Darya\Database\Query\AbstractSqlTranslator

Complexity

Total Complexity

108

Size/Duplication

Total Lines	923
Duplicated Lines	0.98 %

Coupling/Cohesion

Components	1
Dependencies	5

Importance

Changes

0

45 Methods

Rating	Name	Duplication	Size	Complexity
A	concatenate()	0	8	1
A	limitIsUseful()	0	4	2
A	translate()	0	14	2
A	translateCreate()	0	14	3
A	translateRead()	0	21	2
A	translateDatabaseRead()	0	16	1
A	translateUpdate()	0	10	1
A	translateDelete()	0	10	1
	resolveIdentifier()	0	1	?
A	identifier()	0	12	3
A	translatable()	0	4	2
A	translateTranslatable()	0	14	4
A	translateValue()	0	6	1
A	value()	0	12	3
A	resolveValue()	0	12	4
A	resolvesPlaceholder()	0	4	1
A	prepareColumnAliases()	0	11	4
A	prepareColumns()	0	12	2
A	validOperator()	0	6	1
A	prepareRawOperator()	0	6	2
C	prepareOperator()	9	26	7
A	prepareJoinType()	0	8	2
A	prepareJoinTable()	0	7	2
A	prepareJoinCondition()	0	16	2
A	prepareJoinConditions()	0	12	2
A	prepareJoin()	0	15	4
A	prepareJoins()	0	10	2
B	prepareFilterCondition()	0	26	6
A	prepareFilter()	0	14	3
A	prepareWhere()	0	12	3
A	prepareOrder()	0	7	3
A	prepareOrderBy()	0	14	4
	prepareLimit()	0	1	?
A	prepareGroupBy()	0	4	2
A	prepareHaving()	0	10	2
	prepareSelect()	0	11	?
A	prepareInsert()	0	12	1
A	prepareInsertSelect()	0	13	2
	prepareUpdate()	0	1	?
	prepareDelete()	0	1	?
A	columnParameters()	0	16	4
A	dataParameters()	0	12	3
A	joinParameters()	0	10	2
D	filterParameters()	0	36	9
B	parameters()	0	25	3

<?php
namespace Darya\Database\Query;

use InvalidArgumentException;
use Darya\Database;
use Darya\Database\Query\Translator;
use Darya\Database\Storage\Query\Join;
use Darya\Storage;

/**
 * An abstract query translator that prepares SQL common across more than one
 * RDBMS.
 * 
 * @author Chris Andrew <chris@hexus.io>
 */
abstract class AbstractSqlTranslator implements Translator
{
	/**
	 * Filter comparison operators.
	 * 
	 * @var array
	 */
	protected $operators = array('>=', '<=', '>', '<', '=', '!=', '<>', 'in', 'not in', 'is', 'is not', 'like', 'not like');
	
	/**
	 * Placeholder for values in prepared queries.
	 * 
	 * @var string
	 */
	protected $placeholder = '?';
	
	/**
	 * Concatenates the given set of strings that aren't empty.
	 * 
	 * Runs implode() after filtering out empty elements.
	 * 
	 * Delimiter defaults to a single whitespace character.
	 * 
	 * @param array  $strings
	 * @param string $delimiter [optional]
	 * @return string
	 */
	protected static function concatenate($strings, $delimiter = ' ')
	{
		$strings = array_filter($strings, function ($value) {
			return !empty($value);
		});
		
		return implode($delimiter, $strings);
	}
	
	/**
	 * Determine whether the given limit and offset will make a difference to
	 * a statement.
	 * 
	 * Simply determines whether both are non-zero integers.
	 * 
	 * @param int $limit
	 * @param int $offset
	 * @return bool
	 */
	protected static function limitIsUseful($limit, $offset)
	{
		return (int) $limit !== 0 || (int) $offset !== 0;
	}
	
	/**
	 * Translate the given storage query into an SQL query.
	 * 
	 * @param Storage\Query $storageQuery
	 * @return Database\Query
	 * @throws InvalidArgumentException
	 */
	public function translate(Storage\Query $storageQuery)
	{
		$type = $storageQuery->type;
		
