<?php
/**
* @file
* Search query extender and helper functions.
*/
/**
* Do a query on the full-text search index for a word or words.
*
* This function is normally only called by each module that supports the
* indexed search (and thus, implements hook_update_index()).
*
* Results are retrieved in two logical passes. However, the two passes are
* joined together into a single query. And in the case of most simple
* queries the second pass is not even used.
*
* The first pass selects a set of all possible matches, which has the benefit
* of also providing the exact result set for simple "AND" or "OR" searches.
*
* The second portion of the query further refines this set by verifying
* advanced text conditions (such as negative or phrase matches).
*
* The used query object has the tag 'search_$module' and can be further
* extended with hook_query_alter().
*/
class SearchQuery extends SelectQueryExtender {
/**
* The search query that is used for searching.
*
* @var string
*/
protected $searchExpression;
/**
* Type of search (search module).
*
* This maps to the value of the type column in search_index, and is equal
* to the machine-readable name of the module that implements
* hook_search_info().
*
* @var string
*/
protected $type;
/**
* Positive and negative search keys.
*
* @var array
*/
protected $keys = array('positive' => array(), 'negative' => array());
/**
* Indicates whether the first pass query requires complex conditions (LIKE).
*
* @var boolean.
*/
protected $simple = TRUE;
/**
* Conditions that are used for exact searches.
*
* This is always used for the second pass query but not for the first pass,
* unless $this->simple is FALSE.
*
* @var DatabaseCondition
*/
protected $conditions;
/**
* Indicates how many matches for a search query are necessary.
*
* @var int
*/
protected $matches = 0;
/**
* Array of search words.
*
* These words have to match against {search_index}.word.
*
* @var array
*/
protected $words = array();
/**
* Multiplier for the normalized search score.
*
* This value is calculated by the first pass query and multiplied with the
* actual score of a specific word to make sure that the resulting calculated
* score is between 0 and 1.
*
* @var float
*/
protected $normalize;
/**
* Indicates whether the first pass query has been executed.
*
* @var boolean
*/
protected $executedFirstPass = FALSE;
/**
* Stores score expressions.
*
* @var array
*
* @see addScore()
*/
protected $scores = array();
/**
* Stores arguments for score expressions.
*
* @var array
*/
protected $scoresArguments = array();
/**
* Stores multipliers for score expressions.
*
* @var array
*/
protected $multiply = array();
/**
* Whether or not search expressions were ignored.
*
* The maximum number of AND/OR combinations exceeded can be configured to
* avoid Denial-of-Service attacks. Expressions beyond the limit are ignored.
*
* @var boolean
*/
protected $expressionsIgnored = FALSE;
/**
* Sets up the search query expression.
*
* @param $query
* A search query string, which can contain options.
* @param $module
* The search module. This maps to {search_index}.type in the database.
*
* @return
* The SearchQuery object.
*/
public function searchExpression($expression, $module) {
$this->searchExpression = $expression;
$this->type = $module;
// Add a search_* tag. This needs to be added before any preExecute methods
// for decorated queries are called, as $this->prepared will be set to TRUE
// and tags added in the execute method will never get used. For example,
// if $query is extended by 'SearchQuery' then 'PagerDefault', the
// search-specific tag will be added too late (when preExecute() has
// already been called from the PagerDefault extender), and as a
// consequence will not be available to hook_query_alter() implementations,
// nor will the correct hook_query_TAG_alter() implementations get invoked.
// See node_search_execute().
$this->addTag('search_' . $module);
return $this;
}
/**
* Applies a search option and removes it from the search query string.
*
* These options are in the form option:value,value2,value3.
*
* @param $option
* Name of the option.
* @param $column
* Name of the database column to which the value should be applied.
*
* @return
* TRUE if a value for that option was found, FALSE if not.
*/
public function setOption($option, $column) {
if ($values = search_expression_extract($this->searchExpression, $option)) {
$or = db_or();
foreach (explode(',', $values) as $value) {
$or->condition($column, $value);
}
$this->condition($or);
$this->searchExpression = search_expression_insert($this->searchExpression, $option);
return TRUE;
}
return FALSE;
}
/**
* Parses the search query into SQL conditions.
*
* We build two queries that match the dataset bodies.
*/
protected function parseSearchExpression() {
// Matchs words optionally prefixed by a dash. A word in this case is
// something between two spaces, optionally quoted.
preg_match_all('/ (-?)("[^"]+"|[^" ]+)/i', ' ' . $this->searchExpression , $keywords, PREG_SET_ORDER);
if (count($keywords) == 0) {
return;
}
// Classify tokens.
$or = FALSE;
$warning = '';
$limit_combinations = variable_get('search_and_or_limit', 7);
// The first search expression does not count as AND.
$and_count = -1;
$or_count = 0;
foreach ($keywords as $match) {
if ($or_count && $and_count + $or_count >= $limit_combinations) {
// Ignore all further search expressions to prevent Denial-of-Service
// attacks using a high number of AND/OR combinations.
