vos/metaobjects/property/pgdb_property.hh

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/* $Id: pgdb_property.hh,v 1.12 2003/07/24 23:08:35 reed Exp $ */


/** @file pgdb_property.hh
    Defines DBProperty implementation using PostgreSQL DB (using libpq).


    Copyright (C) 2001, 2002 Reed Hedges <reed@zerohour.net>

    This library is free software; you can redistribute it and/or
    modify it under the terms of the GNU Lesser General Public
    License as published by the Free Software Foundation; either
    version 2 of the License, or (at your option) any later version.

    This library is distributed in the hope that it will be useful,
    but WITHOUT ANY WARRANTY; without even the implied warranty of
    MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
    Lesser General Public License for more details.

    You should have received a copy of the GNU Lesser General Public
    License along with this library; if not, write to the Free Software
    Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA 02111-1307  USA

*/

#ifndef _PGDB_PROPERTY_HH_
#define _PGDB_PROPERTY_HH_

#include "db_property.hh"

// Of course, RH 6.2, RH 6.3, and Debian all put libpq-fe.h in different
// places...
#ifdef HAVE_POSTGRESQL_LIBPQ_FE_H
    #include <postgresql/libpq-fe.h>
#else
    #ifdef HAVE_PGSQL_LIBPQ_FE_H
        #include <pgsql/libpq-fe.h>
    #else
        #ifdef HAVE_LIBPQ_FE_H
            #include <libpq-fe.h>
        #else
            #error "Neither HAVE_POSTGRESQL_LIBPQ_FE_H nor HAVE_PGSQL_LIBPQ_FE_H nore HAVE_LIBPQ_FE_H are defined, so I don't know where libpq-fe.h is! (Something is probably wrong with the configure script). Please report this bug to <reed@zerohour.net>."
        #endif
    #endif
#endif

/* Used to define array of functions to call on database update notifications */
//typedef void(POLL_FUNCTION)(void);




/** @class PGDBProperty pgdb_property.hh vos/metaobjects/property/pgdb_property.hh
 *
 * DBProperty subclass for the PostgreSQL database.

    @warning The select query must return a scalar value, currently. (If
    it returns multiple values, only the first field of the first row will
    be used.

    From the VOS point of view, the PG Database is a backend to the
    property metaobject.
    From Postgres point of view, this is a frontend to the database;
    it is a very primitive one, essentially only doing SELECTs to read
    the data and UPDATEs (or INSERTs) to change it. You can talk to the
    database yourself, if you really want to, by using the queryDB()
    function, or by getting the connection handle with getConnectionHandle().
    However, it must be said, Caveat Hackor.

    @note this class will only be available on systems with the postgres 
     development stuff (headers etc) installed, so you probably need to
     download and the source code from 
     http://interreality.org/software/source.html and compile it yourself
     (after installing the PGSQL headers etc. of course) if you want to use 
     this class.
*/

class PGDBProperty : public virtual DBProperty
{
protected:


    PGconn* dbcon;  // connection to the database

public:

    /** basic constructor */
    PGDBProperty(MetaObject *superobject);

    /** Open database.
        @param dbinfo   Informatino to pass to Posgres C library PGconn() function. if empty ("") or omitted, enironment variables and/or defaults are used. */
    void open(const string& dbinfo = "");


    /** Destructoratorizer. Closes database connection. */
    ~PGDBProperty();



    /** called by factory to create a new instance */
    static MetaObject* new_PGDBProperty(MetaObject* superobject, const string& type) {
        return new PGDBProperty(superobject);
    }

    /** Register PGDBProperty Metaobject extender. You must also call Property::registerExtenders() for stuff to work!
    */
    static void registerExtenders() {
        MetaFactory::addLocalObjectExtension(typeid(PGDBProperty).name(), &PGDBProperty::new_PGDBProperty);
    }


    /** Returns underlying database handle. it will really be type PGconn*,
        simply typecast to fit interface. */
    virtual void *getConnectionHandle() { return (void *)dbcon; }

    /** Perform a query on the database, in Postgres' SQL. */
    virtual string queryDB(const string& query) throw(DBAccessError);

};

#endif

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