		$method = 'translate' . ucfirst($type);
		
		if (!method_exists($this, $method)) {
			throw new InvalidArgumentException("Could not translate query of unknown type '$type'");
		}
		
		$query = call_user_func_array(array($this, $method), array($storageQuery));
		
		return $query;
	}
	
	/**
	 * Translate a query that creates a record.
	 * 
	 * @param Storage\Query $storageQuery
	 * @return Database\Query
	 */
	protected function translateCreate(Storage\Query $storageQuery)
	{
		if ($storageQuery instanceof Database\Storage\Query && $storageQuery->insertSubquery) {
			return new Database\Query(
				$this->prepareInsertSelect($storageQuery->resource, $storageQuery->fields, $storageQuery->insertSubquery),

The property $resource is declared protected in Darya\Storage\Query. Since you implemented __get(), maybe consider adding a @property or @property-read annotation. This makes it easier for IDEs to provide auto-completion.

The property $fields is declared protected in Darya\Storage\Query. Since you implemented __get(), maybe consider adding a @property or @property-read annotation. This makes it easier for IDEs to provide auto-completion.

				$this->parameters($storageQuery->insertSubquery)
			);
		}
		
		return new Database\Query(
			$this->prepareInsert($storageQuery->resource, $storageQuery->data),
			$this->parameters($storageQuery)
		);
	}
	
	/**
	 * Translate a query that reads records.
	 * 
	 * @param Storage\Query $storageQuery
	 * @return Database\Query
	 */
	protected function translateRead(Storage\Query $storageQuery)
	{
		if ($storageQuery instanceof Database\Storage\Query) {
			return $this->translateDatabaseRead($storageQuery);
		}
		
		return new Database\Query(
			$this->prepareSelect(
				$storageQuery->resource,
				$this->prepareColumns($storageQuery->fields),
				null,
				$this->prepareWhere($storageQuery->filter),
				$this->prepareOrderBy($storageQuery->order),
				$this->prepareLimit($storageQuery->limit, $storageQuery->offset),
				null,
				null,
				$storageQuery->distinct
			),
			$this->parameters($storageQuery)
		);
	}
	
	/**
	 * Translate a database storage query that reads records.
	 * 
	 * @param Database\Storage\Query $storageQuery
	 */
	protected function translateDatabaseRead(Database\Storage\Query $storageQuery)
	{
		return new Database\Query(
			$this->prepareSelect($storageQuery->resource,

The property $resource is declared protected in Darya\Storage\Query. Since you implemented __get(), maybe consider adding a @property or @property-read annotation. This makes it easier for IDEs to provide auto-completion.

				$this->prepareColumns($storageQuery->fields),

The property $fields is declared protected in Darya\Storage\Query. Since you implemented __get(), maybe consider adding a @property or @property-read annotation. This makes it easier for IDEs to provide auto-completion.

				$this->prepareJoins($storageQuery->joins),
				$this->prepareWhere($storageQuery->filter),

The property $filter is declared protected in Darya\Storage\Query. Since you implemented __get(), maybe consider adding a @property or @property-read annotation. This makes it easier for IDEs to provide auto-completion.

				$this->prepareOrderBy($storageQuery->order),

The property $order is declared protected in Darya\Storage\Query. Since you implemented __get(), maybe consider adding a @property or @property-read annotation. This makes it easier for IDEs to provide auto-completion.

				$this->prepareLimit($storageQuery->limit, $storageQuery->offset),

The property $limit is declared protected in Darya\Storage\Query. Since you implemented __get(), maybe consider adding a @property or @property-read annotation. This makes it easier for IDEs to provide auto-completion.

The property $offset is declared protected in Darya\Storage\Query. Since you implemented __get(), maybe consider adding a @property or @property-read annotation. This makes it easier for IDEs to provide auto-completion.

