[Mageia-webteam] Proposal for maintainers database API

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On Tue, Mar 8, 2011 at 13:13, nicolas vigier <boklm at mars-attacks.org> wrote:
> No comment about using the website to take/drop maintainership, or using
> a command line tool ?

Both in the end. But I am not sure how to manage the authorization (or
the drop) in both cases:
 * through web UI, that's easy: the user that drops has to be the very
maintainer or an admin;
 * through the CLI, would it auth against the maintdb app or through
the buildsystem that, in turn, would notify the maintdb?

(but that may be just over specification to this point)

Aside, I've written down this
http://mageia.org/wiki/doku.php?id=web:maintdb#specs_actions after
having re-read this whole thread; it is likely incomplete but that's a
possible outcome of the discussion: setting down what minimal
behaviour is expected from the maintdb for it to be used.

So that's not exclusive from what has been done by Kosmas until now,
but it makes the app to need a few tweaks I believe.

Romain

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<?php
/**
*
* @package dbal
* @copyright (c) 2007 phpBB Group
* @license http://opensource.org/licenses/gpl-2.0.php GNU General Public License v2
*
*/

namespace phpbb\db;

/**
* Database Tools for handling cross-db actions such as altering columns, etc.
* Currently not supported is returning SQL for creating tables.
*
* @package dbal
*/
class tools
{
	/**
	* Current sql layer
	*/
	var $sql_layer = '';

	/**
	* @var object DB object
	*/
	var $db = null;

	/**
	* The Column types for every database we support
	* @var array
	*/
	var $dbms_type_map = array();

	/**
	* Get the column types for every database we support
	*
	* @return array
	*/
	public static function get_dbms_type_map()
	{
		return array(
			'mysql_41'	=> array(
				'INT:'		=> 'int(%d)',
				'BINT'		=> 'bigint(20)',
				'UINT'		=> 'mediumint(8) UNSIGNED',
				'UINT:'		=> 'int(%d) UNSIGNED',
				'TINT:'		=> 'tinyint(%d)',
				'USINT'		=> 'smallint(4) UNSIGNED',
				'BOOL'		=> 'tinyint(1) UNSIGNED',
				'VCHAR'		=> 'varchar(255)',
				'VCHAR:'	=> 'varchar(%d)',
				'CHAR:'		=> 'char(%d)',
				'XSTEXT'	=> 'text',
				'XSTEXT_UNI'=> 'varchar(100)',
				'STEXT'		=> 'text',
				'STEXT_UNI'	=> 'varchar(255)',
				'TEXT'		=> 'text',
				'TEXT_UNI'	=> 'text',
				'MTEXT'		=> 'mediumtext',
				'MTEXT_UNI'	=> 'mediumtext',
				'TIMESTAMP'	=> 'int(11) UNSIGNED',
				'DECIMAL'	=> 'decimal(5,2)',
				'DECIMAL:'	=> 'decimal(%d,2)',
				'PDECIMAL'	=> 'decimal(6,3)',
				'PDECIMAL:'	=> 'decimal(%d,3)',
				'VCHAR_UNI'	=> 'varchar(255)',
				'VCHAR_UNI:'=> 'varchar(%d)',
				'VCHAR_CI'	=> 'varchar(255)',
				'VARBINARY'	=> 'varbinary(255)',
			),

			'mysql_40'	=> array(
				'INT:'		=> 'int(%d)',
				'BINT'		=> 'bigint(20)',
				'UINT'		=> 'mediumint(8) UNSIGNED',
				'UINT:'		=> 'int(%d) UNSIGNED',
				'TINT:'		=> 'tinyint(%d)',
				'USINT'		=> 'smallint(4) UNSIGNED',
				'BOOL'		=> 'tinyint(1) UNSIGNED',
				'VCHAR'		=> 'varbinary(255)',
				'VCHAR:'	=> 'varbinary(%d)',
				'CHAR:'		=> 'binary(%d)',
				'XSTEXT'	=> 'blob',
				'XSTEXT_UNI'=> 'blob',
				'STEXT'		=> 'blob',
				'STEXT_UNI'	=> 'blob',
				'TEXT'		=> 'blob',
				'TEXT_UNI'	=> 'blob',
				'MTEXT'		=> 'mediumblob',
				'MTEXT_UNI'	=> 'mediumblob',
				'TIMESTAMP'	=> 'int(11) UNSIGNED',
				'DECIMAL'	=> 'decimal(5,2)',
				'DECIMAL:'	=> 'decimal(%d,2)',
				'PDECIMAL'	=> 'decimal(6,3)',
				'PDECIMAL:'	=> 'decimal(%d,3)',
				'VCHAR_UNI'	=> 'blob',
				'VCHAR_UNI:'=> array('varbinary(%d)', 'limit' => array('mult', 3, 255, 'blob')),
				'VCHAR_CI'	=> 'blob',
				'VARBINARY'	=> 'varbinary(255)',
			),

			'firebird'	=> array(
				'INT:'		=> 'INTEGER',
				'BINT'		=> 'DOUBLE PRECISION',
				'UINT'		=> 'INTEGER',
				'UINT:'		=> 'INTEGER',
				'TINT:'		=> 'INTEGER',
				'USINT'		=> 'INTEGER',
				'BOOL'		=> 'INTEGER',
				'VCHAR'		=> 'VARCHAR(255) CHARACTER SET NONE',
				'VCHAR:'	=> 'VARCHAR(%d) CHARACTER SET NONE',
				'CHAR:'		=> 'CHAR(%d) CHARACTER SET NONE',
				'XSTEXT'	=> 'BLOB SUB_TYPE TEXT CHARACTER SET NONE',
				'STEXT'		=> 'BLOB SUB_TYPE TEXT CHARACTER SET NONE',
				'TEXT'		=> 'BLOB SUB_TYPE TEXT CHARACTER SET NONE',
				'MTEXT'		=> 'BLOB SUB_TYPE TEXT CHARACTER SET NONE',
				'XSTEXT_UNI'=> 'VARCHAR(100) CHARACTER SET UTF8',
				'STEXT_UNI'	=> 'VARCHAR(255) CHARACTER SET UTF8',
				'TEXT_UNI'	=> 'BLOB SUB_TYPE TEXT CHARACTER SET UTF8',
				'MTEXT_UNI'	=> 'BLOB SUB_TYPE TEXT CHARACTER SET UTF8',
				'TIMESTAMP'	=> 'INTEGER',
				'DECIMAL'	=> 'DOUBLE PRECISION',
				'DECIMAL:'	=> 'DOUBLE PRECISION',
				'PDECIMAL'	=> 'DOUBLE PRECISION',
				'PDECIMAL:'	=> 'DOUBLE PRECISION',
				'VCHAR_UNI'	=> 'VARCHAR(255) CHARACTER SET UTF8',
				'VCHAR_UNI:'=> 'VARCHAR(%d) CHARACTER SET UTF8',
				'VCHAR_CI'	=> 'VARCHAR(255) CHARACTER SET UTF8',
				'VARBINARY'	=> 'CHAR(255) CHARACTER SET NONE',
			),

			'mssql'		=> array(
				'INT:'		=> '[int]',
				'BINT'		=> '[float]',
				'UINT'		=> '[int]',
				'UINT:'		=> '[int]',
				'TINT:'		=> '[int]',
				'USINT'		=> '[int]',
				'BOOL'		=> '[int]',
				'VCHAR'		=> '[varchar] (255)',
				'VCHAR:'	=> '[varchar] (%d)',
				'CHAR:'		=> '[char] (%d)',
				'XSTEXT'	=> '[varchar] (1000)',
				'STEXT'		=> '[varchar] (3000)',
				'TEXT'		=> '[varchar] (8000)',
				'MTEXT'		=> '[text]',
				'XSTEXT_UNI'=> '[varchar] (100)',
				'STEXT_UNI'	=> '[varchar] (255)',
				'TEXT_UNI'	=> '[varchar] (4000)',
				'MTEXT_UNI'	=> '[text]',
				'TIMESTAMP'	=> '[int]',
				'DECIMAL'	=> '[float]',
				'DECIMAL:'	=> '[float]',
				'PDECIMAL'	=> '[float]',
				'PDECIMAL:'	=> '[float]',
				'VCHAR_UNI'	=> '[varchar] (255)',
				'VCHAR_UNI:'=> '[varchar] (%d)',
				'VCHAR_CI'	=> '[varchar] (255)',
				'VARBINARY'	=> '[varchar] (255)',
			),

			'mssqlnative'	=> array(
				'INT:'		=> '[int]',
				'BINT'		=> '[float]',
				'UINT'		=> '[int]',
				'UINT:'		=> '[int]',
				'TINT:'		=> '[int]',
				'USINT'		=> '[int]',
				'BOOL'		=> '[int]',
				'VCHAR'		=> '[varchar] (255)',
				'VCHAR:'	=> '[varchar] (%d)',
				'CHAR:'		=> '[char] (%d)',
				'XSTEXT'	=> '[varchar] (1000)',
				'STEXT'		=> '[varchar] (3000)',
				'TEXT'		=> '[varchar] (8000)',
				'MTEXT'		=> '[text]',
				'XSTEXT_UNI'=> '[varchar] (100)',
				'STEXT_UNI'	=> '[varchar] (255)',
				'TEXT_UNI'	=> '[varchar] (4000)',
				'MTEXT_UNI'	=> '[text]',
				'TIMESTAMP'	=> '[int]',
				'DECIMAL'	=> '[float]',
				'DECIMAL:'	=> '[float]',
				'PDECIMAL'	=> '[float]',
				'PDECIMAL:'	=> '[float]',
				'VCHAR_UNI'	=> '[varchar] (255)',
				'VCHAR_UNI:'=> '[varchar] (%d)',
				'VCHAR_CI'	=> '[varchar] (255)',
				'VARBINARY'	=> '[varchar] (255)',
			),

