FMDatabase是线程不安全的,当有多线程并非访问的时候会出现崩溃,可以换用 FMDatabaseQueue来解决 FMDatabaseQueue是线程安全的
为什么要使用FMDatabaseQueue
简单的代码实现
#import "DataBaseTool.h"
#import "FMDatabase.h"
#import "FMDatabaseQueue.h"
static DataBaseTool *_instance;
@interface DataBaseTool ()
@property (nonatomic, strong) FMDatabaseQueue *queue;
@end
@implementation DataBaseTool
+ (instancetype)shareInstance {
static dispatch_once_t onceToken;
dispatch_once(&onceToken, ^{
_instance = [[self alloc] init];
});
return _instance;
}
// 懒加载数据库队列
- (FMDatabaseQueue *)queue {
if (_queue == nil) {
_queue = [FMDatabaseQueue databaseQueueWithPath:@"/Users/fanghe/Desktop/数据库/demo.sqlite"];
}
return _queue;
}
// 创建表
- (void)createTableWithSQL:(NSString *)sql {
[self.queue inDatabase:^(FMDatabase *db) {
BOOL result = [db executeUpdate:sql withArgumentsInArray:nil];
if (result) {
NSLog(@"创建表格成功");
} else {
NSLog(@"创建表格失败");
}
}];
}
// 删除表格
- (void)dropTableWithSQL:(NSString *)sql {
[self.queue inDatabase:^(FMDatabase *db) {
BOOL result = [db executeUpdate:sql withArgumentsInArray:nil];
if (result) {
NSLog(@"删除表格成功");
} else {
NSLog(@"删除表格失败");
}
}];
}
// 插入数据
- (void)insertDataWithSQL:(NSString *)sql {
[self.queue inDatabase:^(FMDatabase *db) {
BOOL result = [db executeUpdate:sql withArgumentsInArray:nil];
if (result) {
NSLog(@"插入数据成功");
} else {
NSLog(@"插入数据失败");
}
}];
}
// 查询所有数据
- (void)queryAll {
[self.queue inDatabase:^(FMDatabase *db) {
NSString *sql = @"select * from T_human";
FMResultSet *resultSet = [db executeQuery:sql withArgumentsInArray:nil];
while (resultSet.next) {
NSString *name = [resultSet stringForColumn:@"name"];
int age = [resultSet intForColumn:@"age"];
double height = [resultSet doubleForColumn:@"height"];
NSLog(@"%@, %i, %lf", name, age, height);
}
}];
}
// 执行多条语句
- (void)excuteStaments {
NSString *sql = @"insert into T_human(name, age, height) values('wangwu', 15, 170);insert into T_human(name, age, height) values('zhaoliu', 13, 160);";
[self.queue inDatabase:^(FMDatabase *db) {
BOOL result = [db executeStatements:sql];
if (result) {
NSLog(@"执行多条语句成功");
} else {
NSLog(@"执行多条语句失败");
}
}];
}
// 开启事务执行语句
- (void)transaction {
[self.queue inTransaction:^(FMDatabase *db, BOOL *rollback) {
NSString *sql = @"insert into T_human(name, age, height) values('wangwu', 15, 170);insert into T_human(name, age, height) values('zhaoliu', 13, 160);";
NSString *sql2 = @"insert into T_human(name, age, height) values('zhaoliu', 13, 160);insert into T_human(name, age, height) values('wangwu', 15, 170);";
BOOL result1 = [db executeUpdate:sql withArgumentsInArray:nil];
BOOL result2 = [db executeUpdate:sql2 withArgumentsInArray:nil];
if (result1 && result2) {
NSLog(@"执行成功");
} else {
[db rollback];
}
}];
}
@end
作者:面糊
链接:https://www.jianshu.com/p/75d30176f632
来源:简书
简书著作权归作者所有,任何形式的转载都请联系作者获得授权并注明出处。
sqlite3 多线程和锁 ,优化插入速度及性能优化
这篇博客,着重介绍了sqlite3 多线程和锁。这里针对iOS端写个简单的demo:
验证iOS端sqlite3多线程问题:
sqlite3 线程模式,在iOS上是2,也就是多线程模式:只要一个数据库连接不被多个线程同时使用就是安全的,多个线程同时使用同一个数据库连接就会有问题了。简单的代码模拟下:
- (void)creatSqlite{
