<?php
/**
* Efficient paging for SQL queries.
*
* This program is free software; you can redistribute it and/or modify
* it under the terms of the GNU General Public License as published by
* the Free Software Foundation; either version 2 of the License, or
* (at your option) any later version.
*
* This program is distributed in the hope that it will be useful,
* but WITHOUT ANY WARRANTY; without even the implied warranty of
* MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
* GNU General Public License for more details.
*
* You should have received a copy of the GNU General Public License along
* with this program; if not, write to the Free Software Foundation, Inc.,
* 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301, USA.
* http://www.gnu.org/copyleft/gpl.html
*
* @file
* @ingroup Pager
*/
use MediaWiki\HookContainer\ProtectedHookAccessorTrait;
use MediaWiki\Linker\LinkRenderer;
use MediaWiki\MediaWikiServices;
use MediaWiki\Navigation\PrevNextNavigationRenderer;
use Wikimedia\Rdbms\IDatabase;
use Wikimedia\Rdbms\IResultWrapper;
/**
* IndexPager is an efficient pager which uses a (roughly unique) index in the
* data set to implement paging, rather than a "LIMIT offset,limit" clause.
* In MySQL, such a limit/offset clause requires counting through the
* specified number of offset rows to find the desired data, which can be
* expensive for large offsets.
*
* ReverseChronologicalPager is a child class of the abstract IndexPager, and
* contains some formatting and display code which is specific to the use of
* timestamps as indexes. Here is a synopsis of its operation:
*
* * The query is specified by the offset, limit and direction (dir)
* parameters, in addition to any subclass-specific parameters.
* * The offset is the non-inclusive start of the DB query. A row with an
* index value equal to the offset will never be shown.
* * The query may either be done backwards, where the rows are returned by
* the database in the opposite order to which they are displayed to the
* user, or forwards. This is specified by the "dir" parameter, dir=prev
* means backwards, anything else means forwards. The offset value
* specifies the start of the database result set, which may be either
* the start or end of the displayed data set. This allows "previous"
* links to be implemented without knowledge of the index value at the
* start of the previous page.
* * An additional row beyond the user-specified limit is always requested.
* This allows us to tell whether we should display a "next" link in the
* case of forwards mode, or a "previous" link in the case of backwards
* mode. Determining whether to display the other link (the one for the
* page before the start of the database result set) can be done
* heuristically by examining the offset.
*
* * An empty offset indicates that the offset condition should be omitted
* from the query. This naturally produces either the first page or the
* last page depending on the dir parameter.
*
* Subclassing the pager to implement concrete functionality should be fairly
* simple, please see the examples in HistoryAction.php and
* SpecialBlockList.php. You just need to override formatRow(),
* getQueryInfo() and getIndexField(). Don't forget to call the parent
* constructor if you override it.
*
* @stable to extend
* @ingroup Pager
*/
abstract class IndexPager extends ContextSource implements Pager {
use ProtectedHookAccessorTrait;
/** Backwards-compatible constant for $mDefaultDirection field (do not change) */
public const DIR_ASCENDING = false;
/** Backwards-compatible constant for $mDefaultDirection field (do not change) */
public const DIR_DESCENDING = true;
/** Backwards-compatible constant for reallyDoQuery() (do not change) */
public const QUERY_ASCENDING = true;
/** Backwards-compatible constant for reallyDoQuery() (do not change) */
public const QUERY_DESCENDING = false;
/** @var WebRequest */
public $mRequest;
/** @var int[] List of default entry limit options to be presented to clients */
public $mLimitsShown = [ 20, 50, 100, 250, 500 ];
/** @var int The default entry limit choosen for clients */
public $mDefaultLimit = 50;
/** @var mixed The starting point to enumerate entries */
public $mOffset;
/** @var int The maximum number of entries to show */
public $mLimit;
/** @var bool Whether the listing query completed */
public $mQueryDone = false;
/** @var IDatabase */
public $mDb;
/** @var stdClass|bool|null Extra row fetched at the end to see if the end was reached */
public $mPastTheEndRow;
/**
* The index to actually be used for ordering. This can be a single column,
* an array of single columns, or an array of arrays of columns. See getIndexField
* for more details.
