*
* @since 1.26
*/
-class DBAccessObjectUtils {
+class DBAccessObjectUtils implements IDBAccessObject {
/**
* @param integer $bitfield
* @param integer $flags IDBAccessObject::READ_* constant
}
/**
- * Get an appropriate DB index and options for a query
+ * Get an appropriate DB index, options, and fallback DB index for a query
*
- * @param integer $bitfield
- * @return array (DB_MASTER/DB_SLAVE, SELECT options array)
+ * The fallback DB index and options are to be used if the entity is not found
+ * with the initial DB index, typically querying the master DB to avoid lag
+ *
+ * @param integer $bitfield Bitfield of IDBAccessObject::READ_* constants
+ * @return array List of DB indexes and options in this order:
+ * - DB_MASTER or DB_REPLICA constant for the initial query
+ * - SELECT options array for the initial query
+ * - DB_MASTER constant for the fallback query; null if no fallback should happen
+ * - SELECT options array for the fallback query; empty if no fallback should happen
*/
public static function getDBOptions( $bitfield ) {
- $index = self::hasFlags( $bitfield, IDBAccessObject::READ_LATEST )
- ? DB_MASTER
- : DB_SLAVE;
+ if ( self::hasFlags( $bitfield, self::READ_LATEST_IMMUTABLE ) ) {
+ $index = DB_REPLICA; // override READ_LATEST if set
+ $fallbackIndex = DB_MASTER;
+ } elseif ( self::hasFlags( $bitfield, self::READ_LATEST ) ) {
+ $index = DB_MASTER;
+ $fallbackIndex = null;
+ } else {
+ $index = DB_REPLICA;
+ $fallbackIndex = null;
+ }
+
+ $lockingOptions = [];
+ if ( self::hasFlags( $bitfield, self::READ_EXCLUSIVE ) ) {
+ $lockingOptions[] = 'FOR UPDATE';
+ } elseif ( self::hasFlags( $bitfield, self::READ_LOCKING ) ) {
+ $lockingOptions[] = 'LOCK IN SHARE MODE';
+ }
- $options = array();
- if ( self::hasFlags( $bitfield, IDBAccessObject::READ_EXCLUSIVE ) ) {
- $options[] = 'FOR UPDATE';
- } elseif ( self::hasFlags( $bitfield, IDBAccessObject::READ_LOCKING ) ) {
- $options[] = 'LOCK IN SHARE MODE';
+ if ( $fallbackIndex !== null ) {
+ $options = []; // locks on DB_REPLICA make no sense
+ $fallbackOptions = $lockingOptions;
+ } else {
+ $options = $lockingOptions;
+ $fallbackOptions = []; // no fallback
}
- return array( $index, $options );
+ return [ $index, $options, $fallbackIndex, $fallbackOptions ];
}
}