From: skodak <skodak>
Date: Thu, 28 Aug 2008 21:32:03 +0000 (+0000)
Subject: MDL-15670 Database export/import library - by Andrei Bautu, minor tweaks only - big... 
X-Git-Url: http://git.mjollnir.org/gw?a=commitdiff_plain;h=7cd18ebabf4e03b0df333eea49f7447cd1e5b5d0;p=moodle.git

MDL-15670 Database export/import library - by Andrei Bautu, minor tweaks only - big thanks!
---

diff --git a/admin/dbtransfer/dbdata.xsd b/admin/dbtransfer/dbdata.xsd
index cf23ea77c7..6abf66c027 100644
--- a/admin/dbtransfer/dbdata.xsd
+++ b/admin/dbtransfer/dbdata.xsd
@@ -5,7 +5,7 @@
         <xs:sequence> 
             <xs:element maxOccurs="unbounded" name="table" type="tableType" /> 
         </xs:sequence> 
-        <xs:attribute name="version" type="xs:positiveInteger" use="required" /> 
+        <xs:attribute name="version" type="xs:float" use="required" /> 
         <xs:attribute name="timestamp" type="xs:dateTime" use="required" /> 
         <xs:attribute name="comment" type="xs:string" /> 
     </xs:complexType> 
diff --git a/admin/dbtransfer/exportlib.php b/admin/dbtransfer/exportlib.php
new file mode 100644
index 0000000000..c8bffc0638
--- /dev/null
+++ b/admin/dbtransfer/exportlib.php
@@ -0,0 +1,380 @@
+<?php  //$Id$
+
+/**
+ * General database import classes
+ * @author Andrei Bautu
+ * @license http://www.gnu.org/copyleft/gpl.html GNU Public License
+ * @package dbtransfer
+ */
+
+/**
+ * Base class for database export operations. This class defines basic callbacks
+ * for export operations and implements the @see export_database and
+ * @export_table methods generic export processing. In general, subclasses will
+ * override callback methods to provide specific output and (optionally)
+ * @see export_database to add functionality.
+ * Between a single pair of calls to @see begin_database_export and
+ * @see finish_database_export, multiple non-overlapping pairs of calls may
+ * be made to @see begin_table_export and @see finish_database_export for
+ * different tables. Between one pair of calls to @see begin_table_export and
+ * @see finish_database_export multiple calls may be made to
+ * @see export_table_data for the same table.
+ */
+abstract class database_exporter {
+    /** Connection to the source database (a @see moodle_database object). */
+    protected $mdb;
+    /** Database manager of the source database (a @see database_manager object). */
+    protected $manager;
+    /** Source database schema in XMLDB format (a @see xmldb_structure object). */
+    protected $schema;
+    /**
+     * Boolean flag - whether or not to check that XML database schema matches
+     * the RDBMS database schema before exporting (used by
+     * @see export_database).
+     */
+    protected $check_schema;
+
+    /**
+     * Object constructor.
+     *
+     * @param moodle_database $mdb Connection to the source database (a
+     * @see moodle_database object).
+     * @param xmldb_structure $schema Source database schema in XMLDB format (a
+     * @see xmldb_structure object). Use null to load the schema from the
+     * system's install.xml files.
+     * @param boolean $check_schema - whether or not to check that XML database
+     * schema matches the RDBMS database schema before exporting (used by
+     * @see export_database).
+     */
+    public function __construct(moodle_database $mdb, xmldb_structure $schema=null, $check_schema=true) {
+        if (is_null($schema)) {
+            $schema = database_manager::get_install_xml_schema();
+        }
+        $this->mdb          = $mdb;
+        $this->manager      = $mdb->get_manager();
+        $this->schema       = $schema;
+        $this->check_schema = $check_schema;
+    }
+
+    /**
+     * Callback function. Should be called only once database per export
+     * operation, before any other export operations. Subclasses should export
+     * basic database information (version and timestamp).
