/**
* Optimize query in the context of specified index
*
* @param \Zend\Search\Lucene\SearchIndex $index
* @return \Zend\Search\Lucene\Search\Query\AbstractQuery
*/
public function optimize(Lucene\SearchIndex $index)
{
$subqueries = array();
$signs = array();
// Optimize all subqueries
foreach ($this->_subqueries as $id => $subquery) {
$subqueries[] = $subquery->optimize($index);
$signs[] = ($this->_signs === null)? true : $this->_signs[$id];
}
// Remove insignificant subqueries
foreach ($subqueries as $id => $subquery) {
if ($subquery instanceof Insignificant) {
// Insignificant subquery has to be removed anyway
unset($subqueries[$id]);
unset($signs[$id]);
}
}
if (count($subqueries) == 0) {
// Boolean query doesn't has non-insignificant subqueries
return new Insignificant();
}
// Check if all non-insignificant subqueries are prohibited
$allProhibited = true;
foreach ($signs as $sign) {
if ($sign !== false) {
$allProhibited = false;
break;
}
}
if ($allProhibited) {
return new Insignificant();
}
// Check for empty subqueries
foreach ($subqueries as $id => $subquery) {
if ($subquery instanceof EmptyResult) {
if ($signs[$id] === true) {
// Matching is required, but is actually empty
return new EmptyResult();
} else {
// Matching is optional or prohibited, but is empty
// Remove it from subqueries and signs list
unset($subqueries[$id]);
unset($signs[$id]);
}
}
}
// Check, if reduced subqueries list is empty
if (count($subqueries) == 0) {
return new EmptyResult();
}
// Check if all non-empty subqueries are prohibited
$allProhibited = true;
foreach ($signs as $sign) {
if ($sign !== false) {
$allProhibited = false;
break;
}
}
if ($allProhibited) {
return new EmptyResult();
}
// Check, if reduced subqueries list has only one entry
if (count($subqueries) == 1) {
// It's a query with only one required or optional clause
// (it's already checked, that it's not a prohibited clause)
if ($this->getBoost() == 1) {
return reset($subqueries);
}
$optimizedQuery = clone reset($subqueries);
$optimizedQuery->setBoost($optimizedQuery->getBoost()*$this->getBoost());
return $optimizedQuery;
}
// Prepare first candidate for optimized query
$optimizedQuery = new self($subqueries, $signs);
$optimizedQuery->setBoost($this->getBoost());
$terms = array();
$tsigns = array();
$boostFactors = array();
// Try to decompose term and multi-term subqueries
foreach ($subqueries as $id => $subquery) {
if ($subquery instanceof Term) {
$terms[] = $subquery->getTerm();
$tsigns[] = $signs[$id];
$boostFactors[] = $subquery->getBoost();
// remove subquery from a subqueries list
unset($subqueries[$id]);
unset($signs[$id]);
} else if ($subquery instanceof MultiTerm) {
$subTerms = $subquery->getTerms();
$subSigns = $subquery->getSigns();
if ($signs[$id] === true) {
// It's a required multi-term subquery.
// Something like '... +(+term1 -term2 term3 ...) ...'
// Multi-term required subquery can be decomposed only if it contains
// required terms and doesn't contain prohibited terms:
// ... +(+term1 term2 ...) ... => ... +term1 term2 ...
//
// Check this
$hasRequired = false;
$hasProhibited = false;
if ($subSigns === null) {
// All subterms are required
$hasRequired = true;
} else {
foreach ($subSigns as $sign) {
if ($sign === true) {
$hasRequired = true;
} else if ($sign === false) {
$hasProhibited = true;
break;
}
}
}
// Continue if subquery has prohibited terms or doesn't have required terms
if ($hasProhibited || !$hasRequired) {
continue;
}
foreach ($subTerms as $termId => $term) {
$terms[] = $term;
$tsigns[] = ($subSigns === null)? true : $subSigns[$termId];
$boostFactors[] = $subquery->getBoost();
}
// remove subquery from a subqueries list
unset($subqueries[$id]);
unset($signs[$id]);
} else { // $signs[$id] === null || $signs[$id] === false
// It's an optional or prohibited multi-term subquery.
// Something like '... (+term1 -term2 term3 ...) ...'
// or
// something like '... -(+term1 -term2 term3 ...) ...'
// Multi-term optional and required subqueries can be decomposed
// only if all terms are optional.
//
// Check if all terms are optional.
$onlyOptional = true;
if ($subSigns === null) {
// All subterms are required
$onlyOptional = false;
} else {
foreach ($subSigns as $sign) {
if ($sign !== null) {
$onlyOptional = false;
break;
}
}
}
// Continue if non-optional terms are presented in this multi-term subquery
if (!$onlyOptional) {
continue;
}
foreach ($subTerms as $termId => $term) {
$terms[] = $term;
$tsigns[] = ($signs[$id] === null)? null /* optional */ :
false /* prohibited */;
$boostFactors[] = $subquery->getBoost();
}
// remove subquery from a subqueries list
unset($subqueries[$id]);
unset($signs[$id]);
}
}
}
// Check, if there are no decomposed subqueries
if (count($terms) == 0 ) {
// return prepared candidate
return $optimizedQuery;
}
// Check, if all subqueries have been decomposed and all terms has the same boost factor
if (count($subqueries) == 0 && count(array_unique($boostFactors)) == 1) {
$optimizedQuery = new MultiTerm($terms, $tsigns);
$optimizedQuery->setBoost(reset($boostFactors)*$this->getBoost());
return $optimizedQuery;
}
// This boolean query can't be transformed to Term/MultiTerm query and still contains
// several subqueries
// Separate prohibited terms
$prohibitedTerms = array();
foreach ($terms as $id => $term) {
if ($tsigns[$id] === false) {
$prohibitedTerms[] = $term;
unset($terms[$id]);
unset($tsigns[$id]);
unset($boostFactors[$id]);
}
}
if (count($terms) == 1) {
$clause = new Term(reset($terms));
$clause->setBoost(reset($boostFactors));
$subqueries[] = $clause;
$signs[] = reset($tsigns);
// Clear terms list
$terms = array();
} else if (count($terms) > 1 && count(array_unique($boostFactors)) == 1) {
$clause = new MultiTerm($terms, $tsigns);
$clause->setBoost(reset($boostFactors));
$subqueries[] = $clause;
// Clause sign is 'required' if clause contains required terms. 'Optional' otherwise.
$signs[] = (in_array(true, $tsigns))? true : null;
// Clear terms list
$terms = array();
}
if (count($prohibitedTerms) == 1) {
// (boost factors are not significant for prohibited clauses)
$subqueries[] = new Term(reset($prohibitedTerms));
$signs[] = false;
// Clear prohibited terms list
$prohibitedTerms = array();
} else if (count($prohibitedTerms) > 1) {
// prepare signs array
$prohibitedSigns = array();
foreach ($prohibitedTerms as $id => $term) {
// all prohibited term are grouped as optional into multi-term query
$prohibitedSigns[$id] = null;
}
// (boost factors are not significant for prohibited clauses)
$subqueries[] = new MultiTerm($prohibitedTerms, $prohibitedSigns);
// Clause sign is 'prohibited'
$signs[] = false;
// Clear terms list
$prohibitedTerms = array();
}
/** @todo Group terms with the same boost factors together */
// Check, that all terms are processed
// Replace candidate for optimized query
if (count($terms) == 0 && count($prohibitedTerms) == 0) {
$optimizedQuery = new self($subqueries, $signs);
$optimizedQuery->setBoost($this->getBoost());
}
return $optimizedQuery;
}