* @var string|string[]
*/
protected $mIndexField;
/**
* An array of secondary columns to order by. These fields are not part of the offset.
* This is a column list for one ordering, even if multiple orderings are supported.
* @var string[]
*/
protected $mExtraSortFields;
/** For pages that support multiple types of ordering, which one to use.
* @var string|null
*/
protected $mOrderType;
/**
* $mDefaultDirection gives the direction to use when sorting results:
* DIR_ASCENDING or DIR_DESCENDING. If $mIsBackwards is set, we start from
* the opposite end, but we still sort the page itself according to
* $mDefaultDirection. For example, if $mDefaultDirection is DIR_ASCENDING
* but we're going backwards, we'll display the last page of results, but
* the last result will be at the bottom, not the top.
*
* Like $mIndexField, $mDefaultDirection will be a single value even if the
* class supports multiple default directions for different order types.
* @var bool
*/
public $mDefaultDirection;
/** @var bool */
public $mIsBackwards;
/** @var bool True if the current result set is the first one */
public $mIsFirst;
/** @var bool */
public $mIsLast;
/** @var array */
protected $mLastShown;
/** @var array */
protected $mFirstShown;
/** @var array */
protected $mPastTheEndIndex;
/** @var array */
protected $mDefaultQuery;
/** @var string */
protected $mNavigationBar;
/**
* Whether to include the offset in the query
* @var bool
*/
protected $mIncludeOffset = false;
/**
* Result object for the query. Warning: seek before use.
*
* @var IResultWrapper
*/
public $mResult;
/** @var LinkRenderer */
private $linkRenderer;
/**
* @stable to call
*
* @param IContextSource|null $context
* @param LinkRenderer|null $linkRenderer
*/
public function __construct( IContextSource $context = null, LinkRenderer $linkRenderer = null ) {
if ( $context ) {
$this->setContext( $context );
}
$this->mRequest = $this->getRequest();
# NB: the offset is quoted, not validated. It is treated as an
# arbitrary string to support the widest variety of index types. Be
# careful outputting it into HTML!
$this->mOffset = $this->mRequest->getText( 'offset' );
# Use consistent behavior for the limit options
$this->mDefaultLimit = $this->getUser()->getIntOption( 'rclimit' );
if ( !$this->mLimit ) {
// Don't override if a subclass calls $this->setLimit() in its constructor.
list( $this->mLimit, /* $offset */ ) = $this->mRequest
->getLimitOffsetForUser( $this->getUser() );
}
$this->mIsBackwards = ( $this->mRequest->getVal( 'dir' ) == 'prev' );
# Let the subclass set the DB here; otherwise use a replica DB for the current wiki
$this->mDb = $this->mDb ?: wfGetDB( DB_REPLICA );
$index = $this->getIndexField(); // column to sort on
$extraSort = $this->getExtraSortFields(); // extra columns to sort on for query planning
$order = $this->mRequest->getVal( 'order' );
if ( is_array( $index ) && isset( $index[$order] ) ) {
$this->mOrderType = $order;
$this->mIndexField = $index[$order];
$this->mExtraSortFields = isset( $extraSort[$order] )
? (array)$extraSort[$order]
: [];
} elseif ( is_array( $index ) ) {
# First element is the default
$this->mIndexField = reset( $index );
$this->mOrderType = key( $index );
$this->mExtraSortFields = isset( $extraSort[$this->mOrderType] )
? (array)$extraSort[$this->mOrderType]
: [];
} else {
# $index is not an array
$this->mOrderType = null;
$this->mIndexField = $index;
$isSortAssociative = array_values( $extraSort ) !== $extraSort;
if ( $isSortAssociative ) {
$this->mExtraSortFields = isset( $extraSort[$index] )
? (array)$extraSort[$index]
: [];
} else {
$this->mExtraSortFields = (array)$extraSort;
}
}
if ( !isset( $this->mDefaultDirection ) ) {
$dir = $this->getDefaultDirections();
$this->mDefaultDirection = is_array( $dir )
? $dir[$this->mOrderType]
: $dir;
}
$this->linkRenderer = $linkRenderer;
}
/**
* Get the Database object in use
*
* @return IDatabase
*/
public function getDatabase() {
return $this->mDb;
}
/**
* Do the query, using information from the object context. This function
* has been kept minimal to make it overridable if necessary, to allow for
* result sets formed from multiple DB queries.
