fetch: Speed up fetch of large numbers of refs

When there are large numbers of refs, calling read_ref for each ref is
inefficent (and infact downright slow) - so instead use for_each_ref
to build up a string list of all the refs that we currently have,
which significantly improves the volume.

Signed-off-by: Julian Phillips <julian@quantumfyre.co.uk>
Signed-off-by: Junio C Hamano <gitster@pobox.com>

diff --git a/builtin-fetch.c b/builtin-fetch.c
index a35a6f8cb8030bf9be98a001da26fddf0efdb912..5c7465cfeb5c1bb0649fed6475618ba975955e99 100644 (file)
--- a/builtin-fetch.c
+++ b/builtin-fetch.c
@@ -489,7 +489,8 @@ static int add_existing(const char *refname, const unsigned char *sha1,
                        int flag, void *cbdata)
 {
        struct string_list *list = (struct string_list *)cbdata;
-       string_list_insert(refname, list);
+       struct string_list_item *item = string_list_insert(refname, list);
+       item->util = (void *)sha1;
        return 0;
 }
 
@@ -615,9 +616,14 @@ static void check_not_current_branch(struct ref *ref_map)
 static int do_fetch(struct transport *transport,
                    struct refspec *refs, int ref_count)
 {
+       struct string_list existing_refs = { NULL, 0, 0, 0 };
+       struct string_list_item *peer_item = NULL;
        struct ref *ref_map;
        struct ref *rm;
        int autotags = (transport->remote->fetch_tags == 1);
+
+       for_each_ref(add_existing, &existing_refs);
+
        if (transport->remote->fetch_tags == 2 && tags != TAGS_UNSET)
                tags = TAGS_SET;
        if (transport->remote->fetch_tags == -1)
@@ -640,8 +646,13 @@ static int do_fetch(struct transport *transport,
                check_not_current_branch(ref_map);
 
        for (rm = ref_map; rm; rm = rm->next) {
-               if (rm->peer_ref)
-                       read_ref(rm->peer_ref->name, rm->peer_ref->old_sha1);
+               if (rm->peer_ref) {
+                       peer_item = string_list_lookup(rm->peer_ref->name,
+                                                      &existing_refs);
+                       if (peer_item)
+                               hashcpy(rm->peer_ref->old_sha1,
+                                       peer_item->util);
+               }
        }
 
        if (tags == TAGS_DEFAULT && autotags)