			'oracle'	=> array(
				'INT:'		=> 'number(%d)',
				'BINT'		=> 'number(20)',
				'UINT'		=> 'number(8)',
				'UINT:'		=> 'number(%d)',
				'TINT:'		=> 'number(%d)',
				'USINT'		=> 'number(4)',
				'BOOL'		=> 'number(1)',
				'VCHAR'		=> 'varchar2(255)',
				'VCHAR:'	=> 'varchar2(%d)',
				'CHAR:'		=> 'char(%d)',
				'XSTEXT'	=> 'varchar2(1000)',
				'STEXT'		=> 'varchar2(3000)',
				'TEXT'		=> 'clob',
				'MTEXT'		=> 'clob',
				'XSTEXT_UNI'=> 'varchar2(300)',
				'STEXT_UNI'	=> 'varchar2(765)',
				'TEXT_UNI'	=> 'clob',
				'MTEXT_UNI'	=> 'clob',
				'TIMESTAMP'	=> 'number(11)',
				'DECIMAL'	=> 'number(5, 2)',
				'DECIMAL:'	=> 'number(%d, 2)',
				'PDECIMAL'	=> 'number(6, 3)',
				'PDECIMAL:'	=> 'number(%d, 3)',
				'VCHAR_UNI'	=> 'varchar2(765)',
				'VCHAR_UNI:'=> array('varchar2(%d)', 'limit' => array('mult', 3, 765, 'clob')),
				'VCHAR_CI'	=> 'varchar2(255)',
				'VARBINARY'	=> 'raw(255)',
			),

			'sqlite'	=> array(
				'INT:'		=> 'int(%d)',
				'BINT'		=> 'bigint(20)',
				'UINT'		=> 'INTEGER UNSIGNED', //'mediumint(8) UNSIGNED',
				'UINT:'		=> 'INTEGER UNSIGNED', // 'int(%d) UNSIGNED',
				'TINT:'		=> 'tinyint(%d)',
				'USINT'		=> 'INTEGER UNSIGNED', //'mediumint(4) UNSIGNED',
				'BOOL'		=> 'INTEGER UNSIGNED', //'tinyint(1) UNSIGNED',
				'VCHAR'		=> 'varchar(255)',
				'VCHAR:'	=> 'varchar(%d)',
				'CHAR:'		=> 'char(%d)',
				'XSTEXT'	=> 'text(65535)',
				'STEXT'		=> 'text(65535)',
				'TEXT'		=> 'text(65535)',
				'MTEXT'		=> 'mediumtext(16777215)',
				'XSTEXT_UNI'=> 'text(65535)',
				'STEXT_UNI'	=> 'text(65535)',
				'TEXT_UNI'	=> 'text(65535)',
				'MTEXT_UNI'	=> 'mediumtext(16777215)',
				'TIMESTAMP'	=> 'INTEGER UNSIGNED', //'int(11) UNSIGNED',
				'DECIMAL'	=> 'decimal(5,2)',
				'DECIMAL:'	=> 'decimal(%d,2)',
				'PDECIMAL'	=> 'decimal(6,3)',
				'PDECIMAL:'	=> 'decimal(%d,3)',
				'VCHAR_UNI'	=> 'varchar(255)',
				'VCHAR_UNI:'=> 'varchar(%d)',
				'VCHAR_CI'	=> 'varchar(255)',
				'VARBINARY'	=> 'blob',
			),

			'postgres'	=> array(
				'INT:'		=> 'INT4',
				'BINT'		=> 'INT8',
				'UINT'		=> 'INT4', // unsigned
				'UINT:'		=> 'INT4', // unsigned
				'USINT'		=> 'INT2', // unsigned
				'BOOL'		=> 'INT2', // unsigned
				'TINT:'		=> 'INT2',
				'VCHAR'		=> 'varchar(255)',
				'VCHAR:'	=> 'varchar(%d)',
				'CHAR:'		=> 'char(%d)',
				'XSTEXT'	=> 'varchar(1000)',
				'STEXT'		=> 'varchar(3000)',
				'TEXT'		=> 'varchar(8000)',
				'MTEXT'		=> 'TEXT',
				'XSTEXT_UNI'=> 'varchar(100)',
				'STEXT_UNI'	=> 'varchar(255)',
				'TEXT_UNI'	=> 'varchar(4000)',
				'MTEXT_UNI'	=> 'TEXT',
				'TIMESTAMP'	=> 'INT4', // unsigned
				'DECIMAL'	=> 'decimal(5,2)',
				'DECIMAL:'	=> 'decimal(%d,2)',
				'PDECIMAL'	=> 'decimal(6,3)',
				'PDECIMAL:'	=> 'decimal(%d,3)',
				'VCHAR_UNI'	=> 'varchar(255)',
				'VCHAR_UNI:'=> 'varchar(%d)',
				'VCHAR_CI'	=> 'varchar_ci',
				'VARBINARY'	=> 'bytea',
			),
		);
	}

	/**
	* A list of types being unsigned for better reference in some db's
	* @var array
	*/
	var $unsigned_types = array('UINT', 'UINT:', 'USINT', 'BOOL', 'TIMESTAMP');

	/**
	* A list of supported DBMS. We change this class to support more DBMS, the DBMS itself only need to follow some rules.
	* @var array
	*/
	var $supported_dbms = array('firebird', 'mssql', 'mssqlnative', 'mysql_40', 'mysql_41', 'oracle', 'postgres', 'sqlite');

	/**
	* This is set to true if user only wants to return the 'to-be-executed' SQL statement(s) (as an array).
	* This mode has no effect on some methods (inserting of data for example). This is expressed within the methods command.
	*/
	var $return_statements = false;

	/**
	* Constructor. Set DB Object and set {@link $return_statements return_statements}.
	*
	* @param \phpbb\db\driver\driver	$db					Database connection
	* @param bool		$return_statements	True if only statements should be returned and no SQL being executed
	*/
	public function __construct(\phpbb\db\driver\driver $db, $return_statements = false)
	{
		$this->db = $db;
		$this->return_statements = $return_statements;

		$this->dbms_type_map = self::get_dbms_type_map();

		// Determine mapping database type
		switch ($this->db->sql_layer)
		{
			case 'mysql':
				$this->sql_layer = 'mysql_40';
			break;

			case 'mysql4':
				if (version_compare($this->db->sql_server_info(true), '4.1.3', '>='))
				{
					$this->sql_layer = 'mysql_41';
				}
				else
				{
					$this->sql_layer = 'mysql_40';
				}
			break;

			case 'mysqli':
				$this->sql_layer = 'mysql_41';
			break;

			case 'mssql':
			case 'mssql_odbc':
				$this->sql_layer = 'mssql';
			break;

			case 'mssqlnative':
				$this->sql_layer = 'mssqlnative';
			break;

			default:
				$this->sql_layer = $this->db->sql_layer;
			break;
		}
	}

	/**
	* Setter for {@link $return_statements return_statements}.
	*
	* @param bool $return_statements True if SQL should not be executed but returned as strings
	* @return null
	*/
	public function set_return_statements($return_statements)
	{
		$this->return_statements = $return_statements;
	}

	/**
	* Gets a list of tables in the database.
	*
	* @return array		Array of table names  (all lower case)
	*/
	function sql_list_tables()
	{
		switch ($this->db->sql_layer)
		{
			case 'mysql':
			case 'mysql4':
			case 'mysqli':
				$sql = 'SHOW TABLES';
			break;

			case 'sqlite':
				$sql = 'SELECT name
					FROM sqlite_master
					WHERE type = "table"';
			break;

			case 'mssql':
			case 'mssql_odbc':
			case 'mssqlnative':
				$sql = "SELECT name
					FROM sysobjects
					WHERE type='U'";
			break;

			case 'postgres':
				$sql = 'SELECT relname
					FROM pg_stat_user_tables';
			break;

			case 'firebird':
				$sql = 'SELECT rdb$relation_name
					FROM rdb$relations
					WHERE rdb$view_source is null
						AND rdb$system_flag = 0';
			break;

			case 'oracle':
				$sql = 'SELECT table_name
					FROM USER_TABLES';
			break;
		}

		$result = $this->db->sql_query($sql);

		$tables = array();
		while ($row = $this->db->sql_fetchrow($result))
		{
			$name = current($row);
			$tables[$name] = $name;
		}
		$this->db->sql_freeresult($result);

		return $tables;
	}

	/**
	* Check if table exists
	*
	*
	* @param string	$table_name	The table name to check for
	* @return bool true if table exists, else false
	*/
	function sql_table_exists($table_name)
	{
		$this->db->sql_return_on_error(true);
		$result = $this->db->sql_query_limit('SELECT * FROM ' . $table_name, 1);
		$this->db->sql_return_on_error(false);

		if ($result)
		{
			$this->db->sql_freeresult($result);
			return true;
		}

		return false;
	}

	/**
	* Create SQL Table
	*
	* @param string	$table_name	The table name to create
	* @param array	$table_data	Array containing table data.
	* @return array	Statements if $return_statements is true.
	*/
	function sql_create_table($table_name, $table_data)
	{
		// holds the DDL for a column
		$columns = $statements = array();

		if ($this->sql_table_exists($table_name))
		{
			return $this->_sql_run_sql($statements);
		}

		// Begin transaction
		$statements[] = 'begin';

		// Determine if we have created a PRIMARY KEY in the earliest
		$primary_key_gen = false;

		// Determine if the table requires a sequence
		$create_sequence = false;

		// Begin table sql statement
		switch ($this->sql_layer)
		{
			case 'mssql':
			case 'mssqlnative':
				$table_sql = 'CREATE TABLE [' . $table_name . '] (' . "\n";
			break;

			default:
				$table_sql = 'CREATE TABLE ' . $table_name . ' (' . "\n";
			break;
		}

		if ($this->sql_layer == 'mssql' || $this->sql_layer == 'mssqlnative')
		{
			if (!isset($table_data['PRIMARY_KEY']))
			{
				$table_data['COLUMNS']['mssqlindex'] = array('UINT', null, 'auto_increment');
				$table_data['PRIMARY_KEY'] = 'mssqlindex';
			}
		}

		// Iterate through the columns to create a table
		foreach ($table_data['COLUMNS'] as $column_name => $column_data)
		{
			// here lies an array, filled with information compiled on the column's data
			$prepared_column = $this->sql_prepare_column_data($table_name, $column_name, $column_data);

			if (isset($prepared_column['auto_increment']) && $prepared_column['auto_increment'] && strlen($column_name) > 26) // "${column_name}_gen"
			{
				trigger_error("Index name '${column_name}_gen' on table '$table_name' is too long. The maximum auto increment column length is 26 characters.", E_USER_ERROR);
			}

			// here we add the definition of the new column to the list of columns
			switch ($this->sql_layer)
			{
				case 'mssql':
				case 'mssqlnative':
					$columns[] = "\t [{$column_name}] " . $prepared_column['column_type_sql_default'];
				break;

				default:
					$columns[] = "\t {$column_name} " . $prepared_column['column_type_sql'];
				break;
			}

