Re: Re: [pgsql-zh-general] 随机字符串函数的C语言实现

各位下午好
邮件列表沉寂太久，激活一下大家的情绪。

分享一个C语言实现的随机字符串函数：
PG_FUNCTION_INFO_V1(random_string);
Datum
random_string(PG_FUNCTION_ARGS)
{
int32 length = PG_GETARG_INT32(0);
int32 i;
const char chars[] =
"0123456789ABCDEFGHIJKLMNOPQRSTUVWXYZabcdefghijklmnopqrstuvwxyz";
char *result;

if (length < 0)
PG_RETURN_NULL();

if (length == 0)
PG_RETURN_TEXT_P(cstring_to_text(""));

result = palloc(length + 1);
if (result == NULL)
ereport(ERROR, (errcode(ERRCODE_OUT_OF_MEMORY),
errmsg("out of memory")));

for (i=0; i<length; i++)
{
result[i] = chars[random()%(sizeof(chars)-1)];
}
result[i] = '\0';

PG_RETURN_TEXT_P(cstring_to_text(result));
}

原文见：
https://my.oschina.net/quanzl/blog/1529438

欢迎关注我司公众号：postgresdata-news

--
权宗亮
神州飞象（北京）数据科技有限公司
我们的力量源自最先进的开源数据库PostgreSQL
zongliang(dot)quan(at)postgresdata(dot)com

试一试
md5(random()::text);

select pg_backend_pid(),s,'string '|| md5(random()::text) from (select
generate_series(2000,8000,1) s) as g;
Time: 239.733 ms

2017-09-05 16:28 GMT+08:00 Quan Zongliang <zongliang(dot)quan(at)postgresdata(dot)com>:

> 各位下午好
> 邮件列表沉寂太久，激活一下大家的情绪。
>
> 分享一个C语言实现的随机字符串函数：
> PG_FUNCTION_INFO_V1(random_string);
> Datum
> random_string(PG_FUNCTION_ARGS)
> {
> int32 length = PG_GETARG_INT32(0);
> int32 i;
> const char chars[] = "0123456789ABCDEFGHIJKLMNOPQRS
> TUVWXYZabcdefghijklmnopqrstuvwxyz";
> char *result;
>
> if (length < 0)
> PG_RETURN_NULL();
>
> if (length == 0)
> PG_RETURN_TEXT_P(cstring_to_text(""));
>
> result = palloc(length + 1);
> if (result == NULL)
> ereport(ERROR, (errcode(ERRCODE_OUT_OF_MEMORY),
> errmsg("out of memory")));
>
> for (i=0; i<length; i++)
> {
> result[i] = chars[random()%(sizeof(chars)-1)];
> }
> result[i] = '\0';
>
> PG_RETURN_TEXT_P(cstring_to_text(result));
> }
>
> 原文见：
> https://my.oschina.net/quanzl/blog/1529438
>
> 欢迎关注我司公众号：postgresdata-news
>
> --
> 权宗亮
> 神州飞象（北京）数据科技有限公司
> 我们的力量源自最先进的开源数据库PostgreSQL
> zongliang(dot)quan(at)postgresdata(dot)com
>
>
>
> --
> Sent via pgsql-zh-general mailing list (pgsql-zh-general(at)postgresql(dot)org)
> To make changes to your subscription:
> http://www.postgresql.org/mailpref/pgsql-zh-general
>

权叔有性能测试么？列一下数据啊，哈哈，学习一下。

On 09/05/2017 05:01 PM, Jaimin Pan wrote:
> 试一试
> md5(random()::text);
>
>
> select pg_backend_pid(),s,'string '|| md5(random()::text) from (select
> generate_series(2000,8000,1) s) as g;
> Time: 239.733 ms
>
> 2017-09-05 16:28 GMT+08:00 Quan Zongliang
> <zongliang(dot)quan(at)postgresdata(dot)com
> <mailto:zongliang(dot)quan(at)postgresdata(dot)com>>:
>
> 各位下午好
> 邮件列表沉寂太久，激活一下大家的情绪。
>
> 分享一个C语言实现的随机字符串函数：
> PG_FUNCTION_INFO_V1(random_string);
> Datum
> random_string(PG_FUNCTION_ARGS)
> {
> int32 length = PG_GETARG_INT32(0);
> int32 i;
> const char chars[] =
> "0123456789ABCDEFGHIJKLMNOPQRSTUVWXYZabcdefghijklmnopqrstuvwxyz";
> char *result;
>
> if (length < 0)
> PG_RETURN_NULL();
>
> if (length == 0)
> PG_RETURN_TEXT_P(cstring_to_text(""));
>
> result = palloc(length + 1);
> if (result == NULL)
> ereport(ERROR, (errcode(ERRCODE_OUT_OF_MEMORY),
> errmsg("out of memory")));
>
> for (i=0; i<length; i++)
> {
> result[i] = chars[random()%(sizeof(chars)-1)];
> }
> result[i] = '\0';
>
> PG_RETURN_TEXT_P(cstring_to_text(result));
> }
>
> 原文见：
> https://my.oschina.net/quanzl/blog/1529438
> <https://my.oschina.net/quanzl/blog/1529438>
>
> 欢迎关注我司公众号：postgresdata-news
>
> --
> 权宗亮
> 神州飞象（北京）数据科技有限公司
> 我们的力量源自最先进的开源数据库PostgreSQL
> zongliang(dot)quan(at)postgresdata(dot)com
> <mailto:zongliang(dot)quan(at)postgresdata(dot)com>
>
>
>
> --
> Sent via pgsql-zh-general mailing list
> (pgsql-zh-general(at)postgresql(dot)org
> <mailto:pgsql-zh-general(at)postgresql(dot)org>)
> To make changes to your subscription:
> http://www.postgresql.org/mailpref/pgsql-zh-general
> <http://www.postgresql.org/mailpref/pgsql-zh-general>
>
>

