mirror of
https://github.com/YunoHost-Apps/mediawiki_ynh.git
synced 2024-09-03 19:46:05 +02:00
57 lines
2.6 KiB
PHP
57 lines
2.6 KiB
PHP
<?php
|
|
/**
|
|
* This file contains database access object related constants.
|
|
*
|
|
* 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 Database
|
|
*/
|
|
|
|
/**
|
|
* 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
|
|
*
|
|
* @since 1.20
|
|
*/
|
|
interface IDBAccessObject {
|
|
// 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)
|
|
}
|