move the schema DDL sql off into seperate files for each db we support

3 files changed, 1045 insertions, 1 deletions

diff --git a/lib/schema.mysql.php b/lib/schema.mysql.php
new file mode 100644
index 000000000..1f7c3d092
--- /dev/null
+++ b/lib/schema.mysql.php
@@ -0,0 +1,537 @@
+<?php
+/**
+ * StatusNet, the distributed open-source microblogging tool
+ *
+ * Database schema utilities
+ *
+ * PHP version 5
+ *
+ * LICENCE: This program is free software: you can redistribute it and/or modify
+ * it under the terms of the GNU Affero General Public License as published by
+ * the Free Software Foundation, either version 3 of the License, or
+ * (at your option) any later version.
+ *
+ * This program 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 Affero General Public License for more details.
+ *
+ * You should have received a copy of the GNU Affero General Public License
+ * along with this program.  If not, see <http://www.gnu.org/licenses/>.
+ *
+ * @category  Database
+ * @package   StatusNet
+ * @author    Evan Prodromou <evan@status.net>
+ * @copyright 2009 StatusNet, Inc.
+ * @license   http://www.fsf.org/licensing/licenses/agpl-3.0.html GNU Affero General Public License version 3.0
+ * @link      http://status.net/
+ */
+
+if (!defined('STATUSNET')) {
+    exit(1);
+}
+
+/**
+ * Class representing the database schema
+ *
+ * A class representing the database schema. Can be used to
+ * manipulate the schema -- especially for plugins and upgrade
+ * utilities.
+ *
+ * @category Database
+ * @package  StatusNet
+ * @author   Evan Prodromou <evan@status.net>
+ * @license  http://www.fsf.org/licensing/licenses/agpl-3.0.html GNU Affero General Public License version 3.0
+ * @link     http://status.net/
+ */
+
+class MysqlSchema extends Schema
+{
+    static $_single = null;
+    protected $conn = null;
+
+    /**
+     * Constructor. Only run once for singleton object.
+     */
+
+    protected function __construct()
+    {
+        // XXX: there should be an easier way to do this.
+        $user = new User();
+
+        $this->conn = $user->getDatabaseConnection();
+
+        $user->free();
+
+        unset($user);
+    }
+
+    /**
+     * Main public entry point. Use this to get
+     * the singleton object.
+     *
+     * @return Schema the (single) Schema object
+     */
+
+    static function get()
+    {
+        if (empty(self::$_single)) {
+            self::$_single = new Schema();
+        }
+        return self::$_single;
+    }
+
+    /**
+     * Returns a TableDef object for the table
+     * in the schema with the given name.
+     *
+     * Throws an exception if the table is not found.
+     *
+     * @param string $name Name of the table to get
+     *
+     * @return TableDef tabledef for that table.
+     */
+
+    public function getTableDef($name)
+    {
+        $res = $this->conn->query('DESCRIBE ' . $name);
+
+        if (PEAR::isError($res)) {
+            throw new Exception($res->getMessage());
+        }
+
+        $td = new TableDef();
+
+        $td->name    = $name;
+        $td->columns = array();
+
+        $row = array();
+
+        while ($res->fetchInto($row, DB_FETCHMODE_ASSOC)) {
+
+            $cd = new ColumnDef();
+
+            $cd->name = $row['Field'];
+
+            $packed = $row['Type'];
+
+            if (preg_match('/^(\w+)\((\d+)\)$/', $packed, $match)) {
+                $cd->type = $match[1];
+                $cd->size = $match[2];
+            } else {
+                $cd->type = $packed;
+            }
+
+            $cd->nullable = ($row['Null'] == 'YES') ? true : false;
+            $cd->key      = $row['Key'];
+            $cd->default  = $row['Default'];
+            $cd->extra    = $row['Extra'];
+
+            $td->columns[] = $cd;
+        }
+
+        return $td;
+    }
+
+    /**
+     * Gets a ColumnDef object for a single column.
