diff --git a/lib/Doctrine/Export/Firebird.php b/lib/Doctrine/Export/Firebird.php
index 72f381d48..24c6c6fea 100644
--- a/lib/Doctrine/Export/Firebird.php
+++ b/lib/Doctrine/Export/Firebird.php
@@ -71,7 +71,7 @@ class Doctrine_Export_Firebird extends Doctrine_Export
         if (is_null($start)) {
             $this->conn->beginTransaction();
             $query = 'SELECT MAX(' . $this->conn->quoteIdentifier($name, true) . ') FROM ' . $this->conn->quoteIdentifier($table, true);
-            $start = $this->db->queryOne($query, 'integer');
+            $start = $this->conn->fetchOne($query, 'integer');
 
             ++$start;
             $result = $this->createSequence($table, $start);
@@ -110,23 +110,10 @@ class Doctrine_Export_Firebird extends Doctrine_Export
 
         $result = $this->dropSequence($table);
 
-        /**
-        if (PEAR::isError($result)) {
-            return $db->raiseError(null, null, null,
-                'sequence for autoincrement PK could not be dropped', __FUNCTION__);
-        }
-        */
         //remove autoincrement trigger associated with the table
-        $table = $this->conn->getDbh()->quote(strtoupper($table));
-        $trigger_name = $this->conn->getDbh()->quote(strtoupper($table) . '_AUTOINCREMENT_PK');
-        $result = $this->conn->exec("DELETE FROM RDB\$TRIGGERS WHERE UPPER(RDB\$RELATION_NAME)=$table AND UPPER(RDB\$TRIGGER_NAME)=$trigger_name");
-
-        /**
-        if (PEAR::isError($result)) {
-            return $db->raiseError(null, null, null,
-                'trigger for autoincrement PK could not be dropped', __FUNCTION__);
-        }
-        */
+        $table = $this->conn->quote(strtoupper($table));
+        $trigger_name = $this->conn->quote(strtoupper($table) . '_AUTOINCREMENT_PK');
+        return $this->conn->exec("DELETE FROM RDB\$TRIGGERS WHERE UPPER(RDB\$RELATION_NAME)=$table AND UPPER(RDB\$TRIGGER_NAME)=$trigger_name");
     }
     /**
      * create a new table
@@ -190,15 +177,12 @@ class Doctrine_Export_Firebird extends Doctrine_Export
         foreach ($changes as $change_name => $change) {
             switch ($change_name) {
                 case 'notnull':
-                    return $db->raiseError(MDB2_ERROR_UNSUPPORTED, null, null,
-                        'it is not supported changes to field not null constraint', __FUNCTION__);
+                    throw new Doctrine_DataDict_Firebird_Exception('it is not supported changes to field not null constraint');
                 case 'default':
-                    return $db->raiseError(MDB2_ERROR_UNSUPPORTED, null, null,
-                        'it is not supported changes to field default value', __FUNCTION__);
+                    throw new Doctrine_DataDict_Firebird_Exception('it is not supported changes to field default value');
                 case 'length':
                     /*
-                    return $db->raiseError(MDB2_ERROR_UNSUPPORTED, null, null,
-                        'it is not supported changes to field default length', __FUNCTION__);
+                    return throw new Doctrine_DataDict_Firebird_Exception('it is not supported changes to field default length');
                     */
                 case 'unsigned':
                 case 'type':
@@ -206,11 +190,10 @@ class Doctrine_Export_Firebird extends Doctrine_Export
                 case 'definition':
                     break;
                 default:
-                    return $db->raiseError(MDB2_ERROR_UNSUPPORTED, null, null,
-                        'it is not supported change of type' . $change_name, __FUNCTION__);
+                    throw new Doctrine_DataDict_Firebird_Exception('it is not supported change of type' . $change_name);
             }
         }
-        return MDB2_OK;
+        return true;
     }
     /**
      * drop an existing table
@@ -326,18 +309,15 @@ class Doctrine_Export_Firebird extends Doctrine_Export
                     break;
                 case 'change':
                     foreach ($changes['change'] as $field) {
-                        if (PEAR::isError($err = $this->checkSupportedChanges($field))) {
-                            return $err;
-                        }
+                        $this->checkSupportedChanges($field);
                     }
                     break;
                 default:
-                    return $db->raiseError(MDB2_ERROR_CANNOT_ALTER, null, null,
-                        'change type ' . $change_name . ' not yet supported', __FUNCTION__);
+                    throw new Doctrine_DataDict_Firebird_Exception('change type ' . $change_name . ' not yet supported');
             }
         }
         if ($check) {
-            return MDB2_OK;
+            return true;
         }
         $query = '';
         if (!empty($changes['add']) && is_array($changes['add'])) {
@@ -345,7 +325,7 @@ class Doctrine_Export_Firebird extends Doctrine_Export
                 if ($query) {
                     $query.= ', ';
                 }
-                $query.= 'ADD ' . $db->getDeclaration($field['type'], $field_name, $field, $name);
+                $query.= 'ADD ' . $this->conn->getDeclaration($field['type'], $field_name, $field, $name);
             }
         }
 
