure. And then fix it. @rob_farley

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• Adding SQL Cache Dependencies to the Loosely coupled .NET Cache Provider

  - by Rhames

  This post adds SQL Cache Dependency support to the loosely coupled .NET Cache Provider that I described in the previous post (http://geekswithblogs.net/Rhames/archive/2012/09/11/loosely-coupled-.net-cache-provider-using-dependency-injection.aspx). The sample code is available on github at https://github.com/RobinHames/CacheProvider.git. Each time we want to apply a cache dependency to a call to fetch or cache a data item we need to supply an instance of the relevant dependency implementation. This suggests an Abstract Factory will be useful to create cache dependencies as needed. We can then use Dependency Injection to inject the factory into the relevant consumer. Castle Windsor provides a typed factory facility that will be utilised to implement the cache dependency abstract factory (see http://docs.castleproject.org/Windsor.Typed-Factory-Facility-interface-based-factories.ashx). Cache Dependency Interfaces First I created a set of cache dependency interfaces in the domain layer, which can be used to pass a cache dependency into the cache provider. ICacheDependency The ICacheDependency interface is simply an empty interface that is used as a parent for the specific cache dependency interfaces. This will allow us to place a generic constraint on the Cache Dependency Factory, and will give us a type that can be passed into the relevant Cache Provider methods. namespace CacheDiSample.Domain.CacheInterfaces { public interface ICacheDependency { } }   ISqlCacheDependency.cs The ISqlCacheDependency interface provides specific SQL caching details, such as a Sql Command or a database connection and table. It is the concrete implementation of this interface that will be created by the factory in passed into the Cache Provider. using System; using System.Collections.Generic; using System.Linq; using System.Text;   namespace CacheDiSample.Domain.CacheInterfaces { public interface ISqlCacheDependency : ICacheDependency { ISqlCacheDependency Initialise(string databaseConnectionName, string tableName); ISqlCacheDependency Initialise(System.Data.SqlClient.SqlCommand sqlCommand); } } If we want other types of cache dependencies, such as by key or file, interfaces may be created to support these (the sample code includes an IKeyCacheDependency interface). Modifying ICacheProvider to accept Cache Dependencies Next I modified the exisitng ICacheProvider<T> interface so that cache dependencies may be passed into a Fetch method call. I did this by adding two overloads to the existing Fetch methods, which take an IEnumerable<ICacheDependency> parameter (the IEnumerable allows more than one cache dependency to be included). I also added a method to create cache dependencies. This means that the implementation of the Cache Provider will require a dependency on the Cache Dependency Factory. It is pretty much down to personal choice as to whether this approach is taken, or whether the Cache Dependency Factory is injected directly into the repository or other consumer of Cache Provider. I think, because the cache dependency cannot be used without the Cache Provider, placing the dependency on the factory into the Cache Provider implementation is cleaner. ICacheProvider.cs using System; using System.Collections.Generic;   namespace CacheDiSample.Domain.CacheInterfaces { public interface ICacheProvider<T> { T Fetch(string key, Func<T> retrieveData, DateTime? absoluteExpiry, TimeSpan? relativeExpiry); T Fetch(string key, Func<T> retrieveData, DateTime? absoluteExpiry, TimeSpan? relativeExpiry, IEnumerable<ICacheDependency> cacheDependencies);   IEnumerable<T> Fetch(string key, Func<IEnumerable<T>> retrieveData, DateTime? absoluteExpiry, TimeSpan? relativeExpiry); IEnumerable<T> Fetch(string key, Func<IEnumerable<T>> retrieveData, DateTime? absoluteExpiry, TimeSpan? relativeExpiry, IEnumerable<ICacheDependency> cacheDependencies);   U CreateCacheDependency<U>() where U : ICacheDependency; } }   Cache Dependency Factory Next I created the interface for the Cache Dependency Factory in the domain layer. ICacheDependencyFactory.cs namespace CacheDiSample.Domain.CacheInterfaces { public interface ICacheDependencyFactory { T Create<T>() where T : ICacheDependency;   void Release<T>(T cacheDependency) where T : ICacheDependency; } }   I used the ICacheDependency parent interface as a generic constraint on the create and release methods in the factory interface. Now the interfaces are in place, I moved on to the concrete implementations. ISqlCacheDependency Concrete Implementation The concrete implementation of ISqlCacheDependency will need to provide an instance of System.Web.Caching.SqlCacheDependency to the Cache Provider implementation. Unfortunately this class is sealed, so I cannot simply inherit from this. Instead, I created an interface called IAspNetCacheDependency that will provide a Create method to create an instance of the relevant System.Web.Caching Cache Dependency type. This interface is specific to the ASP.NET implementation of the Cache Provider, so it should be defined in the same layer as the concrete implementation of the Cache Provider (the MVC UI layer in the sample code). IAspNetCacheDependency.cs using System.Web.Caching;   namespace CacheDiSample.CacheProviders { public interface IAspNetCacheDependency { CacheDependency CreateAspNetCacheDependency(); } }   Next, I created the concrete implementation of the ISqlCacheDependency interface. This class also implements the IAspNetCacheDependency interface. This concrete implementation also is defined in the same layer as the Cache Provider implementation. AspNetSqlCacheDependency.cs using System.Web.Caching; using CacheDiSample.Domain.CacheInterfaces;   namespace CacheDiSample.CacheProviders { public class AspNetSqlCacheDependency : ISqlCacheDependency, IAspNetCacheDependency { private string databaseConnectionName;   private string tableName;   private System.Data.SqlClient.SqlCommand sqlCommand;   #region ISqlCacheDependency Members   public ISqlCacheDependency Initialise(string databaseConnectionName, string tableName) { this.databaseConnectionName = databaseConnectionName; this.tableName = tableName; return this; }   public ISqlCacheDependency Initialise(System.Data.SqlClient.SqlCommand sqlCommand) { this.sqlCommand = sqlCommand; return this; }   #endregion   #region IAspNetCacheDependency Members   public System.Web.Caching.CacheDependency CreateAspNetCacheDependency() { if (sqlCommand != null) return new SqlCacheDependency(sqlCommand); else return new SqlCacheDependency(databaseConnectionName, tableName); }   #endregion   } }   ICacheProvider Concrete Implementation The ICacheProvider interface is implemented by the CacheProvider class. This implementation is modified to include the changes to the ICacheProvider interface. First I needed to inject the Cache Dependency Factory into the Cache Provider: private ICacheDependencyFactory cacheDependencyFactory;   public CacheProvider(ICacheDependencyFactory cacheDependencyFactory) { if (cacheDependencyFactory == null) throw new ArgumentNullException("cacheDependencyFactory");   this.cacheDependencyFactory = cacheDependencyFactory; }   Next I implemented the CreateCacheDependency method, which simply passes on the create request to the factory: public U CreateCacheDependency<U>() where U : ICacheDependency { return this.cacheDependencyFactory.Create<U>(); }   The signature of the FetchAndCache helper method was modified to take an additional IEnumerable<ICacheDependency> parameter:   private U FetchAndCache<U>(string key, Func<U> retrieveData, DateTime? absoluteExpiry, TimeSpan? relativeExpiry, IEnumerable<ICacheDependency> cacheDependencies) and the following code added to create the relevant System.Web.Caching.CacheDependency object for any dependencies and pass them to the HttpContext Cache: CacheDependency