recache and uncache the last_change from metadata

The most recent changelog entry is already cached in the metadata as
'last_change' to avoid reading the page changelog on every request.

  - Recache the last change if it is missing and still valid. This is
    needed for when the metadata has been rerendered.

  - Uncaches the last change when it has been invalidated by an external
    edit. Ensures that external edits are not credited to the wrong
    author.

darcs-hash:20061207011005-05dcb-3b1749f6626d07c4cc3de9587c45765423e2e4d9.gz

1 files changed, 16 insertions, 1 deletions

diff --git a/inc/common.php b/inc/common.php
index 8ca29b918..26a0526b8 100644
--- a/inc/common.php
+++ b/inc/common.php
@@ -128,7 +128,22 @@ function pageinfo(){
   if($REV){
     $revinfo = getRevisionInfo($ID, $REV, 1024);
   }else{
-    $revinfo = isset($info['meta']['last_change']) ? $info['meta']['last_change'] : getRevisionInfo($ID,$info['lastmod'],1024);
+    if (isset($info['meta']['last_change'])) { $revinfo = $info['meta']['last_change']; }
+    else {
+      $revinfo = getRevisionInfo($ID, $info['lastmod'], 1024);
+      // cache most recent changelog line in metadata if missing and still valid
+      if ($revinfo!==false) {
+        $info['meta']['last_change'] = $revinfo;
+        p_set_metadata($ID, array('last_change' => $revinfo));
+      }
+    }
+  }
+  //and check for an external edit
+  if($revinfo!==false && $revinfo['date']!=$info['lastmod']){
+    // cached changelog line no longer valid
+    $revinfo = false;
+    $info['meta']['last_change'] = $revinfo;
+    p_set_metadata($ID, array('last_change' => $revinfo));
   }
 
   $info['ip']     = $revinfo['ip'];