I am looking for a good way to implement paging in ormlite and I found another question, which has this snippet:
var data = db.Select<address>(predicate).Skip((int) pageNumber).Take((int) pageSize).ToList();
Problem with the above is that it gets back all the results and then does the skip and take on it which defeats the purpose of paging.
At another google groups post I have found the same problem and a sample in a github issue is mentioned as a solution but the URL no longer works. Does anyone know how to correctly page using servicestack?
Found the answer in ormlite's tests. Essentially we could use SqlExpressionVisitor's Limit() like this:
var result = db.Select<K>( q => q.Where(predicate).Limit(skip:5, rows:10 ) );
I built a higher-level wrapper if you prefer working with Page and PageSize:
public static class PagingExtensions
{
public static SqlExpression<T> Page<T>(this SqlExpression<T> exp, int? page, int? pageSize)
{
if (!page.HasValue || !pageSize.HasValue)
return exp;
if (page <= 0) throw new ArgumentOutOfRangeException("page", "Page must be a number greater than 0.");
if (pageSize <= 0) throw new ArgumentOutOfRangeException("pageSize", "PageSize must be a number greater than 0.");
int skip = (page.Value - 1) * pageSize.Value;
int take = pageSize.Value;
return exp.Limit(skip, take);
}
// http://stackoverflow.com/a/3176628/508681
public static int? LimitToRange(this int? value, int? inclusiveMinimum, int? inclusiveMaximum)
{
if (!value.HasValue) return null;
if (inclusiveMinimum.HasValue && value < inclusiveMinimum) { return inclusiveMinimum; }
if (inclusiveMaximum.HasValue && value > inclusiveMaximum) { return inclusiveMaximum; }
return value;
}
}
Then you can write your query as:
var results = Db.Select<K>(predicate.Page(request.Page, request.PageSize));
Or, using the additional helper method to keep Page and PageSize to sensical and (possibly) performant values:
var results = Db.Select<K>(predicate.Page(request.Page.LimitTo(1,null) ?? 1, request.PageSize.LimitTo(1,100) ?? 100);
Which will enforce reasonable limits on Page and PageSize
Related
I'm playing around and developed a simple custom JsonConverter that takes a min and max temperature and have decorated my model class as follows and validates that the temperature falls in that range.
[JsonConverter(typeof(TemperatureConverter), 5, 10)]
public int Temperature { get; set; }
This is all good but I'm wondering what's the approach to best output the correct decoration in my swagger file generated by swashbuckle... like so:
name: Temperature
schema:
type: integer
minimum: 5
maximum: 10
I know this is a trivial example, but it's more the approach to tying JsonConverter to the generation of the swagger I'm interested in.
I'm currently looking at ISchemaFilter but can't see how I can get the type of converter that decorates the property.
Thanks
You have to be at the parent schema level, looking at it's properties. By the time it gets to the property itself, it is too late, as there is no link back to the parent class.
I was using a custom attribute, not JsonConverter, but something like this should work for detecting the attribute.
public class TemperatureSchemaFilter : ISchemaFilter
{
public void Apply(Schema schema, SchemaFilterContext context)
{
var converterProperties = context.SystemType.GetProperties().Where(
prop => prop.CustomAttributes.Select(
attr => attr.AttributeType == typeof(JsonConverterAttribute)).Any()
).ToList();
foreach (var converterProperty in converterProperties)
{
var converterAttribute = (JsonConverterAttribute)Attribute.GetCustomAttribute(converterProperty.PropertyType, typeof(JsonConverterAttribute));
if (converterAttribute.ConverterType != typeof(TemperatureConverter)) continue;
Schema propertySchema = null;
try
{
propertySchema = schema.Properties.First(x => x.Key.ToLower().Equals(converterProperty.Name.ToLower())).Value;
}
catch (Exception)
{
continue;
}
if (propertySchema == null) continue;
propertySchema.Minimum = (double) converterAttribute.ConverterParameters[0];
propertySchema.Maximum = (double) converterAttribute.ConverterParameters[1];
}
}
}
Unfortunately my environment is currently hosed, so I can't test it out, but I think this is the way to go.
I am asking this question with my limited knowledge of java reflection and AOP.
Background:
I am using annotation based advice in my Java 7 application. Further to get the method parameter which I need to use in my advice I am using spring EL. See below examples:
In first example i want to use second parameter to do my work, whereas in second example I am using a POJO and want to use its "id" field.
#MyAnnotation(param = "args[1]")
public void someMethod(int param1, String param2) {
return null;
}
#MyAnnotation(param = "args[0].id")
public void someMethod(SomeObject someObject) {
return null;
}
But what I actually want is, to get my hands on the parameter names in my AOP. So that I can use #MyAnnotation(param = "param1") or #MyAnnotation(param = "someObject.id") instead.