aspNetCacheDependencies = null;   if (cacheDependencies != null) { if (cacheDependencies.Count() == 1) // We know that the implementations of ICacheDependency will also implement IAspNetCacheDependency // so we can use a cast here and call the CreateAspNetCacheDependency() method aspNetCacheDependencies = ((IAspNetCacheDependency)cacheDependencies.ElementAt(0)).CreateAspNetCacheDependency(); else if (cacheDependencies.Count() > 1) { AggregateCacheDependency aggregateCacheDependency = new AggregateCacheDependency(); foreach (ICacheDependency cacheDependency in cacheDependencies) { // We know that the implementations of ICacheDependency will also implement IAspNetCacheDependency // so we can use a cast here and call the CreateAspNetCacheDependency() method aggregateCacheDependency.Add(((IAspNetCacheDependency)cacheDependency).CreateAspNetCacheDependency()); } aspNetCacheDependencies = aggregateCacheDependency; } }   HttpContext.Current.Cache.Insert(key, value, aspNetCacheDependencies, absoluteExpiry.Value, relativeExpiry.Value);   The full code listing for the modified CacheProvider class is shown below: using System; using System.Collections.Generic; using System.Linq; using System.Web; using System.Web.Caching; using CacheDiSample.Domain.CacheInterfaces;   namespace CacheDiSample.CacheProviders { public class CacheProvider<T> : ICacheProvider<T> { private ICacheDependencyFactory cacheDependencyFactory;   public CacheProvider(ICacheDependencyFactory cacheDependencyFactory) { if (cacheDependencyFactory == null) throw new ArgumentNullException("cacheDependencyFactory");   this.cacheDependencyFactory = cacheDependencyFactory; }   public T Fetch(string key, Func<T> retrieveData, DateTime? absoluteExpiry, TimeSpan? relativeExpiry) { return FetchAndCache<T>(key, retrieveData, absoluteExpiry, relativeExpiry, null); }   public T Fetch(string key, Func<T> retrieveData, DateTime? absoluteExpiry, TimeSpan? relativeExpiry, IEnumerable<ICacheDependency> cacheDependencies) { return FetchAndCache<T>(key, retrieveData, absoluteExpiry, relativeExpiry, cacheDependencies); }   public IEnumerable<T> Fetch(string key, Func<IEnumerable<T>> retrieveData, DateTime? absoluteExpiry, TimeSpan? relativeExpiry) { return FetchAndCache<IEnumerable<T>>(key, retrieveData, absoluteExpiry, relativeExpiry, null); }   public IEnumerable<T> Fetch(string key, Func<IEnumerable<T>> retrieveData, DateTime? absoluteExpiry, TimeSpan? relativeExpiry, IEnumerable<ICacheDependency> cacheDependencies) { return FetchAndCache<IEnumerable<T>>(key, retrieveData, absoluteExpiry, relativeExpiry, cacheDependencies); }   public U CreateCacheDependency<U>() where U : ICacheDependency { return this.cacheDependencyFactory.Create<U>(); }   #region Helper Methods   private U FetchAndCache<U>(string key, Func<U> retrieveData, DateTime? absoluteExpiry, TimeSpan? relativeExpiry, IEnumerable<ICacheDependency> cacheDependencies) { U value; if (!TryGetValue<U>(key, out value)) { value = retrieveData(); if (!absoluteExpiry.HasValue) absoluteExpiry = Cache.NoAbsoluteExpiration;   if (!relativeExpiry.HasValue) relativeExpiry = Cache.NoSlidingExpiration;   CacheDependency aspNetCacheDependencies = null;   if (cacheDependencies != null) { if (cacheDependencies.Count() == 1) // We know that the implementations of ICacheDependency will also implement IAspNetCacheDependency // so we can use a cast here and call the CreateAspNetCacheDependency() method aspNetCacheDependencies = ((IAspNetCacheDependency)cacheDependencies.ElementAt(0)).CreateAspNetCacheDependency(); else if (cacheDependencies.Count() > 1) { AggregateCacheDependency aggregateCacheDependency = new AggregateCacheDependency(); foreach (ICacheDependency cacheDependency in cacheDependencies) { // We know that the implementations of ICacheDependency will also implement IAspNetCacheDependency // so we can use a cast here and call the CreateAspNetCacheDependency() method aggregateCacheDependency.Add( ((IAspNetCacheDependency)cacheDependency).CreateAspNetCacheDependency()); } aspNetCacheDependencies = aggregateCacheDependency; } }   HttpContext.Current.Cache.Insert(key, value, aspNetCacheDependencies, absoluteExpiry.Value, relativeExpiry.Value);   } return value; }   private bool TryGetValue<U>(string key, out U value) { object cachedValue = HttpContext.Current.Cache.Get(key); if (cachedValue == null) { value = default(U); return false; } else { try { value = (U)cachedValue; return true; } catch { value = default(U); return false; } } }   #endregion } }   Wiring up the DI Container Now the implementations for the Cache Dependency are in place, I wired them up in the existing Windsor CacheInstaller. First I needed to register the implementation of the ISqlCacheDependency interface: container.Register( Component.For<ISqlCacheDependency>() .ImplementedBy<AspNetSqlCacheDependency>() .LifestyleTransient());   Next I registered the Cache Dependency Factory. Notice that I have not implemented the ICacheDependencyFactory interface. Castle Windsor will do this for me by using the Type Factory Facility. I do need to bring the Castle.Facilities.TypedFacility namespace into scope: using Castle.Facilities.TypedFactory;   Then I registered the factory: container.AddFacility<TypedFactoryFacility>();   container.Register( Component.For<ICacheDependencyFactory>() .AsFactory()); The full code for the CacheInstaller class is: using Castle.MicroKernel.Registration; using Castle.MicroKernel.SubSystems.Configuration; using Castle.Windsor; using Castle.Facilities.TypedFactory;   using CacheDiSample.Domain.CacheInterfaces; using CacheDiSample.CacheProviders;   namespace CacheDiSample.WindsorInstallers { public class CacheInstaller : IWindsorInstaller { public void Install(IWindsorContainer container, IConfigurationStore store) { container.Register( Component.For(typeof(ICacheProvider<>)) .ImplementedBy(typeof(CacheProvider<>)) .LifestyleTransient());   container.Register( Component.For<ISqlCacheDependency>() .ImplementedBy<AspNetSqlCacheDependency>() .LifestyleTransient());   container.AddFacility<TypedFactoryFacility>();   container.Register( Component.For<ICacheDependencyFactory>() .AsFactory()); } } }   Configuring the ASP.NET SQL Cache Dependency There are a couple of configuration steps required to enable SQL Cache Dependency for the application and database. From the Visual Studio Command Prompt, the following commands should be used to enable the Cache Polling of the relevant database tables: aspnet_regsql -S <servername> -E -d <databasename> –ed aspnet_regsql -S <servername> -E -d CacheSample –et –t <tablename>   (The –t option should be repeated for each table that is to be made available for cache dependencies). Finally the SQL Cache Polling needs to be enabled by adding the following configuration to the <system.web> section of web.config: <caching> <sqlCacheDependency pollTime="10000" enabled="true"> <databases> <add name="BloggingContext" connectionStringName="BloggingContext"/> </databases> </sqlCacheDependency> </caching>   (obviously the name and connection string name should be altered as required). Using a SQL Cache Dependency Now all the coding is complete. To specify a SQL Cache Dependency, I can modify my BlogRepositoryWithCaching decorator class (see the earlier post) as follows: public IList<Blog> GetAll() { var sqlCacheDependency = cacheProvider.CreateCacheDependency<ISqlCacheDependency>() .Initialise("BloggingContext", "Blogs");   ICacheDependency[] cacheDependencies = new ICacheDependency[] { sqlCacheDependency };   string key = string.Format("CacheDiSample.DataAccess.GetAll");   return cacheProvider.Fetch(key, () => { return parentBlogRepository.GetAll(); }, null, null, cacheDependencies) .ToList(); }   This will add a dependency of the “Blogs” table in the database. The data will remain in the cache until the contents of this table change, then the cache item will be invalidated, and the next call to the GetAll() repository method will be routed to the parent repository to refresh the data from the database.