+     *
+     * @param float $version the version of the system which generating the data
+     * @param string $timestamp the timestamp of the data (in ISO 8601) format.
+     * @param string $description a user description of the data.
+     * @return void
+     */
+    public function begin_database_export($version, $timestamp, $description) {
+    }
+
+    /**
+     * Callback function. Should be called only once per table export operation,
+     * before any other table export operations. Subclasses should export
+     * basic database information (name and schema's hash).
+     *
+     * @param xmldb_table $table - XMLDB object for the exported table
+     * @return void
+     */
+    public function begin_table_export(xmldb_table $table) {
+    }
+
+    /**
+     * Callback function. Should be called only once per table export operation,
+     * after all other table export operations.
+     *
+     * @param xmldb_table $table - XMLDB object for the exported table
+     */
+    public function finish_table_export(xmldb_table $table) {
+    }
+
+    /**
+     * Callback function. Should be called only once database per export
+     * operation, after all database export operations.
+     */
+    public function finish_database_export() {
+    }
+
+    /**
+     * Callback function. Should be called only once per record export operation,
+     * only between @see begin_table_export and @see finish_table_export calls.
+     * It will insert table data. Subclasses should export basic record
+     * information (data values).
+     *
+     * @param xmldb_table $table - XMLDB object of the table from which data was retrived
+     * @param object $data - data object (fields and values from record)
+     * @return void
+     */
+    public abstract function export_table_data(xmldb_table $table, $data);
+
+    /**
+     * Generic method to export the database. It checks the schema (if
+     * @see $check_schema is true), queries the database and calls
+     * appropiate callbacks.
+     *
+     * @exception export_exception if any checking (e.g. database schema) fails
+     *
+     * @param string $description a user description of the data.
+     */
+    public function export_database($description=null) {
+        global $CFG;
+
+        if ($this->check_schema && $this->manager->check_database_schema($this->schema)) {
+            //TODO put message in error lang
+            throw new export_exception('XMLDB schema does not match database schema.');
+        }
+        $tables = $this->schema->getTables();
+        $this->begin_database_export($CFG->version, date('c'), $description);
+        foreach ($tables as $table) {
+            $rs = $this->mdb->get_recordset_sql('SELECT * FROM {'.$table->getName().'}');
+            //TODO remove this when dml will have exceptions
+            if (!$rs) {
+                //TODO put message in error lang
+                throw new export_exception('An error occured while reading the database.');
+            }
+            $this->begin_table_export($table);
+            foreach ($rs as $row) {
+                $this->export_table_data($table, $row);
+            }
+            $this->finish_table_export($table);
+        }
+        $this->finish_database_export();
+    }
+
+}
+
+/**
+ * XML format exporter class.
+ * Provides logic for writing XML tags and data inside appropiate callbacks.
+ * Subclasses should define XML data sinks.
+ */
+abstract class xml_database_exporter extends database_exporter {
+    /**
+     * Generic output method. Subclasses should implement it with code specific
+     * to the target XML sink.
+     */
+    protected abstract function output($text);
+
+    /**
+     * Callback function. Outputs open XML PI and moodle_database opening tag.
+     *
+     * @param float $version the version of the system which generating the data
+     * @param string $timestamp the timestamp of the data (in ISO 8601) format.
+     * @param string $description a user description of the data.
+     * @return void
+     */
+    public function begin_database_export($version, $timestamp, $description) {
+        $this->output('<?xml version="1.0" encoding="utf-8"?>');
+        //TODO add xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance" and schema information
+        $this->output('<moodle_database version="'.$version.'" timestamp="'.$timestamp.'"'.(empty ($description) ? '' : ' comment="'.htmlspecialchars($description, ENT_QUOTES).'"').'>');
+    }
+
+    /**
+     * Callback function. Outputs table opening tag.
