> -----Original Message----- > From: [EMAIL PROTECTED] [mailto:pgsql-hackers- > [EMAIL PROTECTED] On Behalf Of Dann Corbit > Sent: Monday, June 11, 2007 1:52 PM > To: Martijn van Oosterhout > Cc: email@example.com > Subject: Re: [HACKERS] Selecting a constant question > > > -----Original Message----- > > From: Martijn van Oosterhout [mailto:[EMAIL PROTECTED] > > Sent: Monday, June 11, 2007 1:46 PM > > To: Dann Corbit > > Subject: Re: [HACKERS] Selecting a constant question > > > > On Mon, Jun 11, 2007 at 01:29:37PM -0700, Dann Corbit wrote: > > > Our application is using the libPQ interface to access postgres. > > > > > > The query is "select '123' from <tablename>" .. the table is not > > > important. > > > > > > After executing the query, we interrogate the metadata of the result > set > > > using the PQfsize, PQfmod and PQftype functions. > > > > Did you read the documentation of the PQfsize function? > > > > PQfsize returns the space allocated for this column in a database row, > > in other words the size of the server's internal representation of the > > data type. (Accordingly, it is not really very useful to clients.) A > > negative value indicates the data type is variable-length. > > > > > http://www.postgresql.org/docs/8.2/interactive/libpq-exec.html#LIBPQ-EXE > C- > > SELECT-INFO > > > > > The size of the column is returned as 65534 (or -2 if you consider > this > > > a signed short value) > > > > It's variable length, you can't say anything more. > > So what you are saying is that the constant '1' is variable length, and > there is no way to find out the maximum length from the database.
I have a PostgreSQL feature request: Report the maximum size of a variable length string from the server. Surely, we cannot be the only people who will need this information. If (for example) someone wants to bind to a grid, then the maximum size has to be known in advance. ---------------------------(end of broadcast)--------------------------- TIP 2: Don't 'kill -9' the postmaster