+     *
+     * Throws an exception if the table is not found.
+     *
+     * @param string $table  name of the table
+     * @param string $column name of the column
+     *
+     * @return ColumnDef definition of the column or null
+     *                   if not found.
+     */
+
+    public function getColumnDef($table, $column)
+    {
+        $td = $this->getTableDef($table);
+
+        foreach ($td->columns as $cd) {
+            if ($cd->name == $column) {
+                return $cd;
+            }
+        }
+
+        return null;
+    }
+
+    /**
+     * Creates a table with the given names and columns.
+     *
+     * @param string $name    Name of the table
+     * @param array  $columns Array of ColumnDef objects
+     *                        for new table.
+     *
+     * @return boolean success flag
+     */
+
+    public function createTable($name, $columns)
+    {
+        $uniques = array();
+        $primary = array();
+        $indices = array();
+
+        $sql = "CREATE TABLE $name (\n";
+
+        for ($i = 0; $i < count($columns); $i++) {
+
+            $cd =& $columns[$i];
+
+            if ($i > 0) {
+                $sql .= ",\n";
+            }
+
+            $sql .= $this->_columnSql($cd);
+
+            switch ($cd->key) {
+            case 'UNI':
+                $uniques[] = $cd->name;
+                break;
+            case 'PRI':
+                $primary[] = $cd->name;
+                break;
+            case 'MUL':
+                $indices[] = $cd->name;
+                break;
+            }
+        }
+
+        if (count($primary) > 0) { // it really should be...
+            $sql .= ",\nconstraint primary key (" . implode(',', $primary) . ")";
+        }
+
+        foreach ($uniques as $u) {
+            $sql .= ",\nunique index {$name}_{$u}_idx ($u)";
+        }
+
+        foreach ($indices as $i) {
+            $sql .= ",\nindex {$name}_{$i}_idx ($i)";
+        }
+
+        $sql .= "); ";
+
+        $res = $this->conn->query($sql);
+
+        if (PEAR::isError($res)) {
+            throw new Exception($res->getMessage());
+        }
+
+        return true;
+    }
+
+    /**
+     * Drops a table from the schema
+     *
+     * Throws an exception if the table is not found.
+     *
+     * @param string $name Name of the table to drop
+     *
+     * @return boolean success flag
+     */
+
+    public function dropTable($name)
+    {
+        $res = $this->conn->query("DROP TABLE $name");
+
+        if (PEAR::isError($res)) {
+            throw new Exception($res->getMessage());
+        }
+
+        return true;
+    }
+
+    /**
+     * Adds an index to a table.
+     *
+     * If no name is provided, a name will be made up based
+     * on the table name and column names.
+     *
+     * Throws an exception on database error, esp. if the table
+     * does not exist.
+     *
+     * @param string $table       Name of the table
+     * @param array  $columnNames Name of columns to index
+     * @param string $name        (Optional) name of the index
+     *
+     * @return boolean success flag
+     */
+
+    public function createIndex($table, $columnNames, $name=null)
+    {
+        if (!is_array($columnNames)) {
+            $columnNames = array($columnNames);
+        }
+
+        if (empty($name)) {
+            $name = "$table_".implode("_", $columnNames)."_idx";
+        }
+
+        $res = $this->conn->query("ALTER TABLE $table ".
+                                   "ADD INDEX $name (".
+                                   implode(",", $columnNames).")");
+
+        if (PEAR::isError($res)) {
+            throw new Exception($res->getMessage());
+        }
+
+        return true;
+    }
+
+    /**
+     * Drops a named index from a table.
+     *
+     * @param string $table name of the table the index is on.
+     * @param string $name  name of the index
+     *
+     * @return boolean success flag
+     */
+
+    public function dropIndex($table, $name)
+    {
+        $res = $this->conn->query("ALTER TABLE $table DROP INDEX $name");
+
+        if (PEAR::isError($res)) {
+            throw new Exception($res->getMessage());
+        }
+
+        return true;
+    }
+
+    /**
+     * Adds a column to a table
+     *
+     * @param string    $table     name of the table
+     * @param ColumnDef $columndef Definition of the new
+     *                             column.
