Some general cleanup

.github/CODEOWNERS

@@ -0,0 +1 @@
+* @gwynne

Package@swift-5.9.swift

@@ -1,14 +1,6 @@
 // swift-tools-version:5.9
 import PackageDescription
 
-let swiftSettings: [SwiftSetting] = [
-    .enableUpcomingFeature("ForwardTrailingClosures"),
-    .enableUpcomingFeature("ExistentialAny"),
-    .enableUpcomingFeature("ConciseMagicFile"),
-    .enableUpcomingFeature("DisableOutwardActorInference"),
-    .enableExperimentalFeature("StrictConcurrency=complete"),
-]
-
 let package = Package(
     name: "QueuesFluentDriver",
     platforms: [
@@ -49,3 +41,12 @@ let package = Package(
         ),
     ]
 )
+
+var swiftSettings: [SwiftSetting] { [
+    .enableUpcomingFeature("ForwardTrailingClosures"),
+    .enableUpcomingFeature("ExistentialAny"),
+    .enableUpcomingFeature("ConciseMagicFile"),
+    .enableUpcomingFeature("DisableOutwardActorInference"),
+    .enableUpcomingFeature("StrictConcurrency"),
+    .enableExperimentalFeature("StrictConcurrency=complete"),
+] }

Sources/QueuesFluentDriver/FluentQueue.swift

@@ -79,7 +79,7 @@ public struct FluentQueue: Queue, Sendable {
                 .where(SQLFunction("coalesce", args: JobModel.sqlColumn(\.$data.$delayUntil), SQLFunction("now")), .lessThanOrEqual, SQLFunction("now"))
                 .orderBy(JobModel.sqlColumn(\.$data.$delayUntil))
                 .limit(1)
-                .lockingClause(SQLSkipLocked.forUpdateSkipLocked)
+                .lockingClause(SQLLockingClauseWithSkipLocked.updateSkippingLocked)
 
             if self.sqlDb.dialect.supportsReturning {
                 return try await self.sqlDb.update(JobModel.sqlTable)

Sources/QueuesFluentDriver/SQLSkipLocked.swift

@@ -1,20 +1,26 @@
 import SQLKit
 
-enum SQLSkipLocked: SQLExpression {
-    case forUpdateSkipLocked
-    case forShareSkipLocked
+enum SQLLockingClauseWithSkipLocked: SQLExpression {
+    /// Request an exclusive "writer" lock, skipping rows that are already locked.
+    case updateSkippingLocked
+
+    /// Request a shared "reader" lock, skipping rows that are already locked.
+    ///
+    /// > Note: This is the "lightest" locking that is supported by both Postgres and MySQL.
+    case shareSkippingLocked
 
+    // See `SQLExpression.serialize(to:)`.
     func serialize(to serializer: inout SQLSerializer) {
-        guard serializer.dialect.name != "sqlite" else {
-            return
-        }
-
-        switch self {
-        case .forUpdateSkipLocked:
-            serializer.write("FOR UPDATE SKIP LOCKED")
-        case .forShareSkipLocked:
-            // This is the "lightest" locking that is supported by both Postgres and Mysql
-            serializer.write("FOR SHARE SKIP LOCKED")
+        serializer.statement {
+            switch self {
+            case .updateSkippingLocked:
+                guard $0.dialect.exclusiveSelectLockExpression != nil else { return }
+                $0.append(SQLLockingClause.update)
+            case .shareSkippingLocked:
+                guard $0.dialect.sharedSelectLockExpression != nil else { return }
+                $0.append(SQLLockingClause.share)
+            }
+            $0.append("SKIP LOCKED")
         }
     }
 }