If $top is not defined in query, return all rows

[SMAH1]

I use asp.net core 3.1 and Microsoft.AspNetCore.OData 7.5.0 with NHibernate and FluentNHibernate.

I config OData in Startup.cs like this:

endpoint.MapControllers();
endpoint.EnableDependencyInjection();
endpoint
	.Select()
	.Expand(QueryOptionSetting.Disabled)
	.Filter()
	.OrderBy()
	.Count()
	.MaxTop(100)
	;

and use in controller like:

[HttpGet("/records"), EnableQuery, Authorize()]
public IQueryable<Record> GetRecords()
{
	return _deviceData.GetRecords();
}

and sevice like:

public interface IDeviceData
{
	...
	IQueryable<Record> GetRecords();
	...
}

Every thing is fine But I have one problem.
When user not define $top in query, return all rows and MaxTop not effect (!!!), but user define $top every thing OK (expected result).

Assemblies affected

I Use only Microsoft.AspNetCore.OData 7.X

Expected result

When user not define $top in query, $top set to equal MaxTop (In my sample, return 100 rows).

[SMAH1]

This is same problem. And solutions don't work.

[SMAH1]

I solve it with Inherit from EnableQueryAttribute.
Add class EnableQueryWithDefaultPageSizeAttribute:

public class EnableQueryWithDefaultPageSizeAttribute : EnableQueryAttribute
{
	const int pageSizeDefault = 10;

	public override IQueryable ApplyQuery(IQueryable queryable, ODataQueryOptions queryOptions)
	{
		int? top = queryOptions?.Top?.Value;
		if (top == null)
		{
			return queryOptions.ApplyTo(queryable, new ODataQuerySettings { PageSize = this.PageSize == 0 ? pageSizeDefault : this.PageSize });
		}

		return queryOptions.ApplyTo(queryable); ;
	}
}

and change EnableQuery in Controller to EnableQueryWithDefaultPageSize.for example (above sample):

[HttpGet("/records"), EnableQueryWithDefaultPageSize, Authorize()]
public IQueryable<Record> GetRecords()
{
	return _deviceData.GetRecords();
}

Note: In above class support PageSize if it is defined.

[KenitoInc]

@SMAH1
MaxTop defines the max value of $top that a client can request. https://docs.microsoft.com/en-us/dotnet/api/microsoft.aspnet.odata.query.defaultquerysettings.maxtop
MaxTop only impacts the scenarios in which the request Uri contains $top. If the $top value exceeds the MaxTop value, you will get an error message.
$top allows us to get a subset of the results.
If you don't use $top in your request Uri, you will get all results, no matter the value you set in MaxTop.
Hope this helps.

[mikepizzo]

Note: there is a subtle but important difference between the client-specified $top and the server returning the first page of results, along with a nextlink that can be used to fetch the next page of results.

$top is a client directive that says "i'm only interested in the first n records". Once the service returns n records, it is done -- there is no next link.

A next link is returned by the service when there are more records to be returned than the service wants to return in a single response. This can occur if the result is large and the client hasn't specified a $top, or if the result is large and the client has specified a $top greater than the number of rows the service is configured to return in a single response. The next link both indicates that there are more records to return as well as providing the link to fetch the next page of records.

It would be a serious protocol violation to arbitrarily impose a $top by returning a subset of requested records without a nextlink. This is likely to result in the client believing they have all of the requested results when they have only received a partial result.

It sounds like you are interested in setting the maximum number of records returned by the service in a single page of results. This is done, as you discovered, through setting the PageSize. However, setting PageSize does not need to be dependent up on $top -- the two are composable. If the client-requested $top is greater than pagesize, then the service should return the first page of results, with a next link that fetches the next page of results up to the maximum specified in the client's $top.

For example, if there are 1000 rows but the client specifies $top=100 and the service has a pagesize of 50, the service would return the first 50 records with a nextLink to return a result containing the remaining 50 of the 100 requested rows with no nextlink.

[SMAH1]

You mean: PageSize is upper bound of $top.For example if PageSize=100 and $top=20,return 20 rows.
But in my experience and #1853 when PageSize=100 and $top=20 then return 100 rows.
In other words, Ignore $top when PageSize is used.

I agree with your scenario. PageSize should be upper bound of $top and MaxTop should be upper bound of both.

If we accept voice of @KenitoInc:

If you don't use $top in your request Uri, you will get all results, no matter the value you set in MaxTop.

There should be a mechanism to limit the number of row count when $top is not defined..

[Ruslan878]

There should be a mechanism to limit the number of row count when $top is not defined..

That mechanism exists. You just need to set the needed PageSize in ODataQuerySettings. You can do that in different ways. One of them the next:

 public static PageResult<T> GetPageResult<T>(IQueryable<T> query, ODataQueryOptions<T> queryOptions) where T: class
        {
            IQueryable filteredList = queryOptions.ApplyTo(query, new ODataQuerySettings { PageSize = DefaultPageSize });
            ...

[SMAH1]

I don't understand.
I define API like:

[HttpGet("/records"), EnableQuery, Authorize()]
public IQueryable<Record> GetRecords()
{
	return _deviceData.GetRecords();
}

Can I apply ODataQuerySettings?

Note: When define

[HttpGet("/records"), EnableQuery(PageSize = 100), Authorize()]
public IQueryable<Record> GetRecords()
{
	return _deviceData.GetRecords();
}

$top is ignored.

[KenitoInc]

I don't understand.
I define API like:

[HttpGet("/records"), EnableQuery, Authorize()]
public IQueryable<Record> GetRecords()
{
	return _deviceData.GetRecords();
}

Can I apply ODataQuerySettings?

Note: When define

[HttpGet("/records"), EnableQuery(PageSize = 100), Authorize()]
public IQueryable<Record> GetRecords()
{
	return _deviceData.GetRecords();
}

$top is ignored.

@SMAH1
I can't reproduce your issue. Everything works as expected.
Can you share a complete repro?
Can you also try using an In-Memory data store and see if it works correctly?

[SMAH1]

Sample code for show bug is here

[KenitoInc]

@SMAH1 Try using an In-Memory data store and see if it works correctly.

[SMAH1]

@SMAH1 Try using an In-Memory data store and see if it works correctly.

In-Memory works correctly. Why does not work correctly in nHibernate?

[KenitoInc]

@SMAH1 Try using an In-Memory data store and see if it works correctly.

In-Memory works correctly. Why does not work correctly in nHibernate?

I am not really conversant with nHibernate. Also try using EntityFramework or EntityFrameworkCore.
If EntityFramework and EntityFrameworkCore work well, the problem is that nHibernate doesn't work well with OData.