+     *
+     * @return boolean success flag
+     */
+
+    public function addColumn($table, $columndef)
+    {
+        $sql = "ALTER TABLE $table ADD COLUMN " . $this->_columnSql($columndef);
+
+        $res = $this->conn->query($sql);
+
+        if (PEAR::isError($res)) {
+            throw new Exception($res->getMessage());
+        }
+
+        return true;
+    }
+
+    /**
+     * Modifies a column in the schema.
+     *
+     * The name must match an existing column and table.
+     *
+     * @param string    $table     name of the table
+     * @param ColumnDef $columndef new definition of the column.
+     *
+     * @return boolean success flag
+     */
+
+    public function modifyColumn($table, $columndef)
+    {
+        $sql = "ALTER TABLE $table MODIFY COLUMN " .
+          $this->_columnSql($columndef);
+
+        $res = $this->conn->query($sql);
+
+        if (PEAR::isError($res)) {
+            throw new Exception($res->getMessage());
+        }
+
+        return true;
+    }
+
+    /**
+     * Drops a column from a table
+     *
+     * The name must match an existing column.
+     *
+     * @param string $table      name of the table
+     * @param string $columnName name of the column to drop
+     *
+     * @return boolean success flag
+     */
+
+    public function dropColumn($table, $columnName)
+    {
+        $sql = "ALTER TABLE $table DROP COLUMN $columnName";
+
+        $res = $this->conn->query($sql);
+
+        if (PEAR::isError($res)) {
+            throw new Exception($res->getMessage());
+        }
+
+        return true;
+    }
+
+    /**
+     * Ensures that a table exists with the given
+     * name and the given column definitions.
+     *
+     * If the table does not yet exist, it will
+     * create the table. If it does exist, it will
+     * alter the table to match the column definitions.
+     *
+     * @param string $tableName name of the table
+     * @param array  $columns   array of ColumnDef
+     *                          objects for the table
+     *
+     * @return boolean success flag
+     */
+
+    public function ensureTable($tableName, $columns)
+    {
+        // XXX: DB engine portability -> toilet
+
+        try {
+            $td = $this->getTableDef($tableName);
+        } catch (Exception $e) {
+            if (preg_match('/no such table/', $e->getMessage())) {
+                return $this->createTable($tableName, $columns);
+            } else {
+                throw $e;
+            }
+        }
+
+        $cur = $this->_names($td->columns);
+        $new = $this->_names($columns);
+
+        $toadd  = array_diff($new, $cur);
+        $todrop = array_diff($cur, $new);
+        $same   = array_intersect($new, $cur);
+        $tomod  = array();
+
+        foreach ($same as $m) {
+            $curCol = $this->_byName($td->columns, $m);
+            $newCol = $this->_byName($columns, $m);
+
+            if (!$newCol->equals($curCol)) {
+                $tomod[] = $newCol->name;
+            }
+        }
+
+        if (count($toadd) + count($todrop) + count($tomod) == 0) {
+            // nothing to do
+            return true;
+        }
+
+        // For efficiency, we want this all in one
+        // query, instead of using our methods.
+
+        $phrase = array();
+
+        foreach ($toadd as $columnName) {
+            $cd = $this->_byName($columns, $columnName);
+
+            $phrase[] = 'ADD COLUMN ' . $this->_columnSql($cd);
+        }
+
+        foreach ($todrop as $columnName) {
+            $phrase[] = 'DROP COLUMN ' . $columnName;
+        }
+
+        foreach ($tomod as $columnName) {
+            $cd = $this->_byName($columns, $columnName);
+
+            $phrase[] = 'MODIFY COLUMN ' . $this->_columnSql($cd);
+        }
+
+        $sql = 'ALTER TABLE ' . $tableName . ' ' . implode(', ', $phrase);
+
+        $res = $this->conn->query($sql);
+
+        if (PEAR::isError($res)) {
+            throw new Exception($res->getMessage());
+        }
+
+        return true;
+    }
+
+    /**
+     * Returns the array of names from an array of
+     * ColumnDef objects.