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• How to best design a date/geographic proximity query on GAE?

  - by Dane

  Hi all, I'm building a directory for finding athletic tournaments on GAE with web2py and a Flex front end. The user selects a location, a radius, and a maximum date from a set of choices. I have a basic version of this query implemented, but it's inefficient and slow. One way I know I can improve it is by condensing the many individual queries I'm using to assemble the objects into bulk queries. I just learned that was possible. But I'm also thinking about a more extensive redesign that utilizes memcache. The main problem is that I can't query the datastore by location because GAE won't allow multiple numerical comparison statements (<,<=,=,) in one query. I'm already using one for date, and I'd need TWO to check both latitude and longitude, so it's a no go. Currently, my algorithm looks like this: 1.) Query by date and select 2.) Use destination function from geopy's distance module to find the max and min latitude and longitudes for supplied distance 3.) Loop through results and remove all with lat/lng outside max/min 4.) Loop through again and use distance function to check exact distance, because step 2 will include some areas outside the radius. Remove results outside supplied distance (is this 2/3/4 combination inefficent?) 5.) Assemble many-to-many lists and attach to objects (this is where I need to switch to bulk operations) 6.) Return to client Here's my plan for using memcache.. let me know if I'm way out in left field on this as I have no prior experience with memcache or server caching in general. -Keep a list in the cache filled with "geo objects" that represent all my data. These have five properties: latitude, longitude, event_id, event_type (in anticipation of expanding beyond tournaments), and start_date. This list will be sorted by date. -Also keep a dict of pointers in the cache which represent the start and end indices in the cache for all the date ranges my app uses (next week, 2 weeks, month, 3 months, 6 months, year, 2 years). -Have a scheduled task that updates the pointers daily at 12am. -Add new inserts to the cache as well as the datastore; update pointers. Using this design, the algorithm would now look like: 1.) Use pointers to slice off appropriate chunk of list based on supplied date. 2-4.) Same as above algorithm, except with geo objects 5.) Use bulk operation to select full tournaments using remaining geo objects' event_ids 6.) Assemble many-to-manys 7.) Return to client Thoughts on this approach? Many thanks for reading and any advice you can give. -Dane

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• Can I redirect a query from default search box in SharePoint to a different search engine.