+     *
+     * @param xmldb_table $table - XMLDB object for the exported table
+     * @return void
+     */
+    public function begin_table_export(xmldb_table $table) {
+        $this->output('<table name="'.$table->getName().'" schemaHash="'.$table->getHash().'">');
+    }
+
+    /**
+     * Callback function. Outputs table closing tag.
+     *
+     * @param xmldb_table $table - XMLDB object for the exported table
+     */
+    public function finish_table_export(xmldb_table $table) {
+        $this->output('</table>');
+    }
+
+    /**
+     * Callback function. Outputs moodle_database closing tag.
+     */
+    public function finish_database_export() {
+        $this->output('</moodle_database>');
+    }
+
+    /**
+     * Callback function. Outputs record tag with field subtags and data.
+     *
+     * @param xmldb_table $table - XMLDB object of the table from which data was retrived
+     * @param object $data - data object (fields and values from record)
+     * @return void
+     */
+    public function export_table_data(xmldb_table $table, $data) {
+        $this->output('<record>');
+        foreach ($data as $key => $value) {
+            if (is_null($value)) {
+                $this->output('<field name="'.$key.'" value="null" />');
+            } else {
+                $this->output('<field name="'.$key.'">'.htmlspecialchars($value, ENT_NOQUOTES).'</field>');
+            }
+        }
+        $this->output('</record>');
+    }
+}
+
+/**
+ * XML format exporter class to file storage.
+ */
+class file_xml_database_exporter extends xml_database_exporter {
+    /** Path to the XML data file. */
+    protected $filepath;
+    /** File descriptor for the output file. */
+    protected $file;
+
+    /**
+     * Object constructor.
+     *
+     * @param string $filepath - path to the XML data file. Use null for PHP
+     * output stream.
+     * @param moodle_database $mdb Connection to the source database
+     * @see xml_database_exporter::__construct()
+     * @param xmldb_structure $schema Source database schema in XMLDB format
+     * @see xml_database_exporter::__construct()
+     * @param boolean $check_schema - whether or not to check that XML database
+     * @see xml_database_exporter::__construct()
+     */
+    function __construct($filepath, moodle_database $mdb, xmldb_structure $schema=null, $check_schema=true) {
+        parent::__construct($mdb, $schema, $check_schema);
+        if (is_null($filepath)) {
+            $filepath = 'php://output';
+        }
+        $this->filepath = $filepath;
+    }
+
+    /**
+     * Specific output method for the file XML sink.
+     */
+    protected function output($text) {
+        fwrite($this->file, $text);
+    }
+
+    /**
+     * Specific implementation for file exporting the database: it opens output stream, calls
+     * superclass @see database_exporter::export_database() and closes output stream.
+     *
+     * @exception export_exception if any checking (e.g. database schema) fails
+     *
+     * @param string $description a user description of the data.
+     */
+    public function export_database($description=null) {
+        $this->file = fopen($this->filepath, 'wb');
+        parent::export_database($description);
+        fclose($this->file);
+    }
+}
+
+/**
+ * XML format exporter class to memory storage (i.e. a string).
+ */
+class string_xml_database_exporter extends xml_database_exporter {
+    /** String with XML data. */
+    protected $data;
+
+    /**
+     * Specific output method for the memory XML sink.
+     */
+    protected function output($text) {
+        $this->data .= $text;
+    }
+
+    /**
+     * Returns the output of the exporters
+     * @return string XML data from exporter
+     */
+    public function get_output() {
+        return $this->data;
+    }
+
+    /**
+     * Specific implementation for memory exporting the database: it clear the buffer
+     * and calls superclass @see database_exporter::export_database().
+     *
+     * @exception export_exception if any checking (e.g. database schema) fails
+     * @param string $description a user description of the data.
+     * @return void
+     */
+    public function export_database($description=null) {
+        $this->data = '';
+        parent::export_database($description);
+    }
+}
+
+class database_mover extends database_exporter {
+    /** Importer object used to transfer data. */
+    protected $importer;
+
+    /**
+     * Object constructor.
+     *
+     * @param moodle_database $mdb_target Connection to the target database (a
+     * @see moodle_database object).