From what I have known, you can not get parameter name using reflection. But recently I came across Spring cache abstraction(link), where I see:
#Cacheable(cacheNames="books", key="#isbn")
public Book findBook(ISBN isbn, boolean checkWarehouse, boolean includeUsed)
Can someone put some light here, how I can achieve similar behavior.
See MethodBasedEvaluationContext and ParameterNameDiscoverer.
CacheEvaluationContext is a subclass of MethodBasedEvaluationContext.
Code here...
// Expose indexed variables as well as parameter names (if discoverable)
String[] paramNames = this.parameterNameDiscoverer.getParameterNames(this.method);
int paramCount = (paramNames != null ? paramNames.length : this.method.getParameterCount());
int argsCount = this.arguments.length;
for (int i = 0; i < paramCount; i++) {
Object value = null;
if (argsCount > paramCount && i == paramCount - 1) {
// Expose remaining arguments as vararg array for last parameter
value = Arrays.copyOfRange(this.arguments, i, argsCount);
}
else if (argsCount > i) {
// Actual argument found - otherwise left as null
value = this.arguments[i];
}
setVariable("a" + i, value);
setVariable("p" + i, value);
if (paramNames != null) {
setVariable(paramNames[i], value);
}
}
I got a problem when debugging my MVC program and I want to acces to my db called "UserActivity".
on the browser, it saying that "The localhost page isn’t working
localhost redirected you too many times."
but without showing the specific error location.
here is my UserActivtyController, GET /UserActivity/Index code:
public class UserActivityController : BaseController
{
//GET /UserActivity/Index
public ActionResult Index(string returnUrl, int page = 1, string sort = "Id", string sortDir = "ASC", string filter = null)
{
String query = #"
SELECT Id
,CreatedBy
,CreatedOn
,ModifiedBy
,ModifiedOn
,ContactId
,EntityName
,EntityId
,ActivityType
,ActivityStatus
,DueDate
,ActualEndDate
,MasqueradeOn
,MasqueradeBy
FROM UserActivity
-- ORDER BY CreatedOn DESC
-- OFFSET (#PageNumber -1) * 30 ROWS
-- FETCH NEXT 30 ROWS ONLY
";
//string countQuery = #""
List<UserActivityModels> userActivity = null;
using (IDbConnection db = new MySqlConnection(ConfigurationManager.ConnectionStrings["CRMPORTALSQLCONN"].ConnectionString))
{
userActivity = (List<UserActivityModels>)db.Query<UserActivityModels>(query, new
{
#PageNumber = page,
});
/*ViewData["TotalCount"] = (int)db.ExecuteScalar(countQuery, new
{
#PageNumber = page,
#Id = string.IsNullOrEmpty(filter) ? null : filter
});
*/
ViewData["PageSize"] = 30;
ViewData["Filter"] = filter;
}
if (userActivity != null)
{
return RedirectToAction(returnUrl);
}
return View(userActivity);
}
}
Really appreciate if there anyone who know something about this problem. Thanks
if (userActivity != null)
{
return RedirectToAction(returnUrl);
}
If the returnUrl points to the same action ("UserActivity/Index") it will create infinite redirect loop. If you want to redirect request to different action make sure you pass correct name.
You have a loop back situation. This is similar to endless while loop. To fix it change your code redirection implementation to redirect to an action method. Notice how I have changed the implementation below. This will fix the issue "localhost redirected you too many times". You can improve on it to support passing in parameters, etc suitable for your situation. Also take a look at RedirectToAction with support for additional parameters, if you want to pass parameters to the action method, this link will be useful.
public class UserActivityController : BaseController
{
//GET /UserActivity/Index
public ActionResult Index(int page = 1, string sort = "Id", string sortDir = "ASC", string filter = null)
{
// Your other implementation here. I have removed it for brevity.
if (userActivity != null)
{
return RedirectToAction("Index");
}
return View(userActivity);
}
public ActionResult Index()
{
return View();
}
}
I don't know what is the value of redirectUrl but I suppose it to be null. I also suppose that your userActivity is not null. So return RedirectToAction(returnUrl); gets called.
When you call RedirectToAction(null) you actually redirect to the same action and everything repeats again.
I also am wondering why would you need to return View(userActivity); when your userActivity is null. I suppose you have a logical error.
I have
public jsonresult update(studentinfo s)
{
for(i=0;i>0;i++)
{
var x = // i am getting some x so i am checking again
if( x != null)
{
var updateuser = student.update(s.student,"","");
**return json(updateuser.ToString());** // if i keep it here i am getting exceptoin saying not all code paths return value bec this return i can not keep it out for loop bec each and evary updateuser i need to return json..
}
}
}
How to overcome this type of things?