  - by Carol

  I dont want the default results that SharePoint returns. I want the query term when entered into SharePoint search box to be redirected to a different search engine? Can I do that. I have seen FAST ESP web parts but could not figure out how they actually transferred the query to FAST search engine. Any help would be really appreciated!!

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• ActiveRecord + CodeIgniter - Return single value from query, not in array form.

  - by txmail

  Say you construct an activerecord query that will always just return a single value, how do you just address that single value instead of getting an array in return? For instance I am using an ActiveRecord query to return the SUM of a single column, it will only return this one single SUM, instead of having to parse the array is there a way to assign the value as a function return equal to that value instead of getting an array?

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• Why is Oracle using a skip scan for this query?

  - by Jason Baker

  Here's the tkprof output for a query that's running extremely slowly (WARNING: it's long :-) ): SELECT mbr_comment_idn, mbr_crt_dt, mbr_data_source, mbr_dol_bl_rmo_ind, mbr_dxcg_ctl_member, mbr_employment_start_dt, mbr_employment_term_dt, mbr_entity_active, mbr_ethnicity_idn, mbr_general_health_status_code, mbr_hand_dominant_code, mbr_hgt_feet, mbr_hgt_inches, mbr_highest_edu_level, mbr_insd_addr_idn, mbr_insd_alt_id, mbr_insd_name, mbr_insd_ssn_tin, mbr_is_smoker, mbr_is_vip, mbr_lmbr_first_name, mbr_lmbr_last_name, mbr_marital_status_cd, mbr_mbr_birth_dt, mbr_mbr_death_dt, mbr_mbr_expired, mbr_mbr_first_name, mbr_mbr_gender_cd, mbr_mbr_idn, mbr_mbr_ins_type, mbr_mbr_isreadonly, mbr_mbr_last_name, mbr_mbr_middle_name, mbr_mbr_name, mbr_mbr_status_idn, mbr_mpi_id, mbr_preferred_am_pm, mbr_preferred_time, mbr_prv_innetwork, mbr_rep_addr_idn, mbr_rep_name, mbr_rp_mbr_id, mbr_same_mbr_ins, mbr_special_needs_cd, mbr_timezone, mbr_upd_dt, mbr_user_idn, mbr_wgt, mbr_work_status_idn FROM (SELECT /*+ FIRST_ROWS(1) */ mbr_comment_idn, mbr_crt_dt, mbr_data_source, mbr_dol_bl_rmo_ind, mbr_dxcg_ctl_member, mbr_employment_start_dt, mbr_employment_term_dt, mbr_entity_active, mbr_ethnicity_idn, mbr_general_health_status_code, mbr_hand_dominant_code, mbr_hgt_feet, mbr_hgt_inches, mbr_highest_edu_level, mbr_insd_addr_idn, mbr_insd_alt_id, mbr_insd_name, mbr_insd_ssn_tin, mbr_is_smoker, mbr_is_vip, mbr_lmbr_first_name, mbr_lmbr_last_name, mbr_marital_status_cd, mbr_mbr_birth_dt, mbr_mbr_death_dt, mbr_mbr_expired, mbr_mbr_first_name, mbr_mbr_gender_cd, mbr_mbr_idn, mbr_mbr_ins_type, mbr_mbr_isreadonly, mbr_mbr_last_name, mbr_mbr_middle_name, mbr_mbr_name, mbr_mbr_status_idn, mbr_mpi_id, mbr_preferred_am_pm, mbr_preferred_time, mbr_prv_innetwork, mbr_rep_addr_idn, mbr_rep_name, mbr_rp_mbr_id, mbr_same_mbr_ins, mbr_special_needs_cd, mbr_timezone, mbr_upd_dt, mbr_user_idn, mbr_wgt, mbr_work_status_idn, ROWNUM AS ora_rn FROM (SELECT mbr.comment_idn AS mbr_comment_idn, mbr.crt_dt AS mbr_crt_dt, mbr.data_source AS mbr_data_source, mbr.dol_bl_rmo_ind AS mbr_dol_bl_rmo_ind, mbr.dxcg_ctl_member AS mbr_dxcg_ctl_member, mbr.employment_start_dt AS mbr_employment_start_dt, mbr.employment_term_dt AS mbr_employment_term_dt, mbr.entity_active AS mbr_entity_active, mbr.ethnicity_idn AS mbr_ethnicity_idn, mbr.general_health_status_code AS mbr_general_health_status_code, mbr.hand_dominant_code AS mbr_hand_dominant_code, mbr.hgt_feet AS mbr_hgt_feet, mbr.hgt_inches AS mbr_hgt_inches, mbr.highest_edu_level AS mbr_highest_edu_level, mbr.insd_addr_idn AS mbr_insd_addr_idn, mbr.insd_alt_id AS mbr_insd_alt_id, mbr.insd_name AS mbr_insd_name, mbr.insd_ssn_tin AS mbr_insd_ssn_tin, mbr.is_smoker AS mbr_is_smoker, mbr.is_vip AS mbr_is_vip, mbr.lmbr_first_name AS mbr_lmbr_first_name, mbr.lmbr_last_name AS mbr_lmbr_last_name, mbr.marital_status_cd AS mbr_marital_status_cd, mbr.mbr_birth_dt AS mbr_mbr_birth_dt, mbr.mbr_death_dt AS mbr_mbr_death_dt, mbr.mbr_expired AS mbr_mbr_expired, mbr.mbr_first_name AS mbr_mbr_first_name, mbr.mbr_gender_cd AS mbr_mbr_gender_cd, mbr.mbr_idn AS mbr_mbr_idn, mbr.mbr_ins_type AS mbr_mbr_ins_type, mbr.mbr_isreadonly AS mbr_mbr_isreadonly, mbr.mbr_last_name AS mbr_mbr_last_name, mbr.mbr_middle_name AS mbr_mbr_middle_name, mbr.mbr_name AS mbr_mbr_name, mbr.mbr_status_idn AS mbr_mbr_status_idn, mbr.mpi_id AS mbr_mpi_id, mbr.preferred_am_pm AS mbr_preferred_am_pm, mbr.preferred_time AS mbr_preferred_time, mbr.prv_innetwork AS mbr_prv_innetwork, mbr.rep_addr_idn AS mbr_rep_addr_idn, mbr.rep_name AS mbr_rep_name, mbr.rp_mbr_id AS mbr_rp_mbr_id, mbr.same_mbr_ins AS mbr_same_mbr_ins, mbr.special_needs_cd AS mbr_special_needs_cd, mbr.timezone AS mbr_timezone, mbr.upd_dt AS mbr_upd_dt, mbr.user_idn AS mbr_user_idn, mbr.wgt AS mbr_wgt, mbr.work_status_idn AS mbr_work_status_idn FROM mbr JOIN mbr_identfn ON mbr.mbr_idn = mbr_identfn.mbr_idn WHERE mbr_identfn.mbr_idn = mbr.mbr_idn AND mbr_identfn.identfd_type = :identfd_type_1 AND mbr_identfn.identfd_number = :identfd_number_1 AND mbr_identfn.entity_active = :entity_active_1) WHERE ROWNUM <= :ROWNUM_1) WHERE ora_rn > :ora_rn_1 call count cpu elapsed disk query current rows ------- ------ -------- ---------- ---------- ---------- ---------- ---------- Parse 9936 0.46 0.49 0 0 0 0 Execute 9936 0.60 0.59 0 0 0 0 Fetch 9936 329.87 404.00 0 136966922 0 0 ------- ------ -------- ---------- ---------- ---------- ---------- ---------- total 29808 330.94 405.09 0 136966922 0 0 Misses in library cache during parse: 0 Optimizer mode: FIRST_ROWS Parsing user id: 36 (JIVA_DEV) Rows Row Source Operation ------- --------------------------------------------------- 0 VIEW (cr=102 pr=0 pw=0 time=2180 us) 0 COUNT STOPKEY (cr=102 pr=0 pw=0 time=2163 us) 0 NESTED LOOPS (cr=102 pr=0 pw=0 time=2152 us) 0 INDEX SKIP SCAN IDX_MBR_IDENTFN (cr=102 pr=0 pw=0 time=2140 us)(object id 341053) 0 TABLE ACCESS BY INDEX ROWID MBR (cr=0 pr=0 pw=0 time=0 us) 0 INDEX UNIQUE SCAN PK_CLAIMANT (cr=0 pr=0 pw=0 time=0 us)(object id 334044) Rows Execution Plan ------- --------------------------------------------------- 0 SELECT STATEMENT MODE: HINT: FIRST_ROWS 0 VIEW 0 COUNT (STOPKEY) 0 NESTED LOOPS 0 INDEX MODE: ANALYZED (SKIP SCAN) OF 'IDX_MBR_IDENTFN' (INDEX (UNIQUE)) 0 TABLE ACCESS MODE: ANALYZED (BY INDEX ROWID) OF 'MBR' (TABLE) 0 INDEX MODE: ANALYZED (UNIQUE SCAN) OF 'PK_CLAIMANT' (INDEX (UNIQUE)) ******************************************************************************** Based on my reading of Oracle's documentation of skip scans, a skip scan is most useful when the first column of an index has a low number of unique values. The thing is that the first index of this column is a unique primary key. So am I correct in assuming that a skip scan is the wrong thing to do here? Also, what kind of scan should it be doing? Should I do some more hinting for this query? EDIT: I should also point out that the query's where clause uses the columns in IDX_MBR_IDENTFN and no columns other than what's in that index. So as far as I can tell, I'm not skipping any columns.