+     * @param moodle_database $mdb Connection to the source database (a
+     * @see moodle_database object).
+     * @param xmldb_structure $schema Source database schema in XMLDB format (a
+     * @see xmldb_structure object). Use null to load the schema from the
+     * system's install.xml files.
+     * @param boolean $check_schema - whether or not to check that XML database
+     * schema matches the RDBMS database schema before exporting (used by
+     * @see export_database).
+     */
+    public function __construct(moodle_database $mdb_target, moodle_database $mdb_source, xmldb_structure $schema=null, $check_schema=true) {
+        parent::__construct($mdb_source, $schema, $check_schema);
+        $this->importer = new database_importer($mdb_target, $schema, $check_schema);
+    }
+
+    /**
+     * Callback function. Calls importer's begin_database_import callback method.
+     *
+     * @param float $version the version of the system which generating the data
+     * @param string $timestamp the timestamp of the data (in ISO 8601) format.
+     * @param string $description a user description of the data.
+     * @return void
+     */
+    public function begin_database_export($version, $timestamp, $description) {
+        $this->importer->init_database();
+        $this->importer->begin_database_import($version, $timestamp, $description);
+    }
+
+    /**
+     * Callback function. Calls importer's begin_table_import callback method.
+     *
+     * @param xmldb_table $table - XMLDB object for the exported table
+     * @return void
+     */
+    public function begin_table_export(xmldb_table $table) {
+        $this->importer->begin_table_import($table->getName(), $table->getHash());
+    }
+
+    /**
+     * Callback function. Calls importer's import_table_data callback method.
+     *
+     * @param xmldb_table $table - XMLDB object of the table from which data
+     * was retrived
+     * @param object $data - data object (fields and values from record)
+     * @return void
+     */
+    public function export_table_data(xmldb_table $table, $data) {
+        $this->importer->import_table_data($table->getName(), $data);
+    }
+
+    /**
+     * Callback function. Calls importer's finish_table_import callback method.
+     * @param xmldb_table $table - XMLDB object for the exported table
+     * @return void
+     */
+    public function finish_table_export(xmldb_table $table) {
+        $this->importer->finish_table_import($table->getName());
+    }
+
+    /**
+     * Callback function. Calls importer's finish_database_import callback method.
+     * @return void
+     */
+    public function finish_database_export() {
+        $this->importer->finish_database_import();
+    }
+}
diff --git a/admin/dbtransfer/importlib.php b/admin/dbtransfer/importlib.php
new file mode 100644
index 0000000000..3f12ec4fdc
--- /dev/null
+++ b/admin/dbtransfer/importlib.php
@@ -0,0 +1,351 @@
+<?php  //$Id$
+
+/**
+ * General database import classes
+ * @author Andrei Bautu
+ * @license http://www.gnu.org/copyleft/gpl.html GNU Public License
+ * @package dbtransfer
+ */
+
+/**
+ * Base class for database import operations. This class implements
+ * basic callbacks for import operations and defines the @see import_database
+ * method as a common method for all importers. In general, subclasses will
+ * override import_database and call other methods in appropriate moments.
+ * Between a single pair of calls to @see begin_database_import and
+ * @see finish_database_import, multiple non-overlapping pairs of calls may
+ * be made to @see begin_table_import and @see finish_database_import for
+ * different tables.
+ * Between one pair of calls to @see begin_table_import and
+ * @see finish_database_import multiple calls may be made to
+ * @see import_table_data for the same table.
+ * This class can be used directly, if the standard control flow (defined above)
+ * is respected.
+ */
+class database_importer {
+    /** Connection to the target database (a @see moodle_database object). */
+    protected $mdb;
+    /** Database manager of the target database (a @see database_manager object). */
+    protected $manager;
+    /** Target database schema in XMLDB format (a @see xmldb_structure object). */
+    protected $schema;
+    /**
+     * Boolean flag - whether or not to check that XML database schema matches
+     * the RDBMS database schema before importing (used by
+     * @see begin_database_import).
