Cleaned up WANObjectCache toy example code blocks

The list order logic was backwards

Change-Id: Id26e13b69d9e1e6ef132792bdcc693836757cbd8

diff --git a/includes/libs/objectcache/WANObjectCache.php b/includes/libs/objectcache/WANObjectCache.php
index e5bc665..7e8db0c 100644 (file)
--- a/includes/libs/objectcache/WANObjectCache.php
+++ b/includes/libs/objectcache/WANObjectCache.php
@@ -593,12 +593,12 @@ class WANObjectCache {
         *         function( $oldValue, &$ttl, array &$setOpts ) {
         *             $dbr = wfGetDB( DB_SLAVE );
         *             // Start off with the last cached list
-        *             $list = $oldValue ? $oldValue : array();
-        *             $last = end( $list );
-        *             // Fetch any rows newer than $last from the DB (in order)
+        *             $list = $oldValue ?: array();
+        *             // Fetch the last 100 relevant rows in descending order;
+        *             // only fetch rows newer than $list[0] to reduce scanning
         *             $rows = iterator_to_array( $dbr->select( ... ) );
         *             // Merge them and get the new "last 100" rows
-        *             $list = array_slice( array_merge( $list, $new ), -100 );
+        *             $list = array_slice( array_merge( $new, $list ), 0, 100 );
         *
         *             // Set age of the transaction snapshot the data came from
         *             $setOpts = array( 'since' => $dbr->trxTimestamp() );
@@ -606,12 +606,12 @@ class WANObjectCache {
         *             return $list;
         *        },
         *        // Time-to-live (seconds)
-        *        10
+        *        10,
         *        // No "check" keys
         *        array(),
         *        // Try to only let one datacenter thread manage cache updates at a time
         *        array( 'lockTSE' => 30 )
-        *     ) );
+        *     );
         * @endcode
         *
         * @see WANObjectCache::get()