				$this->prepareGroupBy($storageQuery->groupings),
				$this->prepareHaving($storageQuery->having),
				$storageQuery->distinct

The property $distinct is declared protected in Darya\Storage\Query. Since you implemented __get(), maybe consider adding a @property or @property-read annotation. This makes it easier for IDEs to provide auto-completion.

			),
			$this->parameters($storageQuery)
		);
	}
	
	/**
	 * Translate a query that updates records.
	 * 
	 * @param Storage\Query $storageQuery
	 * @return Database\Query
	 */
	protected function translateUpdate(Storage\Query $storageQuery)
	{
		return new Database\Query(
			$this->prepareUpdate($storageQuery->resource, $storageQuery->data,
				$this->prepareWhere($storageQuery->filter),
				$this->prepareLimit($storageQuery->limit, $storageQuery->offset)
			),
			$this->parameters($storageQuery)
		);
	}
	
	/**
	 * Translate a query that deletes records.
	 * 
	 * @param Storage\Query $storageQuery
	 * @return Database\Query
	 */
	protected function translateDelete(Storage\Query $storageQuery)

This method seems to be duplicated in your project.

	{
		return new Database\Query(
			$this->prepareDelete($storageQuery->resource,
				$this->prepareWhere($storageQuery->filter),
				$this->prepareLimit($storageQuery->limit, $storageQuery->offset)
			),
			$this->parameters($storageQuery)
		);
	}
	
	/**
	 * Resolve the given value as an identifier.
	 * 
	 * @param mixed $identifier
	 * @return string
	 */
	abstract protected function resolveIdentifier($identifier);
	
	/**
	 * Prepare the given identifier.
	 * 
	 * If the value is translatable, it is translated.
	 * 
	 * If the value is an array, it is recursively prepared.
	 * 
	 * @param mixed $identifier
	 * @return mixed
	 */
	protected function identifier($identifier)

This method seems to be duplicated in your project.

	{
		if (is_array($identifier)) {
			return array_map(array($this, 'identifier'), $identifier);
		}
		
		if ($this->translatable($identifier)) {
			return $this->translateValue($identifier);
		}
		
		return $this->resolveIdentifier($identifier);
	}
	
	/**
	 * Determine whether the given value is translatable.
	 * 
	 * @param mixed $value
	 * @return bool
	 */
	protected function translatable($value)
	{
		return $value instanceof Storage\Query\Builder || $value instanceof Storage\Query;
	}
	
	/**
	 * Translate the given translatable query.
	 * 
	 * Helper for handling the translation of query objects from query builders.
	 * 
	 * @param mixed $query
	 * @return Database\Query
	 */
	protected function translateTranslatable($query)
	{
		if (!$this->translatable($query)) {
			throw new InvalidArgumentException("Cannot translate query of type '" . get_class($query) . "'");
		}
		
		if ($query instanceof Storage\Query\Builder) {
			$query = $query->query;
		}
		
		if ($query instanceof Storage\Query) {
			return $this->translate($query);
		}
	}
	
	/**
	 * Translate the given value if it is a query or query builder.
	 * 
	 * Returns the argument as is otherwise.
	 * 
	 * @param mixed $value
	 * @return string
	 */
	protected function translateValue($value)
	{
		$query = $this->translateTranslatable($value);
		
		return "($query)";
	}
	
	/**
	 * Prepare the given value for a prepared query.
	 * 
	 * If the value translatable, it is translated.
	 * 
	 * If the value is an array, it is recursively prepared.
	 * 
	 * @param mixed $value
	 * @return array|string
	 */
	protected function value($value)

This method seems to be duplicated in your project.

