Optimizing data projection queries ($select)

[swurzinger]

An OData query with a simple projection like /odata/orders?$select=Id seems to ignore the fact that only the Id fields would be necessary in this case and still fetches all fields defined in the entity:

SELECT [o].[Id], [o].[OrderDate], [o].[OrderType], [o].[Weight], [o].[MaterialValue], [o].[Currency], [o].[OrderStatus]
FROM [order].[Order] AS [o]
ORDER BY [o].[Id]

What I'd expect would be a SQL query like this:

SELECT [o].[Id]
FROM [order].[Order] AS [o]
ORDER BY [o].[Id]

This is especially hurts performance when additional tables are joined.

The OData controller implementation is as simple as:

public async Task<ActionResult<IQueryable<Order>>> GetAsync(ODataQueryOptions<Order> options)
{
	var results = await _dbContext.Orders.GetQueryAsync<Dto.Order, Entity.Order>(_mapper, options);
	return Ok(results);
}

Is there an issue somewhere in the implementation/configuration or is this just not supported?

[BlaiseD]

The tests show that $select works. Maybe you're missing explicit expansion in your configuration. See the ReadMe.

[swurzinger]

Thank you. It works indeed when enabling explicit expansion for all fields. I enabled it only for certain fields (navigation properties) because in my case that causes issues with some fields, which aren't correctly expanded then. I think it's the same issue as described in #196 .

I have fields like this:

public record Order(Guid Id, List<OrderRemark> Remarks, ...);
public record OrderRemark(string IsoLanguageCode, string Text);

The Id of OrderRemark is internal and not mapped in the Dto, thus $expand can't be used, as it only works for navigation properties (and navigation properties require a key).
If I enable explicit expansion for Remarks the list will only be populated when explicitly requested in $select (#196).
If I disable explicit expansion for Remarks the order remarks table will always be joined, even if I just select order Id (#228).

[BlaiseD]

Yep - it's a known issue. Today we have a hardcoded list of types which we expand by default (including lists of those types). We need a PR to expand all non-navigation properties by default.

[BlaiseD]

Should be resolved now with PR #229 .