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• how to extract Datatable or DataSet from Linq Query or List.

  - by Azhar

  how to extract DataTable or DataSet from Linq Query or List. e.g I have linq query like this MyDBpDataContext dcSp = new MyDBpDataContext(); dcSp.myProgrammSP().ToList(); I wrote an Sp which sends a Table as result and I have code which is already using DataTable So I want to convert this result in DataTable.

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• Java Google App Engine Datastore: 'IN' operator available on JDO query filters, as with Python?

  - by Jim Blackler

  This page describes an 'IN' operator that can be used in GAE Datastore to compare a field against a list of possible matches, not just a single value: However this is for Python. In Java (App Engine 1.2.5), trying query.setFilter("someField IN param"); on my javax.jdo.query fires a JDOUserException 'Portion of expression could not be parsed: IN param'. Is there a way this can be done?

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• Is there a way to add or remove a line of an LINQ to DB Query based on if the value being checked is

  - by RandomBen

  If I have a query like this: String Category = HttpContext.Current.Request.QueryString["Product"].ToString(); IQueryable<ItemFile> pressReleases = from file in connection.ItemFile where file.Type_ID == 8 && file.Category == Category select file; Is there a way to make this LINQ Query so that I do no use the line file.Category == Category if Category is null or empty?

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• Adding custom query to paginator (KNP Paginator) in Symfony2?

