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    Current File : /home/m/e/h/meharicl/www/portail/db/db_tools.php

    <?php
    /**
    *
    * @package dbal
    * @version $Id$
    * @copyright (c) 2007 phpBB Group
    * @license http://opensource.org/licenses/gpl-license.php GNU Public License
    *
    */
    
    /**
    * @ignore
    */
    if (!defined('IN_PHPBB'))
    {
    	exit;
    }
    
    /**
    * Database Tools for handling cross-db actions such as altering columns, etc.
    * Currently not supported is returning SQL for creating tables.
    *
    * @package dbal
    * @note currently not used within phpBB3, but may be utilized later.
    */
    class phpbb_db_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(
    		'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)',
    		),
    
    		'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', '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_dbal	$db					DBAL object
    	* @param bool		$return_statements	True if only statements should be returned and no SQL being executed
    	*/
    	function phpbb_db_tools(&$db, $return_statements = false)
    	{
    		$this->db = $db;
    		$this->return_statements = $return_statements;
    
    		// 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;
    
    			default:
    				$this->sql_layer = $this->db->sql_layer;
    			break;
    		}
    	}
    
    	/**
    	* 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 must be created with TEXTIMAGE
    		$create_textimage = false;
    
    		// Determine if the table requires a sequence
    		$create_sequence = false;
    
    		// Begin table sql statement
    		switch ($this->sql_layer)
    		{
    			case 'mssql':
    				$table_sql = 'CREATE TABLE [' . $table_name . '] (' . "\n";
    			break;
    
    			default:
    				$table_sql = 'CREATE TABLE ' . $table_name . ' (' . "\n";
    			break;
    		}
    
    		// 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);
    
    			// here we add the definition of the new column to the list of columns
    			switch ($this->sql_layer)
    			{
    				case 'mssql':
    					$columns[] = "\t [{$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 textimage DDL based off of the existance of certain column types
    			if (!$create_textimage)
    			{
    				$create_textimage = isset($prepared_column['textimage']) && $prepared_column['textimage'];
    			}
    
    			// 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':
    				$table_sql .= "\n);";
    				$statements[] = $table_sql;
    			break;
    
    			case 'mssql':
    				$table_sql .= "\n) ON [PRIMARY]" . (($create_textimage) ? ' TEXTIMAGE_ON [PRIMARY]' : '');
    				$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':
    						// 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)
    				{
    					$statements[] = "CREATE SEQUENCE {$table_name}_seq;";
    				}
    			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
    	*	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
    	*
    	* 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;
    		}
    
    		// 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 => $column_data)
    				{
    					// Only add the column if it does not exist yet, else change it (to be consistent)
    					if ($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);
    					}
    				}
    			}
    		}
    
    		// Remove keys?
    		if (!empty($schema_changes['drop_keys']))
    		{
    			foreach ($schema_changes['drop_keys'] as $table => $indexes)
    			{
    				foreach ($indexes as $index_name)
    				{
    					$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)
    				{
    					$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)
    				{
    					$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;
    		}
    	}
    
    	/**
    	* Check if a specified column exist
    	*
    	* @param string	$table			Table to check the column at
    	* @param string	$column_name	The column to check
    	*
    	* @return bool True if column exists, else false
    	*/
    	function sql_column_exists($table, $column_name)
    	{
    		switch ($this->sql_layer)
    		{
    			case 'mysql_40':
    			case 'mysql_41':
    
    				$sql = "SHOW COLUMNS FROM $table";
    				$result = $this->db->sql_query($sql);
    
    				while ($row = $this->db->sql_fetchrow($result))
    				{
    					// lower case just in case
    					if (strtolower($row['Field']) == $column_name)
    					{
    						$this->db->sql_freeresult($result);
    						return true;
    					}
    				}
    				$this->db->sql_freeresult($result);
    				return false;
    			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";
    				$result = $this->db->sql_query($sql);
    				while ($row = $this->db->sql_fetchrow($result))
    				{
    					// lower case just in case
    					if (strtolower($row['attname']) == $column_name)
    					{
    						$this->db->sql_freeresult($result);
    						return true;
    					}
    				}
    				$this->db->sql_freeresult($result);
    
    				return false;
    			break;
    
    			// same deal with PostgreSQL, we must perform more complex operations than
    			// we technically could
    			case 'mssql':
    				$sql = "SELECT c.name
    					FROM syscolumns c
    					LEFT JOIN sysobjects o ON c.id = o.id
    					WHERE o.name = '{$table}'";
    				$result = $this->db->sql_query($sql);
    				while ($row = $this->db->sql_fetchrow($result))
    				{
    					// lower case just in case
    					if (strtolower($row['name']) == $column_name)
    					{
    						$this->db->sql_freeresult($result);
    						return true;
    					}
    				}
    				$this->db->sql_freeresult($result);
    				return false;
    			break;
    