	{
		if (is_array($value)) {
			return array_map(array($this, 'value'), $value);
		}
		
		if ($this->translatable($value)) {
			return $this->translateValue($value);
		}
		
		return $this->resolveValue($value);
	}
	
	/**
	 * Resolve a placeholder or constant for the given parameter value.
	 * 
	 * @param mixed $value
	 * @return string
	 */
	protected function resolveValue($value)
	{
		if ($value === null) {
			return 'NULL';
		}
		
		if (is_bool($value)) {
			return $value ? 'TRUE' : 'FALSE';
		}
		
		return $this->placeholder;
	}
	
	/**
	 * Determine whether the given value resolves a placeholder.
	 * 
	 * @param mixed $value
	 * @return bool
	 */
	protected function resolvesPlaceholder($value)
	{
		return $this->resolveValue($value) === $this->placeholder;
	}
	
	/**
	 * Prepare a set of column aliases.
	 * 
	 * Uses the keys of the given array as identifiers and appends them to their
	 * values.
	 * 
	 * @param array $columns
	 * @return array
	 */
	protected function prepareColumnAliases(array $columns)
	{
		foreach ($columns as $alias => &$column) {
			if (is_string($alias) && preg_match('/^[\w]/', $alias)) {
				$aliasIdentifier = $this->identifier($alias);
				$column = "$column $aliasIdentifier";
			}
		}
		
		return $columns;
	}
	
	/**
	 * Prepare the given columns as a string.
	 * 
	 * @param array|string $columns
	 * @return string
	 */
	protected function prepareColumns($columns)
	{
		if (empty($columns)) {
			return '*';
		}
		
		$columns = (array) $this->identifier($columns);
		
		$columns = $this->prepareColumnAliases($columns);
		
		return implode(', ', $columns);
	}
	
	/**
	 * Determine whether the given operator is valid.
	 * 
	 * @param string $operator
	 * @return bool
	 */
	protected function validOperator($operator)
	{
		$operator = trim($operator);
		
		return in_array(strtolower($operator), $this->operators);
	}
	
	/**
	 * Prepare the given conditional operator.
	 * 
	 * Returns the equals operator if given value is not in the set of valid
	 * operators.
	 * 
	 * @param string $operator
	 * @return string
	 */
	protected function prepareRawOperator($operator)
	{
		$operator = trim($operator);
		
		return $this->validOperator($operator) ? strtoupper($operator) : '=';
	}
	
	/**
	 * Prepare an appropriate conditional operator for the given value.
	 * 
	 * @param string $operator
	 * @param mixed  $value    [optional]
	 * @return string
	 */
	protected function prepareOperator($operator, $value = null)
	{
		$operator = $this->prepareRawOperator($operator);
		
		if (!$this->resolvesPlaceholder($value)) {

This code seems to be duplicated across your project.

			if ($operator === '=') {
				$operator = 'IS';
			}
			
			if ($operator === '!=') {
				$operator = 'IS NOT';
			}
		}
		
		if (is_array($value)) {
			if ($operator === '=') {
				$operator = 'IN';
			}
		
			if ($operator === '!=') {
				$operator = 'NOT IN';
			}
		}
		
		return $operator;
	}
	
	/**
	 * Prepare a join type.
	 * 
	 * @param string $type
	 * @return string
	 */
	protected function prepareJoinType($type)
	{
		if (in_array($type, array('left', 'right'))) {
			return strtoupper($type) . ' JOIN';
		}
		
		return 'JOIN';
	}
	
	/**
	 * Prepare a join table.
	 * 
	 * @param Join $join
	 * @return string
	 */
	protected function prepareJoinTable(Join $join)
	{
		$table = $this->identifier($join->resource);
		$alias = $this->identifier($join->alias);
		
		return $alias ? "$table $alias" : $table;
	}
	
	/**
	 * Prepare a single join condition.
	 * 
	 * TODO: Make this generic for WHERE or JOIN clauses. prepareCondition()?
	 * 
	 * @param string $condition
	 * @return string
	 */
	protected function prepareJoinCondition($condition)
	{
		$parts = preg_split('/\s+/', $condition, 3);
		
		if (count($parts) < 3) {
			return null;
		}
		
		list($first, $operator, $second) = $parts;
		
		return static::concatenate(array(
			$this->identifier($first),
			$this->prepareRawOperator($operator),
			$this->identifier($second)
		));
	}
	
