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/*
* 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.
*/
#import "Firestore/Source/Local/FSTLevelDBMigrations.h"
#include <string>
#import "Firestore/Protos/objc/firestore/local/Target.pbobjc.h"
#import "Firestore/Source/Local/FSTLevelDBKey.h"
#import "Firestore/Source/Local/FSTLevelDBQueryCache.h"
#import "Firestore/Source/Util/FSTAssert.h"
#include "absl/strings/match.h"
#include "leveldb/write_batch.h"
NS_ASSUME_NONNULL_BEGIN
// Current version of the schema defined in this file.
static FSTLevelDBSchemaVersion kSchemaVersion = 2;
using firebase::firestore::local::LevelDbTransaction;
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.
*/
static void EnsureTargetGlobal(LevelDbTransaction *transaction) {
FSTPBTargetGlobal *targetGlobal =
[FSTLevelDBQueryCache readTargetMetadataWithTransaction:transaction];
if (!targetGlobal) {
transaction->Put([FSTLevelDBTargetGlobalKey key], [FSTPBTargetGlobal message]);
}
}
/**
* Save the given version number as the current version of the schema of the database.
* @param version The version to save
* @param transaction The transaction in which to save the new version number
*/
static void SaveVersion(FSTLevelDBSchemaVersion version, LevelDbTransaction *transaction) {
std::string key = [FSTLevelDBVersionKey key];
std::string version_string = std::to_string(version);
transaction->Put(key, version_string);
}
/**
* 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(LevelDbTransaction *transaction) {
auto it = transaction->NewIterator();
std::string start_key = [FSTLevelDBTargetKey keyPrefix];
it->Seek(start_key);
int32_t count = 0;
while (it->Valid() && absl::StartsWith(it->key(), start_key)) {
count++;
it->Next();
}
FSTPBTargetGlobal *targetGlobal =
[FSTLevelDBQueryCache readTargetMetadataWithTransaction:transaction];
FSTCAssert(targetGlobal != nil,
@"We should have a metadata row as it was added in an earlier migration");
targetGlobal.targetCount = count;
transaction->Put([FSTLevelDBTargetGlobalKey key], targetGlobal);
}
@implementation FSTLevelDBMigrations
+ (FSTLevelDBSchemaVersion)schemaVersionWithTransaction:
(firebase::firestore::local::LevelDbTransaction *)transaction {
std::string key = [FSTLevelDBVersionKey key];
std::string version_string;
Status status = transaction->Get(key, &version_string);
if (status.IsNotFound()) {
return 0;
} else {
return stoi(version_string);
}
}
+ (void)runMigrationsWithTransaction:(firebase::firestore::local::LevelDbTransaction *)transaction {
FSTLevelDBSchemaVersion currentVersion = [self schemaVersionWithTransaction:transaction];
// 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(transaction);
// Fallthrough
case 1:
// We're now guaranteed that the target global exists. We can safely add a count to it.
AddTargetCount(transaction);
// Fallthrough
default:
if (currentVersion < kSchemaVersion) {
SaveVersion(kSchemaVersion, transaction);
}
}
}
@end
NS_ASSUME_NONNULL_END
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