sqlite3_exec(db, “insert into name values ‘lxkxf', ‘24'; ”, 0, 0, &zErrMsg);
将会重复的打开关闭数据库文件100万次,所以速度当然会很慢。因此对于这种情况我们应该使用“事务”。
具体方法如下:在执行SQL语句之前和SQL语句执行完毕之后加上
rc = sqlite3_exec(db, "BEGIN;", 0, 0, &zErrMsg);
//执行SQL语句
rc = sqlite3_exec(db, "COMMIT;", 0, 0, &zErrMsg);
这样SQLite将把全部要执行的SQL语句先缓存在内存当中,然后等到COMMIT的时候一次性的写入数据库,这样数据库文件只被打开关闭了一次,效率自然大大的提高。有一组数据对比:
测试1: 1000 INSERTs
CREATE TABLE t1(a INTEGER, b INTEGER, c VARCHAR(100));
INSERT INTO t1 VALUES(1,13153,'thirteen thousand one hundred fifty three');
INSERT INTO t1 VALUES(2,75560,'seventy five thousand five hundred sixty');
... 995 lines omitted
INSERT INTO t1 VALUES(998,66289,'sixty six thousand two hundred eighty nine');
INSERT INTO t1 VALUES(999,24322,'twenty four thousand three hundred twenty two');
INSERT INTO t1 VALUES(1000,94142,'ninety four thousand one hundred forty two');
SQLite 2.7.6:
13.061
SQLite 2.7.6 (nosync):
0.223
测试2: 使用事务 25000 INSERTs
BEGIN;
CREATE TABLE t2(a INTEGER, b INTEGER, c VARCHAR(100));
INSERT INTO t2 VALUES(1,59672,'fifty nine thousand six hundred seventy two');
... 24997 lines omitted
INSERT INTO t2 VALUES(24999,89569,'eighty nine thousand five hundred sixty nine');
INSERT INTO t2 VALUES(25000,94666,'ninety four thousand six hundred sixty six');
COMMIT;
SQLite 2.7.6:
0.914
SQLite 2.7.6 (nosync):
0.757
可见使用了事务之后却是极大的提高了数据库的效率。但是我们也要注意,使用事务也是有一定的开销的,所以对于数据量很小的操作可以不必使用,以免造成而外的消耗。