Обсуждение: PQgetvalue and User defined types/Arrays fields
Hi everybody,
I'm using Postgresql 7.03 (but I'm going to migrate soon to 7.1) and I have a big doubt about how to work with User defined types in my tables using libpq and the documentation does not help at all.
Anyone have any sample about how to use libpq with PQGetValue or similar to read records which have fields defined as Arrays or User defined types?. I looked for samples in the documentation or in the mailing list but I couldn't find anything.
For example, if I define the user-defined type "complex" just like in http://www.postgresql.org/idocs/index.php?xtypes.html#XTYPES-USERDEFINED and then I use it in a table, how can I read the field?. Must I use the complex_in(char *str) function passing as a parameter the PQGetValue result associated to this field number?. I have the same doubt when I define an array field.
By the way, do you know if there is any documentation/sample about libpq explaining these more advanced topics which are not fully explained in the general documentation?
Best regards and thanks in advance,
Jordi
"Jordi" wrote: > This is a multi-part message in MIME format. > > ------=_NextPart_000_0011_01C1265A.0C3D9880 > Content-Type: text/plain; charset="iso-8859-1" > Content-Transfer-Encoding: quoted-printable > > Hi everybody, > > I'm using Postgresql 7.03 (but I'm going to migrate soon to 7.1) and I have= > a big doubt about how to work with User defined types in my tables using l= > ibpq and the documentation does not help at all. > > Anyone have any sample about how to use libpq with PQGetValue or similar to= > read records which have fields defined as Arrays or User defined types?. = > I looked for samples in the documentation or in the mailing list but I coul= > dn't find anything.=20=20=20 > > For example, if I define the user-defined type "complex" just like in http:= > //www.postgresql.org/idocs/index.php?xtypes.html#XTYPES-USERDEFINED and the= > n I use it in a table, how can I read the field?. Must I use the complex_in= > (char *str) function passing as a parameter the PQGetValue result associate= > d to this field number?. I have the same doubt when I define an array fiel= > d. > > By the way, do you know if there is any documentation/sample about libpq ex= > plaining these more advanced topics which are not fully explained in the ge= > neral documentation? > > Best regards and thanks in advance, > > Jordi Basicly, everything returned by PQGetValue is a string representation of the data (ignoring binary cursors for the moment). If you application wants to use an internal representation of the data, you will have to parse/convert the string(eg. strtol() for int2 and int4, strtoll() for int8, etc.). As an example, you can get the source for my PostgreSQL/Pythoninterface (pyPgSQL) which contains code for converting PQgetvalue() results into Python Objects. Currently,the only types that are converted are INT2, INT8, BOOL, date/time types, NUMERIC, MONEY, and arrays of these types. All other types are left as strings. This code may provide some useful examples. In particular, look at pgresult.cand PgSQL.py. -- ____ | Billy G. Allie | Domain....: Bill.Allie@mug.org | /| | 7436 Hartwell | MSN.......: B_G_Allie@email.msn.com |-/-|----- | Dearborn, MI 48126| |/ |LLIE | (313) 582-1540 |