@@ -354,7 +334,7 @@ class Doctrine_Export_Firebird extends Doctrine_Export
                 if ($query) {
                     $query.= ', ';
                 }
-                $field_name = $db->quoteIdentifier($field_name, true);
+                $field_name = $this->conn->quoteIdentifier($field_name, true);
                 $query.= 'DROP ' . $field_name;
             }
         }
@@ -364,32 +344,30 @@ class Doctrine_Export_Firebird extends Doctrine_Export
                 if ($query) {
                     $query.= ', ';
                 }
-                $field_name = $db->quoteIdentifier($field_name, true);
-                $query.= 'ALTER ' . $field_name . ' TO ' . $db->quoteIdentifier($field['name'], true);
+                $field_name = $this->conn->quoteIdentifier($field_name, true);
+                $query.= 'ALTER ' . $field_name . ' TO ' . $this->conn->quoteIdentifier($field['name'], true);
             }
         }
 
         if (!empty($changes['change']) && is_array($changes['change'])) {
             // missing support to change DEFAULT and NULLability
             foreach ($changes['change'] as $field_name => $field) {
-                if (PEAR::isError($err = $this->checkSupportedChanges($field))) {
-                    return $err;
-                }
+                $this->checkSupportedChanges($field);
                 if ($query) {
                     $query.= ', ';
                 }
-                $db->loadModule('Datatype', null, true);
-                $field_name = $db->quoteIdentifier($field_name, true);
-                $query.= 'ALTER ' . $field_name.' TYPE ' . $db->datatype->getTypeDeclaration($field['definition']);
+                $this->conn->loadModule('Datatype', null, true);
+                $field_name = $this->conn->quoteIdentifier($field_name, true);
+                $query.= 'ALTER ' . $field_name.' TYPE ' . $this->conn->datatype->getTypeDeclaration($field['definition']);
             }
         }
 
         if (!strlen($query)) {
-            return MDB2_OK;
+            return false;
         }
 