  - by Unni

  I have the following query , how to write these query in Symfony2 SELECT Inventory_Stock.id, Inventory_Stock.quantity, SUM(InventoryUsage.quantity) ,Inventory_Stock.quantity - SUM(InventoryUsage.quantity) AS Stock FROM Inventory_Stock LEFT JOIN InventoryUsage ON Inventory_Stock.id = InventoryUsage.InventoryStock_id WHERE Inventory_Stock.id = 26 OR Inventory_Stock.id = 27 GROUP BY Inventory_Stock.id ORDER BY Stock DESC I need to paginate this as well Would be great if any one could help me out as this has been pulling my hair out for couple of days.

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• How can I query Google Spreadsheets API with a string value?

  - by ColinM

  I am using Zend_Gdata_SpreadsheetsListQuery. In PHP my query is: "confirmation=$confirmation" The problem is that $confirmation = 'AB-CD-EFG-012345'; Apparently the hyphens are causing problems with the query and the exception thrown is: Uncaught exception 'Zend_Gdata_App_HttpException' with message 'Expected response code 200, got 400 Parse error: Invalid token encountered' How can I quote or escape the value to not cause parse errors? Single quotes cause the same error, double quotes don't throw errors but there are no results to match.

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• Is it possible to LIMIT results from a JOIN query?

  - by Arms

  I've got a query that currently queries a Post table while LEFT JOINing a Comment table. It fetches all Posts and their respective Comments. However, I want to limit the number of Comments returned. I tried adding a sub-select, but ran into errors if I didn't LIMIT the results to 1. I'm really not sure how to go about this while still using only one query. Is this possible?

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• How do I get results from a link query in the order of IDs that I provide?

  - by Keltex

  I'm looking to get query results back from Linq in the order that I pass IDs to the query. So it would look something like this: var IDs = new int [] { 5, 20, 10 } var items = from mytable in db.MyTable where IDs.Contains(mytable.mytableID) orderby // not sure what to do here select mytable; I'm hoping to get items in the order of IDs (5, 20, 10). (Note this is similar to this question, but I would like to do it in Linq instead of SQL)

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• How to optimize this SQL query for a rectangular region?

  - by Andrew B.

  I'm trying to optimize the following query, but it's not clear to me what index or indexes would be best. I'm storing tiles in a two-dimensional plane and querying for rectangular regions of that plane. The table has, for the purposes of this question, the following columns: id: a primary key integer world_id: an integer foreign key which acts as a namespace for a subset of tiles tileY: the Y-coordinate integer tileX: the X-coordinate integer value: the contents of this tile, a varchar if it matters. I have the following indexes: "ywot_tile_pkey" PRIMARY KEY, btree (id) "ywot_tile_world_id_key" UNIQUE, btree (world_id, "tileY", "tileX") "ywot_tile_world_id" btree (world_id) And this is the query I'm trying to optimize: ywot=> EXPLAIN ANALYZE SELECT * FROM "ywot_tile" WHERE ("world_id" = 27685 AND "tileY" <= 6 AND "tileX" <= 9 AND "tileX" >= -2 AND "tileY" >= -1 ); QUERY PLAN ------------------------------------------------------------------------------------------------------------------------------------------- Bitmap Heap Scan on ywot_tile (cost=11384.13..149421.27 rows=65989 width=168) (actual time=79.646..80.075 rows=96 loops=1) Recheck Cond: ((world_id = 27685) AND ("tileY" <= 6) AND ("tileY" >= (-1)) AND ("tileX" <= 9) AND ("tileX" >= (-2))) -> Bitmap Index Scan on ywot_tile_world_id_key (cost=0.00..11367.63 rows=65989 width=0) (actual time=79.615..79.615 rows=125 loops=1) Index Cond: ((world_id = 27685) AND ("tileY" <= 6) AND ("tileY" >= (-1)) AND ("tileX" <= 9) AND ("tileX" >= (-2))) Total runtime: 80.194 ms So the world is fixed, and we are querying for a rectangular region of tiles. Some more information that might be relevant: All the tiles for a queried region may or may not be present The height and width of a queried rectangle are typically about 10x10-20x20 For any given (world, X) or (world, Y) pair, there may be an unbounded number of matching tiles, but the worst case is currently around 10,000, and typically there are far fewer. New tiles are created far less frequently than existing ones are updated (changing the 'value'), and that itself is far less frequent that just reading as in the query above. The only thing I can think of would be to index on (world, X) and (world, Y). My guess is that the database would be able to take those two sets and intersect them. The problem is that there is a potentially unbounded number of matches for either for either of those. Is there some other kind of index that would be more appropriate?

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• Does the speed of the query depend on the number of rows in the table?

  - by Omu

  Let's say I have this query: select * from table1 r where r.x = 5 Does the speed of this query depend on the number of rows that are present in table1?

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• SQL Query Syntax : Using table alias in a count is invalid? Why?

  - by contactmatt

  Could someone please explain to me why the following query is invalid? I'm running this query against an Oracle 10g database. select count(test.*) from my_table test; I get the following error: ORA-01747: invalid user.table.column, table.column, or column specification however, the following two queries are valid. select count(test.column) from my_table test; select test.* from my_table test;

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• LINQ Query returns false when it should be true.