*
* @stable to override
*/
public function doQuery() {
$defaultOrder = ( $this->mDefaultDirection === self::DIR_ASCENDING )
? self::QUERY_ASCENDING
: self::QUERY_DESCENDING;
$order = $this->mIsBackwards ? self::oppositeOrder( $defaultOrder ) : $defaultOrder;
# Plus an extra row so that we can tell the "next" link should be shown
$queryLimit = $this->mLimit + 1;
if ( $this->mOffset == '' ) {
$isFirst = true;
} else {
// If there's an offset, we may or may not be at the first entry.
// The only way to tell is to run the query in the opposite
// direction see if we get a row.
$oldIncludeOffset = $this->mIncludeOffset;
$this->mIncludeOffset = !$this->mIncludeOffset;
$oppositeOrder = self::oppositeOrder( $order );
$isFirst = !$this->reallyDoQuery( $this->mOffset, 1, $oppositeOrder )->numRows();
$this->mIncludeOffset = $oldIncludeOffset;
}
$this->mResult = $this->reallyDoQuery(
$this->mOffset,
$queryLimit,
$order
);
$this->extractResultInfo( $isFirst, $queryLimit, $this->mResult );
$this->mQueryDone = true;
$this->preprocessResults( $this->mResult );
$this->mResult->rewind(); // Paranoia
}
/**
* @param bool $order One of the IndexPager::QUERY_* class constants
* @return bool The opposite query order as an IndexPager::QUERY_ constant
*/
final protected static function oppositeOrder( $order ) {
return ( $order === self::QUERY_ASCENDING )
? self::QUERY_DESCENDING
: self::QUERY_ASCENDING;
}
/**
* @return IResultWrapper The result wrapper.
*/
public function getResult() {
return $this->mResult;
}
/**
* Set the offset from an other source than the request
*
* @param int|string $offset
*/
public function setOffset( $offset ) {
$this->mOffset = $offset;
}
/**
* Set the limit from an other source than the request
*
* Verifies limit is between 1 and 5000
*
* @stable to override
*
* @param int|string $limit
*/
public function setLimit( $limit ) {
$limit = (int)$limit;
// WebRequest::getLimitOffsetForUser() puts a cap of 5000, so do same here.
if ( $limit > 5000 ) {
$limit = 5000;
}
if ( $limit > 0 ) {
$this->mLimit = $limit;
}
}
/**
* Get the current limit
*
* @return int
*/
public function getLimit() {
return $this->mLimit;
}
/**
* Set whether a row matching exactly the offset should be also included
* in the result or not. By default this is not the case, but when the
* offset is user-supplied this might be wanted.
*
* @param bool $include
*/
public function setIncludeOffset( $include ) {
$this->mIncludeOffset = $include;
}
/**
* Extract some useful data from the result object for use by
* the navigation bar, put it into $this
*
* @stable to override
*
* @param bool $isFirst False if there are rows before those fetched (i.e.
