Document DB_SLAVE as deprecated

[lhc/web/wiklou.git] / includes / Defines.php

diff --git a/includes/Defines.php b/includes/Defines.php
index bd92ff0..ca603e7 100644 (file)
--- a/includes/Defines.php
+++ b/includes/Defines.php
@@ -24,11 +24,16 @@ require_once __DIR__ . '/libs/mime/defines.php';
 require_once __DIR__ . '/libs/rdbms/defines.php';
 require_once __DIR__ . '/compat/normal/UtfNormalDefines.php';
 
+use Wikimedia\Rdbms\IDatabase;
+
 /**
  * @defgroup Constants MediaWiki constants
  */
 
 # Obsolete aliases
+/**
+ * @deprecated since 1.28
+ */
 define( 'DB_SLAVE', -1 );
 
 /**@{
@@ -265,3 +270,28 @@ define( 'CONTENT_FORMAT_XML', 'application/xml' );
  */
 define( 'SHELL_MAX_ARG_STRLEN', '100000' );
 /**@}*/
+
+/**@{
+ * Schema change migration flags.
+ *
+ * Used as values of a feature flag for an orderly transition from an old
+ * schema to a new schema.
+ *
+ * - MIGRATION_OLD: Only read and write the old schema. The new schema need not
+ *   even exist. This is used from when the patch is merged until the schema
+ *   change is actually applied to the database.
+ * - MIGRATION_WRITE_BOTH: Write both the old and new schema. Read the new
+ *   schema preferentially, falling back to the old. This is used while the
+ *   change is being tested, allowing easy roll-back to the old schema.
+ * - MIGRATION_WRITE_NEW: Write only the new schema. Read the new schema
+ *   preferentially, falling back to the old. This is used while running the
+ *   maintenance script to migrate existing entries in the old schema to the
+ *   new schema.
+ * - MIGRATION_NEW: Only read and write the new schema. The old schema (and the
+ *   feature flag) may now be removed.
+ */
+define( 'MIGRATION_OLD', 0 );
+define( 'MIGRATION_WRITE_BOTH', 1 );
+define( 'MIGRATION_WRITE_NEW', 2 );
+define( 'MIGRATION_NEW', 3 );
+/**@}*/