+     *
+     * @param array $cds array of ColumnDef objects
+     *
+     * @return array strings for name values
+     */
+
+    private function _names($cds)
+    {
+        $names = array();
+
+        foreach ($cds as $cd) {
+            $names[] = $cd->name;
+        }
+
+        return $names;
+    }
+
+    /**
+     * Get a ColumnDef from an array matching
+     * name.
+     *
+     * @param array  $cds  Array of ColumnDef objects
+     * @param string $name Name of the column
+     *
+     * @return ColumnDef matching item or null if no match.
+     */
+
+    private function _byName($cds, $name)
+    {
+        foreach ($cds as $cd) {
+            if ($cd->name == $name) {
+                return $cd;
+            }
+        }
+
+        return null;
+    }
+
+    /**
+     * Return the proper SQL for creating or
+     * altering a column.
+     *
+     * Appropriate for use in CREATE TABLE or
+     * ALTER TABLE statements.
+     *
+     * @param ColumnDef $cd column to create
+     *
+     * @return string correct SQL for that column
+     */
+
+    private function _columnSql($cd)
+    {
+        $sql = "{$cd->name} ";
+
+        if (!empty($cd->size)) {
+            $sql .= "{$cd->type}({$cd->size}) ";
+        } else {
+            $sql .= "{$cd->type} ";
+        }
+
+        if (!empty($cd->default)) {
+            $sql .= "default {$cd->default} ";
+        } else {
+            $sql .= ($cd->nullable) ? "null " : "not null ";
+        }
+        
+        if (!empty($cd->auto_increment)) {
+            $sql .= " auto_increment ";
+        }
+
+        if (!empty($cd->extra)) {
+            $sql .= "{$cd->extra} ";
+        }
+
+        return $sql;
+    }
+}
diff --git a/lib/schema.pgsql.php b/lib/schema.pgsql.php
new file mode 100644
index 000000000..7291106dc
--- /dev/null
+++ b/lib/schema.pgsql.php
@@ -0,0 +1,504 @@
+<?php
+/**
+ * StatusNet, the distributed open-source microblogging tool
+ *
+ * Database schema utilities
+ *
+ * PHP version 5
+ *
+ * LICENCE: This program is free software: you can redistribute it and/or modify
+ * it under the terms of the GNU Affero General Public License as published by
+ * the Free Software Foundation, either version 3 of the License, or
+ * (at your option) any later version.
+ *
+ * This program 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 Affero General Public License for more details.
+ *
+ * You should have received a copy of the GNU Affero General Public License
+ * along with this program.  If not, see <http://www.gnu.org/licenses/>.
+ *
+ * @category  Database
+ * @package   StatusNet
+ * @author    Evan Prodromou <evan@status.net>
+ * @copyright 2009 StatusNet, Inc.
+ * @license   http://www.fsf.org/licensing/licenses/agpl-3.0.html GNU Affero General Public License version 3.0
+ * @link      http://status.net/
+ */
+
+if (!defined('STATUSNET')) {
+    exit(1);
+}
+
+/**
+ * Class representing the database schema
+ *
+ * A class representing the database schema. Can be used to
+ * manipulate the schema -- especially for plugins and upgrade
+ * utilities.
+ *
+ * @category Database
+ * @package  StatusNet
+ * @author   Evan Prodromou <evan@status.net>
+ * @license  http://www.fsf.org/licensing/licenses/agpl-3.0.html GNU Affero General Public License version 3.0
+ * @link     http://status.net/
+ */
+
+class PgsqlSchema extends Schema
+{
+
+    /**
+     * Returns a TableDef object for the table
+     * in the schema with the given name.
