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<?php
/**
 * CodeIgniter
 *
 * An open source application development framework for PHP
 *
 * This content is released under the MIT License (MIT)
 *
 * Copyright (c) 2014 - 2019, British Columbia Institute of Technology
 *
 * Permission is hereby granted, free of charge, to any person obtaining a copy
 * of this software and associated documentation files (the "Software"), to deal
 * in the Software without restriction, including without limitation the rights
 * to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
 * copies of the Software, and to permit persons to whom the Software is
 * furnished to do so, subject to the following conditions:
 *
 * The above copyright notice and this permission notice shall be included in
 * all copies or substantial portions of the Software.
 *
 * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
 * IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
 * FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
 * AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
 * LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
 * OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN
 * THE SOFTWARE.
 *
 * @package	CodeIgniter
 * @author	EllisLab Dev Team
 * @copyright	Copyright (c) 2008 - 2014, EllisLab, Inc. (https://ellislab.com/)
 * @copyright	Copyright (c) 2014 - 2019, British Columbia Institute of Technology (https://bcit.ca/)
 * @license	https://opensource.org/licenses/MIT	MIT License
 * @link	https://codeigniter.com
 * @since	Version 1.0.0
 * @filesource
 */
defined('BASEPATH') OR exit('No direct script access allowed');

/**
 * Database Forge Class
 *
 * @category	Database
 * @author		EllisLab Dev Team
 * @link		https://codeigniter.com/user_guide/database/
 */
abstract class CI_DB_forge {

/**
	 * Database object
	 *
	 * @var	object
	 */
	protected $db;

/**
	 * Fields data
	 *
	 * @var	array
	 */
	public $fields		= array();

/**
	 * Keys data
	 *
	 * @var	array
	 */
	public $keys		= array();

/**
	 * Primary Keys data
	 *
	 * @var	array
	 */
	public $primary_keys	= array();

/**
	 * Database character set
	 *
	 * @var	string
	 */
	public $db_char_set	= '';

// --------------------------------------------------------------------

/**
	 * CREATE DATABASE statement
	 *
	 * @var	string
	 */
	protected $_create_database	= 'CREATE DATABASE %s';

/**
	 * DROP DATABASE statement
	 *
	 * @var	string
	 */
	protected $_drop_database	= 'DROP DATABASE %s';

/**
	 * CREATE TABLE statement
	 *
	 * @var	string
	 */
	protected $_create_table	= "%s %s (%s\n)";

/**
	 * CREATE TABLE IF statement
	 *
	 * @var	string
	 */
	protected $_create_table_if	= 'CREATE TABLE IF NOT EXISTS';

/**
	 * CREATE TABLE keys flag
	 *
	 * Whether table keys are created from within the
	 * CREATE TABLE statement.
	 *
	 * @var	bool
	 */
	protected $_create_table_keys	= FALSE;

/**
	 * DROP TABLE IF EXISTS statement
	 *
	 * @var	string
	 */
	protected $_drop_table_if	= 'DROP TABLE IF EXISTS';

/**
	 * RENAME TABLE statement
	 *
	 * @var	string
	 */
	protected $_rename_table	= 'ALTER TABLE %s RENAME TO %s;';

/**
	 * UNSIGNED support
	 *
	 * @var	bool|array
	 */
	protected $_unsigned		= TRUE;

/**
	 * NULL value representation in CREATE/ALTER TABLE statements
	 *
	 * @var	string
	 */
	protected $_null		= '';

/**
	 * DEFAULT value representation in CREATE/ALTER TABLE statements
	 *
	 * @var	string
	 */
	protected $_default		= ' DEFAULT ';

// --------------------------------------------------------------------

/**
	 * Class constructor
	 *
	 * @param	object	&$db	Database object
	 * @return	void
	 */
	public function __construct(&$db)
	{
		$this->db =& $db;
		log_message('info', 'Database Forge Class Initialized');
	}