* if a "previous" link would make sense)
* @param int $limit Exact query limit
* @param IResultWrapper $res
*/
protected function extractResultInfo( $isFirst, $limit, IResultWrapper $res ) {
$numRows = $res->numRows();
$firstIndex = [];
$lastIndex = [];
$this->mPastTheEndIndex = [];
$this->mPastTheEndRow = null;
if ( $numRows ) {
$indexColumns = array_map( function ( $v ) {
// Remove any table prefix from index field
$parts = explode( '.', $v );
return end( $parts );
}, (array)$this->mIndexField );
$row = $res->fetchRow();
foreach ( $indexColumns as $indexColumn ) {
$firstIndex[] = $row[$indexColumn];
}
# Discard the extra result row if there is one
if ( $numRows > $this->mLimit && $numRows > 1 ) {
$res->seek( $numRows - 1 );
$this->mPastTheEndRow = $res->fetchObject();
foreach ( $indexColumns as $indexColumn ) {
$this->mPastTheEndIndex[] = $this->mPastTheEndRow->$indexColumn;
}
$res->seek( $numRows - 2 );
$row = $res->fetchRow();
foreach ( $indexColumns as $indexColumn ) {
$lastIndex[] = $row[$indexColumn];
}
} else {
$this->mPastTheEndRow = null;
$res->seek( $numRows - 1 );
$row = $res->fetchRow();
foreach ( $indexColumns as $indexColumn ) {
$lastIndex[] = $row[$indexColumn];
}
}
}
if ( $this->mIsBackwards ) {
$this->mIsFirst = ( $numRows < $limit );
$this->mIsLast = $isFirst;
$this->mLastShown = $firstIndex;
$this->mFirstShown = $lastIndex;
} else {
$this->mIsFirst = $isFirst;
$this->mIsLast = ( $numRows < $limit );
$this->mLastShown = $lastIndex;
$this->mFirstShown = $firstIndex;
}
}
/**
* Get some text to go in brackets in the "function name" part of the SQL comment
*
* @stable to override
*
* @return string
*/
protected function getSqlComment() {
return static::class;
}
/**
* Do a query with specified parameters, rather than using the object context
*
* @note For b/c, query direction is true for ascending and false for descending
*
* @stable to override
*
* @param string $offset Index offset, inclusive
* @param int $limit Exact query limit
* @param bool $order IndexPager::QUERY_ASCENDING or IndexPager::QUERY_DESCENDING
* @return IResultWrapper
*/
public function reallyDoQuery( $offset, $limit, $order ) {
list( $tables, $fields, $conds, $fname, $options, $join_conds ) =
$this->buildQueryInfo( $offset, $limit, $order );
return $this->mDb->select( $tables, $fields, $conds, $fname, $options, $join_conds );
}
/**
* Build variables to use by the database wrapper.
*
* @note For b/c, query direction is true for ascending and false for descending
*
* @stable to override
*
* @param int|string $offset Index offset, inclusive
* @param int $limit Exact query limit
* @param bool $order IndexPager::QUERY_ASCENDING or IndexPager::QUERY_DESCENDING
* @return array
*/
protected function buildQueryInfo( $offset, $limit, $order ) {
$fname = __METHOD__ . ' (' . $this->getSqlComment() . ')';
$info = $this->getQueryInfo();
$tables = $info['tables'];
$fields = $info['fields'];
$conds = $info['conds'] ?? [];
$options = $info['options'] ?? [];
$join_conds = $info['join_conds'] ?? [];
$indexColumns = (array)$this->mIndexField;
$sortColumns = array_merge( $indexColumns, $this->mExtraSortFields );
if ( $order === self::QUERY_ASCENDING ) {
$options['ORDER BY'] = $sortColumns;
$operator = $this->mIncludeOffset ? '>=' : '>';
} else {
$orderBy = [];
foreach ( $sortColumns as $col ) {
$orderBy[] = $col . ' DESC';
}
$options['ORDER BY'] = $orderBy;
$operator = $this->mIncludeOffset ? '<=' : '<';
}
if ( $offset != '' ) {
$offsets = explode( '|', $offset, /* Limit to max of indices */ count( $indexColumns ) );
$conds[] = $this->buildOffsetConds(
$offsets,
$indexColumns,
$operator
);
}
$options['LIMIT'] = intval( $limit );
return [ $tables, $fields, $conds, $fname, $options, $join_conds ];
}
/**
* Build the conditions for the offset, given that we may be paginating on a
* single column or multiple columns. Where we paginate on multiple columns,
* the sort order is defined by the order of the columns in $mIndexField.
*
* Some examples, with up to three columns. Each condition consists of inner
* conditions, at least one of which must be true (joined by OR):
*
* - column X, with offset value 'x':
* WHERE X>'x'
*
* - columns X and Y, with offsets 'x' and 'y':
* WHERE X>'x'
* OR ( X='x' AND Y>'y' )
*
* - columns X, Y and Z, with offsets 'x', 'y' and 'z':
* WHERE X>'x'
* OR ( X='x' AND Y>'y' )
* OR ( X='x' AND Y='y' AND Z>'z' )
*
* - and so on...
*
* (The examples assume we want the next page and do not want to include the
* offset in the results; otherwise the operators will be slightly different,
* as handled in buildQueryInfo.)
*
* Note that the above performs better than: WHERE (X,Y,Z)>('x','y','z').
*
* @param string[] $offsets The offset for each index field
* @param string[] $columns The name of each index field
* @param string $operator Operator for the final part of each inner
* condition. This will be '>' if the query order is ascending, or '<' if
* the query order is descending. If the offset should be included, it will
* also have '=' appended.
* @return string The conditions for getting results from the offset
*/
private function buildOffsetConds( $offsets, $columns, $operator ) {
$innerConds = [];
// $offsets and $columns are the same length
for ( $i = 1; $i <= count( $offsets ); $i++ ) {
$innerConds[] = $this->buildOffsetInnerConds(
array_slice( $offsets, 0, $i ),
array_slice( $columns, 0, $i ),
$operator
);
}
return $this->mDb->makeList( $innerConds, IDatabase::LIST_OR );
}
/**
* Build an inner part of an offset condition, consisting of inequalities
* joined by AND, as described in buildOffsetConds.
*
* @param string[] $offsets
* @param string[] $columns
* @param string $operator
* @return string The inner condition; to be concatenated in buildOffsetConds
*/
private function buildOffsetInnerConds( $offsets, $columns, $operator ) {
$conds = [];
while ( count( $offsets ) > 1 ) {
$conds[] = $columns[0] . '=' . $this->mDb->addQuotes( $offsets[0] );
array_shift( $columns );
array_shift( $offsets );
}
$conds[] = $columns[0] . $operator . $this->mDb->addQuotes( $offsets[0] );
return $this->mDb->makeList( $conds, IDatabase::LIST_AND );
}
/**
* Pre-process results; useful for performing batch existence checks, etc.
*
* @stable to override
*
* @param IResultWrapper $result
*/
protected function preprocessResults( $result ) {
}
/**
* Get the formatted result list. Calls getStartBody(), formatRow() and
* getEndBody(), concatenates the results and returns them.
*
* @stable to override
*
* @return string
*/
public function getBody() {
if ( !$this->mQueryDone ) {
$this->doQuery();
}
if ( $this->mResult->numRows() ) {
# Do any special query batches before display
$this->doBatchLookups();
}
# Don't use any extra rows returned by the query
$numRows = min( $this->mResult->numRows(), $this->mLimit );
$s = $this->getStartBody();
if ( $numRows ) {
if ( $this->mIsBackwards ) {
for ( $i = $numRows - 1; $i >= 0; $i-- ) {
$this->mResult->seek( $i );
$row = $this->mResult->fetchObject();
$s .= $this->formatRow( $row );
}
} else {
$this->mResult->seek( 0 );
for ( $i = 0; $i < $numRows; $i++ ) {
$row = $this->mResult->fetchObject();
$s .= $this->formatRow( $row );
}
}
} else {
$s .= $this->getEmptyBody();
}
$s .= $this->getEndBody();
return $s;
}
/**
* Make a self-link
*
* @stable to override
*
* @param string $text Text displayed on the link
* @param array|null $query Associative array of parameter to be in the query string
* @param string|null $type Link type used to create additional attributes, like "rel", "class" or
* "title". Valid values (non-exhaustive list): 'first', 'last', 'prev', 'next', 'asc', 'desc'.
* @return string HTML fragment
*/
protected function makeLink( $text, array $query = null, $type = null ) {
if ( $query === null ) {
return $text;
}
$attrs = [];
if ( in_array( $type, [ 'prev', 'next' ] ) ) {
$attrs['rel'] = $type;
}
if ( in_array( $type, [ 'asc', 'desc' ] ) ) {
$attrs['title'] = $this->msg( $type == 'asc' ? 'sort-ascending' : 'sort-descending' )->text();
}
if ( $type ) {
$attrs['class'] = "mw-{$type}link";
}
return $this->getLinkRenderer()->makeKnownLink(
$this->getTitle(),
new HtmlArmor( $text ),
$attrs,
$query + $this->getDefaultQuery()
);
}
/**
* Called from getBody(), before getStartBody() is called and
* after doQuery() was called. This will be called only if there
* are rows in the result set.
