* Replaced WikiPage::DATA_FROM_* constants with IDBAccessObject ones.
* Renamed IDBAccessObject constants a bit for visual consistency.
* Removed AVOID_MASTER parameter and replaced calling instances with READ_NORMAL.
Instead of getting page_latest from the master and the revision from a
slave, just get it all from the master in one RTT. Most callers used
AVOID_MASTER (and now READ_NORMAL), so this case is barely hit anymore.
Change-Id: Ifbefdcd4490094b38e49bbb46c95fdb71b5c9e1a
protected $mTitle;
protected $mCurrent;
+ // Revision deletion constants
const DELETED_TEXT = 1;
const DELETED_COMMENT = 2;
const DELETED_USER = 4;
const DELETED_RESTRICTED = 8;
- // Convenience field
- const SUPPRESSED_USER = 12;
+ const SUPPRESSED_USER = 12; // convenience
+
// Audience options for accessors
const FOR_PUBLIC = 1;
const FOR_THIS_USER = 2;
* Returns null if no such revision can be found.
*
* $flags include:
- * IDBAccessObject::LATEST_READ : Select the data from the master
- * IDBAccessObject::LOCKING_READ : Select & lock the data from the master
- * IDBAccessObject::AVOID_MASTER : Avoid master queries; data may be stale
+ * Revision::READ_LATEST : Select the data from the master
+ * Revision::READ_LOCKING : Select & lock the data from the master
*
* @param $id Integer
* @param $flags Integer (optional)
* to that title, will return null.
*
* $flags include:
- * IDBAccessObject::LATEST_READ : Select the data from the master
- * IDBAccessObject::LOCKING_READ : Select & lock the data from the master
- * IDBAccessObject::AVOID_MASTER : Avoid master queries; data may be stale
+ * Revision::READ_LATEST : Select the data from the master
+ * Revision::READ_LOCKING : Select & lock the data from the master
*
* @param $title Title
* @param $id Integer (optional)
* @param $flags Integer Bitfield (optional)
* @return Revision or null
*/
- public static function newFromTitle( $title, $id = 0, $flags = 0 ) {
+ public static function newFromTitle( $title, $id = 0, $flags = null ) {
$conds = array(
'page_namespace' => $title->getNamespace(),
'page_title' => $title->getDBkey()
if ( $id ) {
// Use the specified ID
$conds['rev_id'] = $id;
- } elseif ( !( $flags & self::AVOID_MASTER ) && wfGetLB()->getServerCount() > 1 ) {
- // Get the latest revision ID from the master
- $dbw = wfGetDB( DB_MASTER );
- $latest = $dbw->selectField( 'page', 'page_latest', $conds, __METHOD__ );
- if ( $latest === false ) {
- return null; // page does not exist
- }
- $conds['rev_id'] = $latest;
} else {
// Use a join to get the latest revision
$conds[] = 'rev_id=page_latest';
+ // Callers assume this will be up-to-date
+ $flags = is_int( $flags ) ? $flags : self::READ_LATEST; // b/c
}
- return self::newFromConds( $conds, $flags );
+ return self::newFromConds( $conds, (int)$flags );
}
/**
* Returns null if no such revision can be found.
