Current File : //www/varak.net/wiki.varak.net/includes/Storage/NameTableStore.php
<?php
/**
* 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
*/
namespace MediaWiki\Storage;
use IExpiringStore;
use Psr\Log\LoggerInterface;
use WANObjectCache;
use Wikimedia\Assert\Assert;
use Wikimedia\Rdbms\Database;
use Wikimedia\Rdbms\IDatabase;
use Wikimedia\Rdbms\ILoadBalancer;
/**
* @author Addshore
* @since 1.31
*/
class NameTableStore {
/** @var ILoadBalancer */
private $loadBalancer;
/** @var WANObjectCache */
private $cache;
/** @var LoggerInterface */
private $logger;
/** @var string[] */
private $tableCache = null;
/** @var bool|string */
private $wikiId = false;
/** @var int */
private $cacheTTL;
/** @var string */
private $table;
/** @var string */
private $idField;
/** @var string */
private $nameField;
/** @var null|callable */
private $normalizationCallback = null;
/** @var null|callable */
private $insertCallback = null;
/**
* @param ILoadBalancer $dbLoadBalancer A load balancer for acquiring database connections
* @param WANObjectCache $cache A cache manager for caching data. This can be the local
* wiki's default instance even if $wikiId refers to a different wiki, since
* makeGlobalKey() is used to constructed a key that allows cached names from
* the same database to be re-used between wikis. For example, enwiki and frwiki will
* use the same cache keys for names from the wikidatawiki database, regardless
* of the cache's default key space.
* @param LoggerInterface $logger
* @param string $table
* @param string $idField
* @param string $nameField
* @param callable|null $normalizationCallback Normalization to be applied to names before being
* saved or queried. This should be a callback that accepts and returns a single string.
* @param bool|string $wikiId The ID of the target wiki database. Use false for the local wiki.
* @param callable|null $insertCallback Callback to change insert fields accordingly.
* This parameter was introduced in 1.32
*/
public function __construct(
ILoadBalancer $dbLoadBalancer,
WANObjectCache $cache,
LoggerInterface $logger,
$table,
$idField,
$nameField,
callable $normalizationCallback = null,
$wikiId = false,
callable $insertCallback = null
) {
$this->loadBalancer = $dbLoadBalancer;
$this->cache = $cache;
$this->logger = $logger;
$this->table = $table;
$this->idField = $idField;
$this->nameField = $nameField;
$this->normalizationCallback = $normalizationCallback;
$this->wikiId = $wikiId;
$this->cacheTTL = IExpiringStore::TTL_MONTH;
$this->insertCallback = $insertCallback;
}
/**
* @param int $index A database index, like DB_MASTER or DB_REPLICA
* @param int $flags Database connection flags
*
* @return IDatabase
*/
private function getDBConnection( $index, $flags = 0 ) {
return $this->loadBalancer->getConnection( $index, [], $this->wikiId, $flags );
}
/**
* Gets the cache key for names.
*
* The cache key is constructed based on the wiki ID passed to the constructor, and allows
* sharing of name tables cached for a specific database between wikis.
*
* @return string
*/
private function getCacheKey() {
return $this->cache->makeGlobalKey(
'NameTableSqlStore',
$this->table,
$this->loadBalancer->resolveDomainID( $this->wikiId )
);
}
/**
* @param string $name
* @return string
*/
private function normalizeName( $name ) {
if ( $this->normalizationCallback === null ) {
return $name;
}
return call_user_func( $this->normalizationCallback, $name );
}
/**
* Acquire the id of the given name.
* This creates a row in the table if it doesn't already exist.
*
* @param string $name
* @throws NameTableAccessException
* @return int
*/
public function acquireId( $name ) {
Assert::parameterType( 'string', $name, '$name' );
$name = $this->normalizeName( $name );
$table = $this->getTableFromCachesOrReplica();
$searchResult = array_search( $name, $table, true );
if ( $searchResult === false ) {
$id = $this->store( $name );
if ( $id === null ) {
// RACE: $name was already in the db, probably just inserted, so load from master.
// Use DBO_TRX to avoid missing inserts due to other threads or REPEATABLE-READs.
// ...but not during unit tests, because we need the fake DB tables of the default
// connection.
$connFlags = defined( 'MW_PHPUNIT_TEST' ) ? 0 : ILoadBalancer::CONN_TRX_AUTOCOMMIT;
$table = $this->reloadMap( $connFlags );
$searchResult = array_search( $name, $table, true );
if ( $searchResult === false ) {
// Insert failed due to IGNORE flag, but DB_MASTER didn't give us the data
$m = "No insert possible but master didn't give us a record for " .
"'{$name}' in '{$this->table}'";
$this->logger->error( $m );
throw new NameTableAccessException( $m );
}
} elseif ( isset( $table[$id] ) ) {
throw new NameTableAccessException(
"Expected unused ID from database insert for '$name' "
. " into '{$this->table}', but ID $id is already associated with"
. " the name '{$table[$id]}'! This may indicate database corruption!" );
} else {
$table[$id] = $name;
$searchResult = $id;
// As store returned an ID we know we inserted so delete from WAN cache
$this->purgeWANCache(
function () {
$this->cache->delete( $this->getCacheKey() );
}
);
}
$this->tableCache = $table;
}
return $searchResult;
}
/**
* Reloads the name table from the master database, and purges the WAN cache entry.
*
* @note This should only be called in situations where the local cache has been detected
* to be out of sync with the database. There should be no reason to call this method
* from outside the NameTabelStore during normal operation. This method may however be
* useful in unit tests.
*
* @param int $connFlags ILoadBalancer::CONN_XXX flags. Optional.