	/**
	 * Prepare a join's conditions.
	 * 
	 * @param Join $join
	 * @return string
	 */
	protected function prepareJoinConditions(Join $join)
	{
		$conditions = array();
		
		foreach ($join->conditions as $condition) {
			$conditions[] = $this->prepareJoinCondition($condition);
		}
		
		$conditions = array_merge($conditions, $this->prepareFilter($join->filter));
		
		return static::concatenate($conditions, ' AND ');
	}
	
	/**
	 * Prepare an individual table join.
	 * 
	 * @param Join $join
	 * @return string
	 */
	protected function prepareJoin(Join $join)
	{
		$table = $this->prepareJoinTable($join);
		$conditions = $this->prepareJoinConditions($join);
		
		$clause = $table && $conditions ? "$table ON $conditions" : $table;
		
		if (empty($clause)) {
			return null;
		}
		
		$type = $this->prepareJoinType($join->type);
		
		return "$type $clause";
	}
	
	/**
	 * Prepare table joins.
	 * 
	 * @param array $joins
	 * @return string
	 */
	protected function prepareJoins(array $joins)
	{
		$clauses = array();
		
		foreach ($joins as $join) {
			$clauses[] = $this->prepareJoin($join);
		}
		
		return static::concatenate($clauses);
	}
	
	/**
	 * Prepare an individual filter condition.
	 * 
	 * @param string $column
	 * @param mixed  $given
	 * @return string
	 */
	protected function prepareFilterCondition($column, $given)
	{
		list($left, $right) = array_pad(preg_split('/\s+/', $column, 2), 2, null);
		
		$column = $this->prepareColumns($left);
		
		$operator = $this->prepareOperator($right, $given);
		$value    = $this->value($given);
		
		// If the given value is null and whatever's on the right isn't a valid
		// operator we can attempt to split again and find a second identifier
		if ($given === null && !empty($right) && !$this->validOperator($right)) {
			list($operator, $identifier) = array_pad(preg_split('/\s+([\w\.]+)$/', $right, 2, PREG_SPLIT_DELIM_CAPTURE), 2, null);
			
			if (!empty($identifier)) {
				$operator = $this->prepareRawOperator($operator);
				$value    = $this->identifier($identifier);
			}
		}
		
		if (is_array($value)) {
			$value = "(" . implode(", ", $value) . ")";
		}
		
		return "$column $operator $value";
	}
	
	/**
	 * Prepare a filter as a set of query conditions.
	 * 
	 * TODO: Could numeric keys be dealt with by prepareJoinCondition()?
	 * 
	 * @param array $filter
	 * @return array
	 */
	protected function prepareFilter(array $filter)
	{
		$conditions = array();
		
		foreach ($filter as $column => $value) {
			if (strtolower($column) == 'or') {
				$conditions[] = '(' . $this->prepareWhere($value, 'OR', true) . ')';
			} else {
				$conditions[] = $this->prepareFilterCondition($column, $value);
			}
		}
		
		return $conditions;
	}
	
	/**
	 * Prepare a WHERE clause using the given filter and comparison operator.
	 * 
	 * Example filter key-values and their SQL equivalents:
	 *     'id'        => 1,       // id = '1'
	 *     'name like' => 'Chris', // name LIKE 'Chris'
	 *     'count >'   => 10,      // count > '10'
	 *     'type in'   => [1, 2],  // type IN (1, 2)
	 *     'type'      => [3, 4]   // type IN (3, 4)
	 * 
	 * Comparison operator between conditions defaults to 'AND'.
	 * 
	 * @param array  $filter
	 * @param string $comparison   [optional]
	 * @param bool   $excludeWhere [optional]
	 * @return string
	 */
	protected function prepareWhere(array $filter, $comparison = 'AND', $excludeWhere = false)
	{
		$conditions = $this->prepareFilter($filter);
		
		if (empty($conditions)) {
			return null;
		}
		
		$clause = implode(" $comparison ", $conditions);
		