-        $name = $db->quoteIdentifier($name, true);
-        $result = $db->exec("ALTER TABLE $name $query");
+        $name = $this->conn->quoteIdentifier($name, true);
+        $result = $this->conn->exec("ALTER TABLE $name $query");
         $this->_silentCommit();
         return $result;
     }
@@ -529,7 +507,7 @@ class Doctrine_Export_Firebird extends Doctrine_Export
     public function dropSequence($seq_name)
     {
         $sequence_name = $this->conn->getSequenceName($seq_name);
-        $sequence_name = $this->conn->getDbh()->quote($sequence_name);
+        $sequence_name = $this->conn->quote($sequence_name);
         $query = "DELETE FROM RDB\$GENERATORS WHERE UPPER(RDB\$GENERATOR_NAME)=$sequence_name";
         return $this->conn->exec($query);
     }
diff --git a/lib/Doctrine/Export/Mssql.php b/lib/Doctrine/Export/Mssql.php
index b5765c1c2..cb3b5a2fa 100644
--- a/lib/Doctrine/Export/Mssql.php
+++ b/lib/Doctrine/Export/Mssql.php
@@ -42,14 +42,14 @@ class Doctrine_Export_Mssql extends Doctrine_Export
      */
     public function createDatabase($name)
     {
-        $name = $db->quoteIdentifier($name, true);
+        $name = $this->conn->quoteIdentifier($name, true);
         $query = "CREATE DATABASE $name";
-        if ($db->options['database_device']) {
-            $query.= ' ON '.$db->options['database_device'];
-            $query.= $db->options['database_size'] ? '=' .
-                     $db->options['database_size'] : '';
+        if ($this->conn->options['database_device']) {
+            $query.= ' ON '.$this->conn->options['database_device'];
+            $query.= $this->conn->options['database_size'] ? '=' .
+                     $this->conn->options['database_size'] : '';
         }
-        return $db->standaloneQuery($query, null, true);
+        return $this->conn->standaloneQuery($query, null, true);
     }
     /**
      * drop an existing database
@@ -59,8 +59,8 @@ class Doctrine_Export_Mssql extends Doctrine_Export
      */
     public function dropDatabase($name)
     {
-        $name = $db->quoteIdentifier($name, true);
-        return $db->standaloneQuery("DROP DATABASE $name", null, true);
+        $name = $this->conn->quoteIdentifier($name, true);
+        return $this->conn->standaloneQuery("DROP DATABASE $name", null, true);
     }
     /**
      * alter an existing table
@@ -162,7 +162,7 @@ class Doctrine_Export_Mssql extends Doctrine_Export
                 case 'rename':
                 case 'change':
                 default:
-                    return $db->raiseError(Doctrine::ERR_CANNOT_ALTER, null, null,
+                    return $this->conn->raiseError(Doctrine::ERR_CANNOT_ALTER, null, null,
                         'alterTable: change type "'.$change_name.'" not yet supported');
             }
         }
@@ -188,7 +188,7 @@ class Doctrine_Export_Mssql extends Doctrine_Export
         }
 
         if (!$query) {
-            return MDB2_OK;
+            return false;
         }
 
         $name = $this->conn->quoteIdentifier($name, true);
@@ -203,29 +203,25 @@ class Doctrine_Export_Mssql extends Doctrine_Export
      */
     public function createSequence($seq_name, $start = 1)
     {
-        $sequence_name = $db->quoteIdentifier($db->getSequenceName($seq_name), true);
-        $seqcol_name = $db->quoteIdentifier($db->options['seqcol_name'], true);
+        $sequence_name = $this->conn->quoteIdentifier($this->conn->getSequenceName($seq_name), true);
+        $seqcol_name = $this->conn->quoteIdentifier($this->conn->options['seqcol_name'], true);
         $query = "CREATE TABLE $sequence_name ($seqcol_name " .
                  "INT PRIMARY KEY CLUSTERED IDENTITY($start,1) NOT NULL)";
 
-        $res = $db->exec($query);
+        $res = $this->conn->exec($query);
 
         if ($start == 1) {
             return true;
         }
 
-        $query = 'SET IDENTITY_INSERT $sequence_name ON ' .
-                 'INSERT INTO $sequence_name (' . $seqcol_name . ') VALUES ( ' . $start . ')';
-        $res = $db->exec($query);
-
-        $result = $db->exec("DROP TABLE $sequence_name");
-        if (PEAR::isError($result)) {
-            return $db->raiseError($result, null, null,
-                'createSequence: could not drop inconsistent sequence table');
+        try {
+            $query = 'SET IDENTITY_INSERT $sequence_name ON ' .
+                     'INSERT INTO $sequence_name (' . $seqcol_name . ') VALUES ( ' . $start . ')';
+            $res = $this->conn->exec($query);
+        } catch (Exception $e) {
+            $result = $this->conn->exec("DROP TABLE $sequence_name");
         }
-
-        return $db->raiseError($res, null, null,
-            'createSequence: could not create sequence table');
+        return true;
     }
     /**
      * This function drops an existing sequence
@@ -235,7 +231,7 @@ class Doctrine_Export_Mssql extends Doctrine_Export
      */
     public function dropSequence($seqName)
     {
-        $sequenceName = $db->quoteIdentifier($db->getSequenceName($seqName), true);
+        $sequenceName = $this->conn->quoteIdentifier($this->conn->getSequenceName($seqName), true);
         return $this->conn->exec('DROP TABLE ' . $sequenceName);
     }
 }
diff --git a/lib/Doctrine/Export/Mysql.php b/lib/Doctrine/Export/Mysql.php
index 0dd934685..2a907954b 100644
--- a/lib/Doctrine/Export/Mysql.php
+++ b/lib/Doctrine/Export/Mysql.php
@@ -306,11 +306,11 @@ class Doctrine_Export_Mysql extends Doctrine_Export
         }
 