+     *
+     * Throws an exception if the table is not found.
+     *
+     * @param string $name Name of the table to get
+     *
+     * @return TableDef tabledef for that table.
+     */
+
+    public function getTableDef($name)
+    {
+        $res = $this->conn->query('DESCRIBE ' . $name);
+
+        if (PEAR::isError($res)) {
+            throw new Exception($res->getMessage());
+        }
+
+        $td = new TableDef();
+
+        $td->name    = $name;
+        $td->columns = array();
+
+        $row = array();
+
+        while ($res->fetchInto($row, DB_FETCHMODE_ASSOC)) {
+
+            $cd = new ColumnDef();
+
+            $cd->name = $row['Field'];
+
+            $packed = $row['Type'];
+
+            if (preg_match('/^(\w+)\((\d+)\)$/', $packed, $match)) {
+                $cd->type = $match[1];
+                $cd->size = $match[2];
+            } else {
+                $cd->type = $packed;
+            }
+
+            $cd->nullable = ($row['Null'] == 'YES') ? true : false;
+            $cd->key      = $row['Key'];
+            $cd->default  = $row['Default'];
+            $cd->extra    = $row['Extra'];
+
+            $td->columns[] = $cd;
+        }
+
+        return $td;
+    }
+
+    /**
+     * Gets a ColumnDef object for a single column.
+     *
+     * Throws an exception if the table is not found.
+     *
+     * @param string $table  name of the table
+     * @param string $column name of the column
+     *
+     * @return ColumnDef definition of the column or null
+     *                   if not found.
+     */
+
+    public function getColumnDef($table, $column)
+    {
+        $td = $this->getTableDef($table);
+
+        foreach ($td->columns as $cd) {
+            if ($cd->name == $column) {
+                return $cd;
+            }
+        }
+
+        return null;
+    }
+
+    /**
+     * Creates a table with the given names and columns.
+     *
+     * @param string $name    Name of the table
+     * @param array  $columns Array of ColumnDef objects
+     *                        for new table.
+     *
+     * @return boolean success flag
+     */
+
+    public function createTable($name, $columns)
+    {
+        $uniques = array();
+        $primary = array();
+        $indices = array();
+
+        $sql = "CREATE TABLE $name (\n";
+
+        for ($i = 0; $i < count($columns); $i++) {
+
+            $cd =& $columns[$i];
+
+            if ($i > 0) {
+                $sql .= ",\n";
+            }
+
+            $sql .= $this->_columnSql($cd);
+
+            switch ($cd->key) {
+            case 'UNI':
+                $uniques[] = $cd->name;
+                break;
+            case 'PRI':
+                $primary[] = $cd->name;
+                break;
+            case 'MUL':
+                $indices[] = $cd->name;
+                break;
+            }
+        }
+
+        if (count($primary) > 0) { // it really should be...
+            $sql .= ",\nconstraint primary key (" . implode(',', $primary) . ")";
+        }
+
+        foreach ($uniques as $u) {
+            $sql .= ",\nunique index {$name}_{$u}_idx ($u)";
+        }
+
+        foreach ($indices as $i) {
+            $sql .= ",\nindex {$name}_{$i}_idx ($i)";
+        }
+
+        $sql .= "); ";
+
+        $res = $this->conn->query($sql);
+
+        if (PEAR::isError($res)) {
+            throw new Exception($res->getMessage());
+        }
+
+        return true;
+    }
+
+    /**
+     * Drops a table from the schema
+     *
+     * Throws an exception if the table is not found.
+     *
+     * @param string $name Name of the table to drop
+     *
+     * @return boolean success flag
+     */
+
+    public function dropTable($name)
+    {
+        $res = $this->conn->query("DROP TABLE $name");
+
+        if (PEAR::isError($res)) {
+            throw new Exception($res->getMessage());
+        }
+
+        return true;
+    }
+
+    /**
+     * Adds an index to a table.
