fix(datastore): full sync when sync predicate changes

Author: lawmicha

Amplify/Categories/DataStore/Model/Internal/Persistable.swift

@@ -20,7 +20,7 @@ import Foundation
 /// - `Temporal.Time`
 /// - Warning: Although this has `public` access, it is intended for internal use and should not be used directly
 ///   by host applications. The behavior of this may change without warning.
-public protocol Persistable {}
+public protocol Persistable: Encodable {}
 
 extension Bool: Persistable {}
 extension Double: Persistable {}

Amplify/Categories/DataStore/Query/QueryOperator.swift

@@ -7,7 +7,7 @@
 
 import Foundation
 
-public enum QueryOperator {
+public enum QueryOperator: Encodable {
     case notEqual(_ value: Persistable?)
     case equals(_ value: Persistable?)
     case lessOrEqual(_ value: Persistable)
@@ -18,7 +18,7 @@ public enum QueryOperator {
     case notContains(_ value: String)
     case between(start: Persistable, end: Persistable)
     case beginsWith(_ value: String)
-
+    
     public func evaluate(target: Any) -> Bool {
         switch self {
         case .notEqual(let predicateValue):
@@ -51,4 +51,60 @@ public enum QueryOperator {
         }
         return false
     }
+    
+    private enum CodingKeys: String, CodingKey {
+        case type
+        case value
+        case start
+        case end
+    }
+    
+    public func encode(to encoder: Encoder) throws {
+        var container = encoder.container(keyedBy: CodingKeys.self)
+        
+        switch self {
+        case .notEqual(let value):
+            try container.encode("notEqual", forKey: .type)
+            if let value = value {
+                try container.encode(value, forKey: .value)
+            }
+        case .equals(let value):
+            try container.encode("equals", forKey: .type)
+            if let value = value {
+                try container.encode(value, forKey: .value)
+            }
+        case .lessOrEqual(let value):
+            try container.encode("lessOrEqual", forKey: .type)
+            try container.encode(value, forKey: .value)
+            
+        case .lessThan(let value):
+            try container.encode("lessThan", forKey: .type)
+            try container.encode(value, forKey: .value)
+            
+        case .greaterOrEqual(let value):
+            try container.encode("greaterOrEqual", forKey: .type)
+            try container.encode(value, forKey: .value)
+            
+        case .greaterThan(let value):
+            try container.encode("greaterThan", forKey: .type)
+            try container.encode(value, forKey: .value)
+            
+        case .contains(let value):
+            try container.encode("contains", forKey: .type)
+            try container.encode(value, forKey: .value)
+            
+        case .notContains(let value):
+            try container.encode("notContains", forKey: .type)
+            try container.encode(value, forKey: .value)
+            
+        case .between(let start, let end):
+            try container.encode("between", forKey: .type)
+            try container.encode(start, forKey: .start)
+            try container.encode(end, forKey: .end)
+            
+        case .beginsWith(let value):
+            try container.encode("beginsWith", forKey: .type)
+            try container.encode(value, forKey: .value)
+        }
+    }
 }

Amplify/Categories/DataStore/Query/QueryPredicate.swift

@@ -8,9 +8,9 @@
 import Foundation
 
 /// Protocol that indicates concrete types conforming to it can be used a predicate member.
-public protocol QueryPredicate: Evaluable {}
+public protocol QueryPredicate: Evaluable, Encodable {}
 
-public enum QueryPredicateGroupType: String {
+public enum QueryPredicateGroupType: String, Encodable {
     case and
     case or
     case not
@@ -26,14 +26,14 @@ public func not<Predicate: QueryPredicate>(_ predicate: Predicate) -> QueryPredi
 /// The case `.all` is a predicate used as an argument to select all of a single modeltype. We
 /// chose `.all` instead of `nil` because we didn't want to use the implicit nature of `nil` to
 /// specify an action applies to an entire data set.
-public enum QueryPredicateConstant: QueryPredicate {
+public enum QueryPredicateConstant: QueryPredicate, Encodable {
     case all
     public func evaluate(target: Model) -> Bool {
         return true
     }
 }
 
-public class QueryPredicateGroup: QueryPredicate {
+public class QueryPredicateGroup: QueryPredicate, Encodable {
     public internal(set) var type: QueryPredicateGroupType
     public internal(set) var predicates: [QueryPredicate]
 