         if ( ! $query) {
-            return MDB2_OK;
+            return false;
         }
 
         $name = $this->conn->quoteIdentifier($name, true);
-        return $this->dbh->query("ALTER TABLE $name $query");
+        return $this->conn->exec("ALTER TABLE $name $query");
     }
     /**
      * create sequence
@@ -328,7 +328,7 @@ class Doctrine_Export_Mysql extends Doctrine_Export
                 . strlen($this->dbh->options['default_table_type']) ? ' TYPE = '
                 . $this->dbh->options['default_table_type'] : '';
 
-        $res    = $this->dbh->query($query);
+        $res    = $this->conn->exec($query);
 
         if ($start == 1)
             return true;
@@ -336,11 +336,11 @@ class Doctrine_Export_Mysql extends Doctrine_Export
         $query  = 'INSERT INTO ' . $sequenceName
                 . ' (' . $seqcol_name . ') VALUES (' . ($start-1) . ')';
 
-        $res    = $this->dbh->query($query);
+        $res    = $this->conn->exec($query);
 
         // Handle error
         try {
-            $result = $this->dbh->query('DROP TABLE ' . $sequenceName);
+            $result = $this->conn->exec('DROP TABLE ' . $sequenceName);
         } catch(Exception $e) {
             throw new Doctrine_Export_Mysql_Exception('could not drop inconsistent sequence table');
         }
diff --git a/lib/Doctrine/Export/Oracle.php b/lib/Doctrine/Export/Oracle.php
index d458f6042..1a24b9841 100644
--- a/lib/Doctrine/Export/Oracle.php
+++ b/lib/Doctrine/Export/Oracle.php
@@ -53,19 +53,16 @@ class Doctrine_Export_Oracle extends Doctrine_Export
                     ? ' DEFAULT TABLESPACE '.$this->conn->options['default_tablespace'] : '';
 
         $query  = 'CREATE USER ' . $username . ' IDENTIFIED BY ' . $password . $tablespace;
-        $result = $this->conn->query($query);
+        $result = $this->conn->exec($query);
 
-        $query = 'GRANT CREATE SESSION, CREATE TABLE, UNLIMITED TABLESPACE, CREATE SEQUENCE, CREATE TRIGGER TO ' . $username;
-        $result = $this->conn->query($query);
-        if (PEAR::isError($result)) {
+        try {
+            $query = 'GRANT CREATE SESSION, CREATE TABLE, UNLIMITED TABLESPACE, CREATE SEQUENCE, CREATE TRIGGER TO ' . $username;
+            $result = $this->conn->exec($query);
+        } catch (Exception $e) {
             $query = 'DROP USER '.$username.' CASCADE';
-            $result2 = $this->conn->query($query);
-            if (PEAR::isError($result2)) {
-                return $this->conn->raiseError($result2, null, null,
-                    'could not setup the database user', __FUNCTION__);
-            }
-            return $result;
+            $result2 = $this->conn->exec($query);
         }
+        return true;
     }
     /**
      * drop an existing database
@@ -83,7 +80,7 @@ class Doctrine_Export_Oracle extends Doctrine_Export
 
         $username = sprintf($this->conn->getAttribute(Doctrine::ATTR_DB_NAME_FORMAT), $name);
 