// --------------------------------------------------------------------

/**
	 * Create database
	 *
	 * @param	string	$db_name
	 * @return	bool
	 */
	public function create_database($db_name)
	{
		if ($this->_create_database === FALSE)
		{
			return ($this->db->db_debug) ? $this->db->display_error('db_unsupported_feature') : FALSE;
		}
		elseif ( ! $this->db->query(sprintf($this->_create_database, $this->db->escape_identifiers($db_name), $this->db->char_set, $this->db->dbcollat)))
		{
			return ($this->db->db_debug) ? $this->db->display_error('db_unable_to_drop') : FALSE;
		}

if ( ! empty($this->db->data_cache['db_names']))
		{
			$this->db->data_cache['db_names'][] = $db_name;
		}

return TRUE;
	}

// --------------------------------------------------------------------

/**
	 * Drop database
	 *
	 * @param	string	$db_name
	 * @return	bool
	 */
	public function drop_database($db_name)
	{
		if ($this->_drop_database === FALSE)
		{
			return ($this->db->db_debug) ? $this->db->display_error('db_unsupported_feature') : FALSE;
		}
		elseif ( ! $this->db->query(sprintf($this->_drop_database, $this->db->escape_identifiers($db_name))))
		{
			return ($this->db->db_debug) ? $this->db->display_error('db_unable_to_drop') : FALSE;
		}

if ( ! empty($this->db->data_cache['db_names']))
		{
			$key = array_search(strtolower($db_name), array_map('strtolower', $this->db->data_cache['db_names']), TRUE);
			if ($key !== FALSE)
			{
				unset($this->db->data_cache['db_names'][$key]);
			}
		}

return TRUE;
	}

// --------------------------------------------------------------------

/**
	 * Add Key
	 *
	 * @param	string	$key
	 * @param	bool	$primary
	 * @return	CI_DB_forge
	 */
	public function add_key($key, $primary = FALSE)
	{
		// DO NOT change this! This condition is only applicable
		// for PRIMARY keys because you can only have one such,
		// and therefore all fields you add to it will be included
		// in the same, composite PRIMARY KEY.
		//
		// It's not the same for regular indexes.
		if ($primary === TRUE && is_array($key))
		{
			foreach ($key as $one)
			{
				$this->add_key($one, $primary);
			}

return $this;
		}

if ($primary === TRUE)
		{
			$this->primary_keys[] = $key;
		}
		else
		{
			$this->keys[] = $key;
		}

return $this;
	}

// --------------------------------------------------------------------

/**
	 * Add Field
	 *
	 * @param	array	$field
	 * @return	CI_DB_forge
	 */
	public function add_field($field)
	{
		if (is_string($field))
		{
			if ($field === 'id')
			{
				$this->add_field(array(
					'id' => array(
						'type' => 'INT',
						'constraint' => 9,
						'auto_increment' => TRUE
					)
				));
				$this->add_key('id', TRUE);
			}
			else
			{
				if (strpos($field, ' ') === FALSE)
				{
					show_error('Field information is required for that operation.');
				}

$this->fields[] = $field;
			}
		}

if (is_array($field))
		{
			$this->fields = array_merge($this->fields, $field);
		}

return $this;
	}

// --------------------------------------------------------------------

/**
	 * Create Table
	 *
	 * @param	string	$table		Table name
	 * @param	bool	$if_not_exists	Whether to add IF NOT EXISTS condition
	 * @param	array	$attributes	Associative array of table attributes
	 * @return	bool
	 */
	public function create_table($table, $if_not_exists = FALSE, array $attributes = array())
	{
		if ($table === '')
		{
			show_error('A table name is required for that operation.');
		}
		else
		{
			$table = $this->db->dbprefix.$table;
		}

if (count($this->fields) === 0)
		{
			show_error('Field information is required.');
		}

$sql = $this->_create_table($table, $if_not_exists, $attributes);

if (is_bool($sql))
		{
			$this->_reset();
			if ($sql === FALSE)
			{
				return ($this->db->db_debug) ? $this->db->display_error('db_unsupported_feature') : FALSE;
			}
		}

if (($result = $this->db->query($sql)) !== FALSE)
		{
			if (isset($this->db->data_cache['table_names']))
			{
				$this->db->data_cache['table_names'][] = $table;
			}

// Most databases don't support creating indexes from within the CREATE TABLE statement
			if ( ! empty($this->keys))
			{
				for ($i = 0, $sqls = $this->_process_indexes($table), $c = count($sqls); $i < $c; $i++)
				{
					$this->db->query($sqls[$i]);
				}
			}
		}