What language are you using to write your code? What you've posted doesn't look like any of the valid languages I know for .NET. Here's how the controller action might look in C# (assuming this is the language you are using):
public ActionResult Update(StudentInfo s)
{
// create some collection that will contain all updated users
var updatedUsers = new List<StudentInfo>();
// Revise the loop as it is absolutely not clear from your code
// what you are trying to do. The way you wrote the loop it will
// never execute - for(int i=0; i>0; i++)
for (int i = 0; i < 5; i++)
{
var updatedUser = student.Update(s.student, "", "");
updatedUsers.Add(updatedUser);
}
// return the list of updated users outside the loop so that the compiler
// doesn't complain about paths of the method not returning a value
return Json(updatedUsers);
}
If I understand correctly, you want to return a collection of users. The 'return' keyword does not work like that. You need to return the entire collection at once.
I'm stumped by this easy data problem.
I'm using the Entity framework and have a database of products. My results page returns a paginated list of these products. Right now my results are ordered by the number of sales of each product, so my code looks like this:
return Products.OrderByDescending(u => u.Sales.Count());
This returns an IQueryable dataset of my entities, sorted by the number of sales.
I want my results page to show the rank of each product (in the dataset). My results should look like this:
Page #1
1. Bananas
2. Apples
3. Coffee
Page #2
4. Cookies
5. Ice Cream
6. Lettuce
I'm expecting that I just want to add a column in my results using the SQL ROW_NUMBER variable...but I don't know how to add this column to my results datatable.
My resulting page does contain a foreach loop, but since I'm using a paginated set I'm guessing using that number to fake a ranking number would NOT be the best approach.
So my question is, how do I add a ROW_NUMBER column to my query results in this case?
Use the indexed overload of Select:
var start = page * rowsPerPage;
Products.OrderByDescending(u => u.Sales.Count())
.Skip(start)
.Take(rowsPerPage)
.AsEnumerable()
.Select((u, index) => new { Product = u, Index = index + start });
Actually using OrderBy and then Skip + Take generates ROW_NUMBER in EF 4.5 (you can check with SQL Profiler).
I was searching for a way to do the same thing you are asking for and I was able to get what I need through a simplification of Craig's answer:
var start = page * rowsPerPage;
Products.OrderByDescending(u => u.Sales.Count())
.Skip(start)
.Take(rowsPerPage)
.ToList();
By the way, the generated SQL uses ROW_NUMBER > start and TOP rowsPerPage.
Try this
var x = Products.OrderByDecending(u => u.Sales.Count());
var y = x.ToList();
for(int i = 0; i < y.Count; i++) {
int myNumber = i; // this is your order number
}
As long as the list stays in the same order, which should happen unless the sales number changes. You could be able to get an accurate count;
There is also this way of doing it.
var page = 2;
var count = 10;
var startIndex = page * count;
var x = Products.OrderByDecending(u => u.Sales.Count());
var y = x.Skip(startIndex).Take(count);
This gives the start index for the page, plus it gives you a small set of sales to display on the page. You just start the counting on your website at startIndex.
Here is a long winded answer. First create a class to house the number/item pair like so:
public class NumberedItem<T>
{
public readonly int Number;
public readonly T Item;
public NumberedItem(int number, T item)
{
Item = item;
Number = number;
}
}
Next comes an abstraction around a page of items (numbered or not):
class PageOf<T> : IEnumerable<T>
{
private readonly int startsAt;
private IEnumerable<T> items;
public PageOf(int startsAt, IEnumerable<T> items)
{
this.startsAt = startsAt;
this.items = items;
}
public IEnumerable<NumberedItem<T>> NumberedItems
{
get
{
int index = 0;
foreach (var item in items)
yield return new NumberedItem<T>(startsAt + index++, item);
yield break;
}
}
public IEnumerator<T> GetEnumerator()
{
foreach (var item in items)
yield return item;
}
System.Collections.IEnumerator System.Collections.IEnumerable.GetEnumerator()
{
return this.GetEnumerator();
}
}
Once you have that you can "Paginate" a particular queryable collection using this:
class PaginatedQueryable<T>
{
private readonly int PageSize;
private readonly IQueryable<T> Source;
public PaginatedQueryable(int PageSize, IQueryable<T> Source)
{
this.PageSize = PageSize;
this.Source = Source;
}
public PageOf<T> Page(int pageNum)
{
var start = (pageNum - 1) * PageSize;
return new PageOf<T>(start + 1, Source.Skip(start).Take(PageSize));
}
}
And finally a nice extension method to cover the ugly:
static class PaginationExtension
{
public static PaginatedQueryable<T> InPagesOf<T>(this IQueryable<T> target, int PageSize)
{
return new PaginatedQueryable<T>(PageSize, target);
}
}
Which means you can now do this:
var products = Products.OrderByDescending(u => u.Sales.Count()).InPagesOf(20).Page(1);
foreach (var product in products.NumberedItems)
{
Console.WriteLine("{0} {1}", product.Number, product.Item);
}