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Diffstat (limited to 'includes/pager/IndexPager.php')
-rw-r--r-- | includes/pager/IndexPager.php | 742 |
1 files changed, 742 insertions, 0 deletions
diff --git a/includes/pager/IndexPager.php b/includes/pager/IndexPager.php new file mode 100644 index 00000000..ce6dc50c --- /dev/null +++ b/includes/pager/IndexPager.php @@ -0,0 +1,742 @@ +<?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 + */ + +/** + * 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. + * + * @ingroup Pager + */ +abstract class IndexPager extends ContextSource implements Pager { + /** + * Constants for the $mDefaultDirection field. + * + * These are boolean for historical reasons and should stay boolean for backwards-compatibility. + */ + const DIR_ASCENDING = false; + const DIR_DESCENDING = true; + + public $mRequest; + public $mLimitsShown = array( 20, 50, 100, 250, 500 ); + public $mDefaultLimit = 50; + public $mOffset, $mLimit; + public $mQueryDone = false; + public $mDb; + public $mPastTheEndRow; + + /** + * The index to actually be used for ordering. This is a single column, + * for one ordering, even if multiple orderings are supported. + */ + 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. + */ + protected $mExtraSortFields; + /** For pages that support multiple types of ordering, which one to use. + */ + 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. E.g., if $mDefaultDirection is false 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. + */ + public $mDefaultDirection; + public $mIsBackwards; + + /** True if the current result set is the first one */ + public $mIsFirst; + public $mIsLast; + + protected $mLastShown, $mFirstShown, $mPastTheEndIndex, $mDefaultQuery, $mNavigationBar; + + /** + * Whether to include the offset in the query + */ + protected $mIncludeOffset = false; + + /** + * Result object for the query. Warning: seek before use. + * + * @var ResultWrapper + */ + public $mResult; + + public function __construct( IContextSource $context = 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->getLimitOffset(); + } + + $this->mIsBackwards = ( $this->mRequest->getVal( 'dir' ) == 'prev' ); + # Let the subclass set the DB here; otherwise use a slave DB for the current wiki + $this->mDb = $this->mDb ?: wfGetDB( DB_SLAVE ); + + $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] + : array(); + } elseif ( is_array( $index ) ) { + # First element is the default + reset( $index ); + list( $this->mOrderType, $this->mIndexField ) = each( $index ); + $this->mExtraSortFields = isset( $extraSort[$this->mOrderType] ) + ? (array)$extraSort[$this->mOrderType] + : array(); + } else { + # $index is not an array + $this->mOrderType = null; + $this->mIndexField = $index; + $this->mExtraSortFields = (array)$extraSort; + } + + if ( !isset( $this->mDefaultDirection ) ) { + $dir = $this->getDefaultDirections(); + $this->mDefaultDirection = is_array( $dir ) + ? $dir[$this->mOrderType] + : $dir; + } + } + + /** + * Get the Database object in use + * + * @return DatabaseBase + */ + 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. + */ + public function doQuery() { + # Use the child class name for profiling + $fname = __METHOD__ . ' (' . get_class( $this ) . ')'; + wfProfileIn( $fname ); + + // @todo This should probably compare to DIR_DESCENDING and DIR_ASCENDING constants + $descending = ( $this->mIsBackwards == $this->mDefaultDirection ); + # 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; + $isFirst = !$this->reallyDoQuery( $this->mOffset, 1, !