SQLite数据库中用insert同时插入多条记录的方法和效率比较


Android开发中我们常会遇到这样一种情况:在建立一个SQLite数据库时,想同时插入大量数据。那么应该怎么做呢?

下面笔者以插入20条记录为例:

  1.   将同时插入大量的数据写成一条SQL语句
  2.  最笨的方法用insert语句一条一条的输入
  3. 使用事务

代码如下:

public class DateBaseOpenHelper extends SQLiteOpenHelper {

     public static final String DBNAME="radiomap";
     public static final int VERSION=1;
     public DateBaseOpenHelper(Context context){
      super(context,DBNAME,null,VERSION);
     }
 @Override
 public void onCreate(SQLiteDatabase db) {
  // TODO Auto-generated method stub
       db.execSQL("create table radiomap(location varchar(20),ap1 int,ap2 int)");
       long a=System.currentTimeMillis();
       db.execSQL("insert into radiomap(location,ap1,ap2) select 'x=1,y=1',-80,-73 " +
         "union all select 'x=2,y=3',80,40 union all select 'x=3,y=5',30,20 "+
         "union all select 'x=4,y=5',3,2 union all select 'x=30,y=50',30,20 union all select 'x=3,y=5',40,20"
         +" union all select 'x=3,y=5',6,20 union all select 'x=3,y=5',6,7 union all select 'x=3,y=5',7,8 union all select 'x=3,y=5',8,9 union all select 'x=3,y=5',9,9" +
           " union all select 'x=3,y=5',3,5 union all select 'x=3,y=5',7,20 union all select 'x=3,y=5',4,20 union all select 'x=3,y=5',5,20 union all select 'x=3,y=5',6,20" +
           " union all select 'x=3,y=5',3,6 union all select 'x=3,y=5',7,7 union all select 'x=3,y=5',3,8 union all select 'x=3,y=5',8,2");
       long b=System.currentTimeMillis();
       long c=b-a;
       Log.i("LocationActivity", String.valueOf(c));
      
       a=System.currentTimeMillis();
       db.beginTransaction();
       db.execSQL("insert into radiomap(location,ap1,ap2) values('x=4,y=5',2,3)");
       db.execSQL("insert into radiomap(location,ap1,ap2) values('x=5,y=6',4,5)");
       db.execSQL("insert into radiomap(location,ap1,ap2) values('x=6,y=7',6,7)");
       db.execSQL("insert into radiomap(location,ap1,ap2) values('x=4,y=5',2,3)");
       db.execSQL("insert into radiomap(location,ap1,ap2) values('x=5,y=6',4,5)");
       db.execSQL("insert into radiomap(location,ap1,ap2) values('x=6,y=7',6,7)");
       db.execSQL("insert into radiomap(location,ap1,ap2) values('x=4,y=5',1,3)");
       db.execSQL("insert into radiomap(location,ap1,ap2) values('x=5,y=6',1,5)");
       db.execSQL("insert into radiomap(location,ap1,ap2) values('x=6,y=7',1,7)");
       db.execSQL("insert into radiomap(location,ap1,ap2) values('x=4,y=5',2,3)");
       db.execSQL("insert into radiomap(location,ap1,ap2) values('x=5,y=6',2,5)");
       db.execSQL("insert into radiomap(location,ap1,ap2) values('x=6,y=7',2,7)");
       db.execSQL("insert into radiomap(location,ap1,ap2) values('x=4,y=5',3,3)");
       db.execSQL("insert into radiomap(location,ap1,ap2) values('x=5,y=6',3,5)");
       db.execSQL("insert into radiomap(location,ap1,ap2) values('x=6,y=7',3,7)");
       db.execSQL("insert into radiomap(location,ap1,ap2) values('x=4,y=5',4,3)");
       db.execSQL("insert into radiomap(location,ap1,ap2) values('x=5,y=7',5,5)");
       db.execSQL("insert into radiomap(location,ap1,ap2) values('x=6,y=7',4,7)");
       db.execSQL("insert into radiomap(location,ap1,ap2) values('x=4,y=5',5,3)");
       db.execSQL("insert into radiomap(location,ap1,ap2) values('x=5,y=6',5,5)");
       db.setTransactionSuccessful();
       db.endTransaction();
       b=System.currentTimeMillis();
       Log.i("LocationActivity", String.valueOf(b-a));
       
