Query: Adds translation support for single key single value select GROUP BY LINQ queries

[leminh98]

Pull Request Template

Description

This is the first of a set of PRs to add incremental support for Group By for LINQ queries. Specifically, this PR adds support for Group By queries grouping by a single key, and projecting a single value.

While LINQ has multiple function signatures for GroupBy queries, we will only currently support the current signature:
GroupBy<TSource,TKey,TResult>(IEnumerable, Func<TSource,TKey>, Func<TKey,IEnumerable,TResult>)

GroupBy(<key-selector lambda>, <value-selector lambda>)

Example of use:

query.GroupBy(k => k.Id, (key, values) => key)
 // translate to SELECT VALUE root["id"] FROM root GROUP BY root["id"]

query.GroupBy(k => k.Id, (key, values) => values.Min(value => value.age))
// translate to SELECT VALUE MIN(root["age"]) FROM root GROUP BY root["id"]

Limitations:

• The value selector only accept Parameter and Aggregate Scalar expression
• The GROUP BY query cannot be followed by other method call

These limitations are temporary and will change as more GROUP BY functionality will be supported.

Type of change

Please delete options that are not relevant.

• [] Bug fix (non-breaking change which fixes an issue)
• New feature (non-breaking change which adds functionality)
• [] Breaking change (fix or feature that would cause existing functionality to not work as expected)
• [] This change requires a documentation update

Closing issues

To automatically close an issue: closes #IssueNumber

[github-actions]

All good!

[adityasa]

[sboshra]

[adityasa]

[DM-98]

New here; I'm just confused, got a question: Is this live on nuget package Microsoft.EntityFrameworkCore.Cosmos right now on version 8.0.3?

Getting error on 8.0.3:

Unhandled exception rendering component: The LINQ expression 'DbSet<PropertyView>()
          .GroupBy(
              keySelector: p => p.PropertyId,
              resultSelector: (key, g) => new PropertyWithReadCountDTO{
                  PropertyId = key,
                  PropertyTotalViews = g
                      .AsQueryable()
                      .Count(e => (int)e.EventType == 1),
                  PropertyTotalClicks = g
                      .AsQueryable()
                      .Count(e => (int)e.EventType == 0)
              }
          )' could not be translated...

The code:

List<PropertyWithReadCountDTO> result = await query.GroupBy(
	x => x.PropertyId,
	(key, values) => new PropertyWithReadCountDTO
	{
		PropertyId = key,
		PropertyTotalViews = values.Count(v => v.EventType == EventType.View),
		PropertyTotalClicks = values.Count(v => v.EventType == EventType.Click)
	}).ToListAsync(cancellationToken).ConfigureAwait(false);