  - by deliriousDev

  I have the following LINQ query written by a former developer and it isn't working when it should. public bool IsAvailable(Appointment appointment) { var appointments = _appointmentRepository.Get; var shifts = _scheduleRepository.Get; var city = _customerRepository.Find(appointment.CustomerId).City ?? appointment.Customer.City; const int durationHour = 1; DateTime scheduledEndDate = appointment.ScheduledTime.Add(new TimeSpan(durationHour, 0, 0)); var inWorkingHours = shifts .Where(x => //Check if any available working hours x.Employee.City == city && x.ShiftStart <= appointment.ScheduledTime && x.ShiftEnd >= scheduledEndDate && //check if not booked yet !appointments .Where(a => (appointment.Id == 0 || a.Id != appointment.Id) && a.Employee.Id == x.Employee.Id && ( (a.ScheduledTime <= appointment.ScheduledTime && appointment.ScheduledTime <= EntityFunctions.AddHours(a.ScheduledTime, durationHour)) || (a.ScheduledTime <= scheduledEndDate && scheduledEndDate <= EntityFunctions.AddHours(a.ScheduledTime, durationHour)) )) .Select(a => a.Employee.Id) .Contains(x.Employee.Id) ); if (inWorkingHours.Any()) { var assignedEmployee = inWorkingHours.FirstOrDefault().Employee; appointment.EmployeeId = assignedEmployee.Id; appointment.Employee = assignedEmployee; return true; } return false; } The query is suppose to handle the following scenarios Given An Appointment With A ScheduledTime Between A ShiftStart and ShiftEnd time But Does not match any employees in same city - (Return true, Assign as "Unassigned") Given An Appointment With A ScheduledTime Between A ShiftStart and ShiftEnd time AND Employee for that shift is in the same city as the customer (Return True AND Assign to the employee) If the customer is NOT in the same city as an employee we assign the appointment as "Unassigned" as along as the scheduledTime is within an of the employees shift start/end times If the customer is in the same city as an employee we assign the appointment to one of the employees (firstOrdefault) and occupy that timeslot. Appointments CAN NOT overlap (Assigned Ones). Unassigned can't overlap each other. This query use to work (I've been told). But now it doesn't and I have tried refactoring it and various other paths with no luck. I am now on week two and just don't know where the issue in the query is or how to write it. Let me know if I need to post anything further. I have verified appointments, shifts, city all populate with valid data so the issue doesn't appear to be with null or missing data.

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• How to select all parent objects into DataContext using single LINQ query ?

  - by too

  I am looking for an answer to a specific problem of fetching whole LINQ object hierarchy using single SELECT. At first I was trying to fill as much LINQ objects as possible using LoadOptions, but AFAIK this method allows only single table to be linked in one query using LoadWith. So I have invented a solution to forcibly set all parent objects of entity which of list is to be fetched, although there is a problem of multiple SELECTS going to database - a single query results in two SELECTS with the same parameters in the same LINQ context. For this question I have simplified this query to popular invoice example: public static class Extensions { public static IEnumerable<T> ForEach<T>(this IEnumerable<T> collection, Action<T> func) { foreach(var c in collection) { func(c); } return collection; } } public IEnumerable<Entry> GetResults(AppDataContext context, int CustomerId) { return ( from entry in context.Entries join invoice in context.Invoices on entry.EntryInvoiceId equals invoice.InvoiceId join period in context.Periods on invoice.InvoicePeriodId equals period.PeriodId // LEFT OUTER JOIN, store is not mandatory join store in context.Stores on entry.EntryStoreId equals store.StoreId into condStore from store in condStore.DefaultIfEmpty() where (invoice.InvoiceCustomerId = CustomerId) orderby entry.EntryPrice descending select new { Entry = entry, Invoice = invoice, Period = period, Store = store } ).ForEach(x => { x.Entry.Invoice = Invoice; x.Invoice.Period = Period; x.Entry.Store = Store; } ).Select(x => x.Entry); } When calling this function and traversing through result set, for example: var entries = GetResults(this.Context); int withoutStore = 0; foreach(var k in entries) { if(k.EntryStoreId == null) withoutStore++; } the resulting query to database looks like (single result is fetched): SELECT [t0].[EntryId], [t0].[EntryInvoiceId], [t0].[EntryStoreId], [t0].[EntryProductId], [t0].[EntryQuantity], [t0].[EntryPrice], [t1].[InvoiceId], [t1].[InvoiceCustomerId], [t1].[InvoiceDate], [t1].[InvoicePeriodId], [t2].[PeriodId], [t2].[PeriodName], [t2].[PeriodDateFrom], [t4].[StoreId], [t4].[StoreName] FROM [Entry] AS [t0] INNER JOIN [Invoice] AS [t1] ON [t0].[EntryInvoiceId] = [t1].[InvoiceId] INNER JOIN [Period] AS [t2] ON [t2].[PeriodId] = [t1].[InvoicePeriodId] LEFT OUTER JOIN ( SELECT 1 AS [test], [t3].[StoreId], [t3].[StoreName] FROM [Store] AS [t3] ) AS [t4] ON [t4].[StoreId] = ([t0].[EntryStoreId]) WHERE (([t1].[InvoiceCustomerId]) = @p0) ORDER BY [t0].[InvoicePrice] DESC -- @p0: Input Int (Size = 0; Prec = 0; Scale = 0) [186] -- Context: SqlProvider(Sql2008) Model: AttributedMetaModel Build: 3.5.30729.1 SELECT [t0].[EntryId], [t0].[EntryInvoiceId], [t0].[EntryStoreId], [t0].[EntryProductId], [t0].[EntryQuantity], [t0].[EntryPrice], [t1].[InvoiceId], [t1].[InvoiceCustomerId], [t1].[InvoiceDate], [t1].[InvoicePeriodId], [t2].[PeriodId], [t2].[PeriodName], [t2].[PeriodDateFrom], [t4].[StoreId], [t4].[StoreName] FROM [Entry] AS [t0] INNER JOIN [Invoice] AS [t1] ON [t0].[EntryInvoiceId] = [t1].[InvoiceId] INNER JOIN [Period] AS [t2] ON [t2].[PeriodId] = [t1].[InvoicePeriodId] LEFT OUTER JOIN ( SELECT 1 AS [test], [t3].[StoreId], [t3].[StoreName] FROM [Store] AS [t3] ) AS [t4] ON [t4].[StoreId] = ([t0].[EntryStoreId]) WHERE (([t1].[InvoiceCustomerId]) = @p0) ORDER BY [t0].[InvoicePrice] DESC -- @p0: Input Int (Size = 0; Prec = 0; Scale = 0) [186] -- Context: SqlProvider(Sql2008) Model: AttributedMetaModel Build: 3.5.30729.1 The question is why there are two queries and how can I fetch LINQ objects without such hacks?

