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<?php |
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/** |
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* @defgroup ExternalStorage ExternalStorage |
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*/ |
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/** |
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* Interface for data storage in external repositories. |
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* |
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* This program is free software; you can redistribute it and/or modify |
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* it under the terms of the GNU General Public License as published by |
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* the Free Software Foundation; either version 2 of the License, or |
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* (at your option) any later version. |
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* |
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* This program is distributed in the hope that it will be useful, |
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* but WITHOUT ANY WARRANTY; without even the implied warranty of |
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* MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the |
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* GNU General Public License for more details. |
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* |
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* You should have received a copy of the GNU General Public License along |
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* with this program; if not, write to the Free Software Foundation, Inc., |
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* 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301, USA. |
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* http://www.gnu.org/copyleft/gpl.html |
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* |
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* @file |
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*/ |
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/** |
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* Constructor class for key/value blob data kept in external repositories. |
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* |
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* Objects in external stores are defined by a special URL. The URL is of |
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* the form "<store protocol>://<location>/<object name>". The protocol is used |
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* to determine what ExternalStoreMedium class is used. The location identifies |
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* particular storage instances or database clusters for store class to use. |
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* |
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* When an object is inserted into a store, the calling code uses a partial URL of |
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* the form "<store protocol>://<location>" and receives the full object URL on success. |
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* This is useful since object names can be sequential IDs, UUIDs, or hashes. |
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* Callers are not responsible for unique name generation. |
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* |
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* External repositories might be populated by maintenance/async |
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* scripts, thus partial moving of data may be possible, as well |
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* as the possibility to have any storage format (i.e. for archives). |
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* |
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* @ingroup ExternalStorage |
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*/ |
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class ExternalStore { |
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/** |
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* Get an external store object of the given type, with the given parameters |
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* |
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* @param string $proto Type of external storage, should be a value in $wgExternalStores |
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* @param array $params Associative array of ExternalStoreMedium parameters |
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* @return ExternalStoreMedium|bool The store class or false on error |
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*/ |
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public static function getStoreObject( $proto, array $params = [] ) { |
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global $wgExternalStores; |
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if ( !$wgExternalStores || !in_array( $proto, $wgExternalStores ) ) { |
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return false; // protocol not enabled |
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} |
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$class = 'ExternalStore' . ucfirst( $proto ); |
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// Any custom modules should be added to $wgAutoLoadClasses for on-demand loading |
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return class_exists( $class ) ? new $class( $params ) : false; |
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} |
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/** |
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* Fetch data from given URL |
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* |
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* @param string $url The URL of the text to get |
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* @param array $params Associative array of ExternalStoreMedium parameters |
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* @return string|bool The text stored or false on error |
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* @throws MWException |
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*/ |
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View Code Duplication |
public static function fetchFromURL( $url, array $params = [] ) { |
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$parts = explode( '://', $url, 2 ); |
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if ( count( $parts ) != 2 ) { |
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return false; // invalid URL |
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} |
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list( $proto, $path ) = $parts; |
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if ( $path == '' ) { // bad URL |
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return false; |
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} |
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$store = self::getStoreObject( $proto, $params ); |
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if ( $store === false ) { |
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return false; |
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} |
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return $store->fetchFromURL( $url ); |
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} |
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/** |
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* Fetch data from multiple URLs with a minimum of round trips |
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* |
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* @param array $urls The URLs of the text to get |
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* @return array Map from url to its data. Data is either string when found |
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* or false on failure. |
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*/ |
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public static function batchFetchFromURLs( array $urls ) { |
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$batches = []; |
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foreach ( $urls as $url ) { |
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$scheme = parse_url( $url, PHP_URL_SCHEME ); |
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if ( $scheme ) { |
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$batches[$scheme][] = $url; |
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} |
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} |
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$retval = []; |
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foreach ( $batches as $proto => $batchedUrls ) { |
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$store = self::getStoreObject( $proto ); |
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if ( $store === false ) { |
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continue; |
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} |
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$retval += $store->batchFetchFromURLs( $batchedUrls ); |