			// see if we have found a primary key set due to a column definition if we have found it, we can stop looking
			if (!$primary_key_gen)
			{
				$primary_key_gen = isset($prepared_column['primary_key_set']) && $prepared_column['primary_key_set'];
			}

			// create sequence DDL based off of the existance of auto incrementing columns
			if (!$create_sequence && isset($prepared_column['auto_increment']) && $prepared_column['auto_increment'])
			{
				$create_sequence = $column_name;
			}
		}

		// this makes up all the columns in the create table statement
		$table_sql .= implode(",\n", $columns);

		// Close the table for two DBMS and add to the statements
		switch ($this->sql_layer)
		{
			case 'firebird':
			case 'mssql':
			case 'mssqlnative':
				$table_sql .= "\n);";
				$statements[] = $table_sql;
			break;
		}

		// we have yet to create a primary key for this table,
		// this means that we can add the one we really wanted instead
		if (!$primary_key_gen)
		{
			// Write primary key
			if (isset($table_data['PRIMARY_KEY']))
			{
				if (!is_array($table_data['PRIMARY_KEY']))
				{
					$table_data['PRIMARY_KEY'] = array($table_data['PRIMARY_KEY']);
				}

				switch ($this->sql_layer)
				{
					case 'mysql_40':
					case 'mysql_41':
					case 'postgres':
					case 'sqlite':
						$table_sql .= ",\n\t PRIMARY KEY (" . implode(', ', $table_data['PRIMARY_KEY']) . ')';
					break;

					case 'firebird':
					case 'mssql':
					case 'mssqlnative':
						// We need the data here
						$old_return_statements = $this->return_statements;
						$this->return_statements = true;

						$primary_key_stmts = $this->sql_create_primary_key($table_name, $table_data['PRIMARY_KEY']);
						foreach ($primary_key_stmts as $pk_stmt)
						{
							$statements[] = $pk_stmt;
						}

						$this->return_statements = $old_return_statements;
					break;

					case 'oracle':
						$table_sql .= ",\n\t CONSTRAINT pk_{$table_name} PRIMARY KEY (" . implode(', ', $table_data['PRIMARY_KEY']) . ')';
					break;
				}
			}
		}

		// close the table
		switch ($this->sql_layer)
		{
			case 'mysql_41':
				// make sure the table is in UTF-8 mode
				$table_sql .= "\n) CHARACTER SET `utf8` COLLATE `utf8_bin`;";
				$statements[] = $table_sql;
			break;

			case 'mysql_40':
			case 'sqlite':
				$table_sql .= "\n);";
				$statements[] = $table_sql;
			break;

			case 'postgres':
				// do we need to add a sequence for auto incrementing columns?
				if ($create_sequence)
				{
					$statements[] = "CREATE SEQUENCE {$table_name}_seq;";
				}

				$table_sql .= "\n);";
				$statements[] = $table_sql;
			break;

			case 'oracle':
				$table_sql .= "\n)";
				$statements[] = $table_sql;

				// do we need to add a sequence and a tigger for auto incrementing columns?
				if ($create_sequence)
				{
					// create the actual sequence
					$statements[] = "CREATE SEQUENCE {$table_name}_seq";

					// the trigger is the mechanism by which we increment the counter
					$trigger = "CREATE OR REPLACE TRIGGER t_{$table_name}\n";
					$trigger .= "BEFORE INSERT ON {$table_name}\n";
					$trigger .= "FOR EACH ROW WHEN (\n";
					$trigger .= "\tnew.{$create_sequence} IS NULL OR new.{$create_sequence} = 0\n";
					$trigger .= ")\n";
					$trigger .= "BEGIN\n";
					$trigger .= "\tSELECT {$table_name}_seq.nextval\n";
					$trigger .= "\tINTO :new.{$create_sequence}\n";
					$trigger .= "\tFROM dual;\n";
					$trigger .= "END;";

					$statements[] = $trigger;
				}
			break;

			case 'firebird':
				if ($create_sequence)
				{
					$statements[] = "CREATE GENERATOR {$table_name}_gen;";
					$statements[] = "SET GENERATOR {$table_name}_gen TO 0;";

					$trigger = "CREATE TRIGGER t_$table_name FOR $table_name\n";
					$trigger .= "BEFORE INSERT\nAS\nBEGIN\n";
					$trigger .= "\tNEW.{$create_sequence} = GEN_ID({$table_name}_gen, 1);\nEND;";
					$statements[] = $trigger;
				}
			break;
		}

		// Write Keys
		if (isset($table_data['KEYS']))
		{
			foreach ($table_data['KEYS'] as $key_name => $key_data)
			{
				if (!is_array($key_data[1]))
				{
					$key_data[1] = array($key_data[1]);
				}

				$old_return_statements = $this->return_statements;
				$this->return_statements = true;

				$key_stmts = ($key_data[0] == 'UNIQUE') ? $this->sql_create_unique_index($table_name, $key_name, $key_data[1]) : $this->sql_create_index($table_name, $key_name, $key_data[1]);

				foreach ($key_stmts as $key_stmt)
				{
					$statements[] = $key_stmt;
				}

				$this->return_statements = $old_return_statements;
			}
		}

		// Commit Transaction
		$statements[] = 'commit';

		return $this->_sql_run_sql($statements);
	}

	/**
	* Handle passed database update array.
	* Expected structure...
	* Key being one of the following
	*	drop_tables: Drop tables
	*	add_tables: Add tables
	*	change_columns: Column changes (only type, not name)
	*	add_columns: Add columns to a table
	*	drop_keys: Dropping keys
	*	drop_columns: Removing/Dropping columns
	*	add_primary_keys: adding primary keys
	*	add_unique_index: adding an unique index
	*	add_index: adding an index (can be column:index_size if you need to provide size)
	*
	* The values are in this format:
	*		{TABLE NAME}		=> array(
	*			{COLUMN NAME}		=> array({COLUMN TYPE}, {DEFAULT VALUE}, {OPTIONAL VARIABLES}),
	*			{KEY/INDEX NAME}	=> array({COLUMN NAMES}),
	*		)
	*
	* For more information have a look at /develop/create_schema_files.php (only available through SVN)
	*/
	function perform_schema_changes($schema_changes)
	{
		if (empty($schema_changes))
		{
			return;
		}

		$statements = array();
		$sqlite = false;

		// For SQLite we need to perform the schema changes in a much more different way
		if ($this->db->sql_layer == 'sqlite' && $this->return_statements)
		{
			$sqlite_data = array();
			$sqlite = true;
		}

		// Drop tables?
		if (!empty($schema_changes['drop_tables']))
		{
			foreach ($schema_changes['drop_tables'] as $table)
			{
				// only drop table if it exists
				if ($this->sql_table_exists($table))
				{
					$result = $this->sql_table_drop($table);
					if ($this->return_statements)
					{
						$statements = array_merge($statements, $result);
					}
				}
			}
		}

		// Add tables?
		if (!empty($schema_changes['add_tables']))
		{
			foreach ($schema_changes['add_tables'] as $table => $table_data)
			{
				$result = $this->sql_create_table($table, $table_data);
				if ($this->return_statements)
				{
					$statements = array_merge($statements, $result);
				}
			}
		}

		// Change columns?
		if (!empty($schema_changes['change_columns']))
		{
			foreach ($schema_changes['change_columns'] as $table => $columns)
			{
				foreach ($columns as $column_name => $column_data)
				{
					// If the column exists we change it, else we add it ;)
					if ($column_exists = $this->sql_column_exists($table, $column_name))
					{
						$result = $this->sql_column_change($table, $column_name, $column_data, true);
					}
					else
					{
						$result = $this->sql_column_add($table, $column_name, $column_data, true);
					}

					if ($sqlite)
					{
						if ($column_exists)
						{
							$sqlite_data[$table]['change_columns'][] = $result;
						}
						else
						{
							$sqlite_data[$table]['add_columns'][] = $result;
						}
					}
					else if ($this->return_statements)
					{
						$statements = array_merge($statements, $result);
					}
				}
			}
		}

		// Add columns?
		if (!empty($schema_changes['add_columns']))
		{
			foreach ($schema_changes['add_columns'] as $table => $columns)
			{
				foreach ($columns as $column_name => $column_data)
				{
					// Only add the column if it does not exist yet
					if ($column_exists = $this->sql_column_exists($table, $column_name))
					{
						continue;
						// This is commented out here because it can take tremendous time on updates
//						$result = $this->sql_column_change($table, $column_name, $column_data, true);
					}
					else
					{
						$result = $this->sql_column_add($table, $column_name, $column_data, true);
					}

					if ($sqlite)
					{
						if ($column_exists)
						{
							continue;
//							$sqlite_data[$table]['change_columns'][] = $result;
						}
						else
						{
							$sqlite_data[$table]['add_columns'][] = $result;
						}
					}
					else if ($this->return_statements)
					{
						$statements = array_merge($statements, $result);
					}
				}
			}
		}

		// Remove keys?
		if (!empty($schema_changes['drop_keys']))
		{
			foreach ($schema_changes['drop_keys'] as $table => $indexes)
			{
				foreach ($indexes as $index_name)
				{
					if (!$this->sql_index_exists($table, $index_name))
					{
						continue;
					}

					$result = $this->sql_index_drop($table, $index_name);

					if ($this->return_statements)
					{
						$statements = array_merge($statements, $result);
					}
				}
			}
		}

		// Drop columns?
		if (!empty($schema_changes['drop_columns']))
		{
			foreach ($schema_changes['drop_columns'] as $table => $columns)
			{
				foreach ($columns as $column)
				{
					// Only remove the column if it exists...
					if ($this->sql_column_exists($table, $column))
					{
						$result = $this->sql_column_remove($table, $column, true);

						if ($sqlite)
						{
							$sqlite_data[$table]['drop_columns'][] = $result;
						}
						else if ($this->return_statements)
						{
							$statements = array_merge($statements, $result);
						}
					}
				}
			}
		}

		// Add primary keys?
		if (!empty($schema_changes['add_primary_keys']))
		{
			foreach ($schema_changes['add_primary_keys'] as $table => $columns)
			{
				$result = $this->sql_create_primary_key($table, $columns, true);

				if ($sqlite)
				{
					$sqlite_data[$table]['primary_key'] = $result;
				}
				else if ($this->return_statements)
				{
					$statements = array_merge($statements, $result);
				}
			}
		}

		// Add unqiue indexes?
		if (!empty($schema_changes['add_unique_index']))
		{
			foreach ($schema_changes['add_unique_index'] as $table => $index_array)
			{
				foreach ($index_array as $index_name => $column)
				{
					if ($this->sql_unique_index_exists($table, $index_name))
					{
						continue;
					}