$this->_reset();
		return $result;
	}

// --------------------------------------------------------------------

/**
	 * Create Table
	 *
	 * @param	string	$table		Table name
	 * @param	bool	$if_not_exists	Whether to add 'IF NOT EXISTS' condition
	 * @param	array	$attributes	Associative array of table attributes
	 * @return	mixed
	 */
	protected function _create_table($table, $if_not_exists, $attributes)
	{
		if ($if_not_exists === TRUE && $this->_create_table_if === FALSE)
		{
			if ($this->db->table_exists($table))
			{
				return TRUE;
			}

$if_not_exists = FALSE;
		}

$sql = ($if_not_exists)
			? sprintf($this->_create_table_if, $this->db->escape_identifiers($table))
			: 'CREATE TABLE';

$columns = $this->_process_fields(TRUE);
		for ($i = 0, $c = count($columns); $i < $c; $i++)
		{
			$columns[$i] = ($columns[$i]['_literal'] !== FALSE)
					? "\n\t".$columns[$i]['_literal']
					: "\n\t".$this->_process_column($columns[$i]);
		}

$columns = implode(',', $columns)
				.$this->_process_primary_keys($table);

// Are indexes created from within the CREATE TABLE statement? (e.g. in MySQL)
		if ($this->_create_table_keys === TRUE)
		{
			$columns .= $this->_process_indexes($table);
		}

// _create_table will usually have the following format: "%s %s (%s\n)"
		$sql = sprintf($this->_create_table.'%s',
			$sql,
			$this->db->escape_identifiers($table),
			$columns,
			$this->_create_table_attr($attributes)
		);

return $sql;
	}

// --------------------------------------------------------------------

/**
	 * CREATE TABLE attributes
	 *
	 * @param	array	$attributes	Associative array of table attributes
	 * @return	string
	 */
	protected function _create_table_attr($attributes)
	{
		$sql = '';

foreach (array_keys($attributes) as $key)
		{
			if (is_string($key))
			{
				$sql .= ' '.strtoupper($key).' '.$attributes[$key];
			}
		}

return $sql;
	}

// --------------------------------------------------------------------

/**
	 * Drop Table
	 *
	 * @param	string	$table_name	Table name
	 * @param	bool	$if_exists	Whether to add an IF EXISTS condition
	 * @return	bool
	 */
	public function drop_table($table_name, $if_exists = FALSE)
	{
		if ($table_name === '')
		{
			return ($this->db->db_debug) ? $this->db->display_error('db_table_name_required') : FALSE;
		}

if (($query = $this->_drop_table($this->db->dbprefix.$table_name, $if_exists)) === TRUE)
		{
			return TRUE;
		}

$query = $this->db->query($query);

// Update table list cache
		if ($query && ! empty($this->db->data_cache['table_names']))
		{
			$key = array_search(strtolower($this->db->dbprefix.$table_name), array_map('strtolower', $this->db->data_cache['table_names']), TRUE);
			if ($key !== FALSE)
			{
				unset($this->db->data_cache['table_names'][$key]);
			}
		}

return $query;
	}

// --------------------------------------------------------------------

/**
	 * Drop Table
	 *
	 * Generates a platform-specific DROP TABLE string
	 *
	 * @param	string	$table		Table name
	 * @param	bool	$if_exists	Whether to add an IF EXISTS condition
	 * @return	mixed	(Returns a platform-specific DROP table string, or TRUE to indicate there's nothing to do)
	 */
	protected function _drop_table($table, $if_exists)
	{
		$sql = 'DROP TABLE';

if ($if_exists)
		{
			if ($this->_drop_table_if === FALSE)
			{
				if ( ! $this->db->table_exists($table))
				{
					return TRUE;
				}
			}
			else
			{
				$sql = sprintf($this->_drop_table_if, $this->db->escape_identifiers($table));
			}
		}

return $sql.' '.$this->db->escape_identifiers($table);
	}

// --------------------------------------------------------------------

/**
	 * Rename Table
	 *
	 * @param	string	$table_name	Old table name
	 * @param	string	$new_table_name	New table name
	 * @return	bool
	 */
	public function rename_table($table_name, $new_table_name)
	{
		if ($table_name === '' OR $new_table_name === '')
		{
			show_error('A table name is required for that operation.');
			return FALSE;
		}
		elseif ($this->_rename_table === FALSE)
		{
			return ($this->db->db_debug) ? $this->db->display_error('db_unsupported_feature') : FALSE;
		}

