PQregisterTypes(3) Registers sub-classes, composites and user-defined types.


#include <libpqtypes.h>
int PQregisterTypes(PGconn *
conn, int which, PGregisterType *types,

                    int count, int async);


The PQregisterTypes() function allows an application to register one or more PQT_SUBCLASS, PQT_COMPOSITE or PQT_USERDEFINED types which is defined by the which argument.

When which is PQT_COMPOSITE or PQT_USERDEFINED, this function must execute a query against the backend to retrieve type information, thus this should not be called from within a transaction. It is recommended to register multiple composites at the same time to avoid round trip overhead.

The types argument is an array containing count types to register. Composites do not use the typput or typget members of the PGregisterType structure, thus these memebrs are ignored. If any composite does not exist, the register is aborted. User-defined types must set either typput and/or typget for each type. Sub-classes typname member of the PGregisterType structure must specify an inheritence relationship: ex. "myint=int4" where myint inherits from int4. The '=' is called the inheritence operator. If both typput and typget members of the PGregisterType structure are NULL, the type at that element will behave identically to the type it is inheriting from; an alias. Otherwise, the base type's put and/or get routines will be overridden.

The async argument indicates if the asynchronous type registration should be used. When non-zero, the caller must proceed in the normal async libpq fashion (PQconsumeInput, PQisBusy, PQgetResult) and provide a PGresult to PQregisterResult when obtained to complete the registration.

NOTE: The typname member of the PGregisterType structure can optionally contain the type's schema: schema.typname.

WARNING: PQparamCreate is only aware of types that have already been registered. If you need to put a type into a param, make sure it is first registered.


Using PQregisterTypes

The example registers two composite types.

PGregisterType comp_types[] = {
        {"myschema.simple", NULL, NULL},
        {"complex", NULL, NULL}
if (!PQregisterTypes(conn, PQT_COMPOSITE, comp_types, 2, 0))
        fprintf(stderr, "PQregisterTypes: %s\n", PQgeterror());


On success, both PQregisterTypes returns a non-zero value. On error, zero is returned and PQgeterror(3) will contain an error message.




A contribution of eSilo, LLC. for the PostgreSQL Database Management System. Written by Andrew Chernow.


Report bugs to <[email protected]>.


Copyright (c) 2011 eSilo, LLC. All rights reserved.
This is free software; see the source for copying conditions. There is NO warranty; not even for MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.