*
* @stable to override
*
* @return void
*/
protected function doBatchLookups() {
}
/**
* Hook into getBody(), allows text to be inserted at the start. This
* will be called even if there are no rows in the result set.
*
* @return string
*/
protected function getStartBody() {
return '';
}
/**
* Hook into getBody() for the end of the list
*
* @stable to override
*
* @return string
*/
protected function getEndBody() {
return '';
}
/**
* Hook into getBody(), for the bit between the start and the
* end when there are no rows
*
* @stable to override
*
* @return string
*/
protected function getEmptyBody() {
return '';
}
/**
* Get an array of query parameters that should be put into self-links.
* By default, all parameters passed in the URL are used, except for a
* short blacklist.
*
* @stable to override
*
* @return array Associative array
*/
public function getDefaultQuery() {
if ( !isset( $this->mDefaultQuery ) ) {
$this->mDefaultQuery = $this->getRequest()->getQueryValues();
unset( $this->mDefaultQuery['title'] );
unset( $this->mDefaultQuery['dir'] );
unset( $this->mDefaultQuery['offset'] );
unset( $this->mDefaultQuery['limit'] );
unset( $this->mDefaultQuery['order'] );
unset( $this->mDefaultQuery['month'] );
unset( $this->mDefaultQuery['year'] );
}
return $this->mDefaultQuery;
}
/**
* Get the number of rows in the result set
*
* @return int
*/
public function getNumRows() {
if ( !$this->mQueryDone ) {
$this->doQuery();
}
return $this->mResult->numRows();
}
/**
* Get a URL query array for the prev, next, first and last links.
*
* @stable to override
*
* @return array
*/
public function getPagingQueries() {
if ( !$this->mQueryDone ) {
$this->doQuery();
}
# Don't announce the limit everywhere if it's the default
$urlLimit = $this->mLimit == $this->mDefaultLimit ? null : $this->mLimit;
if ( $this->mIsFirst ) {
$prev = false;
$first = false;
} else {
$prev = [
'dir' => 'prev',
'offset' => implode( '|', (array)$this->mFirstShown ),
'limit' => $urlLimit
];
$first = [ 'limit' => $urlLimit ];
}
if ( $this->mIsLast ) {
$next = false;
$last = false;
} else {
$next = [ 'offset' => implode( '|', (array)$this->mLastShown ), 'limit' => $urlLimit ];
$last = [ 'dir' => 'prev', 'limit' => $urlLimit ];
}
return [
'prev' => $prev,
'next' => $next,
'first' => $first,
'last' => $last
];
}
/**
* Returns whether to show the "navigation bar"
* @stable to override
*
* @return bool
*/
protected function isNavigationBarShown() {
if ( !$this->mQueryDone ) {
$this->doQuery();
}
// Hide navigation by default if there is nothing to page
return !( $this->mIsFirst && $this->mIsLast );
}
/**
* Get paging links. If a link is disabled, the item from $disabledTexts
* will be used. If there is no such item, the unlinked text from
* $linkTexts will be used. Both $linkTexts and $disabledTexts are arrays
* of HTML.
*
* @param array $linkTexts
* @param array $disabledTexts
* @return array
*/
protected function getPagingLinks( $linkTexts, $disabledTexts = [] ) {
$queries = $this->getPagingQueries();
$links = [];
foreach ( $queries as $type => $query ) {
if ( $query !== false ) {
$links[$type] = $this->makeLink(
$linkTexts[$type],
$query,
$type
);
} elseif ( isset( $disabledTexts[$type] ) ) {
$links[$type] = $disabledTexts[$type];
} else {
$links[$type] = $linkTexts[$type];
}
}
return $links;
}
protected function getLimitLinks() {
$links = [];
if ( $this->mIsBackwards ) {
$offset = implode( '|', (array)$this->mPastTheEndIndex );
} else {
$offset = $this->mOffset;
}
foreach ( $this->mLimitsShown as $limit ) {
$links[] = $this->makeLink(
$this->getLanguage()->formatNum( $limit ),
[ 'offset' => $offset, 'limit' => $limit ],
'num'
);
}
return $links;
}
/**
* Returns an HTML string representing the result row $row.