@@ -92,9 +92,37 @@ public class QueryPredicateGroup: QueryPredicate {
             return !predicate.evaluate(target: target)
         }
     }
+    
+    // MARK: - Encodable conformance
+    
+    private enum CodingKeys: String, CodingKey {
+        case type
+        case predicates
+    }
+
+    struct AnyQueryPredicate: Encodable {
+        private let _encode: (Encoder) throws -> Void
+
+        init(_ base: QueryPredicate) {
+            _encode = base.encode
+        }
+
+        func encode(to encoder: Encoder) throws {
+            try _encode(encoder)
+        }
+    }
+    
+    public func encode(to encoder: Encoder) throws {
+        var container = encoder.container(keyedBy: CodingKeys.self)
+        try container.encode(type.rawValue, forKey: .type)
+        
+        let anyPredicates = predicates.map(AnyQueryPredicate.init)
+        try container.encode(anyPredicates, forKey: .predicates)
+    }
+    
 }
 
-public class QueryPredicateOperation: QueryPredicate {
+public class QueryPredicateOperation: QueryPredicate, Encodable {
 
     public let field: String
     public let `operator`: QueryOperator

AmplifyPlugins/Core/AWSPluginsCore/Sync/ModelSync/ModelSyncMetadata+Schema.swift

@@ -15,6 +15,7 @@ extension ModelSyncMetadata {
     public enum CodingKeys: String, ModelKey {
         case id
         case lastSync
+        case syncPredicate
     }
 
     public static let keys = CodingKeys.self
@@ -27,7 +28,8 @@ extension ModelSyncMetadata {
 
         definition.fields(
             .id(),
-            .field(keys.lastSync, is: .optional, ofType: .int)
+            .field(keys.lastSync, is: .optional, ofType: .int),
+            .field(keys.syncPredicate, is: .optional, ofType: .string)
         )
     }
 }

AmplifyPlugins/Core/AWSPluginsCore/Sync/ModelSync/ModelSyncMetadata.swift

@@ -13,10 +13,15 @@ public struct ModelSyncMetadata: Model {
 
     /// The timestamp (in Unix seconds) at which the last sync was started, as reported by the service
     public var lastSync: Int?
+    
+    /// The sync predicate for this model, extracted out from the sync expression.
+    public var syncPredicate: String?
 
     public init(id: String,
-                lastSync: Int?) {
+                lastSync: Int?,
+                syncPredicate: String? = nil) {
         self.id = id
         self.lastSync = lastSync
+        self.syncPredicate = syncPredicate
     }
 }

AmplifyPlugins/DataStore/Sources/AWSDataStorePlugin/Migration/ModelSyncMetadataMigration.swift

