我目前正在开发用java(7)实现的桌面应用程序，它管理sql数据库中的大量数据记录。只有几个表，但它们包含大量的记录。我需要对单个表执行复杂的查询，但不需要执行复杂的联接操作。在

到目前为止，我一直在与博士后合作。但由于它是一个桌面单用户应用程序，我也考虑过使用sqlite(不用说，这也会降低设置的复杂性)。所以我写了一个简单的python脚本来做一些性能测试。令我惊讶的是，首先，sqlite的实际执行情况如何；其次，python中的查询响应时间比java中的要小得多。在

一个常见的场景是根据id列表选择一批记录。在python中，我使用以下代码来测试响应时间：rand_selection = ','.join([str(int(random.random()* MAX_INDEX )) for i in xrange(PAGE_SIZE)])

start = time.time();

c = db.cursor();

res = c.execute("SELECT * FROM bigtable WHERE id in ("+rand_selection+")");

reslist = [str(t) for t in res]; c.close();

print( time.time() - start );

对于MAX_INDEX=111000和PAGE_SIZE=100，这给了我大约5毫秒的增量。在

好吧，太好了。现在，让我们转到java：我使用jdbc-sqlite驱动程序。我在完全相同的表上执行了完全相同的查询，查询时间总是在200毫秒左右，这对于我的用例来说是不可接受的。在

我错过了什么吗？在

我知道这是一个非常普遍的问题。但是也许有人对JDBCSQLite有一定的经验，并且从经验中知道发生了什么

[编辑]：使用timit.default_计时器()正如建议的(谢谢，马蒂恩·皮特斯)给了我相似的结果。在

[Edit2]：根据CL的建议，我编写了java代码的简化版本。使用这段代码，我可以而不是验证结果和响应时间与python代码相同。但是，我在另一台机器上测试了这一点，使用了不同的jdk(openjdk7与oraclejdk7)。诚然，我的其他测试代码很可能有一些问题。在

[编辑2013-08-16]：我现在使用原始设置执行相同的测试。我还把它和博士后做了比较。在

^{pr2}$

测试代码(请原谅草率的编码…)：package ch.dsd;

import java.sql.*;

import java.util.ArrayList;

import java.util.List;

import java.util.Properties;

public class Main {

private static int COL_COUNT = 20;

private static int TESTRUNS = 20;

private static int INDEX_COUNT = 64;

/*

CREATE TABLE bigtable ( id INTEGER PRIMARY KEY ASC, prop0 real, prop1 real, ... , prop19 real );

*/

static class Entity {

private long id;

private ArrayList properties = new ArrayList(COL_COUNT);

public Entity() {

for( int i = 0; i < COL_COUNT; i++) {

properties.add(0.0);

}

}

public long getId() {

return id;

}

public void setId(long id) {

this.id = id;

}

public void setProperty(int idx, double prop) {

properties.set(idx, prop);

}

public double getProperty(int idx) {

return properties.get(idx);

}

@Override

public String toString() {

StringBuilder sb = new StringBuilder();

for( double prop: properties ) {

sb.append(prop);

sb.append(",");

}

sb.delete(sb.length()-1, sb.length());

return sb.toString();

}

}

private static String placeholders( int n ) {

StringBuilder sb = new StringBuilder();

if( n > 0 ) {

sb.append("?");

for( int i = 1; i < n; i++ )

sb.append(",?");

return sb.toString();

}

return "";

}

private static void setRandomIdcs( PreparedStatement ps, int start, int stop, int max ) throws SQLException {

for( int i = start; i <= stop; i++ ) {

ps.setLong(i, (long) ((double) max * Math.random()));

}

}

private static void setRandomValues( PreparedStatement ps, int start, int stop ) throws SQLException {

for( int i = start; i <= stop; i++ ) {

ps.setDouble(i, Math.random());

}

}

private static void readFromResultSet( ResultSet rs, List lst ) throws SQLException {

while(rs.next()) {

final Entity e = new Entity();

e.setId(rs.getLong(1));

for( int i = 0; i < COL_COUNT; i++ )

e.setProperty(i, rs.getDouble(i+2));

lst.add(e);