					$result = $this->sql_create_unique_index($table, $index_name, $column);

					if ($this->return_statements)
					{
						$statements = array_merge($statements, $result);
					}
				}
			}
		}

		// Add indexes?
		if (!empty($schema_changes['add_index']))
		{
			foreach ($schema_changes['add_index'] as $table => $index_array)
			{
				foreach ($index_array as $index_name => $column)
				{
					if ($this->sql_index_exists($table, $index_name))
					{
						continue;
					}

					$result = $this->sql_create_index($table, $index_name, $column);

					if ($this->return_statements)
					{
						$statements = array_merge($statements, $result);
					}
				}
			}
		}

		if ($sqlite)
		{
			foreach ($sqlite_data as $table_name => $sql_schema_changes)
			{
				// Create temporary table with original data
				$statements[] = 'begin';

				$sql = "SELECT sql
					FROM sqlite_master
					WHERE type = 'table'
						AND name = '{$table_name}'
					ORDER BY type DESC, name;";
				$result = $this->db->sql_query($sql);

				if (!$result)
				{
					continue;
				}

				$row = $this->db->sql_fetchrow($result);
				$this->db->sql_freeresult($result);

				// Create a backup table and populate it, destroy the existing one
				$statements[] = preg_replace('#CREATE\s+TABLE\s+"?' . $table_name . '"?#i', 'CREATE TEMPORARY TABLE ' . $table_name . '_temp', $row['sql']);
				$statements[] = 'INSERT INTO ' . $table_name . '_temp SELECT * FROM ' . $table_name;
				$statements[] = 'DROP TABLE ' . $table_name;

				// Get the columns...
				preg_match('#\((.*)\)#s', $row['sql'], $matches);

				$plain_table_cols = trim($matches[1]);
				$new_table_cols = preg_split('/,(?![\s\w]+\))/m', $plain_table_cols);
				$column_list = array();

				foreach ($new_table_cols as $declaration)
				{
					$entities = preg_split('#\s+#', trim($declaration));
					if ($entities[0] == 'PRIMARY')
					{
						continue;
					}
					$column_list[] = $entities[0];
				}

				// note down the primary key notation because sqlite only supports adding it to the end for the new table
				$primary_key = false;
				$_new_cols = array();

				foreach ($new_table_cols as $key => $declaration)
				{
					$entities = preg_split('#\s+#', trim($declaration));
					if ($entities[0] == 'PRIMARY')
					{
						$primary_key = $declaration;
						continue;
					}
					$_new_cols[] = $declaration;
				}

				$new_table_cols = $_new_cols;

				// First of all... change columns
				if (!empty($sql_schema_changes['change_columns']))
				{
					foreach ($sql_schema_changes['change_columns'] as $column_sql)
					{
						foreach ($new_table_cols as $key => $declaration)
						{
							$entities = preg_split('#\s+#', trim($declaration));
							if (strpos($column_sql, $entities[0] . ' ') === 0)
							{
								$new_table_cols[$key] = $column_sql;
							}
						}
					}
				}

				if (!empty($sql_schema_changes['add_columns']))
				{
					foreach ($sql_schema_changes['add_columns'] as $column_sql)
					{
						$new_table_cols[] = $column_sql;
					}
				}

				// Now drop them...
				if (!empty($sql_schema_changes['drop_columns']))
				{
					foreach ($sql_schema_changes['drop_columns'] as $column_name)
					{
						// Remove from column list...
						$new_column_list = array();
						foreach ($column_list as $key => $value)
						{
							if ($value === $column_name)
							{
								continue;
							}

							$new_column_list[] = $value;
						}

						$column_list = $new_column_list;

						// Remove from table...
						$_new_cols = array();
						foreach ($new_table_cols as $key => $declaration)
						{
							$entities = preg_split('#\s+#', trim($declaration));
							if (strpos($column_name . ' ', $entities[0] . ' ') === 0)
							{
								continue;
							}
							$_new_cols[] = $declaration;
						}
						$new_table_cols = $_new_cols;
					}
				}

				// Primary key...
				if (!empty($sql_schema_changes['primary_key']))
				{
					$new_table_cols[] = 'PRIMARY KEY (' . implode(', ', $sql_schema_changes['primary_key']) . ')';
				}
				// Add a new one or the old primary key
				else if ($primary_key !== false)
				{
					$new_table_cols[] = $primary_key;
				}

				$columns = implode(',', $column_list);

				// create a new table and fill it up. destroy the temp one
				$statements[] = 'CREATE TABLE ' . $table_name . ' (' . implode(',', $new_table_cols) . ');';
				$statements[] = 'INSERT INTO ' . $table_name . ' (' . $columns . ') SELECT ' . $columns . ' FROM ' . $table_name . '_temp;';
				$statements[] = 'DROP TABLE ' . $table_name . '_temp';

				$statements[] = 'commit';
			}
		}

		if ($this->return_statements)
		{
			return $statements;
		}
	}

	/**
	* Gets a list of columns of a table.
	*
	* @param string $table		Table name
	*
	* @return array				Array of column names (all lower case)
	*/
	function sql_list_columns($table)
	{
		$columns = array();

		switch ($this->sql_layer)
		{
			case 'mysql_40':
			case 'mysql_41':
				$sql = "SHOW COLUMNS FROM $table";
			break;

			// PostgreSQL has a way of doing this in a much simpler way but would
			// not allow us to support all versions of PostgreSQL
			case 'postgres':
				$sql = "SELECT a.attname
					FROM pg_class c, pg_attribute a
					WHERE c.relname = '{$table}'
						AND a.attnum > 0
						AND a.attrelid = c.oid";
			break;

			// same deal with PostgreSQL, we must perform more complex operations than
			// we technically could
			case 'mssql':
			case 'mssqlnative':
				$sql = "SELECT c.name
					FROM syscolumns c
					LEFT JOIN sysobjects o ON c.id = o.id
					WHERE o.name = '{$table}'";
			break;

			case 'oracle':
				$sql = "SELECT column_name
					FROM user_tab_columns
					WHERE LOWER(table_name) = '" . strtolower($table) . "'";
			break;

			case 'firebird':
				$sql = "SELECT RDB\$FIELD_NAME as FNAME
					FROM RDB\$RELATION_FIELDS
					WHERE RDB\$RELATION_NAME = '" . strtoupper($table) . "'";
			break;

			case 'sqlite':
				$sql = "SELECT sql
					FROM sqlite_master
					WHERE type = 'table'
						AND name = '{$table}'";

				$result = $this->db->sql_query($sql);

				if (!$result)
				{
					return false;
				}

				$row = $this->db->sql_fetchrow($result);
				$this->db->sql_freeresult($result);

				preg_match('#\((.*)\)#s', $row['sql'], $matches);

				$cols = trim($matches[1]);
				$col_array = preg_split('/,(?![\s\w]+\))/m', $cols);

				foreach ($col_array as $declaration)
				{
					$entities = preg_split('#\s+#', trim($declaration));
					if ($entities[0] == 'PRIMARY')
					{
						continue;
					}

					$column = strtolower($entities[0]);
					$columns[$column] = $column;
				}

				return $columns;
			break;
		}

		$result = $this->db->sql_query($sql);

		while ($row = $this->db->sql_fetchrow($result))
		{
			$column = strtolower(current($row));
			$columns[$column] = $column;
		}
		$this->db->sql_freeresult($result);

		return $columns;
	}

	/**
	* Check whether a specified column exist in a table
	*
	* @param string	$table			Table to check
	* @param string	$column_name	Column to check
	*
	* @return bool		True if column exists, false otherwise
	*/
	function sql_column_exists($table, $column_name)
	{
		$columns = $this->sql_list_columns($table);

		return isset($columns[$column_name]);
	}

	/**
	* Check if a specified index exists in table. Does not return PRIMARY KEY and UNIQUE indexes.
	*
	* @param string	$table_name		Table to check the index at
	* @param string	$index_name		The index name to check
	*
	* @return bool True if index exists, else false
	*/
	function sql_index_exists($table_name, $index_name)
	{
		if ($this->sql_layer == 'mssql' || $this->sql_layer == 'mssqlnative')
		{
			$sql = "EXEC sp_statistics '$table_name'";
			$result = $this->db->sql_query($sql);

			while ($row = $this->db->sql_fetchrow($result))
			{
				if ($row['TYPE'] == 3)
				{
					if (strtolower($row['INDEX_NAME']) == strtolower($index_name))
					{
						$this->db->sql_freeresult($result);
						return true;
					}
				}
			}
			$this->db->sql_freeresult($result);

			return false;
		}

		switch ($this->sql_layer)
		{
			case 'firebird':
				$sql = "SELECT LOWER(RDB\$INDEX_NAME) as index_name
					FROM RDB\$INDICES
					WHERE RDB\$RELATION_NAME = '" . strtoupper($table_name) . "'
						AND RDB\$UNIQUE_FLAG IS NULL
						AND RDB\$FOREIGN_KEY IS NULL";
				$col = 'index_name';
			break;

			case 'postgres':
				$sql = "SELECT ic.relname as index_name
					FROM pg_class bc, pg_class ic, pg_index i
					WHERE (bc.oid = i.indrelid)
						AND (ic.oid = i.indexrelid)
						AND (bc.relname = '" . $table_name . "')
						AND (i.indisunique != 't')
						AND (i.indisprimary != 't')";
				$col = 'index_name';
			break;

			case 'mysql_40':
			case 'mysql_41':
				$sql = 'SHOW KEYS
					FROM ' . $table_name;
				$col = 'Key_name';
			break;

			case 'oracle':
				$sql = "SELECT index_name
					FROM user_indexes
					WHERE table_name = '" . strtoupper($table_name) . "'
						AND generated = 'N'
						AND uniqueness = 'NONUNIQUE'";
				$col = 'index_name';
			break;

			case 'sqlite':
				$sql = "PRAGMA index_list('" . $table_name . "');";
				$col = 'name';
			break;
		}

		$result = $this->db->sql_query($sql);
		while ($row = $this->db->sql_fetchrow($result))
		{
			if (($this->sql_layer == 'mysql_40' || $this->sql_layer == 'mysql_41') && !$row['Non_unique'])
			{
				continue;
			}

