| From: | "Florian G(dot) Pflug" <fgp(at)phlo(dot)org> |
|---|---|
| To: | Dann Corbit <DCorbit(at)connx(dot)com> |
| Cc: | Hannu Krosing <hannu(at)skype(dot)net>, Tom Lane <tgl(at)sss(dot)pgh(dot)pa(dot)us>, Gregory Stark <stark(at)enterprisedb(dot)com>, pgsql-hackers(at)postgresql(dot)org |
| Subject: | Re: Selecting a constant question |
| Date: | 2007-06-12 10:32:59 |
| Message-ID: | 466E765B.1010001@phlo.org |
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| Lists: | pgsql-hackers |
Dann Corbit wrote:
>> -----Original Message-----
>> From: Hannu Krosing [mailto:hannu(at)skype(dot)net]
>>> Since libpq function PQfsize returns -2 for all constant character
>>> strings in SQL statements ... What is the proper procedure to determine
>>> the length of a constant character column after query execution but
>>> before fetching the first row of data?
>> Why not just get the first row and determine the width from it before
>> you actually use any of tha data ?
>
> What if the second row is 1000x longer?
Thats exactly the point. Consider
select mytext from mytable ;
How can PostgreSQL possibly know the maximum length
of the returned values *before* it has scanned the
whole table?
greetings, Florian Pflug
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