这样不能指定长度，返回值本身又不够长，今天测试是在看TOAST的变化。

On 2017/9/5 17:01, Jaimin Pan wrote:
> 试一试
> md5(random()::text);
>
>
> select pg_backend_pid(),s,'string '|| md5(random()::text) from (select
> generate_series(2000,8000,1) s) as g;
> Time: 239.733 ms
>
> 2017-09-05 16:28 GMT+08:00 Quan Zongliang
> <zongliang(dot)quan(at)postgresdata(dot)com <mailto:zongliang(dot)quan(at)postgresdata(dot)com>>:
>
> 各位下午好
> 邮件列表沉寂太久，激活一下大家的情绪。
>
> 分享一个C语言实现的随机字符串函数：
> PG_FUNCTION_INFO_V1(random_string);
> Datum
> random_string(PG_FUNCTION_ARGS)
> {
>         int32 length = PG_GETARG_INT32(0);
>         int32 i;
>         const char chars[] =
> "0123456789ABCDEFGHIJKLMNOPQRSTUVWXYZabcdefghijklmnopqrstuvwxyz";
>         char *result;
>
>         if (length < 0)
>                 PG_RETURN_NULL();
>
>         if (length == 0)
>                 PG_RETURN_TEXT_P(cstring_to_text(""));
>
>         result = palloc(length + 1);
>         if (result == NULL)
>                 ereport(ERROR, (errcode(ERRCODE_OUT_OF_MEMORY),
>                                         errmsg("out of memory")));
>
>         for (i=0; i<length; i++)
>         {
>                 result[i] = chars[random()%(sizeof(chars)-1)];
>         }
>         result[i] = '\0';
>
>         PG_RETURN_TEXT_P(cstring_to_text(result));
> }
>
> 原文见：
> https://my.oschina.net/quanzl/blog/1529438
> <https://my.oschina.net/quanzl/blog/1529438>
>
> 欢迎关注我司公众号：postgresdata-news
>
> --
> 权宗亮
> 神州飞象（北京）数据科技有限公司
> 我们的力量源自最先进的开源数据库PostgreSQL
> zongliang(dot)quan(at)postgresdata(dot)com <mailto:zongliang(dot)quan(at)postgresdata(dot)com>
>
>
>
> --
> Sent via pgsql-zh-general mailing list
> (pgsql-zh-general(at)postgresql(dot)org
> <mailto:pgsql-zh-general(at)postgresql(dot)org>)
> To make changes to your subscription:
> http://www.postgresql.org/mailpref/pgsql-zh-general
> <http://www.postgresql.org/mailpref/pgsql-zh-general>
>
>

这篇博文有简单测试：
https://my.oschina.net/quanzl/blog/1529438
天壤之别的性能差距

On 2017/9/5 17:11, winston cheung wrote:
> 权叔有性能测试么？列一下数据啊，哈哈，学习一下。
>
>
> On 09/05/2017 05:01 PM, Jaimin Pan wrote:
>> 试一试
>> md5(random()::text);
>>
>>
>> select pg_backend_pid(),s,'string '|| md5(random()::text) from (select
>> generate_series(2000,8000,1) s) as g;
>> Time: 239.733 ms
>>
>> 2017-09-05 16:28 GMT+08:00 Quan Zongliang
>> <zongliang(dot)quan(at)postgresdata(dot)com
>> <mailto:zongliang(dot)quan(at)postgresdata(dot)com>>:
>>
>> 各位下午好
>> 邮件列表沉寂太久，激活一下大家的情绪。
>>
>> 分享一个C语言实现的随机字符串函数：
>> PG_FUNCTION_INFO_V1(random_string);
>> Datum
>> random_string(PG_FUNCTION_ARGS)
>> {
>>         int32 length = PG_GETARG_INT32(0);
>>         int32 i;
>>         const char chars[] =
>> "0123456789ABCDEFGHIJKLMNOPQRSTUVWXYZabcdefghijklmnopqrstuvwxyz";
>>         char *result;
>>
>>         if (length < 0)
>>                 PG_RETURN_NULL();
>>
>>         if (length == 0)
>>                 PG_RETURN_TEXT_P(cstring_to_text(""));
>>
>>         result = palloc(length + 1);
>>         if (result == NULL)
>>                 ereport(ERROR, (errcode(ERRCODE_OUT_OF_MEMORY),
>>                                         errmsg("out of memory")));
>>
>>         for (i=0; i<length; i++)
>>         {
>>                 result[i] = chars[random()%(sizeof(chars)-1)];
>>         }
>>         result[i] = '\0';
>>
>>         PG_RETURN_TEXT_P(cstring_to_text(result));
>> }
>>
>> 原文见：
>> https://my.oschina.net/quanzl/blog/1529438
>> <https://my.oschina.net/quanzl/blog/1529438>
>>
>> 欢迎关注我司公众号：postgresdata-news
>>
>> --
>> 权宗亮
>> 神州飞象（北京）数据科技有限公司
>> 我们的力量源自最先进的开源数据库PostgreSQL
>> zongliang(dot)quan(at)postgresdata(dot)com
>> <mailto:zongliang(dot)quan(at)postgresdata(dot)com>
>>
>>
>>
>> --
>> Sent via pgsql-zh-general mailing list
>> (pgsql-zh-general(at)postgresql(dot)org
>> <mailto:pgsql-zh-general(at)postgresql(dot)org>)
>> To make changes to your subscription:
>> http://www.postgresql.org/mailpref/pgsql-zh-general
>> <http://www.postgresql.org/mailpref/pgsql-zh-general>
>>
>>
>