			// These DBMS prefix index name with the table name
			switch ($this->sql_layer)
			{
				case 'firebird':
				case 'oracle':
				case 'postgres':
				case 'sqlite':
					$row[$col] = substr($row[$col], strlen($table_name) + 1);
				break;
			}

			if (strtolower($row[$col]) == strtolower($index_name))
			{
				$this->db->sql_freeresult($result);
				return true;
			}
		}
		$this->db->sql_freeresult($result);

		return false;
	}

	/**
	* Check if a specified index exists in table. Does not return PRIMARY KEY and UNIQUE indexes.
	*
	* @param string	$table_name		Table to check the index at
	* @param string	$index_name		The index name to check
	*
	* @return bool True if index exists, else false
	*/
	function sql_unique_index_exists($table_name, $index_name)
	{
		if ($this->sql_layer == 'mssql' || $this->sql_layer == 'mssqlnative')
		{
			$sql = "EXEC sp_statistics '$table_name'";
			$result = $this->db->sql_query($sql);

			while ($row = $this->db->sql_fetchrow($result))
			{
				// Usually NON_UNIQUE is the column we want to check, but we allow for both
				if ($row['TYPE'] == 3)
				{
					if (strtolower($row['INDEX_NAME']) == strtolower($index_name))
					{
						$this->db->sql_freeresult($result);
						return true;
					}
				}
			}
			$this->db->sql_freeresult($result);
			return false;
		}

		switch ($this->sql_layer)
		{
			case 'firebird':
				$sql = "SELECT LOWER(RDB\$INDEX_NAME) as index_name
					FROM RDB\$INDICES
					WHERE RDB\$RELATION_NAME = '" . strtoupper($table_name) . "'
						AND RDB\$UNIQUE_FLAG IS NOT NULL
						AND RDB\$FOREIGN_KEY IS NULL";
				$col = 'index_name';
			break;

			case 'postgres':
				$sql = "SELECT ic.relname as index_name, i.indisunique
					FROM pg_class bc, pg_class ic, pg_index i
					WHERE (bc.oid = i.indrelid)
						AND (ic.oid = i.indexrelid)
						AND (bc.relname = '" . $table_name . "')
						AND (i.indisprimary != 't')";
				$col = 'index_name';
			break;

			case 'mysql_40':
			case 'mysql_41':
				$sql = 'SHOW KEYS
					FROM ' . $table_name;
				$col = 'Key_name';
			break;

			case 'oracle':
				$sql = "SELECT index_name, table_owner
					FROM user_indexes
					WHERE table_name = '" . strtoupper($table_name) . "'
						AND generated = 'N'
						AND uniqueness = 'UNIQUE'";
				$col = 'index_name';
			break;

			case 'sqlite':
				$sql = "PRAGMA index_list('" . $table_name . "');";
				$col = 'name';
			break;
		}

		$result = $this->db->sql_query($sql);
		while ($row = $this->db->sql_fetchrow($result))
		{
			if (($this->sql_layer == 'mysql_40' || $this->sql_layer == 'mysql_41') && ($row['Non_unique'] || $row[$col] == 'PRIMARY'))
			{
				continue;
			}

			if ($this->sql_layer == 'sqlite' && !$row['unique'])
			{
				continue;
			}

			if ($this->sql_layer == 'postgres' && $row['indisunique'] != 't')
			{
				continue;
			}

			// These DBMS prefix index name with the table name
			switch ($this->sql_layer)
			{
				case 'oracle':
					// Two cases here... prefixed with U_[table_owner] and not prefixed with table_name
					if (strpos($row[$col], 'U_') === 0)
					{
						$row[$col] = substr($row[$col], strlen('U_' . $row['table_owner']) + 1);
					}
					else if (strpos($row[$col], strtoupper($table_name)) === 0)
					{
						$row[$col] = substr($row[$col], strlen($table_name) + 1);
					}
				break;

				case 'firebird':
				case 'postgres':
				case 'sqlite':
					$row[$col] = substr($row[$col], strlen($table_name) + 1);
				break;
			}

			if (strtolower($row[$col]) == strtolower($index_name))
			{
				$this->db->sql_freeresult($result);
				return true;
			}
		}
		$this->db->sql_freeresult($result);

		return false;
	}

	/**
	* Private method for performing sql statements (either execute them or return them)
	* @access private
	*/
	function _sql_run_sql($statements)
	{
		if ($this->return_statements)
		{
			return $statements;
		}

		// We could add error handling here...
		foreach ($statements as $sql)
		{
			if ($sql === 'begin')
			{
				$this->db->sql_transaction('begin');
			}
			else if ($sql === 'commit')
			{
				$this->db->sql_transaction('commit');
			}
			else
			{
				$this->db->sql_query($sql);
			}
		}

		return true;
	}

	/**
	* Function to prepare some column information for better usage
	* @access private
	*/
	function sql_prepare_column_data($table_name, $column_name, $column_data)
	{
		if (strlen($column_name) > 30)
		{
			trigger_error("Column name '$column_name' on table '$table_name' is too long. The maximum is 30 characters.", E_USER_ERROR);
		}

		// Get type
		list($column_type, $orig_column_type) = $this->get_column_type($column_data[0]);

		// Adjust default value if db-dependent specified
		if (is_array($column_data[1]))
		{
			$column_data[1] = (isset($column_data[1][$this->sql_layer])) ? $column_data[1][$this->sql_layer] : $column_data[1]['default'];
		}

		$sql = '';

		$return_array = array();

		switch ($this->sql_layer)
		{
			case 'firebird':
				$sql .= " {$column_type} ";
				$return_array['column_type_sql_type'] = " {$column_type} ";

				if (!is_null($column_data[1]))
				{
					$sql .= 'DEFAULT ' . ((is_numeric($column_data[1])) ? $column_data[1] : "'{$column_data[1]}'") . ' ';
					$return_array['column_type_sql_default'] = ((is_numeric($column_data[1])) ? $column_data[1] : "'{$column_data[1]}'") . ' ';
				}

				$sql .= 'NOT NULL';

				// This is a UNICODE column and thus should be given it's fair share
				if (preg_match('/^X?STEXT_UNI|VCHAR_(CI|UNI:?)/', $column_data[0]))
				{
					$sql .= ' COLLATE UNICODE';
				}

				$return_array['auto_increment'] = false;
				if (isset($column_data[2]) && $column_data[2] == 'auto_increment')
				{
					$return_array['auto_increment'] = true;
				}

			break;

			case 'mssql':
			case 'mssqlnative':
				$sql .= " {$column_type} ";
				$sql_default = " {$column_type} ";

				// For adding columns we need the default definition
				if (!is_null($column_data[1]))
				{
					// For hexadecimal values do not use single quotes
					if (strpos($column_data[1], '0x') === 0)
					{
						$return_array['default'] = 'DEFAULT (' . $column_data[1] . ') ';
						$sql_default .= $return_array['default'];
					}
					else
					{
						$return_array['default'] = 'DEFAULT (' . ((is_numeric($column_data[1])) ? $column_data[1] : "'{$column_data[1]}'") . ') ';
						$sql_default .= $return_array['default'];
					}
				}

				if (isset($column_data[2]) && $column_data[2] == 'auto_increment')
				{
//					$sql .= 'IDENTITY (1, 1) ';
					$sql_default .= 'IDENTITY (1, 1) ';
				}

				$return_array['textimage'] = $column_type === '[text]';

				$sql .= 'NOT NULL';
				$sql_default .= 'NOT NULL';

				$return_array['column_type_sql_default'] = $sql_default;

			break;

			case 'mysql_40':
			case 'mysql_41':
				$sql .= " {$column_type} ";

				// For hexadecimal values do not use single quotes
				if (!is_null($column_data[1]) && substr($column_type, -4) !== 'text' && substr($column_type, -4) !== 'blob')
				{
					$sql .= (strpos($column_data[1], '0x') === 0) ? "DEFAULT {$column_data[1]} " : "DEFAULT '{$column_data[1]}' ";
				}
				$sql .= 'NOT NULL';

				if (isset($column_data[2]))
				{
					if ($column_data[2] == 'auto_increment')
					{
						$sql .= ' auto_increment';
					}
					else if ($this->sql_layer === 'mysql_41' && $column_data[2] == 'true_sort')
					{
						$sql .= ' COLLATE utf8_unicode_ci';
					}
				}

			break;

			case 'oracle':
				$sql .= " {$column_type} ";
				$sql .= (!is_null($column_data[1])) ? "DEFAULT '{$column_data[1]}' " : '';

				// In Oracle empty strings ('') are treated as NULL.
				// Therefore in oracle we allow NULL's for all DEFAULT '' entries
				// Oracle does not like setting NOT NULL on a column that is already NOT NULL (this happens only on number fields)
				if (!preg_match('/number/i', $column_type))
				{
					$sql .= ($column_data[1] === '') ? '' : 'NOT NULL';
				}

				$return_array['auto_increment'] = false;
				if (isset($column_data[2]) && $column_data[2] == 'auto_increment')
				{
					$return_array['auto_increment'] = true;
				}

			break;

			case 'postgres':
				$return_array['column_type'] = $column_type;

				$sql .= " {$column_type} ";

				$return_array['auto_increment'] = false;
				if (isset($column_data[2]) && $column_data[2] == 'auto_increment')
				{
					$default_val = "nextval('{$table_name}_seq')";
					$return_array['auto_increment'] = true;
				}
				else if (!is_null($column_data[1]))
				{
					$default_val = "'" . $column_data[1] . "'";
					$return_array['null'] = 'NOT NULL';
					$sql .= 'NOT NULL ';
				}

				$return_array['default'] = $default_val;

				$sql .= "DEFAULT {$default_val}";

				// Unsigned? Then add a CHECK contraint
				if (in_array($orig_column_type, $this->unsigned_types))
				{
					$return_array['constraint'] = "CHECK ({$column_name} >= 0)";
					$sql .= " CHECK ({$column_name} >= 0)";
				}

			break;

			case 'sqlite':
				$return_array['primary_key_set'] = false;
				if (isset($column_data[2]) && $column_data[2] == 'auto_increment')
				{
					$sql .= ' INTEGER PRIMARY KEY';
					$return_array['primary_key_set'] = true;
				}
				else
				{
					$sql .= ' ' . $column_type;
				}