*
* $flags include:
- * IDBAccessObject::LATEST_READ : Select the data from the master
- * IDBAccessObject::LOCKING_READ : Select & lock the data from the master
- * IDBAccessObject::AVOID_MASTER : Avoid master queries; data may be stale
+ * Revision::READ_LATEST : Select the data from the master
+ * Revision::READ_LOCKING : Select & lock the data from the master
*
* @param $revId Integer
* @param $pageId Integer (optional)
* @param $flags Integer Bitfield (optional)
* @return Revision or null
*/
- public static function newFromPageId( $pageId, $revId = 0, $flags = 0 ) {
+ public static function newFromPageId( $pageId, $revId = 0, $flags = null ) {
$conds = array( 'page_id' => $pageId );
if ( $revId ) {
$conds['rev_id'] = $revId;
- } elseif ( !( $flags & self::AVOID_MASTER ) && wfGetLB()->getServerCount() > 1 ) {
- // Get the latest revision ID from the master
- $dbw = wfGetDB( DB_MASTER );
- $latest = $dbw->selectField( 'page', 'page_latest', $conds, __METHOD__ );
- if ( $latest === false ) {
- return null; // page does not exist
- }
- $conds['rev_id'] = $latest;
} else {
+ // Use a join to get the latest revision
$conds[] = 'rev_id = page_latest';
+ // Callers assume this will be up-to-date
+ $flags = is_int( $flags ) ? $flags : self::READ_LATEST; // b/c
}
- return self::newFromConds( $conds, $flags );
+ return self::newFromConds( $conds, (int)$flags );
}
/**
* @return Revision or null
*/
private static function newFromConds( $conditions, $flags = 0 ) {
- $db = wfGetDB( ( $flags & self::LATEST_READ ) ? DB_MASTER : DB_SLAVE );
+ $db = wfGetDB( ( $flags & self::READ_LATEST ) ? DB_MASTER : DB_SLAVE );
$rev = self::loadFromConds( $db, $conditions, $flags );
if ( is_null( $rev ) && wfGetLB()->getServerCount() > 1 ) {
- if ( !( $flags & self::LATEST_READ ) && !( $flags & self::AVOID_MASTER ) ) {
+ if ( !( $flags & self::READ_LATEST ) ) {
$dbw = wfGetDB( DB_MASTER );
$rev = self::loadFromConds( $dbw, $conditions, $flags );
}
self::selectUserFields()
);
$options = array( 'LIMIT' => 1 );
- if ( $flags & self::FOR_UPDATE ) {
+ if ( $flags & self::READ_LOCKING ) {
$options[] = 'FOR UPDATE';
}
return $db->select(
*
* @internal documentation reviewed 15 Mar 2010
*/
-class WikiPage extends Page {
+class WikiPage extends Page implements IDBAccessObject {
// Constants for $mDataLoadedFrom and related
- /**
- * Data has not been loaded yet (or the object was cleared)
- */
- const DATA_NOT_LOADED = 0;
-
- /**
- * Data has been loaded from a slave database
- */
- const DATA_FROM_SLAVE = 1;
-
- /**
- * Data has been loaded from the master database
- */
- const DATA_FROM_MASTER = 2;
-
- /**
- * Data has been loaded from the master database using FOR UPDATE
- */
- const DATA_FOR_UPDATE = 3;
-
/**
* @var Title
*/
/**@}}*/
/**
- * @var int; one of the DATA_* constants
+ * @var int; one of the READ_* constants
*/
- protected $mDataLoadedFrom = self::DATA_NOT_LOADED;
+ protected $mDataLoadedFrom = self::READ_NONE;
/**
* @var Title
*
* @param $id Int article ID to load
* @param $from string|int one of the following values:
- * - "fromdb" or self::DATA_FROM_SLAVE to select from a slave database
- * - "fromdbmaster" or self::DATA_FROM_MASTER to select from the master database
+ * - "fromdb" or WikiPage::READ_NORMAL to select from a slave database
+ * - "fromdbmaster" or WikiPage::READ_LATEST to select from the master database
*
* @return WikiPage|null
*/
public static function newFromID( $id, $from = 'fromdb' ) {
$from = self::convertSelectType( $from );
- $db = wfGetDB( $from === self::DATA_FROM_MASTER ? DB_MASTER : DB_SLAVE );
+ $db = wfGetDB( $from === self::READ_LATEST ? DB_MASTER : DB_SLAVE );
$row = $db->selectRow( 'page', self::selectFields(), array( 'page_id' => $id ), __METHOD__ );
if ( !$row ) {
return null;
* @param $row object: database row containing at least fields returned
* by selectFields().
* @param $from string|int: source of $data:
- * - "fromdb" or self::DATA_FROM_SLAVE: from a slave DB
- * - "fromdbmaster" or self::DATA_FROM_MASTER: from the master DB
- * - "forupdate" or self::DATA_FOR_UPDATE: from the master DB using SELECT FOR UPDATE
+ * - "fromdb" or WikiPage::READ_NORMAL: from a slave DB
+ * - "fromdbmaster" or WikiPage::READ_LATEST: from the master DB
+ * - "forupdate" or WikiPage::READ_LOCKING: from the master DB using SELECT FOR UPDATE
* @return WikiPage
*/
public static function newFromRow( $row, $from = 'fromdb' ) {
}
/**
- * Convert 'fromdb', 'fromdbmaster' and 'forupdate' to DATA_* constants.
+ * Convert 'fromdb', 'fromdbmaster' and 'forupdate' to READ_* constants.