*
* @return \string[] The freshly reloaded name map
*/
public function reloadMap( $connFlags = 0 ) {
$this->tableCache = $this->loadTable(
$this->getDBConnection( DB_MASTER, $connFlags )
);
$this->purgeWANCache(
function () {
$this->cache->reap( $this->getCacheKey(), INF );
}
);
return $this->tableCache;
}
/**
* Get the id of the given name.
* If the name doesn't exist this will throw.
* This should be used in cases where we believe the name already exists or want to check for
* existence.
*
* @param string $name
* @throws NameTableAccessException The name does not exist
* @return int Id
*/
public function getId( $name ) {
Assert::parameterType( 'string', $name, '$name' );
$name = $this->normalizeName( $name );
$table = $this->getTableFromCachesOrReplica();
$searchResult = array_search( $name, $table, true );
if ( $searchResult !== false ) {
return $searchResult;
}
throw NameTableAccessException::newFromDetails( $this->table, 'name', $name );
}
/**
* Get the name of the given id.
* If the id doesn't exist this will throw.
* This should be used in cases where we believe the id already exists.
*
* Note: Calls to this method will result in a master select for non existing IDs.
*
* @param int $id
* @throws NameTableAccessException The id does not exist
* @return string name
*/
public function getName( $id ) {
Assert::parameterType( 'integer', $id, '$id' );
$table = $this->getTableFromCachesOrReplica();
if ( array_key_exists( $id, $table ) ) {
return $table[$id];
}
$fname = __METHOD__;
$table = $this->cache->getWithSetCallback(
$this->getCacheKey(),
$this->cacheTTL,
function ( $oldValue, &$ttl, &$setOpts ) use ( $id, $fname ) {
// Check if cached value is up-to-date enough to have $id
if ( is_array( $oldValue ) && array_key_exists( $id, $oldValue ) ) {
// Completely leave the cache key alone
$ttl = WANObjectCache::TTL_UNCACHEABLE;
// Use the old value
return $oldValue;
}
// Regenerate from replica DB, and master DB if needed
foreach ( [ DB_REPLICA, DB_MASTER ] as $source ) {
// Log a fallback to master
if ( $source === DB_MASTER ) {
$this->logger->info(
$fname . ' falling back to master select from ' .
$this->table . ' with id ' . $id
);
}
$db = $this->getDBConnection( $source );
$cacheSetOpts = Database::getCacheSetOptions( $db );
$table = $this->loadTable( $db );
if ( array_key_exists( $id, $table ) ) {
break; // found it
}
}
// Use the value from last source checked
$setOpts += $cacheSetOpts;
return $table;
},
[ 'minAsOf' => INF ] // force callback run
);
$this->tableCache = $table;
if ( array_key_exists( $id, $table ) ) {
return $table[$id];
}
throw NameTableAccessException::newFromDetails( $this->table, 'id', $id );
}
/**
* Get the whole table, in no particular order as a map of ids to names.
* This method could be subject to DB or cache lag.
*
* @return string[] keys are the name ids, values are the names themselves
* Example: [ 1 => 'foo', 3 => 'bar' ]
*/
public function getMap() {
return $this->getTableFromCachesOrReplica();
}
/**
* @return string[]
*/
private function getTableFromCachesOrReplica() {
if ( $this->tableCache !== null ) {
return $this->tableCache;
}
$table = $this->cache->getWithSetCallback(
$this->getCacheKey(),
$this->cacheTTL,
function ( $oldValue, &$ttl, &$setOpts ) {
$dbr = $this->getDBConnection( DB_REPLICA );
$setOpts += Database::getCacheSetOptions( $dbr );
return $this->loadTable( $dbr );
}
);
$this->tableCache = $table;
return $table;
}
/**
* Reap the WANCache entry for this table.
*
* @param callable $purgeCallback callback to 'purge' the WAN cache
*/
private function purgeWANCache( $purgeCallback ) {
// If the LB has no DB changes don't both with onTransactionPreCommitOrIdle
if ( !$this->loadBalancer->hasOrMadeRecentMasterChanges() ) {
$purgeCallback();
return;
}
$this->getDBConnection( DB_MASTER )
->onTransactionPreCommitOrIdle( $purgeCallback, __METHOD__ );
}
/**
* Gets the table from the db
*
* @param IDatabase $db
*
* @return string[]
*/
private function loadTable( IDatabase $db ) {
$result = $db->select(
$this->table,
[
'id' => $this->idField,
'name' => $this->nameField
],
[],
__METHOD__,
[ 'ORDER BY' => 'id' ]
);
$assocArray = [];
foreach ( $result as $row ) {
$assocArray[$row->id] = $row->name;
}
return $assocArray;
}
/**
* Stores the given name in the DB, returning the ID when an insert occurs.
*
* @param string $name
* @return int|null int if we know the ID, null if we don't
*/
private function store( $name ) {
Assert::parameterType( 'string', $name, '$name' );
Assert::parameter( $name !== '', '$name', 'should not be an empty string' );
// Note: this is only called internally so normalization of $name has already occurred.
$dbw = $this->getDBConnection( DB_MASTER );
$dbw->insert(
$this->table,
$this->getFieldsToStore( $name ),
__METHOD__,
[ 'IGNORE' ]
);
if ( $dbw->affectedRows() === 0 ) {
$this->logger->info(
'Tried to insert name into table ' . $this->table . ', but value already existed.'
);
return null;
}
return $dbw->insertId();
}
/**
* @param string $name
* @return array
*/
private function getFieldsToStore( $name ) {
$fields = [ $this->nameField => $name ];
if ( $this->insertCallback !== null ) {
$fields = call_user_func( $this->insertCallback, $fields );
}
return $fields;
}
}
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