FMDatabase * db=[FMDatabase databaseWithPath:_path];
_db=db;
if ([_db open]) {
[_db executeUpdate:@"CREATE TABLE IF NOT EXISTS Student (id integer PRIMARY KEY AUTOINCREMENT, name text NOT NULL);"];
dispatch_async(dispatch_get_global_queue(0, 0), ^{
for (int i=0; i<10; i++) {
BOOL s = [_db executeUpdate:@"INSERT INTO Student (name) VALUES (?)",@"小明"];
NSLog(@"start %d ===success %d",i,s);
}
});
dispatch_async(dispatch_get_global_queue(0, 0), ^{
FMResultSet *set = [_db executeQuery:@"select id from Student"];
while ([set next]) {
int vl = [set intForColumn:@"id"];
NSLog(@"select %d",vl);
};
});
}
}
运行试下,果然crash了(这里使用了三方库FMDB,由于其源码中有容错处理,有这种多线程处理情况只会打印错误log中断操作,所以并不会crash但操作是失败的;这里将其容错判断注释了)
这是因为:
prepared statement,它是由数据库连接(的pager)来管理的,使用它也可看成使用这个数据库连接。在多线程模式下,并发对同一个数据库连接调用sqlite3_prepare_v2()来创建prepared statement,或者对同一个数据库连接的任何prepared statement并发调用sqlite3_bind_*()和sqlite3_step()等函数都会出错(在iOS上,该线程会出现EXC_BAD_ACCESS而中止)。这种错误无关读写,就是只读也会出错。
crash
控制台错误信息:
BUG IN CLIENT OF sqlite3.dylib: illegal multi-threaded access to database connection
dispatch_async(dispatch_get_global_queue(0, 0), ^{
for (int i=0; i<10; i++) {
BOOL s = [_db executeUpdate:@"INSERT INTO Student (name) VALUES (?)",@"小明"];
NSLog(@"start1 %d ===success %d",i,s);
}
});
for (int i=0; i<10; i++) {
BOOL s = [_db executeUpdate:@"INSERT INTO Student (name) VALUES (?)",@"小芳"];
NSLog(@"start2 %d ===success %d",i,s);
}
结果和上面的一样;
dispatch_async(dispatch_get_global_queue(0, 0), ^{
FMResultSet *set = [_db executeQuery:@"select id from Student"];
while ([set next]) {
int vl = [set intForColumn:@"id"];
NSLog(@"select1 %d",vl);
};
});
FMResultSet *set = [_db executeQuery:@"select id from Student"];
while ([set next]) {
int vl = [set intForColumn:@"id"];
NSLog(@"select2 %d",vl);
};
结果也是一样;
为使得所有线程共用全局的数据库连接,可以将sqlite3线程模式更改为串行模式:在初始化SQLite前,调用sqlite3_config(SQLITE_CONFIG_SERIALIZED)启用。
- (BOOL)open {
if (_db) {
return YES;
}
sqlite3_config(SQLITE_CONFIG_SERIALIZED);
int err = sqlite3_open([self sqlitePath], (sqlite3**)&_db );
if(err != SQLITE_OK) {
NSLog(@"error opening!: %d", err);
return NO;
}
if (_maxBusyRetryTimeInterval > 0.0) {
// set the handler
[self setMaxBusyRetryTimeInterval:_maxBusyRetryTimeInterval];
}
return YES;
}
设置好了后,再看下之前3个的结果,可以正常执行了:
2018-12-15 16:50:48.466926+0800 Test[2527:443214] start 0 ===success 1
2018-12-15 16:50:48.482471+0800 Test[2527:443214] start 1 ===success 1
2018-12-15 16:50:48.494744+0800 Test[2527:443214] start 2 ===success 1
2018-12-15 16:50:48.507210+0800 Test[2527:443214] start 3 ===success 1
2018-12-15 16:50:48.507357+0800 Test[2527:443219] select 1
2018-12-15 16:50:48.523451+0800 Test[2527:443214] start 4 ===success 1
2018-12-15 16:50:48.523487+0800 Test[2527:443219] select 2
2018-12-15 16:50:48.536790+0800 Test[2527:443214] start 5 ===success 1
2018-12-15 16:50:48.536832+0800 Test[2527:443219] select 3
2018-12-15 16:50:48.536972+0800 Test[2527:443219] select 4
2018-12-15 16:50:48.537009+0800 Test[2527:443219] select 5