+     *
+     * If no name is provided, a name will be made up based
+     * on the table name and column names.
+     *
+     * Throws an exception on database error, esp. if the table
+     * does not exist.
+     *
+     * @param string $table       Name of the table
+     * @param array  $columnNames Name of columns to index
+     * @param string $name        (Optional) name of the index
+     *
+     * @return boolean success flag
+     */
+
+    public function createIndex($table, $columnNames, $name=null)
+    {
+        if (!is_array($columnNames)) {
+            $columnNames = array($columnNames);
+        }
+
+        if (empty($name)) {
+            $name = "$table_".implode("_", $columnNames)."_idx";
+        }
+
+        $res = $this->conn->query("ALTER TABLE $table ".
+                                   "ADD INDEX $name (".
+                                   implode(",", $columnNames).")");
+
+        if (PEAR::isError($res)) {
+            throw new Exception($res->getMessage());
+        }
+
+        return true;
+    }
+
+    /**
+     * Drops a named index from a table.
+     *
+     * @param string $table name of the table the index is on.
+     * @param string $name  name of the index
+     *
+     * @return boolean success flag
+     */
+
+    public function dropIndex($table, $name)
+    {
+        $res = $this->conn->query("ALTER TABLE $table DROP INDEX $name");
+
+        if (PEAR::isError($res)) {
+            throw new Exception($res->getMessage());
+        }
+
+        return true;
+    }
+
+    /**
+     * Adds a column to a table
+     *
+     * @param string    $table     name of the table
+     * @param ColumnDef $columndef Definition of the new
+     *                             column.
+     *
+     * @return boolean success flag
+     */
+
+    public function addColumn($table, $columndef)
+    {
+        $sql = "ALTER TABLE $table ADD COLUMN " . $this->_columnSql($columndef);
+
+        $res = $this->conn->query($sql);
+
+        if (PEAR::isError($res)) {
+            throw new Exception($res->getMessage());
+        }
+
+        return true;
+    }
+
+    /**
+     * Modifies a column in the schema.
+     *
+     * The name must match an existing column and table.
+     *
+     * @param string    $table     name of the table
+     * @param ColumnDef $columndef new definition of the column.
+     *
+     * @return boolean success flag
+     */
+
+    public function modifyColumn($table, $columndef)
+    {
+        $sql = "ALTER TABLE $table MODIFY COLUMN " .
+          $this->_columnSql($columndef);
+
+        $res = $this->conn->query($sql);
+
+        if (PEAR::isError($res)) {
+            throw new Exception($res->getMessage());
+        }
+
+        return true;
+    }
+
+    /**
+     * Drops a column from a table
+     *
+     * The name must match an existing column.
+     *
+     * @param string $table      name of the table
+     * @param string $columnName name of the column to drop
+     *
+     * @return boolean success flag
+     */
+
+    public function dropColumn($table, $columnName)
+    {
+        $sql = "ALTER TABLE $table DROP COLUMN $columnName";
+
+        $res = $this->conn->query($sql);
+
+        if (PEAR::isError($res)) {
+            throw new Exception($res->getMessage());
+        }
+
+        return true;
+    }
+
+    /**
+     * Ensures that a table exists with the given
+     * name and the given column definitions.
+     *
+     * If the table does not yet exist, it will
+     * create the table. If it does exist, it will
+     * alter the table to match the column definitions.