-        return $this->conn->query('DROP USER ' . $username . ' CASCADE');
+        return $this->conn->exec('DROP USER ' . $username . ' CASCADE');
     }
     /**
      * add an autoincrement sequence + trigger
@@ -104,32 +101,18 @@ class Doctrine_Export_Oracle extends Doctrine_Export
         );
         $result = $this->createConstraint($table, $index_name, $definition);
 
-        /**
-        if (PEAR::isError($result)) {
-            return $this->conn->raiseError($result, null, null,
-                'primary key for autoincrement PK could not be created', __FUNCTION__);
-        }
-        */
-
         if (is_null($start)) {
             $this->conn->beginTransaction();
             $query = 'SELECT MAX(' . $this->conn->quoteIdentifier($name, true) . ') FROM ' . $this->conn->quoteIdentifier($table, true);
-            $start = $this->db->queryOne($query, 'integer');
-            if (PEAR::isError($start)) {
-                return $start;
-            }
+            $start = $this->conn->fetchOne($query);
+
             ++$start;
             $result = $this->createSequence($table, $start);
             $this->conn->commit();
         } else {
             $result = $this->createSequence($table, $start);
         }
-        /**
-        if (PEAR::isError($result)) {
-            return $this->conn->raiseError($result, null, null,
-                'sequence for autoincrement PK could not be created', __FUNCTION__);
-        }
-        */
+
         $sequence_name = $this->conn->getSequenceName($table);
         $trigger_name  = $this->conn->quoteIdentifier($table . '_AI_PK', true);
         $table = $this->conn->quoteIdentifier($table, true);
@@ -350,13 +333,12 @@ END;
                 case 'rename':
                     break;
                 default:
-                    return $this->conn->raiseError(MDB2_ERROR_CANNOT_ALTER, null, null,
-                        'change type "'.$changeName.'" not yet supported', __FUNCTION__);
+                    throw new Doctrine_Export_Oracle_Exception('change type "'.$changeName.'" not yet supported');
             }
         }
 
         if ($check) {
-            return MDB2_OK;
+            return false;
         }
 
         $name = $this->conn->quoteIdentifier($name, true);
@@ -367,9 +349,6 @@ END;
                 $fields[] = $this->conn->getDeclaration($field['type'], $field_name, $field);
             }
             $result = $this->conn->exec("ALTER TABLE $name ADD (". implode(', ', $fields).')');
-            if (PEAR::isError($result)) {
-                return $result;
-            }
         }
 
         if (!empty($changes['change']) && is_array($changes['change'])) {
@@ -378,9 +357,6 @@ END;
                 $fields[] = $field_name. ' ' . $this->conn->getDeclaration($field['definition']['type'], '', $field['definition']);
             }
             $result = $this->conn->exec("ALTER TABLE $name MODIFY (". implode(', ', $fields).')');
-            if (PEAR::isError($result)) {
-                return $result;
-            }
         }
 
         if (!empty($changes['rename']) && is_array($changes['rename'])) {
@@ -388,9 +364,6 @@ END;
                 $field_name = $this->conn->quoteIdentifier($field_name, true);
                 $query = "ALTER TABLE $name RENAME COLUMN $field_name TO ".$this->conn->quoteIdentifier($field['name']);
                 $result = $this->conn->exec($query);
-                if (PEAR::isError($result)) {
-                    return $result;
-                }
             }
         }
 
@@ -400,17 +373,11 @@ END;
                 $fields[] = $this->conn->quoteIdentifier($field_name, true);
             }
             $result = $this->conn->exec("ALTER TABLE $name DROP COLUMN ". implode(', ', $fields));
-            if (PEAR::isError($result)) {
-                return $result;
-            }
         }
 
