vos/metaobjects/property/pgdb_property.cc

Go to the documentation of this file.

/* $Id: pgdb_property.cc,v 1.9 2003/07/22 05:08:37 tetron Exp $ */



/**
    @file pgdb_property.cc

    Implements DBProperty using PostgreSQL DB (using libpq).
    @see pgdb_property.hh




    @author Reed Hedges <reed@zerohour.net>


    This file is part of the Virtual Object System of
    the Interreality project (http://interreality.org).

    Copyright (C) 2001, 2002 Reed Hedges

    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

*/

#include "pgdb_property.hh"
#include <vos/corelibs/vos/vos.hh>

#ifdef HAVE_POSTGRESQL_LIBPQ_FE_H
    #include <postgresql/libpq-fe.h>
#else
    #ifdef HAVE_PGSQL_LIBPQ_FE_H
        #include <pgsql/libpq-fe.h>
    #else
        #error "Neither HAVE_POSTGRESQL_LIBPQ_FE_H nor HAVE_PGSQL_LIBPQ_FE_H are define, so I don't know where libpq-fe.h is!"
    #endif
#endif


/* basic ctor */
PGDBProperty::PGDBProperty(MetaObject* superobject) :
    DBProperty(superobject), LocalProperty(superobject), Property(superobject), MetaObject(superobject), dbcon(NULL) {
    // yay.
}


/* Open connection. Will create table and/or columns if necesary.  */
void PGDBProperty::open(const string& dbinfo = "")
{
    dbcon = PQconnectdb(dbinfo.c_str());

    LOG("postgres property", 4, "opening connection to database ("<<dbinfo<<")");

    switch(PQstatus(dbcon)) {
        case CONNECTION_OK: /* connection successful. */ break;
        case CONNECTION_BAD: throw DBAccessError("Failed to make database connection."); break;
#ifndef HAVE_PGSQL_LIBPQ_FE_H
        // newer versions return more codes
        case CONNECTION_STARTED: throw DBAccessError("Database connection incomplete. (waiting for connection to be made)"); break;
        case CONNECTION_AWAITING_RESPONSE: throw DBAccessError("Database connection incomplete. (still waiting for response from PG postmaster)"); break;
        case CONNECTION_AUTH_OK: throw DBAccessError("Database connection incomplete. (authorization was okay, backend did not start)"); break;
        case CONNECTION_SETENV: throw DBAccessError("Database connection incomplete. (getting environment variables)"); break;
#endif
        default: throw DBAccessError(string("Failed to make database connection (unkown error at ") + string(__FILE__) + string(" (PGDBProperty::PGDBProperty())."));
    }



}


/* Destructoratorizer. Close database connection. */
PGDBProperty::~PGDBProperty() {
    PQfinish(dbcon);
}






/* Perform a query on the database. Currently only the first field of the first
row is returned if the query returns more than one value. */
string PGDBProperty::queryDB(const string& query) throw(DBAccessError) {

    PGresult *result;
    int ntuples, nfields, t, f;
    string s = "";


    LOG("postgres", 7, "querying db: " << query);

    result = PQexec(dbcon, query.c_str());


    /// XXX BUG: does not free 'result' when errors occur (just throws message)



    switch(PQresultStatus(result)) {

        case PGRES_COMMAND_OK:  // Successful completion of a command returning no data
        case PGRES_COPY_OUT:
        case PGRES_COPY_IN: // actually i think these won't occur, technically

            PQclear(result);
            return "";

        case PGRES_TUPLES_OK:   // The query successfully executed
            ntuples = PQntuples(result);
            nfields = PQnfields(result);
            LOG("postgres", 9, "queryDB: there are "<<ntuples<<" tuples and "<<nfields<<" fields."<< (( (ntuples > 1) || (nfields > 1))?"Warning: only the first field will be returned.":""));
            s = string(PQgetvalue(result, 0, 0));

            /*
            for(t = 0; t < ntuples; t++) {
                if(t != 0) s += "\n";
                for(f = 0; f < nfields; f++) {
                    if(f != 0) s += "\t";
                    s += string(PQgetvalue(result, t, f));
                }
            }
            */

            PQclear(result);
            return s;


        case PGRES_BAD_RESPONSE:    // The server's response was not understood
            throw DBAccessError(string("Error, Postgres server is talking jibba-jabba. ")+PQresultErrorMessage(result));

        case PGRES_NONFATAL_ERROR:
            throw DBAccessError(string("Postgres reports a nonfatal error. But I don't know what to do with it, you try something: ")+PQresultErrorMessage(result));

        case PGRES_EMPTY_QUERY: //The string sent to the backend was empty. I think this is also NULL (0), for really fatal error.
        case PGRES_FATAL_ERROR:
            throw DBAccessError(string("Fatal error querying Postgres database! ")+PQresultErrorMessage(result));
    }

    PQclear(result);
    return "";

}

---