$descending )->numRows(); + $this->mIncludeOffset = $oldIncludeOffset; + } + + $this->mResult = $this->reallyDoQuery( + $this->mOffset, + $queryLimit, + $descending + ); + + $this->extractResultInfo( $isFirst, $queryLimit, $this->mResult ); + $this->mQueryDone = true; + + $this->preprocessResults( $this->mResult ); + $this->mResult->rewind(); // Paranoia + + wfProfileOut( $fname ); + } + + /** + * @return ResultWrapper The result wrapper. + */ + function getResult() { + return $this->mResult; + } + + /** + * Set the offset from an other source than the request + * + * @param int|string $offset + */ + function setOffset( $offset ) { + $this->mOffset = $offset; + } + + /** + * Set the limit from an other source than the request + * + * Verifies limit is between 1 and 5000 + * + * @param int|string $limit + */ + function setLimit( $limit ) { + $limit = (int)$limit; + // WebRequest::getLimitOffset() 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 + */ + 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 + * + * @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 ResultWrapper $res + */ + function extractResultInfo( $isFirst, $limit, ResultWrapper $res ) { + $numRows = $res->numRows(); + if ( $numRows ) { + # Remove any table prefix from index field + $parts = explode( '.', $this->mIndexField ); + $indexColumn = end( $parts ); + + $row = $res->fetchRow(); + $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(); + $this->mPastTheEndIndex = $this->mPastTheEndRow->$indexColumn; + $res->seek( $numRows - 2 ); + $row = $res->fetchRow(); + $lastIndex = $row[$indexColumn]; + } else { + $this->mPastTheEndRow = null; + # Setting indexes to an empty string means that they will be + # omitted if they would otherwise appear in URLs. It just so + # happens that this is the right thing to do in the standard + # UI, in all the relevant cases. + $this->mPastTheEndIndex = ''; + $res->seek( $numRows - 1 ); + $row = $res->fetchRow(); + $lastIndex = $row[$indexColumn]; + } + } else { + $firstIndex = ''; + $lastIndex = ''; + $this->mPastTheEndRow = null; + $this->mPastTheEndIndex = ''; + } + + 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 + * + * @return string + */ + function getSqlComment() { + return get_class( $this ); + } + + /** + * Do a query with specified parameters, rather than using the object + * context + * + * @param string $offset Index offset, inclusive + * @param int $limit Exact query limit + * @param bool $descending Query direction, false for ascending, true for descending + * @return ResultWrapper + */ + public function reallyDoQuery( $offset, $limit, $descending ) { + list( $tables, $fields, $conds, $fname, $options, $join_conds ) = + $this->buildQueryInfo( $offset, $limit, $descending ); + + return $this->mDb->select( $tables, $fields, $conds, $fname, $options, $join_conds ); + } + + /** + * Build variables to use by the database wrapper. + * + * @param string $offset Index offset, inclusive + * @param int $limit Exact query limit + * @param bool $descending Query direction, false for ascending, true for descending + * @return array + */ + protected function buildQueryInfo( $offset, $limit, $descending ) { + $fname = __METHOD__ . ' (' . $this->getSqlComment() . ')'; + $info = $this->getQueryInfo(); + $tables = $info['tables']; + $fields = $info['fields']; + $conds = isset( $info['conds'] ) ? $info['conds'] : array(); + $options = isset( $info['options'] ) ? $info['options'] : array(); + $join_conds = isset( $info['join_conds'] ) ? $info['join_conds'] : array(); + $sortColumns = array_merge( array( $this->mIndexField ), $this->mExtraSortFields ); + if ( $descending ) { + $options['ORDER BY'] = $sortColumns; + $operator = $this->mIncludeOffset ? '>=' : '>'; + } else { + $orderBy = array(); + foreach ( $sortColumns as $col ) { + $orderBy[] = $col . ' DESC'; + } + $options['ORDER BY'] = $orderBy; + $operator = $this->mIncludeOffset ? '<=' : '<'; + } + if ( $offset != '' ) { + $conds[] = $this->mIndexField . $operator . $this->mDb->addQuotes( $offset ); + } + $options['LIMIT'] = intval( $limit ); + return array( $tables, $fields, $conds, $fname, $options, $join_conds ); + } + + /** + * Pre-process results; useful for performing batch existence checks, etc. + * + * @param ResultWrapper $result + */ + protected function preprocessResults( $result ) { + } + + /** + * Get the formatted result list. Calls getStartBody(), formatRow() and + * getEndBody(), concatenates the results and returns them. + * + * @return string + */ + public function getBody() { + if ( !