本文主要演示sqlite开源项目中的数据库方法类索引操作使用说明（包括新建索引、查询数据、检查索引是否存在等）。本项目旨在分享知识和经验，欢迎广大网友一起加入到开源项目中一起分享贡献知识和经验。

话不多说，先上测试代码

/******************************************************************************
  > File Name		: samples_add_index.cpp
  > Author			: Wseldom
  > Mail			: 3235459847@qq.com
  > Created Time	: Mon 27 Nov 2023 03:36:28 PM CST
******************************************************************************/
#include "./samples_add_index.hpp"
#include "sqlite/sqlite.h"
#include <stdlib.h>
#include<time.h>
#include <sys/time.h>


int samples_add_index (int argc, char** argv)
{
	if (argc < 3) {
		printf ("请输入正确的格式，如：./exec 1 test.db\n");
		return -1;
	}
	sql::sqlite db(argv[2]);
	db.exec ("create table if not exists employee("
		"ID INTEGER PRIMARY KEY  AUTOINCREMENT, "
		"NAME           TEXT    NOT NULL, "
		"AGE            INT     NOT NULL, "
		"ADDRESS        CHAR(50), "
		"SALARY         REAL"
	");");
	switch (atoi (argv[1])) {
		case 0:
		{// 添加数据
			char buff[1024];
			int pos = snprintf (buff, sizeof (buff), "insert into employee(ID,NAME,AGE,ADDRESS,SALARY)values(NULL,'员工");
			srand((unsigned)time(NULL));
			for (int i = 0; i < 3000000; i++) {
				snprintf (buff + pos, sizeof (buff) -  pos, "%d',%d,'城市%d',%d);", i, rand() % 60, i % 30, rand () % 30000);
				db.exec (buff);
				printf ("加载%%%f......\n", i / 3000000.0 * 100);
			}
			break;
		}
		case 1:
		{// 带索引查询
			struct timeval start,end;
			long long us_count;
			long long s_count;
			db.exec (SQLCMD_CREATE_IDX ("employee", "city", "ADDRESS"));
			sql::query* query = NULL;
			gettimeofday (&start, NULL);
			query = db.query ("select * from employee where ADDRESS='城市28';");
			gettimeofday (&end, NULL);
			if (end.tv_usec >= start.tv_usec) {
				us_count = end.tv_usec - start.tv_usec;
				s_count = end.tv_sec - start.tv_sec;
			} else {
				us_count = 1000000 + end.tv_usec - start.tv_usec;
				s_count = end.tv_sec - start.tv_sec - 1;
			}
			printf ("耗时：%lld s %lld ms %lld us\n"
				, s_count
				, (us_count / 1000), us_count % 1000);
			if (query) delete query;
			break;
		}
		case 2:
		{// 不带索引查询
			struct timeval start,end;
			long long us_count;
			long long s_count;
			sql::query* query = NULL;
			db.exec (SQLCMD_DROP_IDX ("city"));
			gettimeofday (&start, NULL);
			query = db.query ("select * from employee where ADDRESS='城市28';");
			gettimeofday (&end, NULL);
			if (end.tv_usec >= start.tv_usec) {
				us_count = end.tv_usec - start.tv_usec;
				s_count = end.tv_sec - start.tv_sec;
			} else {
				us_count = 1000000 + end.tv_usec - start.tv_usec;
				s_count = end.tv_sec - start.tv_sec - 1;
			}
			printf ("耗时：%lld s %lld ms %lld us\n"
				, s_count
				, (us_count / 1000), us_count % 1000);
			if (query) delete query;
			break;
		}
		case 3:
		{
			if (db.record_count (SQLCMD_IDX_EXIST ("city"))) {
				db.exec (SQLCMD_DROP_IDX ("city"));
				printf ("删除索引city\n");
			} else {
				printf ("创建索引city\n");
				db.exec (SQLCMD_CREATE_IDX ("employee", "city", "ADDRESS"));
			}
			break;
		}
	}
	return 0;
}

插入3000000条记录

先执行make type=4编译上面的测试代码。
然后执行如下命令插入记录

./exec 0 test.db

插入数据量大，需要比较长的实践，可以先泡杯咖啡慢慢等。

不使用索引查询

现在先不使用索引查询一次看看需要多长时间。

添加索引查询

然后新建索引进行查询看看需要多长时间。
从实验结果看，新建了索引后查询速度快了约一倍。

检查索引是否存在

检查索引是否存在，如存在则删除索引，如不存在则新建索引。