From: | silly sad <sad(at)bankir(dot)ru> |
---|---|
To: | pgsql-sql(at)postgresql(dot)org |
Subject: | Re: LIMIT problem |
Date: | 2010-05-01 09:05:11 |
Message-ID: | 4BDBEEC7.5030405@bankir.ru |
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Thread: | |
Lists: | pgsql-sql |
On 05/01/10 03:58, Jasen Betts wrote:
> On 2010-04-30, silly sad<sad(at)bankir(dot)ru> wrote:
>> suppose i request
>>
>> SELECT foo(t.x) FROM t LIMIT 1;
>>
>> Whither it DEFINED how many times foo() will be executed?
>
> foo will be executed repeatedly until it returns a result or all the
> rows in t are exhausted.
>
>> May anyone rely on it?
>
> not sure
>
>> Or we have to avoid this non SQLish trick?
>
>
> This will execute it once (or not at all where t has no rows)
>
> SELECT foo(x) FROM (SELECT x FROM t LIMIT 1) as bar;
>
this subselect "isolation" looks like a safe way.
Unlike LIMITed select looks unpredictable to me.
Thanx for assistance :)
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