+     *
+     * @param string $tableName name of the table
+     * @param array  $columns   array of ColumnDef
+     *                          objects for the table
+     *
+     * @return boolean success flag
+     */
+
+    public function ensureTable($tableName, $columns)
+    {
+        // XXX: DB engine portability -> toilet
+
+        try {
+            $td = $this->getTableDef($tableName);
+        } catch (Exception $e) {
+            if (preg_match('/no such table/', $e->getMessage())) {
+                return $this->createTable($tableName, $columns);
+            } else {
+                throw $e;
+            }
+        }
+
+        $cur = $this->_names($td->columns);
+        $new = $this->_names($columns);
+
+        $toadd  = array_diff($new, $cur);
+        $todrop = array_diff($cur, $new);
+        $same   = array_intersect($new, $cur);
+        $tomod  = array();
+
+        foreach ($same as $m) {
+            $curCol = $this->_byName($td->columns, $m);
+            $newCol = $this->_byName($columns, $m);
+
+            if (!$newCol->equals($curCol)) {
+                $tomod[] = $newCol->name;
+            }
+        }
+
+        if (count($toadd) + count($todrop) + count($tomod) == 0) {
+            // nothing to do
+            return true;
+        }
+
+        // For efficiency, we want this all in one
+        // query, instead of using our methods.
+
+        $phrase = array();
+
+        foreach ($toadd as $columnName) {
+            $cd = $this->_byName($columns, $columnName);
+
+            $phrase[] = 'ADD COLUMN ' . $this->_columnSql($cd);
+        }
+
+        foreach ($todrop as $columnName) {
+            $phrase[] = 'DROP COLUMN ' . $columnName;
+        }
+
+        foreach ($tomod as $columnName) {
+            $cd = $this->_byName($columns, $columnName);
+
+            $phrase[] = 'MODIFY COLUMN ' . $this->_columnSql($cd);
+        }
+
+        $sql = 'ALTER TABLE ' . $tableName . ' ' . implode(', ', $phrase);
+
+        $res = $this->conn->query($sql);
+
+        if (PEAR::isError($res)) {
+            throw new Exception($res->getMessage());
+        }
+
+        return true;
+    }
+
+    /**
+     * Returns the array of names from an array of
+     * ColumnDef objects.
+     *
+     * @param array $cds array of ColumnDef objects
+     *
+     * @return array strings for name values
+     */
+
+    private function _names($cds)
+    {
+        $names = array();
+
+        foreach ($cds as $cd) {
+            $names[] = $cd->name;
+        }
+
+        return $names;
+    }
+
+    /**
+     * Get a ColumnDef from an array matching
+     * name.
+     *
+     * @param array  $cds  Array of ColumnDef objects
+     * @param string $name Name of the column
+     *
+     * @return ColumnDef matching item or null if no match.
+     */
+
+    private function _byName($cds, $name)
+    {
+        foreach ($cds as $cd) {
+            if ($cd->name == $name) {
+                return $cd;
+            }
+        }
+
+        return null;
+    }
+
+    /**
+     * Return the proper SQL for creating or
+     * altering a column.
+     *
+     * Appropriate for use in CREATE TABLE or
+     * ALTER TABLE statements.
+     *
+     * @param ColumnDef $cd column to create
+     *
+     * @return string correct SQL for that column
+     */
+
+    private function _columnSql($cd)
+    {
+        $sql = "{$cd->name} ";
+
+        if (!empty($cd->size)) {
+            $sql .= "{$cd->type}({$cd->size}) ";
+        } else {
+            $sql .= "{$cd->type} ";
+        }
+
+        if (!empty($cd->default)) {
+            $sql .= "default {$cd->default} ";
+        } else {
+            $sql .= ($cd->nullable) ? "null " : "not null ";
+        }
+        
+        if (!empty($cd->auto_increment)) {
+            $sql .= " auto_increment ";
+        }
+
+        if (!empty($cd->extra)) {
+            $sql .= "{$cd->extra} ";
+        }
+
+        return $sql;
+    }
+}
diff --git a/lib/schema.php b/lib/schema.php
index a7f64ebed..164387ff3 100644
--- a/lib/schema.php
+++ b/lib/schema.php
@@ -75,8 +75,11 @@ class Schema
 
     static function get()
     {
+        $type = common_config('db', 'type');
         if (empty(self::$_single)) {
-            self::$_single = new Schema();
+            include "lib/schema.{$type}.php";
+            $class = $type.='Schema';
+            self::$_single = new $class();
         }
         return self::$_single;
     }