/* * Copyright 2018 Google * * Licensed under the Apache License, Version 2.0 (the "License"); * you may not use this file except in compliance with the License. * You may obtain a copy of the License at * * http://www.apache.org/licenses/LICENSE-2.0 * * Unless required by applicable law or agreed to in writing, software * distributed under the License is distributed on an "AS IS" BASIS, * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. * See the License for the specific language governing permissions and * limitations under the License. */ #include "Firestore/Source/Local/FSTLevelDBMigrations.h" #include "leveldb/write_batch.h" #import "Firestore/Protos/objc/firestore/local/Target.pbobjc.h" #import "Firestore/Source/Local/FSTLevelDB.h" #import "Firestore/Source/Local/FSTLevelDBKey.h" #import "Firestore/Source/Local/FSTLevelDBQueryCache.h" #import "Firestore/Source/Local/FSTWriteGroup.h" #import "Firestore/Source/Util/FSTAssert.h" NS_ASSUME_NONNULL_BEGIN // Current version of the schema defined in this file. static FSTLevelDBSchemaVersion kSchemaVersion = 2; using leveldb::DB; using leveldb::Iterator; using leveldb::Status; using leveldb::Slice; using leveldb::WriteOptions; /** * Ensures that the global singleton target metadata row exists in LevelDB. * @param db The db in which to require the row. */ static void EnsureTargetGlobal(std::shared_ptr db, FSTWriteGroup *group) { FSTPBTargetGlobal *targetGlobal = [FSTLevelDBQueryCache readTargetMetadataFromDB:db]; if (!targetGlobal) { [group setMessage:[FSTPBTargetGlobal message] forKey:[FSTLevelDBTargetGlobalKey key]]; } } /** * Save the given version number as the current version of the schema of the database. * @param version The version to save * @param group The transaction in which to save the new version number */ static void SaveVersion(FSTLevelDBSchemaVersion version, FSTWriteGroup *group) { std::string key = [FSTLevelDBVersionKey key]; std::string version_string = std::to_string(version); [group setData:version_string forKey:key]; } /** * This function counts the number of targets that currently exist in the given db. It * then reads the target global row, adds the count to the metadata from that row, and writes * the metadata back. * * It assumes the metadata has already been written and is able to be read in this transaction. */ static void AddTargetCount(std::shared_ptr db, FSTWriteGroup *group) { std::unique_ptr it(db->NewIterator([FSTLevelDB standardReadOptions])); Slice start_key = [FSTLevelDBTargetKey keyPrefix]; it->Seek(start_key); int32_t count = 0; while (it->Valid() && it->key().starts_with(start_key)) { count++; it->Next(); } FSTPBTargetGlobal *targetGlobal = [FSTLevelDBQueryCache readTargetMetadataFromDB:db]; FSTCAssert(targetGlobal != nil, @"We should have a metadata row as it was added in an earlier migration"); targetGlobal.targetCount = count; [group setMessage:targetGlobal forKey:[FSTLevelDBTargetGlobalKey key]]; } @implementation FSTLevelDBMigrations + (FSTLevelDBSchemaVersion)schemaVersionForDB:(std::shared_ptr)db { std::string key = [FSTLevelDBVersionKey key]; std::string version_string; Status status = db->Get([FSTLevelDB standardReadOptions], key, &version_string); if (status.IsNotFound()) { return 0; } else { return stoi(version_string); } } + (void)runMigrationsOnDB:(std::shared_ptr)db { FSTWriteGroup *group = [FSTWriteGroup groupWithAction:@"Migrations"]; FSTLevelDBSchemaVersion currentVersion = [self schemaVersionForDB:db]; // Each case in this switch statement intentionally falls through. This lets us // start at the current schema version and apply any migrations that have not yet // been applied, to bring us up to current, as defined by the kSchemaVersion constant. switch (currentVersion) { case 0: EnsureTargetGlobal(db, group); // Fallthrough case 1: // We need to make sure we have metadata, since we're going to read and modify it // in this migration. Commit the current transaction and start a new one. Since we're // committing, we need to save a version. It's safe to save this one, if we crash // after saving we'll resume from this step when we try to migrate. SaveVersion(1, group); [group writeToDB:db]; group = [FSTWriteGroup groupWithAction:@"Migrations"]; AddTargetCount(db, group); // Fallthrough default: if (currentVersion < kSchemaVersion) { SaveVersion(kSchemaVersion, group); } } if (!group.isEmpty) { [group writeToDB:db]; } } @end NS_ASSUME_NONNULL_END