Problem with data types when using aggregate functions

[nerzh]

Describe the issue

Unable to interpret value of PSQL type NUMERIC

Vapor version

4.102.1

Operating system and version

macos 15

Swift version

swiftlang-6.0.0.6.8

Steps to reproduce

1 - Create a table with columns using other tools

2 - Fluent code that causes an exception

final class CleanedShares: Model, @unchecked Sendable {
    
    static var schema: String { "cleaned_shares" }
    
    @ID(custom: "id", generatedBy: .database)
    var id: Int64?
    @Timestamp(key: "created_at", on: .create)
    var createdAt: Date?
    @Timestamp(key: "updated_at", on: .update)
    var updatedAt: Date?
    
    @Field(key: "user_id")
    var userId: Int64
    
    @Field(key: "shares")
    var shares: Int64
    
    /// See `Table`
    init() {}
    
    init(
        userId: Int64,
        shares: Int64
    ) {
        self.userId = userId
        self.shares = shares
    }
}

struct Sum: Codable {
    var sum: Int64
}

3 - Calling the following functions causes a postgres error

let object = try await db.query(CleanedShares.self).sum(\.$shares) // CRASH
let object = try await db.query(CleanedShares.self).aggregate(.sum, \.$shares, as: Sum.self) // CRASH

---

Swift.DecodingError.dataCorrupted(Swift.DecodingError.Context(codingPath: [SomeCodingKey(stringValue: "aggregate (0)", intValue: nil)], debugDescription: "Unable to interpret value of PSQL type NUMERIC: ByteBuffer { readerIndex: 0, writerIndex: 14, readableBytes: 14, capacity: 14, storageCapacity: 2048, slice: _ByteBufferSlice { 63..<77 }, storage: 0x0000000135011400 (2048 bytes) }", underlyingError: nil))

---

4. How to "fix"

• works if you change the type to Decaimal in the mode

@Field(key: "shares")
var shares: Decimal

and

struct Sum: Codable {
    var sum: Decimal
}

but at the same time we remember that in the database it is Int8 byte, that is, it is Int64, and we specified the Decimal floating point type

• the only acceptable working option is to write raw sql

guard
   let object = try await sqlDataBase.raw(
      """
      SELECT SUM(\(unsafeRaw: try CleanedShares.field(\CleanedShares.$shares))) AS sum
      FROM \(unsafeRaw: CleanedShares.schema);
      """
      ).first(decoding: Sum.self)
  else {
      throw AppError("Aggregate sum - failed")
  }

But codable struct must have Decimal type of the "sum" property anyway

struct Sum: Codable {
    var sum: Decimal
}

Total:

in total, everything works “normally” only if in the model and in the encoded structure this field is in Decimal format

Outcome

No response

Additional notes

No response