       a=System.currentTimeMillis();
       db.execSQL("insert into radiomap(location,ap1,ap2) values('x=7,y=8',7,8)");
       db.execSQL("insert into radiomap(location,ap1,ap2) values('x=8,y=9',8,9)");
       db.execSQL("insert into radiomap(location,ap1,ap2) values('x=9,y=10',9,10)");
       db.execSQL("insert into radiomap(location,ap1,ap2) values('x=4,y=5',2,3)");
       db.execSQL("insert into radiomap(location,ap1,ap2) values('x=5,y=6',4,5)");
       db.execSQL("insert into radiomap(location,ap1,ap2) values('x=6,y=7',6,7)");
       db.execSQL("insert into radiomap(location,ap1,ap2) values('x=4,y=5',2,3)");
       db.execSQL("insert into radiomap(location,ap1,ap2) values('x=5,y=6',2,5)");
       db.execSQL("insert into radiomap(location,ap1,ap2) values('x=6,y=7',2,7)");
       db.execSQL("insert into radiomap(location,ap1,ap2) values('x=4,y=5',3,3)");
       db.execSQL("insert into radiomap(location,ap1,ap2) values('x=5,y=6',3,5)");
       db.execSQL("insert into radiomap(location,ap1,ap2) values('x=6,y=7',3,7)");
       db.execSQL("insert into radiomap(location,ap1,ap2) values('x=4,y=5',4,3)");
       db.execSQL("insert into radiomap(location,ap1,ap2) values('x=5,y=6',4,4)");
       db.execSQL("insert into radiomap(location,ap1,ap2) values('x=6,y=7',4,7)");
       db.execSQL("insert into radiomap(location,ap1,ap2) values('x=4,y=5',5,3)");
       db.execSQL("insert into radiomap(location,ap1,ap2) values('x=5,y=7',6,5)");
       db.execSQL("insert into radiomap(location,ap1,ap2) values('x=6,y=7',5,7)");
       db.execSQL("insert into radiomap(location,ap1,ap2) values('x=4,y=5',6,3)");
       db.execSQL("insert into radiomap(location,ap1,ap2) values('x=5,y=6',6,5)");
       b=System.currentTimeMillis();
       Log.i("LocationActivity", String.valueOf(b-a));
 }

 

第一种方式及:

insert into 表名(列名1,列名2)    
 select  值1,值2
 union all 
 select 值1,值2  
 union all 
 select 值1,值2 

以上三种方式测试结果,及运行效率:

第一种方式为9ms

用事务的为:86ms

第三种直接用insert插入的为:29ms

这是因为本次测试用了20条数据,所以用事务的反而比不用的开销大时间长。若1000条以上则明显快于直接用insert插入的。

 

 