*
* @param $type object|string|int
* @return mixed
private static function convertSelectType( $type ) {
switch ( $type ) {
case 'fromdb':
- return self::DATA_FROM_SLAVE;
+ return self::READ_NORMAL;
case 'fromdbmaster':
- return self::DATA_FROM_MASTER;
+ return self::READ_LATEST;
case 'forupdate':
- return self::DATA_FOR_UPDATE;
+ return self::READ_LOCKING;
default:
// It may already be an integer or whatever else
return $type;
*/
public function clear() {
$this->mDataLoaded = false;
- $this->mDataLoadedFrom = self::DATA_NOT_LOADED;
+ $this->mDataLoadedFrom = self::READ_NONE;
$this->clearCacheFields();
}
*
* @param $from object|string|int One of the following:
* - A DB query result object
- * - "fromdb" or self::DATA_FROM_SLAVE to get from a slave DB
- * - "fromdbmaster" or self::DATA_FROM_MASTER to get from the master DB
- * - "forupdate" or self::DATA_FOR_UPDATE to get from the master DB using SELECT FOR UPDATE
+ * - "fromdb" or WikiPage::READ_NORMAL to get from a slave DB
+ * - "fromdbmaster" or WikiPage::READ_LATEST to get from the master DB
+ * - "forupdate" or WikiPage::READ_LOCKING to get from the master DB using SELECT FOR UPDATE
*
* @return void
*/
return;
}
- if ( $from === self::DATA_FOR_UPDATE ) {
+ if ( $from === self::READ_LOCKING ) {
$data = $this->pageDataFromTitle( wfGetDB( DB_MASTER ), $this->mTitle, array( 'FOR UPDATE' ) );
- } elseif ( $from === self::DATA_FROM_MASTER ) {
+ } elseif ( $from === self::READ_LATEST ) {
$data = $this->pageDataFromTitle( wfGetDB( DB_MASTER ), $this->mTitle );
- } elseif ( $from === self::DATA_FROM_SLAVE ) {
+ } elseif ( $from === self::READ_NORMAL ) {
$data = $this->pageDataFromTitle( wfGetDB( DB_SLAVE ), $this->mTitle );
# Use a "last rev inserted" timestamp key to dimish the issue of slave lag.
# Note that DB also stores the master position in the session and checks it.
$touched = $this->getCachedLastEditTime();
if ( $touched ) { // key set
if ( !$data || $touched > wfTimestamp( TS_MW, $data->page_touched ) ) {
- $from = self::DATA_FROM_MASTER;
+ $from = self::READ_LATEST;
$data = $this->pageDataFromTitle( wfGetDB( DB_MASTER ), $this->mTitle );
}
}
} else {
// No idea from where the caller got this data, assume slave database.
$data = $from;
- $from = self::DATA_FROM_SLAVE;
+ $from = self::READ_NORMAL;
}
$this->loadFromRow( $data, $from );
* @param $data object: database row containing at least fields returned
* by selectFields()
* @param $from string|int One of the following:
- * - "fromdb" or self::DATA_FROM_SLAVE if the data comes from a slave DB
- * - "fromdbmaster" or self::DATA_FROM_MASTER if the data comes from the master DB
- * - "forupdate" or self::DATA_FOR_UPDATE if the data comes from from
+ * - "fromdb" or WikiPage::READ_NORMAL if the data comes from a slave DB
+ * - "fromdbmaster" or WikiPage::READ_LATEST if the data comes from the master DB
+ * - "forupdate" or WikiPage::READ_LOCKING if the data comes from from
* the master DB using SELECT FOR UPDATE
*/
public function loadFromRow( $data, $from ) {
// also gets the revision row FOR UPDATE; otherwise, it may not find it since a page row
// UPDATE and revision row INSERT by S2 may have happened after the first S1 SELECT.
// http://dev.mysql.com/doc/refman/5.0/en/set-transaction.html#isolevel_repeatable-read.
- $flags = ( $this->mDataLoadedFrom == self::DATA_FOR_UPDATE ) ? Revision::LOCKING_READ : 0;
+ $flags = ( $this->mDataLoadedFrom == self::READ_LOCKING ) ? Revision::READ_LOCKING : 0;
$revision = Revision::newFromPageId( $this->getId(), $latest, $flags );
if ( $revision ) { // sanity
$this->setLastEdit( $revision );
*/
/**
- * Interface for database access objects
+ * Interface for database access objects.
+ *
+ * Classes using this support a set of constants in a bitfield argument to their data loading
+ * functions. In general, objects should assume READ_NORMAL if no flags are explicitly given,
+ * though certain objects may assume READ_LATEST for common use case or legacy reasons.
+ *
+ * There are three types of reads:
+ * - READ_NORMAL : Potentially cached read of data (e.g. from a slave or stale replica)
+ * - READ_LATEST : Up-to-date read as of transaction start (e.g. from master or a quorum read)
+ * - READ_LOCKING : Up-to-date read as of now, that locks the records for the transaction
+ *
+ * Callers should use READ_NORMAL (or pass in no flags) unless the read determines a write.
+ * In theory, such cases may require READ_LOCKING, though to avoid contention, READ_LATEST is
+ * often good enough. If UPDATE race condition checks are required on a row and expensive code
+ * must run after the row is fetched to determine the UPDATE, it may help to do something like:
+ * - a) Read the current row
+ * - b) Determine the new row (expensive, so we don't want to hold locks now)
+ * - c) Re-read the current row with READ_LOCKING; if it changed then bail out
+ * - d) otherwise, do the updates
*/
interface IDBAccessObject {
- const LATEST_READ = 1; // read from the master
- const FOR_UPDATE = 2; // lock the rows read
- const LOCKING_READ = 3; // LATEST_READ | FOR_UPDATE
- const AVOID_MASTER = 4; // avoiding checking the master
+ // Constants for object loading bitfield flags (higher => higher QoS)
+ const READ_LATEST = 1; // read from the master
+ const READ_LOCKING = 3; // READ_LATEST and "FOR UPDATE"
+
+ // Convenience constant for callers to explicitly request slave data
+ const READ_NORMAL = 0; // read from the slave
+
+ // Convenience constant for tracking how data was loaded (higher => higher QoS)
+ const READ_NONE = -1; // not loaded yet (or the object was cleared)
}
// Load the new revision object
$this->mNewRev = $this->mNewid
? Revision::newFromId( $this->mNewid )
- : Revision::newFromTitle( $this->getTitle(), false, Revision::AVOID_MASTER );
+ : Revision::newFromTitle( $this->getTitle(), false, Revision::READ_NORMAL );
if ( !$this->mNewRev instanceof Revision ) {
return false;
*/
function getDescriptionText() {
global $wgParser;
- $revision = Revision::newFromTitle( $this->title, false, Revision::AVOID_MASTER );
+ $revision = Revision::newFromTitle( $this->title, false, Revision::READ_NORMAL );
if ( !$revision ) return false;
$text = $revision->getText();
if ( !$text ) return false;
wfGetLB()->waitFor( $this->params['masterPos'] );
}
- $revision = Revision::newFromTitle( $this->title, 0, Revision::AVOID_MASTER );
+ $revision = Revision::newFromTitle( $this->title, 0, Revision::READ_NORMAL );
if ( !$revision ) {
$this->error = 'refreshLinks: Article not found "' .
$this->title->getPrefixedDBkey() . '"';
}
# Re-parse each page that transcludes this page and update their tracking links...
foreach ( $titles as $title ) {
- $revision = Revision::newFromTitle( $title, 0, Revision::AVOID_MASTER );
+ $revision = Revision::newFromTitle( $title, 0, Revision::READ_NORMAL );
if ( !$revision ) {
$this->error = 'refreshLinks: Article not found "' .
$title->getPrefixedDBkey() . '"';
# Get the revision
$rev = $id
? Revision::newFromId( $id )
- : Revision::newFromTitle( $title, 0, Revision::AVOID_MASTER );
+ : Revision::newFromTitle( $title, 0, Revision::READ_NORMAL );
$rev_id = $rev ? $rev->getId() : 0;
# If there is no current revision, there is no page
if ( $id === false && !$rev ) {
$this->mTitle = $title;
if ( !is_null( $this->mTitle ) ) {
$this->mRevision = Revision::newFromTitle(
- $this->mTitle, false, Revision::AVOID_MASTER );
+ $this->mTitle, false, Revision::READ_NORMAL );
if ( $this->mTitle->getNamespace() === NS_FILE )
$this->mImage = wfFindFile( $this->mTitle );
}
$page = $this->msg( 'booksources' )->inContentLanguage()->text();
$title = Title::makeTitleSafe( NS_PROJECT, $page ); # Show list in content language
if( is_object( $title ) && $title->exists() ) {
- $rev = Revision::newFromTitle( $title, false, Revision::AVOID_MASTER );
+ $rev = Revision::newFromTitle( $title, false, Revision::READ_NORMAL );
$this->getOutput()->addWikiText( str_replace( 'MAGICNUMBER', $this->isbn, $rev->getText() ) );
return true;
}
dépôts / lhc / web / wiklou.git / commitdiff