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phab/src/infrastructure/query/policy/PhabricatorCursorPagedPolicyQuery.php
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PhabricatorCursorPagedPolicyQuery.php
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<?php
/*
* Copyright 2012 Facebook, Inc.
*
* Licensed under the Apache License, Version 2.0 (the "License");
* you may not use this file except in compliance with the License.
* You may obtain a copy of the License at
*
* http://www.apache.org/licenses/LICENSE-2.0
*
* Unless required by applicable law or agreed to in writing, software
* distributed under the License is distributed on an "AS IS" BASIS,
* WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
* See the License for the specific language governing permissions and
* limitations under the License.
*/
/**
* A query class which uses cursor-based paging. This paging is much more
* performant than offset-based paging in the presence of policy filtering.
*/
abstract class PhabricatorCursorPagedPolicyQuery
extends PhabricatorPolicyQuery {
private $afterID;
private $beforeID;
protected function getPagingColumn() {
return 'id';
}
protected function getPagingValue($result) {
return $result->getID();
}
protected function nextPage(array $page) {
if ($this->beforeID) {
$this->beforeID = $this->getPagingValue(head($page));
} else {
$this->afterID = $this->getPagingValue(last($page));
}
}
final public function setAfterID($object_id) {
$this->afterID = $object_id;
return $this;
}
final public function setBeforeID($object_id) {
$this->beforeID = $object_id;
return $this;
}
final protected function buildLimitClause(AphrontDatabaseConnection $conn_r) {
if ($this->getLimit()) {
return qsprintf($conn_r, 'LIMIT %d', $this->getLimit());
} else {
return '';
}
}
final protected function buildPagingClause(
AphrontDatabaseConnection $conn_r) {
if ($this->beforeID) {
return qsprintf(
$conn_r,
'%Q > %s',
$this->getPagingColumn(),
$this->beforeID);
} else if ($this->afterID) {
return qsprintf(
$conn_r,
'%Q < %s',
$this->getPagingColumn(),
$this->afterID);
}
return null;
}
final protected function buildOrderClause(AphrontDatabaseConnection $conn_r) {
if ($this->beforeID) {
return qsprintf(
$conn_r,
'ORDER BY %Q ASC',
$this->getPagingColumn());
} else {
return qsprintf(
$conn_r,
'ORDER BY %Q DESC',
$this->getPagingColumn());
}
}
final protected function processResults(array $results) {
if ($this->beforeID) {
$results = array_reverse($results, $preserve_keys = true);
}
return $results;
}
final public function executeWithCursorPager(AphrontCursorPagerView $pager) {
$this->setLimit($pager->getPageSize() + 1);
if ($pager->getAfterID()) {
$this->setAfterID($pager->getAfterID());
} else if ($pager->getBeforeID()) {
$this->setBeforeID($pager->getBeforeID());
}
$results = $this->execute();
$sliced_results = $pager->sliceResults($results);
if ($this->beforeID || (count($results) > $pager->getPageSize())) {
$pager->setNextPageID($this->getPagingValue(last($sliced_results)));
}
if ($this->afterID ||
($this->beforeID && (count($results) > $pager->getPageSize()))) {
$pager->setPrevPageID($this->getPagingValue(head($sliced_results)));
}
return $sliced_results;
}
}
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