    			case 'oracle':
    				$sql = "SELECT column_name
    					FROM user_tab_columns
    					WHERE LOWER(table_name) = '" . strtolower($table) . "'";
    				$result = $this->db->sql_query($sql);
    				while ($row = $this->db->sql_fetchrow($result))
    				{
    					// lower case just in case
    					if (strtolower($row['column_name']) == $column_name)
    					{
    						$this->db->sql_freeresult($result);
    						return true;
    					}
    				}
    				$this->db->sql_freeresult($result);
    				return false;
    			break;
    
    			case 'firebird':
    				$sql = "SELECT RDB\$FIELD_NAME as FNAME
    					FROM RDB\$RELATION_FIELDS
    					WHERE RDB\$RELATION_NAME = '" . strtoupper($table) . "'";
    				$result = $this->db->sql_query($sql);
    				while ($row = $this->db->sql_fetchrow($result))
    				{
    					// lower case just in case
    					if (strtolower($row['fname']) == $column_name)
    					{
    						$this->db->sql_freeresult($result);
    						return true;
    					}
    				}
    				$this->db->sql_freeresult($result);
    				return false;
    			break;
    
    			// ugh, SQLite
    			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;
    					}
    
    					if (strtolower($entities[0]) == $column_name)
    					{
    						return true;
    					}
    				}
    				return false;
    			break;
    		}
    	}
    
    	/**
    	* 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, $column_data)
    	{
    		// Get type
    		if (strpos($column_data[0], ':') !== false)
    		{
    			list($orig_column_type, $column_length) = explode(':', $column_data[0]);
    			if (!is_array($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_data[0];
    			$column_type = $this->dbms_type_map[$this->sql_layer][$column_data[0]];
    		}
    
    		// Adjust default value if db-dependant 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':
    				$sql .= " {$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;
    	}
    
    	/**
    	* 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':
    				$statements[] = 'ALTER TABLE ' . $table_name . ' ADD "' . strtoupper($column_name) . '" ' . $column_data['column_type_sql'];
    			break;
    
    			case 'mssql':
    				$statements[] = 'ALTER TABLE [' . $table_name . '] ADD [' . $column_name . '] ' . $column_data['column_type_sql_default'];
    			break;
    
    			case 'mysql_40':
    			case 'mysql_41':
    				$statements[] = 'ALTER TABLE `' . $table_name . '` ADD COLUMN `' . $column_name . '` ' . $column_data['column_type_sql'];
    			break;
    
    			case 'oracle':
    				$statements[] = 'ALTER TABLE ' . $table_name . ' ADD ' . $column_name . ' ' . $column_data['column_type_sql'];
    			break;
    
    			case 'postgres':
    				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':
    				$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_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':
    				$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);
    
    			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':
    				$sql = "ALTER TABLE [{$table_name}] WITH NOCHECK ADD ";
    				$sql .= "CONSTRAINT [PK_{$table_name}] PRIMARY KEY  CLUSTERED (";
    				$sql .= '[' . implode("],\n\t\t[", $column) . ']';
    				$sql .= ') ON [PRIMARY]';
    
    				$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();
    
    		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[] = 'CREATE UNIQUE INDEX ' . $index_name . ' ON ' . $table_name . '(' . implode(', ', $column) . ')';
    			break;
    
    			case 'mssql':
    				$statements[] = 'CREATE UNIQUE INDEX ' . $index_name . ' ON ' . $table_name . '(' . implode(', ', $column) . ') ON [PRIMARY]';
    			break;
    		}
    
    		return $this->_sql_run_sql($statements);
    	}
    
    	/**
    	* Add index
    	*/
    	function sql_create_index($table_name, $index_name, $column)
    	{
    		$statements = array();
    
    		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':
    			case 'mysql_41':
    				$statements[] = 'CREATE INDEX ' . $index_name . ' ON ' . $table_name . '(' . implode(', ', $column) . ')';
    			break;
    
    			case 'mssql':
    				$statements[] = 'CREATE INDEX ' . $index_name . ' ON ' . $table_name . '(' . implode(', ', $column) . ') ON [PRIMARY]';
    			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')
    		{
    			$sql = "EXEC sp_statistics '$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
    				{
    					$statements[] = 'ALTER TABLE ' . $table_name . ' ALTER COLUMN "' . strtoupper($column_name) . '" TYPE ' . ' ' . $column_data['column_type_sql_type'];
    				}
    			break;
    
    			case 'mssql':
    				$statements[] = 'ALTER TABLE [' . $table_name . '] ALTER COLUMN [' . $column_name . '] ' . $column_data['column_type_sql'];
    
    				if (!empty($column_data['default']))
    				{
    					// Using TRANSACT-SQL for this statement because we do not want to have colliding data if statements are executed at a later stage
    					$statements[] = "DECLARE @drop_default_name VARCHAR(100), @cmd VARCHAR(1000)
    						SET @drop_default_name =
    							(SELECT so.name FROM sysobjects so
    							JOIN sysconstraints sc ON so.id = sc.constid
    							WHERE object_name(so.parent_obj) = '{$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)";
    				}
    			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);
    	}
    }
    
    ?>