I have an Infragistics Ultragrid that is being used to display a list of attributes. Sometimes the attribute is an array so I am adding a sub row for each element so the user can optionally expand the row showing the array attribute and see all the element values.
So for each element I use:
var addedRow = mGrid.DisplayLayout.Bands[1].AddNew();
which if I have 300 elements gets called 300 times and takes around 9 seconds (I have profiled the application and this call is taking 98% of the elapsed time)
Is there a way to add these sub rows more efficiently?
I know I'm late with an answer, but hopefully someone can use my answer anyway. Whenever I need to set rows and subrows for ultragrid, I simply set the datasource by using linq and anonymous types to generate the propper collection.
say you have a list of persons (id, Name), and a list of cars (id, CarName, and OwnerId (personId))
now you like to show a gridview showing all persons, with an expandabel subrow providing which cars they own. simply do the following.
List<Person> persons = GetAllPersons();
List<Car> cars = GetAllCars();
grid.DataSource = persons.Select(x => new {x.Id, x.Name, Cars = cars.Where(z => z.OwnerId == x.Id).ToList()}).ToList();
Note the anonymous type I make, this will generate a list of objects having an id, Name, and a collection of cars. Also note that I call the ToList method twice in the last line, this is necessary in order to get ultragrid to bind properly.
Note further more that if you need to edit the gridview, the above method migth not be sufficient, as the ultragrid needs an underlaying datasource for modifying, and I dont believe that this will cope. BUT on the internet you'll find some extensions that can copy a Linq collection into a DataTable, doing that and then you should also be able of editing the grid.
I have often used the above method and it performs extremely well, even for huge collections.
Hope this helps somebody
you might want to use ultraGrid1.BeginUpdate(); and ultraGrid1.EndUpdate(true); to stop screen from repainting. made huge performance benefit for my app.
Also in my case I was populating nearly >10,000 rows, so have used UltraDataSource
Related
I've got 2 classes
Reports - objectID, Title, Date & relationItem ( Relation type column linked up to Items)
Items - ObjectID, Title, Date etc
I want to query all the Items that are equal to a objectID in reports. Users create reports then add items to them. These items are found in the Items table.
I've looked at the https://parseplatform.github.io/docs/ios/guide/#relations but don't see anything for swift3.
I've tried a few things with little success. This snipplet below i did find, but not sure how to apply it to my classes.
var relation = currentUser.relationForKey("product")
relation.query()?.findObjectsInBackgroundWithBlock({
Would love somebody to direct me into the right direction! Thanks
Tried this code below too!
var query = PFQuery(className:"Items")
query.whereKey("relationItem ", equalTo: PFObject(withoutDataWithClassName:"Reports", objectId:"MZmMHtobwQ"))
Ok so i had to change the table slightly to get this to work to prevent a query within a query.
I've added a relation Type to the Items table instead of the Reports Table
Then i managed to retrieve all the Items based of that report ObjectId like this:
let query = PFQuery(className:"Items")
query.whereKey("reportRelation", equalTo: PFObject(withoutDataWithClassName:"Reports", objectId:"3lWMYwWNEj"))
This then worked. Note that reportRelation is the Relational Type Column.
Thanks
When you’re thinking about one-to-many relationships and whether to implement Pointers or Arrays, there are several factors to consider. First, how many objects are involved in this relationship? If the “many” side of the relationship could contain a very large number (greater than 100 or so) of objects, then you have to use Pointers. If the number of objects is small (fewer than 100 or so), then Arrays may be more convenient, especially if you typically need to get all of the related objects (the “many” in the “one-to-many relationship”) at the same time as the parent object.
http://parseplatform.github.io/docs/ios/guide/#relations
If you are working with one to many relation, use pointer or array. See the guide for examples and more explanation.
I have built an MVC 5 application, using EF 6 to query the database. One page show a cross table of two dimensions: substances against properties of these substances. It is rendered as an html table.Many cells do not have a value. This is what it looks like:
sub 1 sub 2 sub 3
prop A 1.0
prop B 1.5 X
prop C 0.6 Y
The cell values are actually more complex, including tool tips, footnotes, etc.
I implemented the generation of the html table, by the following steps:
create a list of unique properties;
create a list of unique substances;
loop through the properties;
render a row for each;
loop through the substances;
See if there is a value for the combination of property and substances;
render the cell's value or an empty one.
Using the ANTS performance profiler, I found out that step 6 has a huge performance issue with increasing numbers of substances and properties, the hit count exploding to hundreds of millions, with a few hundred substances and a few tens of properties (the largest selection the user can make). The execution time is many minutes. It seems to scale N(substances)^2 * N(properties)^2.
The code looks like:
Value currentValue =
values.Where(val => val.substance.Id == currentSubstanceId
&& val.property.Id == currentPropertyId).SingleOrDefault();
where values is a List and Value is an entity, which I read from to render the cells. values had been pre-loaded from the database and no queries are shown by the SQL Server Profiler.
Since not all cells have a value, I thought it best to loop through the row and columns and see if there is a value. I cannot just loop through the list of values.
What could I try to improve this? I thought about:
Create some sort of C# object, using the substance.Id and property.Id as a compound key and fill it from the List object. Which would be fastest?
Create some Linq query which returns an object which already contains the empty cells, like (substance cross join properties) left join values. I could do this in SQL easily, but could this be done with Linq? Could the object which stores the result have the Value as a member field, so I can still use it to render the cells?
Stop pre-loading and just run a database query for the value of each combination, possibly benefiting from database indexes.
I am considering restricting the number of substances and properties the user may select, but I would rather not do that.
Addtional info
As requested by C.Zonnenberg, some more info about the query.