$this->expressionsIgnored = TRUE;
break;
}
$phrase = FALSE;
// Strip off phrase quotes.
if ($match[2][0] == '"') {
$match[2] = substr($match[2], 1, -1);
$phrase = TRUE;
$this->simple = FALSE;
}
// Simplify keyword according to indexing rules and external
// preprocessors. Use same process as during search indexing, so it
// will match search index.
$words = search_simplify($match[2]);
// Re-explode in case simplification added more words, except when
// matching a phrase.
$words = $phrase ? array($words) : preg_split('/ /', $words, -1, PREG_SPLIT_NO_EMPTY);
// Negative matches.
if ($match[1] == '-') {
$this->keys['negative'] = array_merge($this->keys['negative'], $words);
}
// OR operator: instead of a single keyword, we store an array of all
// OR'd keywords.
elseif ($match[2] == 'OR' && count($this->keys['positive'])) {
$last = array_pop($this->keys['positive']);
// Starting a new OR?
if (!is_array($last)) {
$last = array($last);
}
$this->keys['positive'][] = $last;
$or = TRUE;
$or_count++;
continue;
}
// AND operator: implied, so just ignore it.
elseif ($match[2] == 'AND' || $match[2] == 'and') {
$warning = $match[2];
continue;
}
// Plain keyword.
else {
if ($match[2] == 'or') {
$warning = $match[2];
}
if ($or) {
// Add to last element (which is an array).
$this->keys['positive'][count($this->keys['positive']) - 1] = array_merge($this->keys['positive'][count($this->keys['positive']) - 1], $words);
}
else {
$this->keys['positive'] = array_merge($this->keys['positive'], $words);
$and_count++;
}
}
$or = FALSE;
}
// Convert keywords into SQL statements.
$this->conditions = db_and();
$simple_and = FALSE;
$simple_or = FALSE;
// Positive matches.
foreach ($this->keys['positive'] as $key) {
// Group of ORed terms.
if (is_array($key) && count($key)) {
$simple_or = TRUE;
$any = FALSE;
$queryor = db_or();
foreach ($key as $or) {
list($num_new_scores) = $this->parseWord($or);
$any |= $num_new_scores;
$queryor->condition('d.data', "% $or %", 'LIKE');
}
if (count($queryor)) {
$this->conditions->condition($queryor);
// A group of OR keywords only needs to match once.
$this->matches += ($any > 0);
}
}
// Single ANDed term.
else {
$simple_and = TRUE;
list($num_new_scores, $num_valid_words) = $this->parseWord($key);
$this->conditions->condition('d.data', "% $key %", 'LIKE');
if (!$num_valid_words) {
$this->simple = FALSE;
}
// Each AND keyword needs to match at least once.
$this->matches += $num_new_scores;
}
}
if ($simple_and && $simple_or) {
$this->simple = FALSE;
}
// Negative matches.
foreach ($this->keys['negative'] as $key) {
$this->conditions->condition('d.data', "% $key %", 'NOT LIKE');
$this->simple = FALSE;
}
if ($warning == 'or') {
drupal_set_message(t('Search for either of the two terms with uppercase <strong>OR</strong>. For example, <strong>cats OR dogs</strong>.'));
}
}
/**
* Helper function for parseQuery().
*/
protected function parseWord($word) {
$num_new_scores = 0;
$num_valid_words = 0;
// Determine the scorewords of this word/phrase.
$split = explode(' ', $word);
foreach ($split as $s) {
$num = is_numeric($s);
if ($num || drupal_strlen($s) >= variable_get('minimum_word_size', 3)) {
if (!isset($this->words[$s])) {
$this->words[$s] = $s;
$num_new_scores++;
}
$num_valid_words++;
}
}
// Return matching snippet and number of added words.
return array($num_new_scores, $num_valid_words);
}
/**
* Executes the first pass query.
*
* This can either be done explicitly, so that additional scores and
* conditions can be applied to the second pass query, or implicitly by
* addScore() or execute().
*
* @return
* TRUE if search items exist, FALSE if not.
*/
public function executeFirstPass() {
$this->parseSearchExpression();
if (count($this->words) == 0) {
form_set_error('keys', format_plural(variable_get('minimum_word_size', 3), 'You must include at least one positive keyword with 1 character or more.', 'You must include at least one positive keyword with @count characters or more.'));
return FALSE;
}
if ($this->expressionsIgnored) {
drupal_set_message(t('Your search used too many AND/OR expressions. Only the first @count terms were included in this search.', array('@count' => variable_get('search_and_or_limit', 7))), 'warning');
}
$this->executedFirstPass = TRUE;
if (!empty($this->words)) {
$or = db_or();
foreach ($this->words as $word) {
$or->condition('i.word', $word);
}
$this->condition($or);
}
// Build query for keyword normalization.