今天有个朋友测试 SQLite,然后得出的结论是:SQLite 效率太低,批量插入1000条记录,居然耗时2分钟!
下面是他发给我的测试代码。我晕~~~~~~
usingSystem.Data;
usingSystem.Data.Common;
usingSystem.Data.SQLite;
//创建数据库文件
File.Delete("test1.db3");
SQLiteConnection.CreateFile("test1.db3");
DbProviderFactory factory=SQLiteFactory.Instance;
using(DbConnection conn=factory.CreateConnection())
{
//连接数据库
conn.ConnectionString="Data Source=test1.db3";
conn.Open();
//创建数据表
stringsql="create table [test1] ([id] INTEGER PRIMARY KEY, [s] TEXT COLLATE NOCASE)";
DbCommand cmd=conn.CreateCommand();
cmd.Connection=conn;
cmd.CommandText=sql;
cmd.ExecuteNonQuery();
//添加参数
cmd.Parameters.Add(cmd.CreateParameter());
//开始计时
Stopwatch watch=newStopwatch();
watch.Start();
//连续插入1000条记录
for(inti=0; i<1000; i++)
{
cmd.CommandText="insert into [test1] ([s]) values (?)";
cmd.Parameters[0].Value=i.ToString();
cmd.ExecuteNonQuery();
}
//停止计时
watch.Stop();
Console.WriteLine(watch.Elapsed);
}
哎~~~~一个常识性的错误,我加几行代码 (新增代码标记"// <-------------------")。
usingSystem.Data;
usingSystem.Data.Common;
usingSystem.Data.SQLite;
//创建数据库文件
File.Delete("test1.db3");
SQLiteConnection.CreateFile("test1.db3");
DbProviderFactory factory=SQLiteFactory.Instance;
using(DbConnection conn=factory.CreateConnection())
{
//连接数据库
conn.ConnectionString="Data Source=test1.db3";
conn.Open();
//创建数据表
stringsql="create table [test1] ([id] INTEGER PRIMARY KEY, [s] TEXT COLLATE NOCASE)";
DbCommand cmd=conn.CreateCommand();
cmd.Connection=conn;
cmd.CommandText=sql;
cmd.ExecuteNonQuery();
//添加参数
cmd.Parameters.Add(cmd.CreateParameter());
//开始计时
Stopwatch watch=newStopwatch();
watch.Start();
DbTransaction trans=conn.BeginTransaction();//<-------------------
try
{
//连续插入1000条记录
for(inti=0; i<1000; i++)
{
cmd.CommandText="insert into [test1] ([s]) values (?)";
cmd.Parameters[0].Value=i.ToString();
cmd.ExecuteNonQuery();
}
trans.Commit();//<-------------------
}
catch
{
trans.Rollback();//<-------------------
throw;//<-------------------
}
//停止计时
watch.Stop();
Console.WriteLine(watch.Elapsed);
}
执行一下,耗时0.2秒。这差距是不是太大了点?
为什么只是简单启用了一个事务会有这么大的差距呢?很简单,SQLite 缺省为每个操作启动一个事务,那么原代码1000次插入起码开启了1000个事务,"事务开启 + SQL 执行 + 事务关闭"自然耗费了大量的时间,这也是后面显示启动事务后为什么如此快的原因。其实这是数据库操作的基本常识,大家要紧记,不好的代码效率差的不是一点半点。

 

 

最近在做android项目的时候遇到一个问题,应用程序初始化时需要批量的向sqlite中插入大量数,导致应用启动过慢。
android使用的是sqlite数据库,sqlite是比较轻量级的数据库,在Google了之后发现,sqlite事务处理的问题,在sqlite插入数据的时候默认一条语句就是一个事务,有多少条数据就有多少次磁盘操作。我的应用初始5000条记录也就是要5000次读写磁盘操作。

解决方法:

添加事务处理,把5000条插入作为一个事务

dataBase.beginTransaction();       //手动设置开始事务

//数据插入操作循环

dataBase.setTransactionSuccessful();       //设置事务处理成功,不设置会自动回滚不提交

dataBase.endTransaction();       //处理完成

 


SQLite的数据库本质上来讲就是一个磁盘上的文件,所以一切的数据库操作其实都会转化为对文件的操作,而频繁的文件操作将会是一个很好时的过程,会极大地影响数据库存取的速度。
例如:向数据库中插入100万条数据,在默认的情况下如果仅仅是执行
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1:1000INSERTs
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');
...995lines 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');
SQLite2.7.6:
13.061
SQLite2.7.6(nosync):
0.223

测试2: 使用事务25000INSERTs
BEGIN;
CREATE TABLE t2(a INTEGER, b INTEGER, c VARCHAR(100));
INSERT INTO t2 VALUES(1,59672,'fifty nine thousand six hundred seventy two');
...24997lines 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;
SQLite2.7.6:
0.914
SQLite2.7.6(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。

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