X-Git-Url: http://git.heureux-cyclage.org/?a=blobdiff_plain;f=includes%2Fdeferred%2FMergeableUpdate.php;h=6ae2bcc9e16a9fdaee206dd8ccf239bdb8376c73;hb=1ee66489826e596d3d37814d6c68145046503e20;hp=8eeef13bbe6a0e038f1232741b4258cd3ed04609;hpb=967a96e7fa5910f8fc451590decb381dbfb481ba;p=lhc%2Fweb%2Fwiklou.git

diff --git a/includes/deferred/MergeableUpdate.php b/includes/deferred/MergeableUpdate.php
index 8eeef13bbe..6ae2bcc9e1 100644
--- a/includes/deferred/MergeableUpdate.php
+++ b/includes/deferred/MergeableUpdate.php
@@ -1,8 +1,17 @@
 <?php
 
 /**
- * Interface that deferrable updates can implement. DeferredUpdates uses this to merge
- * all pending updates of PHP class into a single update by calling merge().
+ * Interface that deferrable updates can implement to signal that updates can be combined.
+ *
+ * DeferredUpdates uses this to merge all pending updates of PHP class into a single update
+ * by calling merge(). Note that upon merge(), the combined update goes to the back of the FIFO
+ * queue so that such updates occur after related non-mergeable deferred updates. For example,
+ * suppose updates that purge URLs can be merged, and the calling pattern is:
+ *   - a) DeferredUpdates::addUpdate( $purgeCdnUrlsA );
+ *   - b) DeferredUpdates::addUpdate( $deleteContentUrlsB );
+ *   - c) DeferredUpdates::addUpdate( $purgeCdnUrlsB )
+ *
+ * The purges for urls A and B will all happen after the $deleteContentUrlsB update.
  *
  * @since 1.27
  */