From: Bruce Momjian <pgman@candle.pha.pa.us>
To: Michael Meskes <meskes@postgresql.org>
Cc: Tilo Schwarz <mail@tilo-schwarz.de>
Cc: pgsql-interfaces@postgresql.org
Subject: Re: ECPG Problem (Bug?)
Date: Thu, 4 Sep 2003 23:56:30 -0400 (EDT)
Message-ID: <200309050356.h853uUs28864@candle.pha.pa.us> (raw)
In-Reply-To: <20030824092513.GC1151@feivel.fam-meskes.de>
Michael, would you make the mentioned doc corrections? Thanks.
---------------------------------------------------------------------------
Michael Meskes wrote:
> > 1.)
> > The first problem started while I was trying to use a cursor. The docs show an
> > ECPG example to use cursors like this:
> >
> >
> > 4.4. Running SQL Commands
> > [...]
> > Select using Cursors:
> >
> > EXEC SQL DECLARE foo_bar CURSOR FOR
> > SELECT number, ascii FROM foo
> > ORDER BY ascii;
> > EXEC SQL FETCH foo_bar INTO :FooBar, DooDad;
>
> This is a bug in the docs. In PGSQL there is no open command yes, but
> embedded sql wants and needs it. In fact ecpg only copies the declare to
> the position of the open command.
>
> > 4.11. For the Developer
> >
> > Note that not all SQL commands are treated in this way. For instance, an open
> > cursor statement like
> >
> > EXEC SQL OPEN cursor;
> >
> > is not copied to the output. Instead, the cursor's DECLARE command is used
> > because it opens the cursor as well.
>
> That is correct. The DECLARE is used at the position of the OPEN to open
> the cursor.
>
> > 2.)
> > The docs say:
> >
> >
> > 4.5. Passing Data
> >
> > [...]
> >
> > The special types VARCHAR and VARCHAR2 are converted into a named struct for
> > every variable.
> >
> >
> > But I observed that
> >
> > EXEC SQL BEGIN DECLARE SECTION;
> > VARCHAR name;
> > EXEC SQL END DECLARE SECTION;
> >
> > works well, but
> >
> > EXEC SQL BEGIN DECLARE SECTION;
> > VARCHAR2 name;
> > EXEC SQL END DECLARE SECTION;
> >
> > gives:
> > pg.pgc:8: ERROR: invalid datatype 'VARCHAR2'
>
> VARCHAR2 does not exist anymore.
>
> > 3.)
> > String truncation in case of too short buffer.
> > In this example
> > EXEC SQL WHENEVER sqlwarning sqlprint;
> > EXEC SQL WHENEVER sqlerror sqlprint;
> > is used.
> >
> > If a VARCHAR field has a long enough buffer, every thing works fine (no error,
> > correct field 'fn' content):
> > > ./a.out
> > sqlca.sqlcode: 0
> > sqlca.sqlwarn[1]:
> > fn: gaze0000027524/gaze0000027525.pgm
> >
> > Now if the VARCHAR field is too short to hold the data from the query, I get:
> > > ./a.out
> > sql error
> > sqlca.sqlcode: 0
> > sqlca.sqlwarn[1]: W
> > fn: gaze00000275(???H?????@
> >
> > Two issues:
> > 1.)
> > The sqlprint gives me only the message "sql error", but no further information
> > as it does in case of other errors. I would be nice to have some output like
> > "VARCHAR field truncated" here.
>
> sqlprint is normally used for errors. No one ever implemented warnings
> in there.
>
> > 2.)
> > It seems, that the truncated string in 'fn' is not null-terminated (it prints
> > like gaze00000275(???H?????@). Wouldn't it be much safer, if the following
> > truncation rule would be used?:
> > Given a buffer 'buf' with n characters and query data 'dat' with m >= n
> > characters, copy the first n-1 charaters 'dat' to 'buf' and set buf[n] = 0.
> > This would make the handling of truncated data much easier.
>
> I beg to disagree as varchar has an additional length entry it does not
> have to NULL terminated.
>
> Michael
> --
> Michael Meskes
> Email: Michael at Fam-Meskes dot De
> ICQ: 179140304, AIM: michaelmeskes, Jabber: meskes@jabber.org
> Go SF 49ers! Go Rhein Fire! Use Debian GNU/Linux! Use PostgreSQL!
>
> ---------------------------(end of broadcast)---------------------------
> TIP 1: subscribe and unsubscribe commands go to majordomo@postgresql.org
>
--
Bruce Momjian | http://candle.pha.pa.us
pgman@candle.pha.pa.us | (610) 359-1001
+ If your life is a hard drive, | 13 Roberts Road
+ Christ can be your backup. | Newtown Square, Pennsylvania 19073
Reply instructions:
You may reply publicly to this message via plain-text email
using any one of the following methods:
* Reply to all the recipients using the --to and --cc options:
reply via email
To: pgsql-interfaces@postgresql.org
Cc: pgman@candle.pha.pa.us, meskes@postgresql.org, mail@tilo-schwarz.de
Subject: Re: ECPG Problem (Bug?)
In-Reply-To: <200309050356.h853uUs28864@candle.pha.pa.us>
* Save the following mbox file, import it into your mail client,
and reply-to-all from there: mbox
This inbox is served by DDX for PostgreSQL; see mirroring instructions
for how to clone and mirror all data and code used for this inbox