Unnecessary view re-evaluations caused by @Query wrapper

[manueldidonna]

Hi, I think I’ve encountered an issue with @Query causing unexpected view invalidations in SwiftUI.

I have a View that uses @Query with a SeasonEpisodeCountsRequest. The problem is that the view’s body is being recomputed continuously, even when the underlying data has not changed.

This happens both when:

• the query is initialized inline

@Query(SeasonEpisodeCountsRequest(seasonID: nil, filters: .init()))
private var episodesCount: SeasonViewState.EpisodeCounts

• the query is initialized in init using Query(constant:)

@Query<SeasonEpisodeCountsRequest>
private var episodesCount: SeasonViewState.EpisodeCounts

init(seasons: [Season], selection: Binding<Season.ID?>) {
  _episodesCount = Query(constant: .init(seasonID: selection.wrappedValue, filters: .init()))
  self.seasons = seasons
  self._selection = selection
}

To debug, I added:

let _ = Self._printChanges()

and noticed that the view is re-rendered repeatedly even when:

• selection does not change
• filters do not change
• the database content remains the same

Additional context:

• The view is embedded inside a ScrollView
• The request uses a simple filter struct
• the behavior does not change whether I:
  update the query parameters (e.g. seasonID, filters)
  or leave them completely unchanged

Expected behavior:
The view should only re-render when the query result actually changes.

Actual behavior:
@Query seems to trigger continuous invalidations, causing unnecessary body recomputations.

Questions:

• Is this expected behavior for @Query?
• Could this be related to how the request is evaluated or compared for equality?
• Is there a recommended pattern to avoid these redundant updates?

If needed, I can provide a minimal reproducible example.

Thanks in advance!

[manueldidonna]

As a workaround, making the View conform to Equatable mitigates the issue.

[groue]

Hello @manueldidonna,

It might be easier to understand what's happening with a reproducible example. You don't need a full project for that: see below a sample code that is self-sufficient and can run as is.

Sample code

import Foundation
import GRDB
import GRDBQuery
import SwiftUI

struct Issue68View: View {
    @Environment(\.databaseContext) var dbContext
    @Query(PlayerCountRequest()) var playerCount: Int
    
    var body: some View {
        VStack {
            Text("\(playerCount) players")
            
            Button("Create Player") {
                try! dbContext.writer.write { db in
                    try Player(name: "Arthur").insert(db)
                }
            }
        }
        .padding()
    }
}

struct PlayerCountRequest: ValueObservationQueryable {
    static let defaultValue = 0
    
    func fetch(_ db: Database) throws -> Int {
        try Player.fetchCount(db)
    }
}

struct Player: Codable, FetchableRecord, PersistableRecord {
    var id: String = UUID().uuidString
    var name: String
}

#Preview {
    Issue68View()
        .databaseContext(.readWrite {
            let dbQueue = try DatabaseQueue()
            try dbQueue.write { db in
                try db.create(table: "player") { t in
                    t.primaryKey("id", .text)
                    t.column("name", .text).notNull()
                }
            }
            return dbQueue
        })
}

As a workaround, making the View conform to Equatable mitigates the issue.

Good to know 👍