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From: "creid" <creid(at)netbcg(dot)com>
To: <pgsql-interfaces(at)postgresql(dot)org>
Date: 2003-10-30 15:11:23
Message-ID: (view raw, whole thread or download thread mbox)
Lists: pgsql-interfaces
I am experimenting with LIBPGEASY

Problem: When I access a "varchar(30)" column using "DECLARE.....FOR SELECT column from schema.table WHERE pkey='KEY'"

When I fetch to a declared variable to return to a calling procedure, my program does a (segmentation error) unless I declare the char variable to some much higher value than it is seemingly necessary.  Moreover, the problem does not occur when I manipulate the result in the called procedure.  In fact, in my experimentation, I have noticed that I can declare a char variable array less than what the result is and it still works.  The crash only occurs in the calling procedure.

What might I be doing wrong?


-----Original Message-----
From: pgsql-interfaces-owner(at)postgresql(dot)org
[mailto:pgsql-interfaces-owner(at)postgresql(dot)org]On Behalf Of Igor
Sent: Monday, October 27, 2003 2:25 AM
To: Tomasz Myrta
Cc: pgsql-interfaces(at)postgresql(dot)org
Subject: Re: [INTERFACES] LIBPQ Question

On Monday 27 October 2003 09:15, Tomasz Myrta wrote:
> Dnia 2003-10-27 00:08, Użytkownik creid napisał:
> > Problem:  Assigning a COUNT(*) result into an integer variable in my C
> > program consistently fails except when I assign the same result to a char
> > variable.  I can only assume that the internal data type the COUNT
> > function uses is integer.
> >
> > Can anyone help put me in the proper mindset so I may deal with this,
> > seemingly simple issue, to resolution.
> >
> > I need the integer result to to help me satisfy a dynamic memory
> > requirement... COUNT(*) result will tell me how many rows of data I need
> > to malloc and I cannot perform a math operation on a char variable.
> All libpq results are strings.
> some_int_value=atoi(PQgetvalue(...))

Not true anymore with protocol v3, which added the binary format. Text format 
is still the default.

> Anyway why do you need count(*) ? When you retrieve your rows, you can
> always check how many are them using PQntuples(...) and then malloc your
> memory tables.
> Regards,
> Tomasz Myrta
> ---------------------------(end of broadcast)---------------------------
> TIP 9: the planner will ignore your desire to choose an index scan if your
>       joining column's datatypes do not match

Best regards,
Igor Shevchenko

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