$this->join('search_total', 't', 'i.word = t.word');
$this
->condition('i.type', $this->type)
->groupBy('i.type')
->groupBy('i.sid')
->having('COUNT(*) >= :matches', array(':matches' => $this->matches));
// Clone the query object to do the firstPass query;
$first = clone $this->query;
// For complex search queries, add the LIKE conditions to the first pass query.
if (!$this->simple) {
$first->join('search_dataset', 'd', 'i.sid = d.sid AND i.type = d.type');
$first->condition($this->conditions);
}
// Calculate maximum keyword relevance, to normalize it.
$first->addExpression('SUM(i.score * t.count)', 'calculated_score');
$this->normalize = $first
->range(0, 1)
->orderBy('calculated_score', 'DESC')
->execute()
->fetchField();
if ($this->normalize) {
return TRUE;
}
return FALSE;
}
/**
* Adds a custom score expression to the search query.
*
* Score expressions are used to order search results. If no calls to
* addScore() have taken place, a default keyword relevance score will be
* used. However, if at least one call to addScore() has taken place, the
* keyword relevance score is not automatically added.
*
* Note that you must use this method to add ordering to your searches, and
* not call orderBy() directly, when using the SearchQuery extender. This is
* because of the two-pass system the SearchQuery class uses to normalize
* scores.
*
* @param $score
* The score expression, which should evaluate to a number between 0 and 1.
* The string 'i.relevance' in a score expression will be replaced by a
* measure of keyword relevance between 0 and 1.
* @param $arguments
* Query arguments needed to provide values to the score expression.
* @param $multiply
* If set, the score is multiplied with this value. However, all scores
* with multipliers are then divided by the total of all multipliers, so
* that overall, the normalization is maintained.
*
* @return object
* The updated query object.
*/
public function addScore($score, $arguments = array(), $multiply = FALSE) {
if ($multiply) {
$i = count($this->multiply);
// Modify the score expression so it is multiplied by the multiplier,
// with a divisor to renormalize.
$score = "CAST(:multiply_$i AS DECIMAL) * COALESCE(( " . $score . "), 0) / CAST(:total_$i AS DECIMAL)";
// Add an argument for the multiplier. The :total_$i argument is taken
// care of in the execute() method, which is when the total divisor is
// calculated.
$arguments[':multiply_' . $i] = $multiply;
$this->multiply[] = $multiply;
}
$this->scores[] = $score;
$this->scoresArguments += $arguments;
return $this;
}
/**
* Executes the search.
*
* If not already done, this executes the first pass query. Then the complex
* conditions are applied to the query including score expressions and
* ordering.
*
* @return
* FALSE if the first pass query returned no results, and a database result
* set if there were results.
*/
public function execute()
{
if (!$this->executedFirstPass) {
$this->executeFirstPass();
}
if (!$this->normalize) {
return new DatabaseStatementEmpty();
}
// Add conditions to query.
$this->join('search_dataset', 'd', 'i.sid = d.sid AND i.type = d.type');
$this->condition($this->conditions);
if (empty($this->scores)) {
// Add default score.
$this->addScore('i.relevance');
}
if (count($this->multiply)) {
// Re-normalize scores with multipliers by dividing by the total of all
// multipliers. The expressions were altered in addScore(), so here just
// add the arguments for the total.
$i = 0;
$sum = array_sum($this->multiply);
foreach ($this->multiply as $total) {
$this->scoresArguments[':total_' . $i] = $sum;
$i++;
}
}
// Replace the pseudo-expression 'i.relevance' with a measure of keyword
// relevance in all score expressions, using string replacement. Careful
// though! If you just print out a float, some locales use ',' as the
// decimal separator in PHP, while SQL always uses '.'. So, make sure to
// set the number format correctly.
$relevance = number_format((1.0 / $this->normalize), 10, '.', '');
$this->scores = str_replace('i.relevance', '(' . $relevance . ' * i.score * t.count)', $this->scores);
// Add all scores together to form a query field.
$this->addExpression('SUM(' . implode(' + ', $this->scores) . ')', 'calculated_score', $this->scoresArguments);
// If an order has not yet been set for this query, add a default order
// that sorts by the calculated sum of scores.
if (count($this->getOrderBy()) == 0) {
$this->orderBy('calculated_score', 'DESC');
}
// Add useful metadata.
$this
->addMetaData('normalize', $this->normalize)
->fields('i', array('type', 'sid'));
return $this->query->execute();
}
/**
* Builds the default count query for SearchQuery.
*
* Since SearchQuery always uses GROUP BY, we can default to a subquery. We
* also add the same conditions as execute() because countQuery() is called
* first.
*/
public function countQuery() {
// Clone the inner query.
$inner = clone $this->query;
// Add conditions to query.
$inner->join('search_dataset', 'd', 'i.sid = d.sid AND i.type = d.type');
$inner->condition($this->conditions);
// Remove existing fields and expressions, they are not needed for a count
// query.
$fields =& $inner->getFields();
$fields = array();
$expressions =& $inner->getExpressions();
$expressions = array();
// Add the sid as the only field and count them as a subquery.
$count = db_select($inner->fields('i', array('sid')), NULL, array('target' => 'slave'));
// Add the COUNT() expression.
$count->addExpression('COUNT(*)');
return $count;
}
}