Optimized copyFileBackend to use MD5 from listing if given (e.g. Swift)

Change-Id: Ic495d6c8c6dffb0b34e6b5eefb8de4d057a51069

diff --git a/maintenance/copyFileBackend.php b/maintenance/copyFileBackend.php
index 09b9295..8bacb26 100644 (file)
--- a/maintenance/copyFileBackend.php
+++ b/maintenance/copyFileBackend.php
@@ -347,15 +347,33 @@ class CopyFileBackend extends Maintenance {
                } else {
                        $dstStat = $dst->getFileStat( array( 'src' => $dPath ) );
                }
-               return (
+               // Initial fast checks to see if files are obviously different
+               $sameFast = (
                        is_array( $srcStat ) // sanity check that source exists
                        && is_array( $dstStat ) // dest exists
                        && $srcStat['size'] === $dstStat['size']
-                       && ( !$skipHash || $srcStat['mtime'] <= $dstStat['mtime'] )
-                       && ( $skipHash || $src->getFileSha1Base36( array( 'src' => $sPath, 'latest' => 1 ) )
-                               === $dst->getFileSha1Base36( array( 'src' => $dPath, 'latest' => 1 ) )
-                       )
                );
+               // More thorough checks against files
+               if ( !$sameFast ) {
+                       $same = false; // no need to look farther
+               } elseif ( isset( $srcStat['md5'] ) && isset( $dstStat['md5'] ) ) {
+                       // If MD5 was already in the stat info, just use it.
+                       // This is useful as many objects stores can return this in object listing,
+                       // so we can use it to avoid slow per-file HEADs.
+                       $same = ( $srcStat['md5'] === $dstStat['md5'] );
+               } elseif ( $skipHash ) {
+                       // This mode is good for copying to a backup location or resyncing clone
+                       // backends in FileBackendMultiWrite (since they get writes second, they have
+                       // higher timestamps). However, when copying the other way, this hits loads of
+                       // false positives (possibly 100%) and wastes a bunch of time on GETs/PUTs.
+                       $same = ( $srcStat['mtime'] <= $dstStat['mtime'] );
+               } else {
+                       // This is the slowest method which does many per-file HEADs (unless an object
+                       // store tracks SHA-1 in listings).
+                       $same = ( $src->getFileSha1Base36( array( 'src' => $sPath, 'latest' => 1 ) )
+                               === $dst->getFileSha1Base36( array( 'src' => $dPath, 'latest' => 1 ) ) );
+               }
+               return $same;
        }
 }