Re: Determining C type for a given OID

Graham Wilson wrote:
> Hi all,
>
> I'm using the libpq `PQgetvalue` function to get
> specific results from my datase. Many of these
> results are numeric types. Is there an internal
> function in libpq that will convert the returned
> string to an appropriate C-type based on the oid
> values in src/include/catalog/pg_type.h?

Well, in most queries, the returned value is a C string that you have
to convert in the client. I think ecpg handles such conversions
natively so you don't have to worry about them, and most of the
scripting languages handle a C string numeric value just like any other
value (they don't have data types). It would be great if we could
assign it right to a double, but you can't.

You can make such assignments of float4 to float and float8 to double if
you use a binary cursor _and_ your client and server have the same
internal representation for such values. However, NUMERIC is stored
internally a binary-coded decimal-like format that isn't going to make
any sense to your client code at all.

--
Bruce Momjian | http://candle.pha.pa.us
pgman(at)candle(dot)pha(dot)pa(dot)us | (610) 359-1001
+ If your life is a hard drive, | 13 Roberts Road
+ Christ can be your backup. | Newtown Square, Pennsylvania 19073