$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 + * + * @param string $text Text displayed on the link + * @param array $query Associative array of parameter to be in the query string + * @param string $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 + */ + function makeLink( $text, array $query = null, $type = null ) { + if ( $query === null ) { + return $text; + } + + $attrs = array(); + if ( in_array( $type, array( 'prev', 'next' ) ) ) { + $attrs['rel'] = $type; + } + + if ( in_array( $type, array( 'asc', 'desc' ) ) ) { + $attrs['title'] = wfMessage( $type == 'asc' ? 'sort-ascending' : 'sort-descending' )->text(); + } + + if ( $type ) { + $attrs['class'] = "mw-{$type}link"; + } + + + return Linker::linkKnown( + $this->getTitle(), + $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. + * + * @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 + * + * @return string + */ + protected function getEndBody() { + return ''; + } + + /** + * Hook into getBody(), for the bit between the start and the + * end when there are no rows + * + * @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. + * + * @return array Associative array + */ + 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 $this->mDefaultQuery; + } + + /** + * Get the number of rows in the result set + * + * @return int + */ + function getNumRows() { + if ( !$this->mQueryDone ) { + $this->doQuery(); + } + return $this->mResult->numRows(); + } + + /** + * Get a URL query array for the prev, next, first and last links. + * + * @return array + */ + function getPagingQueries() { + if ( !$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 = array( + 'dir' => 'prev', + 'offset' => $this->mFirstShown, + 'limit' => $urlLimit + ); + $first = array( 'limit' => $urlLimit ); + } + if ( $this->mIsLast ) { + $next = false; + $last = false; + } else { + $next = array( 'offset' => $this->mLastShown, 'limit' => $urlLimit ); + $last = array( 'dir' => 'prev', 'limit' => $urlLimit ); + } + return array( + 'prev' => $prev, + 'next' => $next, + 'first' => $first, + 'last' => $last + ); + } + + /** + * Returns whether to show the "navigation bar" + * + * @return bool + */ + function isNavigationBarShown() { + if ( !$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 + */ + function getPagingLinks( $linkTexts, $disabledTexts = array() ) { + $queries = $this->getPagingQueries(); + $links = array(); + + foreach ( $queries as $type => $query ) { + if ( $query !== false ) { + $links[$type] = $this->makeLink( + $linkTexts[$type], + $queries[$type], + $type + ); + } elseif ( isset( $disabledTexts[$type] ) ) { + $links[$type] = $disabledTexts[$type]; + } else { + $links[$type] = $linkTexts[$type]; + } + } + + return $links; + } + + function getLimitLinks() { + $links = array(); + if ( $this->mIsBackwards ) { + $offset = $this->mPastTheEndIndex; + } else { + $offset = $this->mOffset; + } + foreach ( $this->mLimitsShown as $limit ) { + $links[] = $this->makeLink( + $this->getLanguage()->formatNum( $limit ), + array( 'offset' => $offset, 'limit' => $limit ), + 'num' + ); + } + return $links; + } + + /** + * Abstract formatting function. This should return 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 function formatRow( $row ); + + /** + * This function should be overridden to provide 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 function getQueryInfo(); + + /** + * This function should be overridden to return the name of the index fi- + * eld. If the pager supports multiple orders, it may return an array of + * 'querykey' => 'indexfield' pairs, so that a request with &count=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. + * + * @return string|array + */ + abstract function getIndexField(); + + /** + * This function should be overridden to return 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' => array( fields...) pairs + * in order for a request with &count=querykey to use array( fields...) to sort. + * + * 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. + * + * @return array + */ + protected function getExtraSortFields() { + return array(); + } + + /** + * 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. + * + * @return bool + */ + protected function getDefaultDirections() { + return IndexPager::DIR_ASCENDING; + } +} |