The query to fill the list of values is basically as follows:
I create an IQueryable to which I add filters for requested substances and properties. I then include the substances, property and value details, found in related entities. I then execute query.ToList(). The actual SQL query, as seen by the SQL Profiler looks complex, involving SubstanceId IN () and PropertyId IN (), but it takes far less then a second to execute.
It returns a list of proxies, like: {System.Data.Entity.DynamicProxies.SubstancePropertyValue_078F758A4FF9831024D2690C4B546F07240FAC82A1E9D95D3826A834DCD91D1E}
I think your best bet is your first option. But to do that efficiently I would also modify the source data (values) and turn it into a dictionary, so you have a structure that's optimized for indexed lookup:
var dict = values.ToDictionary(e =>
Tuple.Create(e.substance.id, e.propertyid),
e => e.Value);
Then for each cell:
Value currentValue ;
dict.TryGetValue(Tuple.Create(currentSubstanceId, currentPropertyId),
out currentValue );
Further, you may benefit from parallelization by fetching the cell values in a Parallel.ForEach looping through all substances, for instance.
Is there a way to get the IQueryable object that the LinqDataSource has used to retrieve data? I thought that it might be possible from the selected event, but it doesn't appear to be.
Each row in my table has a category field, and I want to determine how many rows there are per category in the results.
I should also note that I'm using a DataPager, so not all of the rows are being returned. That's why I want to get the IQueryable, so that I can do something like
int count = query.Where(i => i.Category == "Category1").Count();
Use the QueryCreated event. QueryCreatedEventArgs has a Query property that contains the IQueryable.
The event is raised after the original LINQ query is created, and contains the query expression before to it is sent to the database, without the ordering and paging parameters.
There's no "Selected" event in IQueryable. Furthermore, if you're filtering your data on the server, there'd be no way you can access it, even if the API exposed it, but to answer a part of the question, let's say you have category -> product where each category has many products and you want the count of the products in each category. It'd be a simple LINQ query:
var query = GetListOfCategories();
var categoryCount = query.Select(c => c.Products).Count();
Again, depending on the type of object GetListOfCategories return, you might end up having correct value for all the entries, or just the ones that are loaded and are in memory, but that's the different between Linq-to-Objects (in memory) and Linq-to-other data sources (lazy loaded).
We are pulling in a giant dataset of records (in the 100's of thousands) and then need to update a field on each one, one at a time in an atomic transation. They records are unrelated to each other and we don't want to do a blind update to all couple hundred thousand (there are views and indexes on this table that make that very prohibitive). The ONLY way that I could get this to work without doing a giant transation was as follows (container is a reference to a custom ObjectContext):
var expiredWorkflows = from iw in container.InitiatedWorkflows
where iw.InitiationStatusID != 1 && iw.ExpirationDate < DateTime.Now
select iw.ID;
foreach (int expiredWorkflow in expiredWorkflows)
container.ExecuteStoreCommand("UPDATE dbo.InitiatedWorkflow SET InitiationStatusID = 7 WHERE ID = #ID", new SqlParameter() { ParameterName = "#ID", Value = expiredWorkflow.ToString() } );
We tried looping through each one and just updating the field via the container and then calling SaveChanges(), but that runs everything as one transaction. We tried calling SaveChanges() in the foreach loop, but that threw transaction exceptions. Is there any way to what we are trying to do using the ObjectContext, so it would do something like (the above select would be changed to return the full object, not just the ID):
foreach (var expiredWorkflow in expiredWorkflows)
expiredWorkflow.InitiationStatusID = 7
container.SaveChanges(SaveOptions.OneAtATime);
Speaking generally, if the operation you need to carry out is as simple as the sort of UPDATE your code above suggests, this is the sort of operation that will run far better on the back end database--assuming, of course, there's some clear way to select only the rows that need to be changed. Entity Framework is intended more for manipulating small to medium sets of objects that can easily be loaded into memory and twiddled there, not large bulk-processing operations for which stored procedures are often best. EF can certainly perform those big operations, but it will take a lot longer to execute one SQL statement per row.
I am building a school management app where they track student tardiness and absences. I've got three entities to help me in this. A Students entity (first name, last name, ID, etc.); a SystemAbsenceTypes entity with SystemAbsenceTypeID values for Late, Absent-with-Reason, Absent-without-Reason; and a cross-reference table called StudentAbsences (matching the student IDs with the absence-type ID, plus a date, and a Notes field).
What I want to do is query my entities for a given student, and then add up the number of each kind of Absence, for a given date range. I prepare my currentStudent object without a problem, then I do this...
Me.Data.LoadProperty(currentStudent, "StudentAbsences") 'Loads the cross-ref data
lblDaysLate.Text = (From ab In currentStudent.StudentAbsences Where ab.SystemAbsenceTypes.SystemAbsenceTypeID = Common.enuStudentAbsenceTypes.Late).Count.ToString
...and this second line fails, complaining "Object reference not set to an instance of an object."
I presume the problem is that while it DOES see that there are (let's say) four absences for the currentStudent (ie, currentStudent.StudentAbsences.Count = 4) -- it can't yet "peer into" each one of the absences to look at its type. In fact, each of the four StudentAbsence objects has a property called SystemAbsenceType, which then finally has the SystemAbsenceTypeID.
How do I use .Expand or .LoadProperty to make this happen? Do I need to blindly loop through all these collections, firing off .LoadProperty on everything before I can do my query?
Is there some other technique?
When you load the student, try expanding the related properties.
var currentStudent = context.Students.Expand("StudentAbsences")
.Expand("StudentAbsences/SystemAbsenceTypes")
.Where(....).First();