}

}

public static void performTest(Connection c) throws SQLException {

final PreparedStatement ps = c.prepareStatement("SELECT * FROM bigtable WHERE id in ("+placeholders(INDEX_COUNT)+")");

ArrayList entities = new ArrayList();

for( int i = 0; i < TESTRUNS; i++ ) {

setRandomIdcs( ps, 1, INDEX_COUNT, 1000000 ); // there are one million entries stored in the test table

long start = System.currentTimeMillis();

final ResultSet rs = ps.executeQuery();

readFromResultSet(rs, entities);

// System.out.println(entities.get(INDEX_COUNT-1));

System.out.println("Time used:" + (System.currentTimeMillis() - start));

System.out.println("Items read:" + entities.size());

rs.close();

entities.clear();

}

ps.close();

}

public static void createPSQLTable(Connection c) throws SQLException {

final String create_stmt = "CREATE TABLE IF NOT EXISTS bigtable (id SERIAL PRIMARY KEY, " +

"prop0 double precision,prop1 double precision,prop2 double precision,prop3 double precision,prop4 double precision,prop5 double precision,prop6 double precision,prop7 double precision,prop8 double precision,prop9 double precision,prop10 double precision,prop11 double precision,prop12 double precision,prop13 double precision,prop14 double precision,prop15 double precision,prop16 double precision,prop17 double precision,prop18 double precision,prop19 double precision)";

final PreparedStatement ps = c.prepareStatement(create_stmt);

ps.executeUpdate();

ps.close();

}

public static void loadPSQLTable( Connection c ) throws SQLException {

final String insert_stmt = "INSERT INTO bigtable VALUES (default, " + placeholders(20) + ")";

final PreparedStatement ps = c.prepareStatement(insert_stmt);

for( int i = 0; i < 1000000; i++ ) {

setRandomValues(ps, 1, 20);

ps.executeUpdate();

}

c.commit();

}

public static void main(String[] args) {

Connection c = null;

try {

Class.forName("org.sqlite.JDBC");

c = DriverManager.getConnection("jdbc:sqlite:/Users/dsd/tmp/sqlitetest/testdb.db");

c.setAutoCommit(false);

performTest(c);

c.close();

System.out.println("POSTGRES");

System.out.println("========");

final Properties props = new Properties();

props.setProperty("user", "dsd");

c = DriverManager.getConnection("jdbc:postgresql:testdb", props);

c.setAutoCommit(false);

createPSQLTable(c);

// loadPSQLTable(c);

performTest(c);

c.close();

} catch ( Exception e ) {

System.err.println( e.getClass().getName() + ": " + e.getMessage() );

System.exit(0);

}

}

}

结果：Time used:348

Items read:64

Time used:407

Items read:64

Time used:259

Items read:64

Time used:341

Items read:64

Time used:325

Items read:64

Time used:145

Items read:64

Time used:70

Items read:64

Time used:98

Items read:64

Time used:91

Items read:64

Time used:134

Items read:64

Time used:68

Items read:64

Time used:51

Items read:64

Time used:51

Items read:64

Time used:51

Items read:64

Time used:55

Items read:64

Time used:67

Items read:64

Time used:56

Items read:64

Time used:90

Items read:64

Time used:56

Items read:64

Time used:51

Items read:64

POSTGRES

========

Time used:75

Items read:64

Time used:58

Items read:64

Time used:31

Items read:64

Time used:26

Items read:64

Time used:34

Items read:64

Time used:6

Items read:64

Time used:5

Items read:64

Time used:4

Items read:64

Time used:5

Items read:64

Time used:6

Items read:64

Time used:5

Items read:64

Time used:6

Items read:64

Time used:4

Items read:64

Time used:28

Items read:64

Time used:3

Items read:64

Time used:4

Items read:64

Time used:4

Items read:64

Time used:4

Items read:64

Time used:3

Items read:64

Time used:5

Items read:64