Support primary key when testing the existence of an association to a view

Author: groue

GRDB/Core/Database+Schema.swift

@@ -580,7 +580,6 @@ extension Database {
 
     /// Returns whether the column identifies the rowid column
     func columnIsRowID(_ column: String, of tableName: String) throws -> Bool {
-        #warning("TODO: test with database views")
         let pk = try primaryKey(tableName)
         return pk.rowIDColumn == column || (pk.tableHasRowID && column.uppercased() == "ROWID")
     }
@@ -1153,8 +1152,8 @@ extension Database {
     ///
     /// The returned array is never empty.
     func existenceCheckColumns(in tableName: String) throws -> [String] {
-        if try tableExists(tableName) {
-            // Table: only check the primary key columns for existence
+        do {
+            // Check the primary key columns for existence
             let primaryKey = try self.primaryKey(tableName)
             if let rowIDColumn = primaryKey.rowIDColumn {
                 // Prefer the user-provided name of the rowid
@@ -1175,10 +1174,15 @@ extension Database {
                 //  try db.existenceCheckColumns(in: "player") // ["uuid"]
                 return primaryKey.columns
             }
-        } else {
-            #warning("TODO: use the primary key if available")
-            // View: check all columns for existence
-            return try columns(in: tableName).map(\.name)
+        } catch let error as DatabaseError {
+            if case .SQLITE_ERROR = error.resultCode,
+               (try? viewExists(tableName)) == true
+            {
+                // View without primary key: check all columns for existence
+                return try columns(in: tableName).map(\.name)
+            } else {
+                throw error
+            }
         }
     }
 }

Tests/GRDBTests/AssociationBelongsToSQLTests.swift

@@ -2359,5 +2359,41 @@ class AssociationBelongsToSQLTests: GRDBTestCase {
                     """)
             }
         }
+        
+        do {
+            // View with custom primary key.
+            // Existence check is performed on the primary key.
+            struct SchemaSource: DatabaseSchemaSource {
+                func columnsForPrimaryKey(_ db: Database, inView view: DatabaseObjectID) throws -> [String]? {
+                    ["id"]
+                }
+            }
+            dbConfiguration.schemaSource = SchemaSource()
+            let dbQueue = try makeDatabaseQueue()
+            try dbQueue.write { db in
+                try db.create(table: "author") { t in
+                    t.autoIncrementedPrimaryKey("id")
+                    t.column("name", .text)
+                }
+                try db.create(table: "book") { t in
+                    t.autoIncrementedPrimaryKey("id")
+                    t.column("authorID", .integer)
+                }
+                try db.execute(sql: """
+                    CREATE VIEW authorView AS SELECT * FROM author
+                    """)
+                
+                let association = Book.belongsTo(Table("authorView"), using: ForeignKey(["authorId"], to: ["id"]))
+                let authorAlias = TableAlias()
+                let request = Book
+                    .joining(optional: association.aliased(authorAlias))
+                    .filter(!authorAlias.exists)
+                try assertEqualSQL(db, request, """
+                    SELECT "book".* FROM "book" \
+                    LEFT JOIN "authorView" ON "authorView"."id" = "book"."authorId" \
+                    WHERE "authorView"."id" IS NULL
+                    """)
+            }
+        }
     }
 }