2018-12-15 16:50:48.537036+0800 Test[2527:443219] select 6
2018-12-15 16:50:48.550073+0800 Test[2527:443214] start 6 ===success 1
2018-12-15 16:50:48.564827+0800 Test[2527:443214] start 7 ===success 1
2018-12-15 16:50:48.582215+0800 Test[2527:443214] start 8 ===success 1
2018-12-15 16:50:48.597302+0800 Test[2527:443214] start 9 ===success 1
2018-12-15 15:21:08.631764+0800 Test[2460:430481] start2 0 ===success 1
2018-12-15 15:21:08.658209+0800 Test[2460:430481] start2 1 ===success 1
2018-12-15 15:21:08.658218+0800 Test[2460:430524] start1 0 ===success 1
2018-12-15 15:21:08.675203+0800 Test[2460:430481] start2 2 ===success 1
2018-12-15 15:21:08.703780+0800 Test[2460:430481] start2 3 ===success 1
2018-12-15 15:21:08.704322+0800 Test[2460:430524] start1 1 ===success 1
2018-12-15 15:21:08.714927+0800 Test[2460:430481] start2 4 ===success 1
2018-12-15 15:21:08.729898+0800 Test[2460:430524] start1 2 ===success 1
2018-12-15 15:21:08.745181+0800 Test[2460:430481] start2 5 ===success 1
2018-12-15 15:21:08.772671+0800 Test[2460:430481] start2 6 ===success 1
2018-12-15 15:21:08.772672+0800 Test[2460:430524] start1 3 ===success 1
2018-12-15 15:21:08.790474+0800 Test[2460:430481] start2 7 ===success 1
2018-12-15 15:21:08.821707+0800 Test[2460:430481] start2 8 ===success 1
2018-12-15 15:21:08.821727+0800 Test[2460:430524] start1 4 ===success 1
2018-12-15 15:21:08.835536+0800 Test[2460:430481] start2 9 ===success 1
2018-12-15 15:21:08.854285+0800 Test[2460:430524] start1 5 ===success 1
2018-12-15 15:21:08.881196+0800 Test[2460:430524] start1 6 ===success 1
2018-12-15 15:21:08.895294+0800 Test[2460:430524] start1 7 ===success 1
2018-12-15 15:21:08.909748+0800 Test[2460:430524] start1 8 ===success 1
2018-12-15 15:21:08.926922+0800 Test[2460:430524] start1 9 ===success 1
2018-12-15 15:12:13.531765+0800 Test[2454:429163] select2 1
2018-12-15 15:12:13.531776+0800 Test[2454:429205] select1 1
2018-12-15 15:12:13.531841+0800 Test[2454:429163] select2 2
2018-12-15 15:12:13.531842+0800 Test[2454:429205] select1 2
2018-12-15 15:12:13.531872+0800 Test[2454:429163] select2 3
2018-12-15 15:12:13.531885+0800 Test[2454:429205] select1 3
2018-12-15 15:12:13.531899+0800 Test[2454:429163] select2 4
2018-12-15 15:12:13.531912+0800 Test[2454:429205] select1 4
2018-12-15 15:12:13.531925+0800 Test[2454:429163] select2 5
2018-12-15 15:12:13.531939+0800 Test[2454:429205] select1 5
2018-12-15 15:12:13.531951+0800 Test[2454:429163] select2 6
2018-12-15 15:12:13.531965+0800 Test[2454:429205] select1 6
2018-12-15 15:12:13.531977+0800 Test[2454:429163] select2 7
2018-12-15 15:12:13.531990+0800 Test[2454:429205] select1 7
2018-12-15 15:12:13.532002+0800 Test[2454:429163] select2 8
2018-12-15 15:12:13.532016+0800 Test[2454:429205] select1 8
2018-12-15 15:12:13.532028+0800 Test[2454:429163] select2 9
2018-12-15 15:12:13.532107+0800 Test[2454:429163] select2 10
2018-12-15 15:12:13.532043+0800 Test[2454:429205] select1 9
2018-12-15 15:12:13.533345+0800 Test[2454:429205] select1 10