+     */
+    protected $check_schema;
+
+    /**
+     * Object constructor.
+     *
+     * @param moodle_database $mdb Connection to the target database (a
+     * @see moodle_database object). Use null to use the curent $DB connection.
+     * @param xmldb_structure $schema Target database schema in XMLDB format (a
+     * @see xmldb_structure object). Use null to load the schema from the
+     * system's install.xml files.
+     * @param boolean $check_schema - whether or not to check that XML database
+     * schema matches the RDBMS database schema before importing (inside
+     * @see begin_database_import).
+     */
+    public function __construct(moodle_database $mdb, xmldb_structure $schema=null, $check_schema=true) {
+        if (is_null($schema)) {
+            $schema = database_manager::get_install_xml_schema();
+        }
+        $this->mdb          = $mdb;
+        $this->manager      = $mdb->get_manager();
+        $this->schema       = $schema;
+        $this->check_schema = $check_schema;
+    }
+
+    /**
+     * Callback function. Should be called only once database per import
+     * operation, before any database changes are made. It will check the database
+     * schema if @see check_schema is true
+     *
+     * @exception import_exception if any checking (e.g. database schema, Moodle
+     * version) fails
+     *
+     * @param float $version the version of the system which generated the data
+     * @param string $timestamp the timestamp of the data (in ISO 8601) format.
+     * @return void
+     */
+    public function begin_database_import($version, $timestamp) {
+        global $CFG;
+
+        if (round($version, 2) !== round($CFG->version, 2)) { // version might be in decimal format too
+            //TODO put message in error lang
+            throw new import_exception('Current Moodle version does not match exported Moodle version.');
+        }
+        if ($this->check_schema && $this->manager->check_database_schema($this->schema)) {
+            //TODO put message in error lang
+            throw new import_exception('XMLDB schema does not match database schema.');
+        }
+        $this->mdb->begin_sql();
+    }
+
+    /**
+     * Callback function. Should be called only once per table import operation,
+     * before any table changes are made. It will delete all table data.
+     *
+     * @exception import_exception an unknown table import is attempted
+     * @exception ddl_table_missing_exception if the table is missing
+     *
+     * @param string $tablename - the name of the table that will be imported
+     * @param string $schemaHash - the hash of the xmldb_table schema of the table
+     * @return void
+     */
+    public function begin_table_import($tablename, $schemaHash) {
+        $table = $this->schema->getTable($tablename);
+        if (is_null($table)) {
+            //TODO put message in error lang
+            throw new import_exception('Unknown table in import data');
+        }
+        if ($schemaHash != $table->getHash()) {
+            throw new import_exception('XMLDB schema does not match database schema.');
+        }
+        // this should not happen, unless someone drops tables after import started
+        if (!$this->manager->table_exists($table)) {
+            // in the future, missing tables will be recreated with
+            //$this->manager->create_table($table);
+            throw new ddl_table_missing_exception($tablename);
+        }
+        $this->mdb->delete_records($tablename);
+    }
+
+    /**
+     * Callback function. Should be called only once per table import operation,
+     * after all table changes are made. It will reset table sequences if any.
+     * @param string $tablename
+     * @return void
+     */
+    public function finish_table_import($tablename) {
+        $table  = $this->schema->getTable($tablename);
+        $fields = $table->getFields();
+        foreach ($fields as $field) {
+            if ($field->getSequence()) {
+                //TODO make sure that there aren't tables using two sequences (probably there is none)
+                $this->mdb->reset_sequence($tablename);
+                return;
+            }
+        }
+    }
+
+    /**
+     * Callback function. Should be called only once database per import
+     * operation, after all database changes are made. It will commit changes.
+     * @return void
+     */
+    public function finish_database_import() {
+        $this->mdb->commit_sql();
+    }
+
+    /**
+     * Callback function. Should be called only once per record import operation, only
+     * between @see begin_table_import and @see finish_table_import calls.