$result = $this->db->query(sprintf($this->_rename_table,
						$this->db->escape_identifiers($this->db->dbprefix.$table_name),
						$this->db->escape_identifiers($this->db->dbprefix.$new_table_name))
					);

if ($result && ! empty($this->db->data_cache['table_names']))
		{
			$key = array_search(strtolower($this->db->dbprefix.$table_name), array_map('strtolower', $this->db->data_cache['table_names']), TRUE);
			if ($key !== FALSE)
			{
				$this->db->data_cache['table_names'][$key] = $this->db->dbprefix.$new_table_name;
			}
		}

return $result;
	}

// --------------------------------------------------------------------

/**
	 * Column Add
	 *
	 * @todo	Remove deprecated $_after option in 3.1+
	 * @param	string	$table	Table name
	 * @param	array	$field	Column definition
	 * @param	string	$_after	Column for AFTER clause (deprecated)
	 * @return	bool
	 */
	public function add_column($table, $field, $_after = NULL)
	{
		// Work-around for literal column definitions
		is_array($field) OR $field = array($field);

foreach (array_keys($field) as $k)
		{
			// Backwards-compatibility work-around for MySQL/CUBRID AFTER clause (remove in 3.1+)
			if ($_after !== NULL && is_array($field[$k]) && ! isset($field[$k]['after']))
			{
				$field[$k]['after'] = $_after;
			}

$this->add_field(array($k => $field[$k]));
		}

$sqls = $this->_alter_table('ADD', $this->db->dbprefix.$table, $this->_process_fields());
		$this->_reset();
		if ($sqls === FALSE)
		{
			return ($this->db->db_debug) ? $this->db->display_error('db_unsupported_feature') : FALSE;
		}

for ($i = 0, $c = count($sqls); $i < $c; $i++)
		{
			if ($this->db->query($sqls[$i]) === FALSE)
			{
				return FALSE;
			}
		}

return TRUE;
	}

// --------------------------------------------------------------------

/**
	 * Column Drop
	 *
	 * @param	string	$table		Table name
	 * @param	string	$column_name	Column name
	 * @return	bool
	 */
	public function drop_column($table, $column_name)
	{
		$sql = $this->_alter_table('DROP', $this->db->dbprefix.$table, $column_name);
		if ($sql === FALSE)
		{
			return ($this->db->db_debug) ? $this->db->display_error('db_unsupported_feature') : FALSE;
		}

return $this->db->query($sql);
	}

// --------------------------------------------------------------------

/**
	 * Column Modify
	 *
	 * @param	string	$table	Table name
	 * @param	string	$field	Column definition
	 * @return	bool
	 */
	public function modify_column($table, $field)
	{
		// Work-around for literal column definitions
		is_array($field) OR $field = array($field);

foreach (array_keys($field) as $k)
		{
			$this->add_field(array($k => $field[$k]));
		}

if (count($this->fields) === 0)
		{
			show_error('Field information is required.');
		}

$sqls = $this->_alter_table('CHANGE', $this->db->dbprefix.$table, $this->_process_fields());
		$this->_reset();
		if ($sqls === FALSE)
		{
			return ($this->db->db_debug) ? $this->db->display_error('db_unsupported_feature') : FALSE;
		}

for ($i = 0, $c = count($sqls); $i < $c; $i++)
		{
			if ($this->db->query($sqls[$i]) === FALSE)
			{
				return FALSE;
			}
		}

return TRUE;
	}

// --------------------------------------------------------------------

/**
	 * ALTER TABLE
	 *
	 * @param	string	$alter_type	ALTER type
	 * @param	string	$table		Table name
	 * @param	mixed	$field		Column definition
	 * @return	string|string[]
	 */
	protected function _alter_table($alter_type, $table, $field)
	{
		$sql = 'ALTER TABLE '.$this->db->escape_identifiers($table).' ';

// DROP has everything it needs now.
		if ($alter_type === 'DROP')
		{
			return $sql.'DROP COLUMN '.$this->db->escape_identifiers($field);
		}

$sql .= ($alter_type === 'ADD')
			? 'ADD '
			: $alter_type.' COLUMN ';

$sqls = array();
		for ($i = 0, $c = count($field); $i < $c; $i++)
		{
			$sqls[] = $sql
				.($field[$i]['_literal'] !== FALSE ? $field[$i]['_literal'] : $this->_process_column($field[$i]));
		}

return $sqls;
	}

// --------------------------------------------------------------------

/**
	 * Process fields
	 *
	 * @param	bool	$create_table
	 * @return	array
	 */
	protected function _process_fields($create_table = FALSE)
	{
		$fields = array();

foreach ($this->fields as $key => $attributes)
		{
			if (is_int($key) && ! is_array($attributes))
			{
				$fields[] = array('_literal' => $attributes);
				continue;
			}