				$sql .= ' NOT NULL ';
				$sql .= (!is_null($column_data[1])) ? "DEFAULT '{$column_data[1]}'" : '';

			break;
		}

		$return_array['column_type_sql'] = $sql;

		return $return_array;
	}

	/**
	* Get the column's database type from the type map
	*
	* @param string $column_map_type
	* @return array		column type for this database
	*					and map type without length
	*/
	function get_column_type($column_map_type)
	{
		if (strpos($column_map_type, ':') !== false)
		{
			list($orig_column_type, $column_length) = explode(':', $column_map_type);
			if (!is_array($this->dbms_type_map[$this->sql_layer][$orig_column_type . ':']))
			{
				$column_type = sprintf($this->dbms_type_map[$this->sql_layer][$orig_column_type . ':'], $column_length);
			}
			else
			{
				if (isset($this->dbms_type_map[$this->sql_layer][$orig_column_type . ':']['rule']))
				{
					switch ($this->dbms_type_map[$this->sql_layer][$orig_column_type . ':']['rule'][0])
					{
						case 'div':
							$column_length /= $this->dbms_type_map[$this->sql_layer][$orig_column_type . ':']['rule'][1];
							$column_length = ceil($column_length);
							$column_type = sprintf($this->dbms_type_map[$this->sql_layer][$orig_column_type . ':'][0], $column_length);
						break;
					}
				}

				if (isset($this->dbms_type_map[$this->sql_layer][$orig_column_type . ':']['limit']))
				{
					switch ($this->dbms_type_map[$this->sql_layer][$orig_column_type . ':']['limit'][0])
					{
						case 'mult':
							$column_length *= $this->dbms_type_map[$this->sql_layer][$orig_column_type . ':']['limit'][1];
							if ($column_length > $this->dbms_type_map[$this->sql_layer][$orig_column_type . ':']['limit'][2])
							{
								$column_type = $this->dbms_type_map[$this->sql_layer][$orig_column_type . ':']['limit'][3];
							}
							else
							{
								$column_type = sprintf($this->dbms_type_map[$this->sql_layer][$orig_column_type . ':'][0], $column_length);
							}
						break;
					}
				}
			}
			$orig_column_type .= ':';
		}
		else
		{
			$orig_column_type = $column_map_type;
			$column_type = $this->dbms_type_map[$this->sql_layer][$column_map_type];
		}

		return array($column_type, $orig_column_type);
	}

	/**
	* Add new column
	*/
	function sql_column_add($table_name, $column_name, $column_data, $inline = false)
	{
		$column_data = $this->sql_prepare_column_data($table_name, $column_name, $column_data);
		$statements = array();

		switch ($this->sql_layer)
		{
			case 'firebird':
				// Does not support AFTER statement, only POSITION (and there you need the column position)
				$statements[] = 'ALTER TABLE ' . $table_name . ' ADD "' . strtoupper($column_name) . '" ' . $column_data['column_type_sql'];
			break;

			case 'mssql':
			case 'mssqlnative':
				// Does not support AFTER, only through temporary table
				$statements[] = 'ALTER TABLE [' . $table_name . '] ADD [' . $column_name . '] ' . $column_data['column_type_sql_default'];
			break;

			case 'mysql_40':
			case 'mysql_41':
				$after = (!empty($column_data['after'])) ? ' AFTER ' . $column_data['after'] : '';
				$statements[] = 'ALTER TABLE `' . $table_name . '` ADD COLUMN `' . $column_name . '` ' . $column_data['column_type_sql'] . $after;
			break;

			case 'oracle':
				// Does not support AFTER, only through temporary table
				$statements[] = 'ALTER TABLE ' . $table_name . ' ADD ' . $column_name . ' ' . $column_data['column_type_sql'];
			break;

			case 'postgres':
				// Does not support AFTER, only through temporary table
				if (version_compare($this->db->sql_server_info(true), '8.0', '>='))
				{
					$statements[] = 'ALTER TABLE ' . $table_name . ' ADD COLUMN "' . $column_name . '" ' . $column_data['column_type_sql'];
				}
				else
				{
					// old versions cannot add columns with default and null information
					$statements[] = 'ALTER TABLE ' . $table_name . ' ADD COLUMN "' . $column_name . '" ' . $column_data['column_type'] . ' ' . $column_data['constraint'];

					if (isset($column_data['null']))
					{
						if ($column_data['null'] == 'NOT NULL')
						{
							$statements[] = 'ALTER TABLE ' . $table_name . ' ALTER COLUMN ' . $column_name . ' SET NOT NULL';
						}
					}

					if (isset($column_data['default']))
					{
						$statements[] = 'ALTER TABLE ' . $table_name . ' ALTER COLUMN ' . $column_name . ' SET DEFAULT ' . $column_data['default'];
					}
				}

			break;

			case 'sqlite':

				if ($inline && $this->return_statements)
				{
					return $column_name . ' ' . $column_data['column_type_sql'];
				}

				if (version_compare(sqlite_libversion(), '3.0') == -1)
				{
					$sql = "SELECT sql
						FROM sqlite_master
						WHERE type = 'table'
							AND name = '{$table_name}'
						ORDER BY type DESC, name;";
					$result = $this->db->sql_query($sql);

					if (!$result)
					{
						break;
					}

					$row = $this->db->sql_fetchrow($result);
					$this->db->sql_freeresult($result);

					$statements[] = 'begin';

					// Create a backup table and populate it, destroy the existing one
					$statements[] = preg_replace('#CREATE\s+TABLE\s+"?' . $table_name . '"?#i', 'CREATE TEMPORARY TABLE ' . $table_name . '_temp', $row['sql']);
					$statements[] = 'INSERT INTO ' . $table_name . '_temp SELECT * FROM ' . $table_name;
					$statements[] = 'DROP TABLE ' . $table_name;

					preg_match('#\((.*)\)#s', $row['sql'], $matches);

					$new_table_cols = trim($matches[1]);
					$old_table_cols = preg_split('/,(?![\s\w]+\))/m', $new_table_cols);
					$column_list = array();

					foreach ($old_table_cols as $declaration)
					{
						$entities = preg_split('#\s+#', trim($declaration));
						if ($entities[0] == 'PRIMARY')
						{
							continue;
						}
						$column_list[] = $entities[0];
					}

					$columns = implode(',', $column_list);

					$new_table_cols = $column_name . ' ' . $column_data['column_type_sql'] . ',' . $new_table_cols;

					// create a new table and fill it up. destroy the temp one
					$statements[] = 'CREATE TABLE ' . $table_name . ' (' . $new_table_cols . ');';
					$statements[] = 'INSERT INTO ' . $table_name . ' (' . $columns . ') SELECT ' . $columns . ' FROM ' . $table_name . '_temp;';
					$statements[] = 'DROP TABLE ' . $table_name . '_temp';

					$statements[] = 'commit';
				}
				else
				{
					$statements[] = 'ALTER TABLE ' . $table_name . ' ADD ' . $column_name . ' [' . $column_data['column_type_sql'] . ']';
				}
			break;
		}

		return $this->_sql_run_sql($statements);
	}

	/**
	* Drop column
	*/
	function sql_column_remove($table_name, $column_name, $inline = false)
	{
		$statements = array();

		switch ($this->sql_layer)
		{
			case 'firebird':
				$statements[] = 'ALTER TABLE ' . $table_name . ' DROP "' . strtoupper($column_name) . '"';
			break;

			case 'mssql':
			case 'mssqlnative':
				$sql = "SELECT CAST(SERVERPROPERTY('productversion') AS VARCHAR(25)) AS mssql_version";
				$result = $this->db->sql_query($sql);
				$row = $this->db->sql_fetchrow($result);
				$this->db->sql_freeresult($result);

				// Remove default constraints
				if ($row['mssql_version'][0] == '8')	// SQL Server 2000
				{
					// http://msdn.microsoft.com/en-us/library/aa175912%28v=sql.80%29.aspx
					// Deprecated in SQL Server 2005
					$statements[] = "DECLARE @drop_default_name VARCHAR(100), @cmd VARCHAR(1000)
						SET @drop_default_name =
							(SELECT so.name FROM sysobjects so
							JOIN sysconstraints sc ON so.id = sc.constid
							WHERE object_name(so.parent_obj) = '{$table_name}'
								AND so.xtype = 'D'
								AND sc.colid = (SELECT colid FROM syscolumns
									WHERE id = object_id('{$table_name}')
										AND name = '{$column_name}'))
						IF @drop_default_name <> ''
						BEGIN
							SET @cmd = 'ALTER TABLE [{$table_name}] DROP CONSTRAINT [' + @drop_default_name + ']'
							EXEC(@cmd)
						END";
				}
				else
				{
					$sql = "SELECT dobj.name AS def_name
					FROM sys.columns col 
						LEFT OUTER JOIN sys.objects dobj ON (dobj.object_id = col.default_object_id AND dobj.type = 'D')
					WHERE col.object_id = object_id('{$table_name}') 
					AND col.name = '{$column_name}'
					AND dobj.name IS NOT NULL";
					$result = $this->db->sql_query($sql);
					$row = $this->db->sql_fetchrow($result);
					$this->db->sql_freeresult($result);

					if ($row)
					{
						$statements[] = 'ALTER TABLE [' . $table_name . '] DROP CONSTRAINT [' . $row['def_name'] . ']';
					}
				}

				$statements[] = 'ALTER TABLE [' . $table_name . '] DROP COLUMN [' . $column_name . ']';
			break;

			case 'mysql_40':
			case 'mysql_41':
				$statements[] = 'ALTER TABLE `' . $table_name . '` DROP COLUMN `' . $column_name . '`';
			break;

			case 'oracle':
				$statements[] = 'ALTER TABLE ' . $table_name . ' DROP COLUMN ' . $column_name;
			break;

			case 'postgres':
				$statements[] = 'ALTER TABLE ' . $table_name . ' DROP COLUMN "' . $column_name . '"';
			break;

			case 'sqlite':

				if ($inline && $this->return_statements)
				{
					return $column_name;
				}

				if (version_compare(sqlite_libversion(), '3.0') == -1)
				{
					$sql = "SELECT sql
						FROM sqlite_master
						WHERE type = 'table'
							AND name = '{$table_name}'
						ORDER BY type DESC, name;";
					$result = $this->db->sql_query($sql);

					if (!$result)
					{
						break;
					}

					$row = $this->db->sql_fetchrow($result);
					$this->db->sql_freeresult($result);

					$statements[] = 'begin';

					// Create a backup table and populate it, destroy the existing one
					$statements[] = preg_replace('#CREATE\s+TABLE\s+"?' . $table_name . '"?#i', 'CREATE TEMPORARY TABLE ' . $table_name . '_temp', $row['sql']);
					$statements[] = 'INSERT INTO ' . $table_name . '_temp SELECT * FROM ' . $table_name;
					$statements[] = 'DROP TABLE ' . $table_name;

					preg_match('#\((.*)\)#s', $row['sql'], $matches);