**sqlite3多线程模式下,编码实现线程安全:(异步线程下)
要实现线程安全,满足以下一个条件即可:
那么有以下方式编码实现:
_lock = [[NSLock alloc] init];
dispatch_async(dispatch_get_global_queue(0, 0), ^{
[_lock lock];
for (int i=0; i<10; i++) {
BOOL s = [_db executeUpdate:@"INSERT INTO Student (name) VALUES (?)",@"小明"];
NSLog(@"start %d ===success %d",i,s);
}
[_lock unlock];
});
dispatch_async(dispatch_get_global_queue(0, 0), ^{
[_lock lock];
FMResultSet *set = [_db executeQuery:@"select id from Student"];
while ([set next]) {
int vl = [set intForColumn:@"id"];
NSLog(@"select %d",vl);
};
[_lock unlock];
});
dispatch_queue_t queue = dispatch_queue_create("queue", DISPATCH_QUEUE_SERIAL);
dispatch_async(queue, ^{
for (int i=0; i<10; i++) {
BOOL s = [_db executeUpdate:@"INSERT INTO Student (name) VALUES (?)",@"小明"];
NSLog(@"start %d ===success %d",i,s);
}
});
dispatch_async(queue, ^{
FMResultSet *set = [_db executeQuery:@"select id from Student"];
while ([set next]) {
int vl = [set intForColumn:@"id"];
NSLog(@"select %d",vl);
};
});
FMDatabaseQueue *queue = [[FMDatabaseQueue alloc] initWithPath:_path];
dispatch_async(dispatch_get_global_queue(0, 0), ^{
[queue inDatabase:^(FMDatabase *db) {
for (int i=0; i<10; i++) {
BOOL s = [_db executeUpdate:@"INSERT INTO Student (name) VALUES (?)",@"小明"];
NSLog(@"start %d ===success %d",i,s);
}
}];
});
dispatch_async(dispatch_get_global_queue(0, 0), ^{
[queue inDatabase:^(FMDatabase *db) {
FMResultSet *set = [_db executeQuery:@"select id from Student"];
while ([set next]) {
int vl = [set intForColumn:@"id"];
NSLog(@"select %d",vl);
};
}];
});
结果都一致
2018-12-15 16:53:55.330335+0800 Test[2530:443778] start 0 ===success 1
2018-12-15 16:53:55.345812+0800 Test[2530:443778] start 1 ===success 1
2018-12-15 16:53:55.363252+0800 Test[2530:443778] start 2 ===success 1
2018-12-15 16:53:55.378892+0800 Test[2530:443778] start 3 ===success 1
2018-12-15 16:53:55.396974+0800 Test[2530:443778] start 4 ===success 1
2018-12-15 16:53:55.411347+0800 Test[2530:443778] start 5 ===success 1
2018-12-15 16:53:55.425837+0800 Test[2530:443778] start 6 ===success 1
2018-12-15 16:53:55.442600+0800 Test[2530:443778] start 7 ===success 1
2018-12-15 16:53:55.460784+0800 Test[2530:443778] start 8 ===success 1
2018-12-15 16:53:55.478188+0800 Test[2530:443778] start 9 ===success 1
2018-12-15 16:53:55.480301+0800 Test[2530:443780] select 1
2018-12-15 16:53:55.480416+0800 Test[2530:443780] select 2
2018-12-15 16:53:55.480493+0800 Test[2530:443780] select 3
2018-12-15 16:53:55.480968+0800 Test[2530:443780] select 4
2018-12-15 16:53:55.481118+0800 Test[2530:443780] select 5
2018-12-15 16:53:55.481443+0800 Test[2530:443780] select 6
2018-12-15 16:53:55.481587+0800 Test[2530:443780] select 7
2018-12-15 16:53:55.481679+0800 Test[2530:443780] select 8
2018-12-15 16:53:55.481905+0800 Test[2530:443780] select 9
2018-12-15 16:53:55.481991+0800 Test[2530:443780] select 10
作者:_小沫
链接:https://www.jianshu.com/p/068ecd1cf1b5
来源:简书
简书著作权归作者所有,任何形式的转载都请联系作者获得授权并注明出处。
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