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From: Quan Zongliang <zongliang.quan@postgresdata.com>
To: Jaimin Pan <jaimin.pan@gmail.com>
Cc: pgsql-zh-general@postgresql.org <pgsql-zh-general@postgresql.org>
Subject: Re: [pgsql-zh-general] 随机字符串函数的C语言实现
Date: Tue, 5 Sep 2017 18:26:42 +0800
Message-ID: <b737e130-2a28-f863-41ff-8ca310b1e9fd@postgresdata.com> (raw)
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References: <e4b2ab08-6847-e431-9ccb-d42ac805a3d7@postgresdata.com>
	<CABP8UDTSWgKpSSg2bO45t9sQatVzyasPv4Nm6rG0HPx55JKJxQ@mail.gmail.com>
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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.quan@postgresdata.com <mailto:zongliang.quan@postgresdata.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.quan@postgresdata.com <mailto:zongliang.quan@postgresdata.com>
> 
> 
> 
>     -- 
>     Sent via pgsql-zh-general mailing list
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> 



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