					$new_table_cols = trim($matches[1]);
					$old_table_cols = preg_split('/,(?![\s\w]+\))/m', $new_table_cols);
					$column_list = array();

					foreach ($old_table_cols as $declaration)
					{
						$entities = preg_split('#\s+#', trim($declaration));
						if ($entities[0] == 'PRIMARY' || $entities[0] === $column_name)
						{
							continue;
						}
						$column_list[] = $entities[0];
					}

					$columns = implode(',', $column_list);

					$new_table_cols = preg_replace('/' . $column_name . '[^,]+(?:,|$)/m', '', $new_table_cols);

					// create a new table and fill it up. destroy the temp one
					$statements[] = 'CREATE TABLE ' . $table_name . ' (' . $new_table_cols . ');';
					$statements[] = 'INSERT INTO ' . $table_name . ' (' . $columns . ') SELECT ' . $columns . ' FROM ' . $table_name . '_temp;';
					$statements[] = 'DROP TABLE ' . $table_name . '_temp';

					$statements[] = 'commit';
				}
				else
				{
					$statements[] = 'ALTER TABLE ' . $table_name . ' DROP COLUMN ' . $column_name;
				}
			break;
		}

		return $this->_sql_run_sql($statements);
	}

	/**
	* Drop Index
	*/
	function sql_index_drop($table_name, $index_name)
	{
		$statements = array();

		switch ($this->sql_layer)
		{
			case 'mssql':
			case 'mssqlnative':
				$statements[] = 'DROP INDEX ' . $table_name . '.' . $index_name;
			break;

			case 'mysql_40':
			case 'mysql_41':
				$statements[] = 'DROP INDEX ' . $index_name . ' ON ' . $table_name;
			break;

			case 'firebird':
			case 'oracle':
			case 'postgres':
			case 'sqlite':
				$statements[] = 'DROP INDEX ' . $table_name . '_' . $index_name;
			break;
		}

		return $this->_sql_run_sql($statements);
	}

	/**
	* Drop Table
	*/
	function sql_table_drop($table_name)
	{
		$statements = array();

		if (!$this->sql_table_exists($table_name))
		{
			return $this->_sql_run_sql($statements);
		}

		// the most basic operation, get rid of the table
		$statements[] = 'DROP TABLE ' . $table_name;

		switch ($this->sql_layer)
		{
			case 'firebird':
				$sql = 'SELECT RDB$GENERATOR_NAME as gen
					FROM RDB$GENERATORS
					WHERE RDB$SYSTEM_FLAG = 0
						AND RDB$GENERATOR_NAME = \'' . strtoupper($table_name) . "_GEN'";
				$result = $this->db->sql_query($sql);

				// does a generator exist?
				if ($row = $this->db->sql_fetchrow($result))
				{
					$statements[] = "DROP GENERATOR {$row['gen']};";
				}
				$this->db->sql_freeresult($result);
			break;

			case 'oracle':
				$sql = 'SELECT A.REFERENCED_NAME
					FROM USER_DEPENDENCIES A, USER_TRIGGERS B
					WHERE A.REFERENCED_TYPE = \'SEQUENCE\'
						AND A.NAME = B.TRIGGER_NAME
						AND B.TABLE_NAME = \'' . strtoupper($table_name) . "'";
				$result = $this->db->sql_query($sql);

				// any sequences ref'd to this table's triggers?
				while ($row = $this->db->sql_fetchrow($result))
				{
					$statements[] = "DROP SEQUENCE {$row['referenced_name']}";
				}
				$this->db->sql_freeresult($result);
			break;

			case 'postgres':
				// PGSQL does not "tightly" bind sequences and tables, we must guess...
				$sql = "SELECT relname
					FROM pg_class
					WHERE relkind = 'S'
						AND relname = '{$table_name}_seq'";
				$result = $this->db->sql_query($sql);

				// We don't even care about storing the results. We already know the answer if we get rows back.
				if ($this->db->sql_fetchrow($result))
				{
					$statements[] =  "DROP SEQUENCE {$table_name}_seq;\n";
				}
				$this->db->sql_freeresult($result);
			break;
		}

		return $this->_sql_run_sql($statements);
	}

	/**
	* Add primary key
	*/
	function sql_create_primary_key($table_name, $column, $inline = false)
	{
		$statements = array();

		switch ($this->sql_layer)
		{
			case 'firebird':
			case 'postgres':
			case 'mysql_40':
			case 'mysql_41':
				$statements[] = 'ALTER TABLE ' . $table_name . ' ADD PRIMARY KEY (' . implode(', ', $column) . ')';
			break;

			case 'mssql':
			case 'mssqlnative':
				$sql = "ALTER TABLE [{$table_name}] WITH NOCHECK ADD ";
				$sql .= "CONSTRAINT [PK_{$table_name}] PRIMARY KEY  CLUSTERED (";
				$sql .= '[' . implode("],\n\t\t[", $column) . ']';
				$sql .= ')';

				$statements[] = $sql;
			break;

			case 'oracle':
				$statements[] = 'ALTER TABLE ' . $table_name . 'add CONSTRAINT pk_' . $table_name . ' PRIMARY KEY (' . implode(', ', $column) . ')';
			break;

			case 'sqlite':

				if ($inline && $this->return_statements)
				{
					return $column;
				}

				$sql = "SELECT sql
					FROM sqlite_master
					WHERE type = 'table'
						AND name = '{$table_name}'
					ORDER BY type DESC, name;";
				$result = $this->db->sql_query($sql);

				if (!$result)
				{
					break;
				}

				$row = $this->db->sql_fetchrow($result);
				$this->db->sql_freeresult($result);

				$statements[] = 'begin';

				// Create a backup table and populate it, destroy the existing one
				$statements[] = preg_replace('#CREATE\s+TABLE\s+"?' . $table_name . '"?#i', 'CREATE TEMPORARY TABLE ' . $table_name . '_temp', $row['sql']);
				$statements[] = 'INSERT INTO ' . $table_name . '_temp SELECT * FROM ' . $table_name;
				$statements[] = 'DROP TABLE ' . $table_name;

				preg_match('#\((.*)\)#s', $row['sql'], $matches);

				$new_table_cols = trim($matches[1]);
				$old_table_cols = preg_split('/,(?![\s\w]+\))/m', $new_table_cols);
				$column_list = array();

				foreach ($old_table_cols as $declaration)
				{
					$entities = preg_split('#\s+#', trim($declaration));
					if ($entities[0] == 'PRIMARY')
					{
						continue;
					}
					$column_list[] = $entities[0];
				}

				$columns = implode(',', $column_list);

				// create a new table and fill it up. destroy the temp one
				$statements[] = 'CREATE TABLE ' . $table_name . ' (' . $new_table_cols . ', PRIMARY KEY (' . implode(', ', $column) . '));';
				$statements[] = 'INSERT INTO ' . $table_name . ' (' . $columns . ') SELECT ' . $columns . ' FROM ' . $table_name . '_temp;';
				$statements[] = 'DROP TABLE ' . $table_name . '_temp';

				$statements[] = 'commit';
			break;
		}

		return $this->_sql_run_sql($statements);
	}

	/**
	* Add unique index
	*/
	function sql_create_unique_index($table_name, $index_name, $column)
	{
		$statements = array();

		$table_prefix = substr(CONFIG_TABLE, 0, -6); // strlen(config)
		if (strlen($table_name . $index_name) - strlen($table_prefix) > 24)
		{
			$max_length = strlen($table_prefix) + 24;
			trigger_error("Index name '{$table_name}_$index_name' on table '$table_name' is too long. The maximum is $max_length characters.", E_USER_ERROR);
		}

		switch ($this->sql_layer)
		{
			case 'firebird':
			case 'postgres':
			case 'oracle':
			case 'sqlite':
				$statements[] = 'CREATE UNIQUE INDEX ' . $table_name . '_' . $index_name . ' ON ' . $table_name . '(' . implode(', ', $column) . ')';
			break;

			case 'mysql_40':
			case 'mysql_41':
				$statements[] = 'ALTER TABLE ' . $table_name . ' ADD UNIQUE INDEX ' . $index_name . '(' . implode(', ', $column) . ')';
			break;

			case 'mssql':
			case 'mssqlnative':
				$statements[] = 'CREATE UNIQUE INDEX [' . $index_name . '] ON [' . $table_name . ']([' . implode('], [', $column) . '])';
			break;
		}

		return $this->_sql_run_sql($statements);
	}

	/**
	* Add index
	*/
	function sql_create_index($table_name, $index_name, $column)
	{
		$statements = array();

		$table_prefix = substr(CONFIG_TABLE, 0, -6); // strlen(config)
		if (strlen($table_name . $index_name) - strlen($table_prefix) > 24)
		{
			$max_length = strlen($table_prefix) + 24;
			trigger_error("Index name '{$table_name}_$index_name' on table '$table_name' is too long. The maximum is $max_length characters.", E_USER_ERROR);
		}