$attributes = array_change_key_case($attributes, CASE_UPPER);

if ($create_table === TRUE && empty($attributes['TYPE']))
			{
				continue;
			}

isset($attributes['TYPE']) && $this->_attr_type($attributes);

$field = array(
				'name'			=> $key,
				'new_name'		=> isset($attributes['NAME']) ? $attributes['NAME'] : NULL,
				'type'			=> isset($attributes['TYPE']) ? $attributes['TYPE'] : NULL,
				'length'		=> '',
				'unsigned'		=> '',
				'null'			=> NULL,
				'unique'		=> '',
				'default'		=> '',
				'auto_increment'	=> '',
				'_literal'		=> FALSE
			);

isset($attributes['TYPE']) && $this->_attr_unsigned($attributes, $field);

if ($create_table === FALSE)
			{
				if (isset($attributes['AFTER']))
				{
					$field['after'] = $attributes['AFTER'];
				}
				elseif (isset($attributes['FIRST']))
				{
					$field['first'] = (bool) $attributes['FIRST'];
				}
			}

$this->_attr_default($attributes, $field);

if (isset($attributes['NULL']))
			{
				if ($attributes['NULL'] === TRUE)
				{
					$field['null'] = empty($this->_null) ? '' : ' '.$this->_null;
				}
				else
				{
					$field['null'] = ' NOT NULL';
				}
			}
			elseif ($create_table === TRUE)
			{
				$field['null'] = ' NOT NULL';
			}

$this->_attr_auto_increment($attributes, $field);
			$this->_attr_unique($attributes, $field);

if (isset($attributes['COMMENT']))
			{
				$field['comment'] = $this->db->escape($attributes['COMMENT']);
			}

if (isset($attributes['TYPE']) && ! empty($attributes['CONSTRAINT']))
			{
				switch (strtoupper($attributes['TYPE']))
				{
					case 'ENUM':
					case 'SET':
						$attributes['CONSTRAINT'] = $this->db->escape($attributes['CONSTRAINT']);
					default:
						$field['length'] = is_array($attributes['CONSTRAINT'])
							? '('.implode(',', $attributes['CONSTRAINT']).')'
							: '('.$attributes['CONSTRAINT'].')';
						break;
				}
			}

$fields[] = $field;
		}

return $fields;
	}

// --------------------------------------------------------------------

/**
	 * Process column
	 *
	 * @param	array	$field
	 * @return	string
	 */
	protected function _process_column($field)
	{
		return $this->db->escape_identifiers($field['name'])
			.' '.$field['type'].$field['length']
			.$field['unsigned']
			.$field['default']
			.$field['null']
			.$field['auto_increment']
			.$field['unique'];
	}

// --------------------------------------------------------------------

/**
	 * Field attribute TYPE
	 *
	 * Performs a data type mapping between different databases.
	 *
	 * @param	array	&$attributes
	 * @return	void
	 */
	protected function _attr_type(&$attributes)
	{
		// Usually overridden by drivers
	}

// --------------------------------------------------------------------

/**
	 * Field attribute UNSIGNED
	 *
	 * Depending on the _unsigned property value:
	 *
	 *	- TRUE will always set $field['unsigned'] to 'UNSIGNED'
	 *	- FALSE will always set $field['unsigned'] to ''
	 *	- array(TYPE) will set $field['unsigned'] to 'UNSIGNED',
	 *		if $attributes['TYPE'] is found in the array
	 *	- array(TYPE => UTYPE) will change $field['type'],
	 *		from TYPE to UTYPE in case of a match
	 *
	 * @param	array	&$attributes
	 * @param	array	&$field
	 * @return	void
	 */
	protected function _attr_unsigned(&$attributes, &$field)
	{
		if (empty($attributes['UNSIGNED']) OR $attributes['UNSIGNED'] !== TRUE)
		{
			return;
		}