		return !$excludeWhere ? "WHERE $clause" : $clause;
	}
	
	/**
	 * Prepare an individual order condition.
	 * 
	 * @param string $column
	 * @param string $direction [optional]
	 * @return string
	 */
	protected function prepareOrder($column, $direction = null)
	{
		$column = $this->identifier($column);
		$direction = $direction !== null ? strtoupper($direction) : 'ASC';
		
		return !empty($column) ? "$column $direction" : null;
	}
	
	/**
	 * Prepare an ORDER BY clause using the given order.
	 * 
	 * Example order key-values:
	 *     'column',
	 *     'other_column'   => 'ASC',
	 *     'another_column' => 'DESC
	 * 
	 * Ordered ascending by default.
	 * 
	 * @param array|string $order
	 * @return string
	 */
	protected function prepareOrderBy($order)
	{
		$conditions = array();
		
		foreach ((array) $order as $key => $value) {
			if (is_numeric($key)) {
				$conditions[] = $this->prepareOrder($value);
			} else {
				$conditions[] = $this->prepareOrder($key, $value);
			}
		}
		
		return count($conditions) ? 'ORDER BY ' . implode(', ', $conditions) : null;
	}
	
	/**
	 * Prepare a LIMIT clause using the given limit and offset.
	 * 
	 * @param int $limit  [optional]
	 * @param int $offset [optional]
	 * @return string
	 */
	abstract protected function prepareLimit($limit = 0, $offset = 0);
	
	/**
	 * Prepare a GROUP BY clause using the given groupings.
	 * 
	 * @param string[] $groupings
	 * @return string
	 */
	protected function prepareGroupBy(array $groupings)
	{
		return count($groupings) ? 'GROUP BY ' . implode(', ', $this->identifier($groupings)) : null;
	}
	
	/**
	 * Prepare a HAVING clause using the given filter.
	 * 
	 * @param array $filter
	 * @return string
	 */
	protected function prepareHaving(array $filter)
	{
		$clause = $this->prepareWhere($filter, 'AND', true);
		
		if (empty($clause)) {
			return null;
		}
		
		return "HAVING $clause";
	}
	
	/**
	 * Prepare a SELECT statement using the given columns, table, clauses and
	 * options.
	 * 
	 * TODO: Simplify this so that prepareSelect only actually prepares the
	 *       SELECT and FROM clauses. The rest could be concatenated by
	 *       translateRead().
	 * 
	 * @param string       $table
	 * @param array|string $columns
	 * @param string       $joins     [optional]
	 * @param string       $where     [optional]
	 * @param string       $order     [optional]
	 * @param string       $limit     [optional]
	 * @param string       $groupings [optional]
	 * @param string       $having    [optional]
	 * @param bool         $distinct  [optional]
	 * @return string
	 */
	abstract protected function prepareSelect(
		$table,
		$columns,
		$joins = null,
		$where = null,
		$order = null,
		$limit = null,
		$groupings = null,
		$having = null,
		$distinct = false
	);
	
	/**
	 * Prepare an INSERT INTO statement using the given table and data.
	 * 
	 * @param string $table
	 * @param array  $data
	 * @return string
	 */
	protected function prepareInsert($table, array $data)
	{
		$table = $this->identifier($table);
		
		$columns = $this->identifier(array_keys($data));
		$values  = $this->value(array_values($data));
		
		$columns = '(' . implode(', ', $columns) . ')';
		$values  = '(' . implode(', ', $values) . ')';
		
		return static::concatenate(array('INSERT INTO', $table, $columns, 'VALUES', $values));
	}
	
	/**
	 * Prepare an INSERT SELECT statement using the given table and
	 * subquery.
	 * 
	 * @param string        $table
	 * @param array         $columns
	 * @param Storage\Query $subquery
	 * @return string
	 */
	public function prepareInsertSelect($table, array $columns, Storage\Query $subquery)
	{
		$table = $this->identifier($table);
		
		if (!empty($columns)) {
			$columns = $this->identifier($columns);
			$columns = "(" . implode(", ", $columns) . ")";
		}
		