         if (!empty($changes['name'])) {
             $change_name = $this->conn->quoteIdentifier($changes['name'], true);
             $result = $this->conn->exec("ALTER TABLE $name RENAME TO ".$change_name);
-            if (PEAR::isError($result)) {
-                return $result;
-            }
         }
     }
     /**
diff --git a/lib/Doctrine/Export/Pgsql.php b/lib/Doctrine/Export/Pgsql.php
index b793c4520..193a0213b 100644
--- a/lib/Doctrine/Export/Pgsql.php
+++ b/lib/Doctrine/Export/Pgsql.php
@@ -167,8 +167,8 @@ class Doctrine_Export_Pgsql extends Doctrine_Export
 
         if (!empty($changes['add']) && is_array($changes['add'])) {
             foreach ($changes['add'] as $field_name => $field) {
-                $query = 'ADD ' . $db->getDeclaration($field['type'], $field_name, $field);
-                $this->dbh->query("ALTER TABLE $name $query");
+                $query = 'ADD ' . $this->conn->getDeclaration($field['type'], $field_name, $field);
+                $this->conn->exec("ALTER TABLE $name $query");
             }
         }
 
@@ -176,7 +176,7 @@ class Doctrine_Export_Pgsql extends Doctrine_Export
             foreach ($changes['remove'] as $field_name => $field) {
                 $field_name = $this->conn->quoteIdentifier($field_name, true);
                 $query = 'DROP ' . $field_name;
-                $this->dbh->query("ALTER TABLE $name $query");
+                $this->conn->exec("ALTER TABLE $name $query");
             }
         }
 
@@ -184,21 +184,21 @@ class Doctrine_Export_Pgsql extends Doctrine_Export
             foreach ($changes['change'] as $field_name => $field) {
                 $field_name = $this->conn->quoteIdentifier($field_name, true);
                 if (!empty($field['type'])) {
-                    $server_info = $db->getServerVersion();
+                    $server_info = $this->conn->getServerVersion();
 
                     if (is_array($server_info) && $server_info['major'] < 8) {
                         throw new Doctrine_Export_Pgsql_Exception('changing column type for "'.$change_name.'\" requires PostgreSQL 8.0 or above');
                     }
-                    $query = "ALTER $field_name TYPE ".$db->datatype->getTypeDeclaration($field['definition']);
-                    $this->dbh->query("ALTER TABLE $name $query");
+                    $query = "ALTER $field_name TYPE ".$this->conn->datatype->getTypeDeclaration($field['definition']);
+                    $this->conn->exec("ALTER TABLE $name $query");
                 }
                 if (array_key_exists('default', $field)) {
-                    $query = "ALTER $field_name SET DEFAULT ".$db->quote($field['definition']['default'], $field['definition']['type']);
-                    $this->dbh->query("ALTER TABLE $name $query");
+                    $query = "ALTER $field_name SET DEFAULT ".$this->conn->quote($field['definition']['default'], $field['definition']['type']);
+                    $this->conn->exec("ALTER TABLE $name $query");
                 }
                 if (!empty($field['notnull'])) {
                     $query = "ALTER $field_name ".($field['definition']['notnull'] ? "SET" : "DROP").' NOT NULL';
-                    $this->dbh->query("ALTER TABLE $name $query");
+                    $this->conn->exec("ALTER TABLE $name $query");
 
                 }
             }
@@ -207,14 +207,14 @@ class Doctrine_Export_Pgsql extends Doctrine_Export
         if (!empty($changes['rename']) && is_array($changes['rename'])) {
             foreach ($changes['rename'] as $field_name => $field) {
                 $field_name = $this->conn->quoteIdentifier($field_name, true);
-                $this->dbh->query("ALTER TABLE $name RENAME COLUMN $field_name TO ".$this->conn->quoteIdentifier($field['name'], true));
+                $this->conn->exec("ALTER TABLE $name RENAME COLUMN $field_name TO ".$this->conn->quoteIdentifier($field['name'], true));
             }
         }
 
         $name = $this->conn->quoteIdentifier($name, true);
         if (!empty($changes['name'])) {
             $change_name = $this->conn->quoteIdentifier($changes['name'], true);
-            $this->dbh->query("ALTER TABLE $name RENAME TO ".$change_name);
+            $this->conn->exec("ALTER TABLE $name RENAME TO ".$change_name);
         }
     }
 }