Re: [HACKERS] Re: [INTERFACES] retrieving varchar size

From: Bruce Momjian <maillist(at)candle(dot)pha(dot)pa(dot)us>
To: hannu(at)trust(dot)ee (Hannu Krosing)
Cc: byronn(at)insightdist(dot)com, pgsql-hackers(at)postgreSQL(dot)org, pgsql-interfaces(at)postgreSQL(dot)org
Subject: Re: [HACKERS] Re: [INTERFACES] retrieving varchar size
Date: 1998-04-23 16:45:42
Message-ID: 199804231645.MAA26157@candle.pha.pa.us
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>
> Byron Nikolaidis wrote:
> >
> > Hello,
> >
> > I was wondering if it would be possible, in the Postgres backend, to
> > send back the defined column size for the varchar data type (and
> > possibly the char() type, i.e., bpchar) on a query? Currently, it just
> > sends back -1 for the size, which makes it difficult in the frontend
> > (i.e., odbc driver) to determine what the size of the column is.
>
> While the right solution to this is of course getting the size from
> backend, there exists a workaround now (assuming that the query is not
> too expensive). While ASCII cursors always hide the varchar sizes,
> binary ones return the size in actual data (by zero-padding the
> returned data to max size), so one can determine the actual max
> sizes by opening the query in binary cursor and then examining
> enough records to get one non-null field for each varchar field.

As of 6.3, this is only true of char() fields. Varchar() is now
variable length.

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