+     * It will insert table data.
+     *
+     * @exception dml_exception if data insert operation failed
+     *
+     * @param string $tablename - the name of the table in which data will be
+     * imported
+     * @param object $data - data object (fields and values will be inserted
+     * into table)
+     * @return void
+     */
+    public function import_table_data($tablename, $data) {
+        $this->mdb->import_record($tablename, $data);
+    }
+
+    /**
+     * All subclases must call this
+     * @return void
+     */
+    public function init_database() {
+        if (!$this->mdb->get_tables()) {
+            // not tables yet, time to create all tables
+            $this->manager->install_from_xmldb_structure($this->schema);
+        }
+    }
+}
+
+/**
+ * XML format importer class (uses SAX for speed and low memory footprint).
+ * Provides logic for parsing XML data and calling appropiate callbacks.
+ * Subclasses should define XML data sources.
+ */
+abstract class xml_database_importer extends database_importer {
+    /**
+     * Creates and setups a SAX parser. Subclasses should use this method to
+     * create the XML parser.
+     *
+     * @return resource XML parser resource.
+     */
+    protected function get_parser() {
+        $parser = xml_parser_create();
+        xml_set_object($parser, $this);
+        xml_set_element_handler($parser, 'tag_open', 'tag_close');
+        xml_set_character_data_handler($parser, 'cdata');
+        xml_parser_set_option($parser, XML_OPTION_CASE_FOLDING, false);
+        return $parser;
+    }
+
+    /**
+     * Callback function. Called by the XML parser for opening tags processing.
+     *
+     * @param resource $parser XML parser resource.
+     * @param string $tag name of opening tag
+     * @param array $attributes set of opening tag XML attributes
+     * @return void
+     */
+    protected function tag_open($parser, $tag, $attributes) {
+        switch ($tag) {
+            case 'moodle_database' :
+                $this->begin_database_import($attributes['version'], $attributes['timestamp']);
+                break;
+            case 'table' :
+                $this->current_table = $attributes['name'];
+                $this->begin_table_import($this->current_table, $attributes['schemaHash']);
+                break;
+            case 'record' :
+                $this->current_row = new object();
+                break;
+            case 'field' :
+                $this->current_field = $attributes['name'];
+                $this->current_data = @$attributes['value'] == 'null' ? null : '';
+                break;
+            default :
+                //TODO put message in error lang
+                throw new import_exception('XML content not valid for import operation.');
+        }
+    }
+
+    /**
+     * Callback function. Called by the XML parser for closing tags processing.
+     *
+     * @param resource $parser XML parser resource.
+     * @param string $tag name of opening tag
+     * @return void
+     */
+    protected function tag_close($parser, $tag) {
+        switch ($tag) {
+            case 'moodle_database' :
+                $this->finish_database_import();
+                break;
+            case 'table' :
+                $this->finish_table_import($this->current_table);
+                unset ($this->current_table);
+                break;
+            case 'record' :
+                $this->import_table_data($this->current_table, $this->current_row);
+                unset ($this->current_row);
+                break;
+            case 'field' :
+                $field = $this->current_field;
+                unset ($this->current_field);
+                $this->current_row-> $field = $this->current_data;
+                unset ($this->current_data);
+                break;
+            default :
+                //TODO put message in error lang
+                throw new import_exception('XML content not valid for import operation.');
+        }
+    }
+
+    /**
+     * Callback function. Called by the XML parser for character data processing.
+     *
+     * @param resource $parser XML parser resource.
+     * @param string $data character data to be processed
+     * @return void
+     */
+    protected function cdata($parser, $cdata) {
+        if (isset($this->current_field)) {
+            $this->current_data .= $cdata;
+        }
+    }
+
+    /**
+     * Common import method
+     * @return void
+     */
+    public abstract function import_database();
+}
+
+/**
+ * XML format importer class from file storage.