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• .NET: Is there a way to finagle a default namespace in an XPath 1.0 query?

  - by Cheeso

  I'm building a tool that performs xpath 1.0 queries on XHTML documents. The requirement to use a namespace prefix in the query is killing me. The query looks like this: html/body/div[@class='contents']/div[@class='body']/ div[@class='pgdbbyauthor']/h2[a[@name][starts-with(.,'Quick')]]/ following-sibling::ul[1]/li/a (all on one line) ...which is bad enough, except because it's xpath 1.0, I need to use an explicit namespace prefix on each QName, so it looks like this: ns1:html/ns1:body/ns1:div[@class='contents']/ns1:div[@class='body']/ ns1:div[@class='pgdbbyauthor']/ns1:h2[ns1:a[@name][starts-with(.,'Quick')]]/ following-sibling::ns1:ul[1]/ns1:li/ns1:a To set up the query, I do something like this: var xpathDoc = new XPathDocument(new StringReader(theText)); var nav = xpathDoc.CreateNavigator(); var xmlns = new XmlNamespaceManager(nav.NameTable); foreach (string prefix in xmlNamespaces.Keys) xmlns.AddNamespace(prefix, xmlNamespaces[prefix]); XPathNodeIterator selection = nav.Select(xpathExpression, xmlns); But what I want is for the xpathExpression to use the implicit default namespace. Is there a way for me to transform the unadorned xpath expression, after it's been written, to inject a namespace prefix for each element name in the query? I'm thinking, anything between two slashes, I could inject a prefix there. Excepting of course axis names like "parent::" and "preceding-sibling::" . And wildcards. That's what I mean by "finagle a default namespace". Is this hack gonna work? Addendum Here's what I mean. suppose I have an xpath expression, and before passing it to nav.Select(), I transform it. Something like this: string FixupWithDefaultNamespace(string expr) { string s = expr; s = Regex.Replace(s, "^(?!::)([^/:]+)(?=/)", "ns1:$1"); // beginning s = Regex.Replace(s, "/([^/:]+)(?=/)", "/ns1:$1"); // stanza s = Regex.Replace(s, "::([A-Za-z][^/:*]*)(?=/)", "::ns1:$1"); // axis specifier s = Regex.Replace(s, "\\[([A-Za-z][^/:*\\(]*)(?=[\\[\\]])", "[ns1:$1"); // predicate s = Regex.Replace(s, "/([A-Za-z][^/:]*)(?!<::)$", "/ns1:$1"); // end s = Regex.Replace(s, "^([A-Za-z][^/:]*)$", "ns1:$1"); // edge case s = Regex.Replace(s, "([-A-Za-z]+)\\(([^/:\\.,\\)]+)(?=[,\\)])", "$1(ns1:$2"); // xpath functions return s; } This actually works for simple cases I tried. To use the example from above - if the input is the first xpath expression, the output I get is the 2nd one, with all the ns1 prefixes. The real question is, is it hopeless to expect this Regex.Replace approach to work, as the xpath expressions get more complicated?

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• How would I change this Query builder from Kohana 2.4 to Kohana 3?

  - by Thorpe Obazee

  I have had this website built for a few months and I am just getting on Kohana 3. I'd just like to convert this K2.4 query builder to K3 query builder. return DB::select(array('posts.id', 'posts.created', 'posts.uri', 'posts.price', 'posts.description', 'posts.title', 'image_count' => db::expr('COUNT(images.id)'))) ->from('posts') ->join('images')->on('images.post_id', '=', 'posts.id') ->group_by(array('posts.id')) ->order_by('posts.id', 'DESC') ->limit($limit) ->offset($offset) ->execute();

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• how to run Make table query that i have in access in C# code ?

  - by Gold

  hi i have query (DO2) in access that makes a table and inserting any data. how to run this query in C# code ? i try this: SQL = "Select * from DO2"; Cmd = new OleDbCommand(SQL, Conn); Cmd.ExecuteNonQuery(); Cmd.Dispose(); but i get error

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• Do the speed of the query depends on the number of rows in the table ?

  - by Omu

  let's say I have this query: select * from table1 r where r.x = 5 do the speed of this query depends on the number of rows that are present in table1 ?

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• Is there a way that i can read from mysql binarylog file with php code and insert query statement in

  - by mohammad mirzadeh

  I want insert query statement in DB for LOG. Is there a way that i can read from mysql binarylog file with php code and insert query statement in DB?

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• In an MS Access Maketable query, how to create an Autonumber field?

  - by PowerUser

  I have a Maketable query in an Access db that could use an Autonumber field. I can't find a built-in function for my purpose. Do i need to write my own? Ideally, I'd just like to create a field in the Access designer as "Autonum: CreateAutoNumber()" Edit: If it can't be done in the query itself, I can also run a procedure afterward.

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• how to store a value returned from a sql query in a variable in batch programming ?

  - by Arunachalam

  how to store a value returned from a sql query in a variable in batch programming ? i can invoke sqlserver queries from my cmd prompt using sqlcmd server name then the qwery this is query statement i m going to use SELECT CASE WHEN DATEDIFF(minute, record_timestamp, GETDATE()) < 10 THEN 1 ELSE 0 END how to store the value returned i tried using set variablename but it save the statement rather than the return value .. and if i save this in a variable what type of variable it will can i compare it with numeric values in if condition

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