		// remove index length unless MySQL4
		if ('mysql_40' != $this->sql_layer)
		{
			$column = preg_replace('#:.*$#', '', $column);
		}

		switch ($this->sql_layer)
		{
			case 'firebird':
			case 'postgres':
			case 'oracle':
			case 'sqlite':
				$statements[] = 'CREATE INDEX ' . $table_name . '_' . $index_name . ' ON ' . $table_name . '(' . implode(', ', $column) . ')';
			break;

			case 'mysql_40':
				// add index size to definition as required by MySQL4
				foreach ($column as $i => $col)
				{
					if (false !== strpos($col, ':'))
					{
						list($col, $index_size) = explode(':', $col);
						$column[$i] = "$col($index_size)";
					}
				}
			// no break
			case 'mysql_41':
				$statements[] = 'ALTER TABLE ' . $table_name . ' ADD INDEX ' . $index_name . '(' . implode(', ', $column) . ')';
			break;

			case 'mssql':
			case 'mssqlnative':
				$statements[] = 'CREATE INDEX [' . $index_name . '] ON [' . $table_name . ']([' . implode('], [', $column) . '])';
			break;
		}

		return $this->_sql_run_sql($statements);
	}

	/**
	* List all of the indices that belong to a table,
	* does not count:
	* * UNIQUE indices
	* * PRIMARY keys
	*/
	function sql_list_index($table_name)
	{
		$index_array = array();

		if ($this->sql_layer == 'mssql' || $this->sql_layer == 'mssqlnative')
		{
			$sql = "EXEC sp_statistics '$table_name'";
			$result = $this->db->sql_query($sql);
			while ($row = $this->db->sql_fetchrow($result))
			{
				if ($row['TYPE'] == 3)
				{
					$index_array[] = $row['INDEX_NAME'];
				}
			}
			$this->db->sql_freeresult($result);
		}
		else
		{
			switch ($this->sql_layer)
			{
				case 'firebird':
					$sql = "SELECT LOWER(RDB\$INDEX_NAME) as index_name
						FROM RDB\$INDICES
						WHERE RDB\$RELATION_NAME = '" . strtoupper($table_name) . "'
							AND RDB\$UNIQUE_FLAG IS NULL
							AND RDB\$FOREIGN_KEY IS NULL";
					$col = 'index_name';
				break;

				case 'postgres':
					$sql = "SELECT ic.relname as index_name
						FROM pg_class bc, pg_class ic, pg_index i
						WHERE (bc.oid = i.indrelid)
							AND (ic.oid = i.indexrelid)
							AND (bc.relname = '" . $table_name . "')
							AND (i.indisunique != 't')
							AND (i.indisprimary != 't')";
					$col = 'index_name';
				break;

				case 'mysql_40':
				case 'mysql_41':
					$sql = 'SHOW KEYS
						FROM ' . $table_name;
					$col = 'Key_name';
				break;

				case 'oracle':
					$sql = "SELECT index_name
						FROM user_indexes
						WHERE table_name = '" . strtoupper($table_name) . "'
							AND generated = 'N'
							AND uniqueness = 'NONUNIQUE'";
					$col = 'index_name';
				break;

				case 'sqlite':
					$sql = "PRAGMA index_info('" . $table_name . "');";
					$col = 'name';
				break;
			}

			$result = $this->db->sql_query($sql);
			while ($row = $this->db->sql_fetchrow($result))
			{
				if (($this->sql_layer == 'mysql_40' || $this->sql_layer == 'mysql_41') && !$row['Non_unique'])
				{
					continue;
				}

				switch ($this->sql_layer)
				{
					case 'firebird':
					case 'oracle':
					case 'postgres':
					case 'sqlite':
						$row[$col] = substr($row[$col], strlen($table_name) + 1);
					break;
				}

				$index_array[] = $row[$col];
			}
			$this->db->sql_freeresult($result);
		}

		return array_map('strtolower', $index_array);
	}

	/**
	* Change column type (not name!)
	*/
	function sql_column_change($table_name, $column_name, $column_data, $inline = false)
	{
		$column_data = $this->sql_prepare_column_data($table_name, $column_name, $column_data);
		$statements = array();

		switch ($this->sql_layer)
		{
			case 'firebird':
				// Change type...
				if (!empty($column_data['column_type_sql_default']))
				{
					$statements[] = 'ALTER TABLE ' . $table_name . ' ALTER COLUMN "' . strtoupper($column_name) . '" TYPE ' . ' ' . $column_data['column_type_sql_type'];
					$statements[] = 'ALTER TABLE ' . $table_name . ' ALTER COLUMN "' . strtoupper($column_name) . '" SET DEFAULT ' . ' ' . $column_data['column_type_sql_default'];
				}
				else
				{
					// TODO: try to change pkey without removing trigger, generator or constraints. ATM this query may fail.
					$statements[] = 'ALTER TABLE ' . $table_name . ' ALTER COLUMN "' . strtoupper($column_name) . '" TYPE ' . ' ' . $column_data['column_type_sql_type'];
				}
			break;

			case 'mssql':
			case 'mssqlnative':
				$statements[] = 'ALTER TABLE [' . $table_name . '] ALTER COLUMN [' . $column_name . '] ' . $column_data['column_type_sql'];

				if (!empty($column_data['default']))
				{
					$sql = "SELECT CAST(SERVERPROPERTY('productversion') AS VARCHAR(25)) AS mssql_version";
					$result = $this->db->sql_query($sql);
					$row = $this->db->sql_fetchrow($result);
					$this->db->sql_freeresult($result);

					// Using TRANSACT-SQL for this statement because we do not want to have colliding data if statements are executed at a later stage
					if ($row['mssql_version'][0] == '8')	// SQL Server 2000
					{
						$statements[] = "DECLARE @drop_default_name VARCHAR(100), @cmd VARCHAR(1000)
							SET @drop_default_name =
								(SELECT so.name FROM sysobjects so
								JOIN sysconstraints sc ON so.id = sc.constid
								WHERE object_name(so.parent_obj) = '{$table_name}'
									AND so.xtype = 'D'
									AND sc.colid = (SELECT colid FROM syscolumns
										WHERE id = object_id('{$table_name}')
											AND name = '{$column_name}'))
							IF @drop_default_name <> ''
							BEGIN
								SET @cmd = 'ALTER TABLE [{$table_name}] DROP CONSTRAINT [' + @drop_default_name + ']'
								EXEC(@cmd)
							END
							SET @cmd = 'ALTER TABLE [{$table_name}] ADD CONSTRAINT [DF_{$table_name}_{$column_name}_1] {$column_data['default']} FOR [{$column_name}]'
							EXEC(@cmd)";
					}
					else
					{
						$statements[] = "DECLARE @drop_default_name VARCHAR(100), @cmd VARCHAR(1000)
							SET @drop_default_name =
								(SELECT dobj.name FROM sys.columns col 
									LEFT OUTER JOIN sys.objects dobj ON (dobj.object_id = col.default_object_id AND dobj.type = 'D')
								WHERE col.object_id = object_id('{$table_name}') 
								AND col.name = '{$column_name}'
								AND dobj.name IS NOT NULL)
							IF @drop_default_name <> ''
							BEGIN
								SET @cmd = 'ALTER TABLE [{$table_name}] DROP CONSTRAINT [' + @drop_default_name + ']'
								EXEC(@cmd)
							END
							SET @cmd = 'ALTER TABLE [{$table_name}] ADD CONSTRAINT [DF_{$table_name}_{$column_name}_1] {$column_data['default']} FOR [{$column_name}]'
							EXEC(@cmd)";
					}
				}
			break;

			case 'mysql_40':
			case 'mysql_41':
				$statements[] = 'ALTER TABLE `' . $table_name . '` CHANGE `' . $column_name . '` `' . $column_name . '` ' . $column_data['column_type_sql'];
			break;

			case 'oracle':
				$statements[] = 'ALTER TABLE ' . $table_name . ' MODIFY ' . $column_name . ' ' . $column_data['column_type_sql'];
			break;

			case 'postgres':
				$sql = 'ALTER TABLE ' . $table_name . ' ';

				$sql_array = array();
				$sql_array[] = 'ALTER COLUMN ' . $column_name . ' TYPE ' . $column_data['column_type'];

				if (isset($column_data['null']))
				{
					if ($column_data['null'] == 'NOT NULL')
					{
						$sql_array[] = 'ALTER COLUMN ' . $column_name . ' SET NOT NULL';
					}
					else if ($column_data['null'] == 'NULL')
					{
						$sql_array[] = 'ALTER COLUMN ' . $column_name . ' DROP NOT NULL';
					}
				}

				if (isset($column_data['default']))
				{
					$sql_array[] = 'ALTER COLUMN ' . $column_name . ' SET DEFAULT ' . $column_data['default'];
				}

				// we don't want to double up on constraints if we change different number data types
				if (isset($column_data['constraint']))
				{
					$constraint_sql = "SELECT consrc as constraint_data
								FROM pg_constraint, pg_class bc
								WHERE conrelid = bc.oid
									AND bc.relname = '{$table_name}'
									AND NOT EXISTS (
										SELECT *
											FROM pg_constraint as c, pg_inherits as i
											WHERE i.inhrelid = pg_constraint.conrelid
												AND c.conname = pg_constraint.conname
												AND c.consrc = pg_constraint.consrc
												AND c.conrelid = i.inhparent
									)";

					$constraint_exists = false;

					$result = $this->db->sql_query($constraint_sql);
					while ($row = $this->db->sql_fetchrow($result))
					{
						if (trim($row['constraint_data']) == trim($column_data['constraint']))
						{
							$constraint_exists = true;
							break;
						}
					}
					$this->db->sql_freeresult($result);

					if (!$constraint_exists)
					{
						$sql_array[] = 'ADD ' . $column_data['constraint'];
					}
				}

				$sql .= implode(', ', $sql_array);

				$statements[] = $sql;
			break;

			case 'sqlite':

				if ($inline && $this->return_statements)
				{
					return $column_name . ' ' . $column_data['column_type_sql'];
				}

				$sql = "SELECT sql
					FROM sqlite_master
					WHERE type = 'table'
						AND name = '{$table_name}'
					ORDER BY type DESC, name;";
				$result = $this->db->sql_query($sql);

				if (!$result)
				{
					break;
				}

				$row = $this->db->sql_fetchrow($result);
				$this->db->sql_freeresult($result);

				$statements[] = 'begin';

				// Create a temp table and populate it, destroy the existing one
				$statements[] = preg_replace('#CREATE\s+TABLE\s+"?' . $table_name . '"?#i', 'CREATE TEMPORARY TABLE ' . $table_name . '_temp', $row['sql']);
				$statements[] = 'INSERT INTO ' . $table_name . '_temp SELECT * FROM ' . $table_name;
				$statements[] = 'DROP TABLE ' . $table_name;

				preg_match('#\((.*)\)#s', $row['sql'], $matches);

				$new_table_cols = trim($matches[1]);
				$old_table_cols = preg_split('/,(?![\s\w]+\))/m', $new_table_cols);
				$column_list = array();

				foreach ($old_table_cols as $key => $declaration)
				{
					$entities = preg_split('#\s+#', trim($declaration));
					$column_list[] = $entities[0];
					if ($entities[0] == $column_name)
					{
						$old_table_cols[$key] = $column_name . ' ' . $column_data['column_type_sql'];
					}
				}

				$columns = implode(',', $column_list);

				// create a new table and fill it up. destroy the temp one
				$statements[] = 'CREATE TABLE ' . $table_name . ' (' . implode(',', $old_table_cols) . ');';
				$statements[] = 'INSERT INTO ' . $table_name . ' (' . $columns . ') SELECT ' . $columns . ' FROM ' . $table_name . '_temp;';
				$statements[] = 'DROP TABLE ' . $table_name . '_temp';

				$statements[] = 'commit';

			break;
		}

		return $this->_sql_run_sql($statements);
	}
}