		$subquery = (string) $this->translate($subquery);
		
		return static::concatenate(array('INSERT INTO', $table, $columns, $subquery));
	}
	
	/**
	 * Prepare an UPDATE statement with the given table, data and clauses.
	 * 
	 * @param string $table
	 * @param array  $data
	 * @param string $where [optional]
	 * @param string $limit [optional]
	 * @return string
	 */
	abstract protected function prepareUpdate($table, $data, $where = null, $limit = null);
	
	/**
	 * Prepare a DELETE statement with the given table and clauses.
	 * 
	 * @param string $table
	 * @param string $where [optional]
	 * @param string $limit [optional]
	 * @return string
	 */
	abstract protected function prepareDelete($table, $where = null, $limit = null);
	
	/**
	 * Prepare a set of query parameters from the given set of columns.
	 * 
	 * @param array $columns
	 * @return array
	 */
	protected function columnParameters($columns)
	{
		$parameters = array();
		
		foreach ($columns as $column) {
			if ($column instanceof Storage\Query\Builder) {
				$column = $column->query;
			}
			
			if ($column instanceof Storage\Query) {
				$parameters = array_merge($parameters, $this->parameters($column));
			}
		}
		
		return $parameters;
	}
	
	/**
	 * Prepare a set of query parameters from the given data.
	 * 
	 * @param array $data
	 * @return array
	 */
	protected function dataParameters($data)
	{
		$parameters = array();
		
		foreach ($data as $value) {
			if ($this->resolvesPlaceholder($value)) {
				$parameters[] = $value;
			}
		}
		
		return $parameters;
	}
	
	/**
	 * Prepare a set of query parameters from the given set of joins.
	 * 
	 * @param Join[] $joins
	 * @return array
	 */
	protected function joinParameters($joins)
	{
		$parameters = array();
		
		foreach ($joins as $join) {
			$parameters = array_merge($parameters, $this->filterParameters($join->filter));
		}
		
		return $parameters;
	}
	
	/**
	 * Prepare a set of query parameters from the given filter.
	 * 
	 * @param array $filter
	 * @return array
	 */
	protected function filterParameters($filter)
	{
		$parameters = array();
		
		foreach ($filter as $index => $value) {
			if (is_array($value)) {
				if (strtolower($index) === 'or') {
					$parameters = array_merge($parameters, $this->filterParameters($value));
				} else {
					foreach ($value as $in) {
						if ($this->resolvesPlaceholder($value)) {
							$parameters[] = $in;
						}
					}
				}
				
				continue;
			}
			
			if ($value instanceof Storage\Query\Builder) {
				$value = $value->query;
			}
			
			if ($value instanceof Storage\Query) {
				$parameters = array_merge($parameters, $this->parameters($value));
				
				continue;
			}
			
			if ($this->resolvesPlaceholder($value)) {
				$parameters[] = $value;
			}
		}
		
		return $parameters;
	}
	
	/**
	 * Retrieve an array of parameters from the given query for executing a
	 * prepared query.
	 * 
	 * @param Storage\Query $storageQuery
	 * @return array
	 */
	public function parameters(Storage\Query $storageQuery)
	{
		$parameters = $this->columnParameters($storageQuery->fields);
		
		if (in_array($storageQuery->type, array(Storage\Query::CREATE, Storage\Query::UPDATE))) {
			$parameters = $this->dataParameters($storageQuery->data);
		}
		
		$joinParameters = array();
		$havingParameters = array();
		
		if ($storageQuery instanceof Database\Storage\Query) {
			$joinParameters = $this->joinParameters($storageQuery->joins);
			$havingParameters = $this->filterParameters($storageQuery->having);
		}
		
		$parameters = array_merge(
			$parameters,
			$joinParameters,
			$this->filterParameters($storageQuery->filter),
			$havingParameters
		);
		
		return $parameters;
	}
}