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} |
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// invalid, not found, db dead, etc. |
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$missing = array_diff( $urls, array_keys( $retval ) ); |
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if ( $missing ) { |
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foreach ( $missing as $url ) { |
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$retval[$url] = false; |
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} |
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} |
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return $retval; |
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} |
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/** |
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* Store a data item to an external store, identified by a partial URL |
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* The protocol part is used to identify the class, the rest is passed to the |
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* class itself as a parameter. |
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* |
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* @param string $url A partial external store URL ("<store type>://<location>") |
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* @param string $data |
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* @param array $params Associative array of ExternalStoreMedium parameters |
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* @return string|bool The URL of the stored data item, or false on error |
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* @throws MWException |
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*/ |
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View Code Duplication |
public static function insert( $url, $data, array $params = [] ) { |
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$parts = explode( '://', $url, 2 ); |
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if ( count( $parts ) != 2 ) { |
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return false; // invalid URL |
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} |
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list( $proto, $path ) = $parts; |
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if ( $path == '' ) { // bad URL |
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return false; |
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} |
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$store = self::getStoreObject( $proto, $params ); |
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if ( $store === false ) { |
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return false; |
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} else { |
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return $store->store( $path, $data ); |
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} |
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} |
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/** |
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* Like insert() above, but does more of the work for us. |
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* This function does not need a url param, it builds it by |
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* itself. It also fails-over to the next possible clusters |
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* provided by $wgDefaultExternalStore. |
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* |
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* @param string $data |
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* @param array $params Associative array of ExternalStoreMedium parameters |
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* @return string|bool The URL of the stored data item, or false on error |
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* @throws MWException |
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*/ |
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public static function insertToDefault( $data, array $params = [] ) { |
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global $wgDefaultExternalStore; |
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return self::insertWithFallback( (array)$wgDefaultExternalStore, $data, $params ); |
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} |
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/** |
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* Like insert() above, but does more of the work for us. |
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* This function does not need a url param, it builds it by |
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* itself. It also fails-over to the next possible clusters |
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* as provided in the first parameter. |
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* |
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* @param array $tryStores Refer to $wgDefaultExternalStore |
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* @param string $data |
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* @param array $params Associative array of ExternalStoreMedium parameters |
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* @return string|bool The URL of the stored data item, or false on error |
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* @throws MWException |
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*/ |
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public static function insertWithFallback( array $tryStores, $data, array $params = [] ) { |
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$error = false; |
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while ( count( $tryStores ) > 0 ) { |
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$index = mt_rand( 0, count( $tryStores ) - 1 ); |
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$storeUrl = $tryStores[$index]; |
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wfDebug( __METHOD__ . ": trying $storeUrl\n" ); |
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list( $proto, $path ) = explode( '://', $storeUrl, 2 ); |
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$store = self::getStoreObject( $proto, $params ); |
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if ( $store === false ) { |
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throw new MWException( "Invalid external storage protocol - $storeUrl" ); |
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} |
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try { |
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$url = $store->store( $path, $data ); // Try to save the object |
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} catch ( Exception $error ) { |
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$url = false; |
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} |
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if ( strlen( $url ) ) { |
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return $url; // Done! |
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} else { |
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unset( $tryStores[$index] ); // Don't try this one again! |
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$tryStores = array_values( $tryStores ); // Must have consecutive keys |
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wfDebugLog( 'ExternalStorage', |
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"Unable to store text to external storage $storeUrl" ); |
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} |
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} |
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// All stores failed |
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if ( $error ) { |
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throw $error; // rethrow the last error |
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} else { |
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throw new MWException( "Unable to store text to external storage" ); |
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} |
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} |
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/** |
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* @param string $data |
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* @param string $wiki |
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* @return string|bool The URL of the stored data item, or false on error |
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* @throws MWException |
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*/ |
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public static function insertToForeignDefault( $data, $wiki ) { |
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return self::insertToDefault( $data, [ 'wiki' => $wiki ] ); |
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} |
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} |
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In PHP, under loose comparison (like
==, or!=, orswitchconditions), values of different types might be equal.For
stringvalues, the empty string''is a special case, in particular the following results might be unexpected: