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PhabricatorCursorPagedPolicyAwareQuery.php
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Fri, May 30, 20:35

PhabricatorCursorPagedPolicyAwareQuery.php
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<?php
/**
* A query class which uses cursor-based paging. This paging is much more
* performant than offset-based paging in the presence of policy filtering.
*
* @task appsearch Integration with ApplicationSearch
*/
abstract class PhabricatorCursorPagedPolicyAwareQuery
extends PhabricatorPolicyAwareQuery {
private $afterID;
private $beforeID;
private $applicationSearchConstraints = array();
private $internalPaging;
protected function getPagingColumn() {
return 'id';
}
protected function getPagingValue($result) {
return $result->getID();
}
protected function getReversePaging() {
return false;
}
protected function nextPage(array $page) {
// See getPagingViewer() for a description of this flag.
$this->internalPaging = true;
if ($this->beforeID) {
$this->beforeID = $this->getPagingValue(last($page));
} else {
$this->afterID = $this->getPagingValue(last($page));
}
}
final public function setAfterID($object_id) {
$this->afterID = $object_id;
return $this;
}
final protected function getAfterID() {
return $this->afterID;
}
final public function setBeforeID($object_id) {
$this->beforeID = $object_id;
return $this;
}
final protected function getBeforeID() {
return $this->beforeID;
}
/**
* Get the viewer for making cursor paging queries.
*
* NOTE: You should ONLY use this viewer to load cursor objects while
* building paging queries.
*
* Cursor paging can happen in two ways. First, the user can request a page
* like `/stuff/?after=33`, which explicitly causes paging. Otherwise, we
* can fall back to implicit paging if we filter some results out of a
* result list because the user can't see them and need to go fetch some more
* results to generate a large enough result list.
*
* In the first case, want to use the viewer's policies to load the object.
* This prevents an attacker from figuring out information about an object
* they can't see by executing queries like `/stuff/?after=33&order=name`,
* which would otherwise give them a hint about the name of the object.
* Generally, if a user can't see an object, they can't use it to page.
*
* In the second case, we need to load the object whether the user can see
* it or not, because we need to examine new results. For example, if a user
* loads `/stuff/` and we run a query for the first 100 items that they can
* see, but the first 100 rows in the database aren't visible, we need to
* be able to issue a query for the next 100 results. If we can't load the
* cursor object, we'll fail or issue the same query over and over again.
* So, generally, internal paging must bypass policy controls.
*
* This method returns the appropriate viewer, based on the context in which
* the paging is occuring.
*
* @return PhabricatorUser Viewer for executing paging queries.
*/
final protected function getPagingViewer() {
if ($this->internalPaging) {
return PhabricatorUser::getOmnipotentUser();
} else {
return $this->getViewer();
}
}
final protected function buildLimitClause(AphrontDatabaseConnection $conn_r) {
if ($this->getRawResultLimit()) {
return qsprintf($conn_r, 'LIMIT %d', $this->getRawResultLimit());
} else {
return '';
}
}
protected function buildPagingClause(
AphrontDatabaseConnection $conn_r) {
if ($this->beforeID) {
return qsprintf(
$conn_r,
'%Q %Q %s',
$this->getPagingColumn(),
$this->getReversePaging() ? '<' : '>',
$this->beforeID);
} else if ($this->afterID) {
return qsprintf(
$conn_r,
'%Q %Q %s',
$this->getPagingColumn(),
$this->getReversePaging() ? '>' : '<',
$this->afterID);
}
return null;
}
final protected function buildOrderClause(AphrontDatabaseConnection $conn_r) {
if ($this->beforeID) {
return qsprintf(
$conn_r,
'ORDER BY %Q %Q',
$this->getPagingColumn(),
$this->getReversePaging() ? 'DESC' : 'ASC');
} else {
return qsprintf(
$conn_r,
'ORDER BY %Q %Q',
$this->getPagingColumn(),
$this->getReversePaging() ? 'ASC' : 'DESC');
}
}
final protected function didLoadResults(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 ($sliced_results) {
if ($pager->getBeforeID() || (count($results) > $pager->getPageSize())) {
$pager->setNextPageID($this->getPagingValue(last($sliced_results)));
}
if ($pager->getAfterID() ||
($pager->getBeforeID() && (count($results) > $pager->getPageSize()))) {
$pager->setPrevPageID($this->getPagingValue(head($sliced_results)));
}
}
return $sliced_results;
}
/**
* Simplifies the task of constructing a paging clause across multiple
* columns. In the general case, this looks like:
*
* A > a OR (A = a AND B > b) OR (A = a AND B = b AND C > c)
*
* To build a clause, specify the name, type, and value of each column
* to include:
*
* $this->buildPagingClauseFromMultipleColumns(
* $conn_r,
* array(
* array(
* 'name' => 'title',
* 'type' => 'string',
* 'value' => $cursor->getTitle(),
* 'reverse' => true,
* ),
* array(
* 'name' => 'id',
* 'type' => 'int',
* 'value' => $cursor->getID(),
* ),
* ),
* array(
* 'reversed' => $is_reversed,
* ));
*
* This method will then return a composable clause for inclusion in WHERE.
*
* @param AphrontDatabaseConnection Connection query will execute on.
* @param list<map> Column description dictionaries.
* @param map Additional constuction options.
* @return string Query clause.
*/
final protected function buildPagingClauseFromMultipleColumns(
AphrontDatabaseConnection $conn,
array $columns,
array $options) {
foreach ($columns as $column) {
PhutilTypeSpec::checkMap(
$column,
array(
'name' => 'string',
'value' => 'wild',
'type' => 'string',
'reverse' => 'optional bool',
));
}
PhutilTypeSpec::checkMap(
$options,
array(
'reversed' => 'optional bool',
));
$is_query_reversed = idx($options, 'reversed', false);
$clauses = array();
$accumulated = array();
$last_key = last_key($columns);
foreach ($columns as $key => $column) {
$name = $column['name'];
$type = $column['type'];
switch ($type) {
case 'int':
$value = qsprintf($conn, '%d', $column['value']);
break;
case 'string':
$value = qsprintf($conn, '%s', $column['value']);
break;
default:
throw new Exception("Unknown column type '{$type}'!");
}
$is_column_reversed = idx($column, 'reverse', false);
$reverse = ($is_query_reversed xor $is_column_reversed);
$clause = $accumulated;
$clause[] = qsprintf(
$conn,
'%Q %Q %Q',
$name,
$reverse ? '>' : '<',
$value);
$clauses[] = '('.implode(') AND (', $clause).')';
$accumulated[] = qsprintf(
$conn,
'%Q = %Q',
$name,
$value);
}
return '('.implode(') OR (', $clauses).')';
}
/* -( Application Search )------------------------------------------------- */
/**
* Constrain the query with an ApplicationSearch index. This adds a constraint
* which requires objects to have one or more corresponding rows in the index
* with one of the given values. Combined with appropriate indexes, it can
* build the most common types of queries, like:
*
* - Find users with shirt sizes "X" or "XL".
* - Find shoes with size "13".
*
* @param PhabricatorCustomFieldIndexStorage Table where the index is stored.
* @param string|list<string> One or more values to filter by.
* @task appsearch
*/
public function withApplicationSearchContainsConstraint(
PhabricatorCustomFieldIndexStorage $index,
$value) {
$this->applicationSearchConstraints[] = array(
'type' => $index->getIndexValueType(),
'cond' => '=',
'table' => $index->getTableName(),
'index' => $index->getIndexKey(),
'value' => $value,
);
return $this;
}
/**
* Get the name of the query's primary object PHID column, for constructing
* JOIN clauses. Normally (and by default) this is just `"phid"`, but if the
* query construction requires a table alias it may be something like
* `"task.phid"`.
*
* @return string Column name.
* @task appsearch
*/
protected function getApplicationSearchObjectPHIDColumn() {
return 'phid';
}
/**
* Determine if the JOINs built by ApplicationSearch might cause each primary
* object to return multiple result rows. Generally, this means the query
* needs an extra GROUP BY clause.
*
* @return bool True if the query may return multiple rows for each object.
* @task appsearch
*/
protected function getApplicationSearchMayJoinMultipleRows() {
foreach ($this->applicationSearchConstraints as $constraint) {
$type = $constraint['type'];
$value = $constraint['value'];
switch ($type) {
case 'string':
case 'int':
if (count((array)$value) > 1) {
return true;
}
break;
default:
throw new Exception("Unknown constraint type '{$type}!");
}
}
return false;
}
/**
* Construct a GROUP BY clause appropriate for ApplicationSearch constraints.
*
* @param AphrontDatabaseConnection Connection executing the query.
* @return string Group clause.
* @task appsearch
*/
protected function buildApplicationSearchGroupClause(
AphrontDatabaseConnection $conn_r) {
if ($this->getApplicationSearchMayJoinMultipleRows()) {
return qsprintf(
$conn_r,
'GROUP BY %Q',
$this->getApplicationSearchObjectPHIDColumn());
} else {
return '';
}
}
/**
* Construct a JOIN clause appropriate for applying ApplicationSearch
* constraints.
*
* @param AphrontDatabaseConnection Connection executing the query.
* @return string Join clause.
* @task appsearch
*/
protected function buildApplicationSearchJoinClause(
AphrontDatabaseConnection $conn_r) {
$joins = array();
foreach ($this->applicationSearchConstraints as $key => $constraint) {
$table = $constraint['table'];
$alias = 'appsearch_'.$key;
$index = $constraint['index'];
$cond = $constraint['cond'];
$phid_column = $this->getApplicationSearchObjectPHIDColumn();
if ($cond !== '=') {
throw new Exception("Unknown constraint condition '{$cond}'!");
}
$type = $constraint['type'];
switch ($type) {
case 'string':
$joins[] = qsprintf(
$conn_r,
'JOIN %T %T ON %T.objectPHID = %Q
AND %T.indexKey = %s
AND %T.indexValue IN (%Ls)',
$table,
$alias,
$alias,
$phid_column,
$alias,
$index,
$alias,
(array)$constraint['value']);
break;
case 'int':
$joins[] = qsprintf(
$conn_r,
'JOIN %T %T ON %T.objectPHID = %Q
AND %T.indexKey = %s
AND %T.indexValue IN (%Ld)',
$table,
$alias,
$alias,
$phid_column,
$alias,
$index,
$alias,
(array)$constraint['value']);
break;
default:
throw new Exception("Unknown constraint type '{$type}'!");
}
}
return implode(' ', $joins);
}
}

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