@@ -0,0 +1,108 @@
+//
+// Copyright Amazon.com Inc. or its affiliates.
+// All Rights Reserved.
+//
+// SPDX-License-Identifier: Apache-2.0
+//
+
+import Amplify
+import Foundation
+import SQLite
+import AWSPluginsCore
+
+class ModelSyncMetadataMigration: ModelMigration {
+    
+    weak var storageAdapter: SQLiteStorageEngineAdapter?
+    
+    func apply() throws {
+        try performModelMetadataSyncPredicateUpgrade()
+    }
+    
+    init(storageAdapter: SQLiteStorageEngineAdapter? = nil) {
+        self.storageAdapter = storageAdapter
+    }
+    
+    /// Add the new syncPredicate column for the ModelSyncMetadata system table.
+    ///
+    /// ModelSyncMetadata's syncPredicate column was added in Amplify version 2.22.0 to
+    /// support a bug fix related to persisting the sync predicate of the sync expression.
+    /// Apps before upgrading to this version of the plugin will have created the table already.
+    /// Upgraded apps will not re-create the table with the CreateTableStatement, neither will throw an error
+    /// (CreateTableStatement is run with 'create table if not exists' doing a no-op). This function
+    /// checks if the column exists on the table, and if it doesn't, alter the table to add the new column.
+    ///
+    /// For more details, see https://github.com/aws-amplify/amplify-swift/pull/2757.
+    /// - Returns: `true` if upgrade occured, `false` otherwise.
+    @discardableResult
+    func performModelMetadataSyncPredicateUpgrade() throws -> Bool {
+        do {
+            guard let field = ModelSyncMetadata.schema.field(
+                withName: ModelSyncMetadata.keys.syncPredicate.stringValue) else {
+                log.error("Could not find corresponding ModelField from ModelSyncMetadata for syncPredicate")
+                return false
+            }
+            let exists = try columnExists(modelSchema: ModelSyncMetadata.schema,
+                                          field: field)
+            guard !exists else {
+                log.debug("Detected ModelSyncMetadata table has syncPredicate column. No migration needed")
+                return false
+            }
+            
+            log.debug("Detected ModelSyncMetadata table exists without syncPredicate column.")
+            guard let storageAdapter = storageAdapter else {
+                log.debug("Missing SQLiteStorageEngineAdapter for model migration")
+                throw DataStoreError.nilStorageAdapter()
+            }
+            guard let connection = storageAdapter.connection else {
+                throw DataStoreError.nilSQLiteConnection()
+            }
+            let addColumnStatement = AlterTableAddColumnStatement(
+                modelSchema: ModelSyncMetadata.schema,
+                field: field).stringValue
+            try connection.execute(addColumnStatement)
+            log.debug("ModelSyncMetadata table altered to add syncPredicate column.")
+            return true
+        } catch {
+            throw DataStoreError.invalidOperation(causedBy: error)
+        }
+    }
+
+    func columnExists(modelSchema: ModelSchema, field: ModelField) throws -> Bool {
+        guard let storageAdapter = storageAdapter else {
+            log.debug("Missing SQLiteStorageEngineAdapter for model migration")
+            throw DataStoreError.nilStorageAdapter()
+        }
+        guard let connection = storageAdapter.connection else {
+            throw DataStoreError.nilSQLiteConnection()
+        }
+        
+        let tableInfoStatement = TableInfoStatement(modelSchema: modelSchema)
+        do {
+            let existingColumns = try connection.prepare(tableInfoStatement.stringValue).run()
+            let columnToFind = field.name
+            var columnExists = false
+            for column in existingColumns {
+                // The second element is the column name
+                if column.count >= 2,
+                    let columnName = column[1],
+                    let columNameString = columnName as? String,
+                    columnToFind == columNameString {
+                    columnExists = true
+                    break
+                }
+            }
+            return columnExists
+        } catch {
+            throw DataStoreError.invalidOperation(causedBy: error)
+        }
+    }
+}
+
+extension ModelSyncMetadataMigration: DefaultLogger {
+    public static var log: Logger {
+        Amplify.Logging.logger(forCategory: CategoryType.dataStore.displayName, forNamespace: String(describing: self))
+    }
+    public var log: Logger {
+        Self.log
+    }
+}

AmplifyPlugins/DataStore/Sources/AWSDataStorePlugin/Storage/SQLite/SQLStatement+AlterTable.swift

@@ -22,3 +22,13 @@ struct AlterTableStatement: SQLStatement {
         self.modelSchema = toModelSchema
     }
 }
+
+struct AlterTableAddColumnStatement: SQLStatement {
+    var modelSchema: ModelSchema
+    var field: ModelField
+    
+    var stringValue: String {
+        "ALTER TABLE \"\(modelSchema.name)\" ADD COLUMN \"\(field.sqlName)\" \"\(field.sqlType)\";"
+    }
+}
+

AmplifyPlugins/DataStore/Sources/AWSDataStorePlugin/Storage/SQLite/SQLStatement+TableInfoStatement.swift

@@ -0,0 +1,18 @@
+//
+// Copyright Amazon.com Inc. or its affiliates.
+// All Rights Reserved.
+//
+// SPDX-License-Identifier: Apache-2.0
+//
+
+import Amplify
+import Foundation
+import SQLite
+
+struct TableInfoStatement: SQLStatement {
+    let modelSchema: ModelSchema
+
+    var stringValue: String {
+        return "PRAGMA table_info(\"\(modelSchema.name)\");"
+    }
+}

AmplifyPlugins/DataStore/Sources/AWSDataStorePlugin/Storage/SQLite/StorageEngineAdapter+SQLite.swift

@@ -117,8 +117,12 @@ final class SQLiteStorageEngineAdapter: StorageEngineAdapter {
         let delegate = SQLiteMutationSyncMetadataMigrationDelegate(
             storageAdapter: self,
             modelSchemas: modelSchemas)
-        let modelMigration = MutationSyncMetadataMigration(delegate: delegate)
-        let modelMigrations = ModelMigrations(modelMigrations: [modelMigration])
+        let mutationSyncMetadataMigration = MutationSyncMetadataMigration(delegate: delegate)
+        
+        let modelSyncMetadataMigration = ModelSyncMetadataMigration(storageAdapter: self)
+        
+        let modelMigrations = ModelMigrations(modelMigrations: [mutationSyncMetadataMigration,
+                                                                modelSyncMetadataMigration])
         do {
             try modelMigrations.apply()
         } catch {