* Rows will be concatenated and returned by getBody()
*
* @param array|stdClass $row Database row
* @return string
*/
abstract public function formatRow( $row );
/**
* Provides all parameters needed for the main paged query. It returns
* an associative array with the following elements:
* tables => Table(s) for passing to Database::select()
* fields => Field(s) for passing to Database::select(), may be *
* conds => WHERE conditions
* options => option array
* join_conds => JOIN conditions
*
* @return array
*/
abstract public function getQueryInfo();
/**
* Returns the name of the index field. If the pager supports multiple
* orders, it may return an array of 'querykey' => 'indexfield' pairs,
* so that a request with &order=querykey will use indexfield to sort.
* In this case, the first returned key is the default.
*
* Needless to say, it's really not a good idea to use a non-unique index
* for this! That won't page right.
*
* The pager may paginate on multiple fields in combination. If paginating
* on multiple fields, they should be unique in combination (e.g. when
* paginating on user and timestamp, rows may have the same user, rows may
* have the same timestamp, but rows should all have a different combination
* of user and timestamp).
*
* Examples:
* - Always paginate on the user field:
* 'user'
* - Paginate on either the user or the timestamp field (default to user):
* [
* 'name' => 'user',
* 'time' => 'timestamp',
* ]
* - Always paginate on the combination of user and timestamp:
* [
* [ 'user', 'timestamp' ]
* ]
* - Paginate on the user then timestamp, or the timestamp then user:
* [
* 'nametime' => [ 'user', 'timestamp' ],
* 'timename' => [ 'timestamp', 'user' ],
* ]
*
*
* @return string|string[]|array[]
*/
abstract public function getIndexField();
/**
* Returns the names of secondary columns to order by in addition to the
* column in getIndexField(). These fields will not be used in the pager
* offset or in any links for users.
*
* If getIndexField() returns an array of 'querykey' => 'indexfield' pairs then
* this must return a corresponding array of 'querykey' => [ fields... ] pairs
* in order for a request with &order=querykey to use [ fields... ] to sort.
*
* If getIndexField() returns a string with the field to sort by, this must either:
* 1 - return an associative array like above, but only the elements for the current
* field will be used.
* 2 - return a non-associative array, for secondary keys to use always.
*
* This is useful for pagers that GROUP BY a unique column (say page_id)
* and ORDER BY another (say page_len). Using GROUP BY and ORDER BY both on
* page_len,page_id avoids temp tables (given a page_len index). This would
* also work if page_id was non-unique but we had a page_len,page_id index.
*
* @stable to override
*
* @return string[]|array[]
*/
protected function getExtraSortFields() {
return [];
}
/**
* Return the default sorting direction: DIR_ASCENDING or DIR_DESCENDING.
* You can also have an associative array of ordertype => dir,
* if multiple order types are supported. In this case getIndexField()
* must return an array, and the keys of that must exactly match the keys
* of this.
*
* For backward compatibility, this method's return value will be ignored
* if $this->mDefaultDirection is already set when the constructor is
* called, for instance if it's statically initialized. In that case the
* value of that variable (which must be a boolean) will be used.
*
* Note that despite its name, this does not return the value of the
* $this->mDefaultDirection member variable. That's the default for this
* particular instantiation, which is a single value. This is the set of
* all defaults for the class.
*
* @stable to override
*
* @return bool
*/
protected function getDefaultDirections() {
return self::DIR_ASCENDING;
}
/**
* Generate (prev x| next x) (20|50|100...) type links for paging
*
* @param Title $title
* @param int $offset
* @param int $limit
* @param array $query Optional URL query parameter string
* @param bool $atend Optional param for specified if this is the last page
* @return string
*/
protected function buildPrevNextNavigation(
Title $title,
$offset,
$limit,
array $query = [],
$atend = false
) {
$prevNext = new PrevNextNavigationRenderer( $this );
return $prevNext->buildPrevNextNavigation( $title, $offset, $limit, $query, $atend );
}
protected function getLinkRenderer() {
if ( $this->linkRenderer === null ) {
$this->linkRenderer = MediaWikiServices::getInstance()->getLinkRenderer();
}
return $this->linkRenderer;
}
}