// Reset the attribute in order to avoid issues if we do type conversion
		$attributes['UNSIGNED'] = FALSE;

if (is_array($this->_unsigned))
		{
			foreach (array_keys($this->_unsigned) as $key)
			{
				if (is_int($key) && strcasecmp($attributes['TYPE'], $this->_unsigned[$key]) === 0)
				{
					$field['unsigned'] = ' UNSIGNED';
					return;
				}
				elseif (is_string($key) && strcasecmp($attributes['TYPE'], $key) === 0)
				{
					$field['type'] = $key;
					return;
				}
			}

return;
		}

$field['unsigned'] = ($this->_unsigned === TRUE) ? ' UNSIGNED' : '';
	}

// --------------------------------------------------------------------

/**
	 * Field attribute DEFAULT
	 *
	 * @param	array	&$attributes
	 * @param	array	&$field
	 * @return	void
	 */
	protected function _attr_default(&$attributes, &$field)
	{
		if ($this->_default === FALSE)
		{
			return;
		}

if (array_key_exists('DEFAULT', $attributes))
		{
			if ($attributes['DEFAULT'] === NULL)
			{
				$field['default'] = empty($this->_null) ? '' : $this->_default.$this->_null;

// Override the NULL attribute if that's our default
				$attributes['NULL'] = TRUE;
				$field['null'] = empty($this->_null) ? '' : ' '.$this->_null;
			}
			else
			{
				$field['default'] = $this->_default.$this->db->escape($attributes['DEFAULT']);
			}
		}
	}

// --------------------------------------------------------------------

/**
	 * Field attribute UNIQUE
	 *
	 * @param	array	&$attributes
	 * @param	array	&$field
	 * @return	void
	 */
	protected function _attr_unique(&$attributes, &$field)
	{
		if ( ! empty($attributes['UNIQUE']) && $attributes['UNIQUE'] === TRUE)
		{
			$field['unique'] = ' UNIQUE';
		}
	}

// --------------------------------------------------------------------

/**
	 * Field attribute AUTO_INCREMENT
	 *
	 * @param	array	&$attributes
	 * @param	array	&$field
	 * @return	void
	 */
	protected function _attr_auto_increment(&$attributes, &$field)
	{
		if ( ! empty($attributes['AUTO_INCREMENT']) && $attributes['AUTO_INCREMENT'] === TRUE && stripos($field['type'], 'int') !== FALSE)
		{
			$field['auto_increment'] = ' AUTO_INCREMENT';
		}
	}

// --------------------------------------------------------------------

/**
	 * Process primary keys
	 *
	 * @param	string	$table	Table name
	 * @return	string
	 */
	protected function _process_primary_keys($table)
	{
		$sql = '';

for ($i = 0, $c = count($this->primary_keys); $i < $c; $i++)
		{
			if ( ! isset($this->fields[$this->primary_keys[$i]]))
			{
				unset($this->primary_keys[$i]);
			}
		}

if (count($this->primary_keys) > 0)
		{
			$sql .= ",\n\tCONSTRAINT ".$this->db->escape_identifiers('pk_'.$table)
				.' PRIMARY KEY('.implode(', ', $this->db->escape_identifiers($this->primary_keys)).')';
		}

return $sql;
	}

// --------------------------------------------------------------------

/**
	 * Process indexes
	 *
	 * @param	string	$table	Table name
	 * @return	string[] list of SQL statements
	 */
	protected function _process_indexes($table)
	{
		$sqls = array();

for ($i = 0, $c = count($this->keys); $i < $c; $i++)
		{
			if (is_array($this->keys[$i]))
			{
				for ($i2 = 0, $c2 = count($this->keys[$i]); $i2 < $c2; $i2++)
				{
					if ( ! isset($this->fields[$this->keys[$i][$i2]]))
					{
						unset($this->keys[$i][$i2]);
						continue;
					}
				}
			}
			elseif ( ! isset($this->fields[$this->keys[$i]]))
			{
				unset($this->keys[$i]);
				continue;
			}

is_array($this->keys[$i]) OR $this->keys[$i] = array($this->keys[$i]);

$sqls[] = 'CREATE INDEX '.$this->db->escape_identifiers($table.'_'.implode('_', $this->keys[$i]))
				.' ON '.$this->db->escape_identifiers($table)
				.' ('.implode(', ', $this->db->escape_identifiers($this->keys[$i])).');';
		}

return $sqls;
	}

// --------------------------------------------------------------------

/**
	 * Reset
	 *
	 * Resets table creation vars
	 *
	 * @return	void
	 */
	protected function _reset()
	{
		$this->fields = $this->keys = $this->primary_keys = array();
	}

}