+ */
+class file_xml_database_importer extends xml_database_importer {
+    /** Path to the XML data file. */
+    protected $filepath;
+
+    /**
+     * Object constructor.
+     *
+     * @param string $filepath - path to the XML data file. Use null for PHP
+     * input stream.
+     * @param moodle_database $mdb Connection to the target database
+     * @see xml_database_importer::__construct()
+     * @param xmldb_structure $schema Target database schema in XMLDB format
+     * @see xml_database_importer::__construct()
+     * @param boolean $check_schema - whether or not to check that XML database
+     * @see xml_database_importer::__construct()
+     */
+    public function __construct($filepath, moodle_database $mdb, xmldb_structure $schema=null) {
+        parent::__construct($mdb, $schema);
+        if (is_null($filepath)) {
+            $filepath = 'php://input';
+        }
+        $this->filepath = $filepath;
+    }
+
+    /**
+     * Common import method: it opens the file storage, creates the parser, feeds
+     * the XML parser with data, releases the parser and closes the file storage.
+     * @return void
+     */
+    public function import_database() {
+        $this->init_database();
+        $file = fopen($this->filepath, 'r');
+        $parser = $this->get_parser();
+        while (($data = fread($file, 65536)) && xml_parse($parser, $data, feof($file)));
+        xml_parser_free($parser);
+        fclose($file);
+    }
+}
+
+/**
+ * XML format importer class from memory storage (i.e. string).
+ */
+class string_xml_database_importer extends xml_database_importer {
+    /** String with XML data. */
+    protected $data;
+
+    /**
+     * Object constructor.
+     *
+     * @param string data - string with XML data
+     * @param moodle_database $mdb Connection to the target database
+     * @see xml_database_importer::__construct()
+     * @param xmldb_structure $schema Target database schema in XMLDB format
+     * @see xml_database_importer::__construct()
+     * @param boolean $check_schema - whether or not to check that XML database
+     * @see xml_database_importer::__construct()
+     */
+    public function __construct($data, moodle_database $mdb, xmldb_structure $schema=null) {
+        parent::__construct($mdb, $schema);
+        $this->data = $data;
+    }
+
+    /**
+     * Common import method: it creates the parser, feeds the XML parser with
+     * data, releases the parser.
+     * @return void
+     */
+    public function import_database() {
+        $this->init_database();
+        $parser = $this->get_parser();
+        xml_parse($parser, $this->data, true);
+        xml_parser_free($parser);
+    }
+}
diff --git a/admin/dbtransfer/lib.php b/admin/dbtransfer/lib.php
new file mode 100644
index 0000000000..daf000ee15
--- /dev/null
+++ b/admin/dbtransfer/lib.php
@@ -0,0 +1,35 @@
+<?php  //$Id$
+
+/**
+ * Database transfer related code.
+ * @author Andrei Bautu
+ * @license http://www.gnu.org/copyleft/gpl.html GNU Public License
+ * @package dbtransfer
+*/
+
+require_once $CFG->libdir.'/xmldb/xmldb_structure.php';
+require_once $CFG->libdir.'/ddl/database_manager.php';
+require_once $CFG->dirroot.'/'.$CFG->admin.'/dbtransfer/exportlib.php';
+require_once $CFG->dirroot.'/'.$CFG->admin.'/dbtransfer/importlib.php';
+
+/**
+ * Exception class for export operations.
+ * @see moodle_exception
+ * TODO subclass for specific purposes
+ */
+class export_exception extends moodle_exception {
+    function __construct($errorcode, $a=null, $debuginfo=null) {
+        parent::__construct($errorcode, '', '', $a, $debuginfo);
+    }
+}
+
+/**
+ * Exception class for import operations.
+ * @see moodle_exception
+ * TODO subclass for specific purposes
+ */
+class import_exception extends moodle_exception {
+    function __construct($errorcode, $a=null, $debuginfo=null) {
+        parent::__construct($errorcode, '', '', $a, $debuginfo);
+    }
+}