Composed query with groupBy clause in subquery fails

Abierto
#746 0 comentarios 0 reacciones 0 asignados Ver en GitHub

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Evaluación

Dificultad
3/5
Tiempo estimado
1-2 días
Aptitud para principiantes
45/100
Tipo de issue
Error
Claridad
Bien especificado
Estado de actividad
Estancado
Stack tecnológico
fsharp, sql
Área
databases

Línea de trabajo

Comienza rastreando la traducción de SQLProvider de consultas F# compuestas con una cláusula groupBy e inspecciona la subconsulta generada para la reproducción. Se considera terminado cuando la subconsulta IN selecciona únicamente la columna de agregado solicitada, mientras que seleccionar explícitamente la clave de agrupación sigue incluyéndola; añade o ejecuta una prueba de regresión que cubra ambos casos.

Escrito por el modelo de indexación a partir del texto del issue.

Descripción

Describe the bug
SqlException "Only one expression can be specified in the select list when the subquery is not introduced with EXISTS." returned when using a composed query when the subquery has a groupBy clause. This is because SQLProvider includes the groupBy key in the select clause even if you haven't asked for it.

To Reproduce
Steps to reproduce the behavior:

  1. Take a query that uses a subquery with a groupBy clause, e.g.:
let test =
    let lastAddresses =
        query {
            for a in dbContext.Address do
            where (a.Deleted.IsNone)
            groupBy a.UserId into g
            select (g.Max(fun a -> a.Id))
        }
    let result =
        query {
            for a in dbContext.Address do
            where (lastAddresses.Contains(a.Id))
            select a
        }
    result
  1. Run the query, and you get the SqlException described above.
  2. Inspecting the SQL produced, you can see the problem:
SELECT *
FROM [address] as [a] 
WHERE (([a].[Id] IN (
	SELECT [a].[UserId] as '[a].[UserId]', MAX([a].[Id]) as '[a].[MAX_Id]'
	FROM [address] as [a]
	WHERE (([a].[Deleted] IS NOT NULL))
	GROUP BY [a].[UserId]))
)
  1. Basically SQLProvider is including [a].[UserId] as '[a].[UserId]' in the select clause of the subquery. The IN clause is only expecting a single column in the subquery so fails.

Expected behavior

SQLProvider should only return the columns requested in the query. The SQL produced should be:

SELECT *
FROM [address] as [a] 
WHERE (([a].[Id] IN (
	SELECT MAX([a].[Id]) as '[a].[MAX_Id]'
	FROM [address] as [a]
	WHERE (([a].[Deleted] IS NOT NULL))
	GROUP BY [a].[UserId]))
)

Additional context
If we wanted the groupBy key included in the select statement, we could do so by requesting it explicitly, so there is no reason why SQLProvider should do this for us unsolicitedly:

let test =
    let lastAddresses =
        query {
            for a in dbContext.Address do
            where (a.Deleted.IsNone)
            groupBy a.UserId into g
            select (g.Key, g.Max(fun a -> a.Id))
        }
    let result =
        query {
            for a in dbContext.Address do
            where (lastAddresses.Contains(a.Id))
            select a
        }
    result
Lenguaje dominante
F#
Estrellas
627
Forks
147
Merge medio
2 h 2 min
PR fusionados (30 d)
1

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