@matheusbsbs / matheus-bagliano / commits / 6c4a060d7d

peel_ref: check object type before loading

The point of peel_ref is to dereference tags; if the base object is not a tag, then we can return early without even loading the object into memory. This patch accomplishes that by checking sha1_object_info for the type. For a packed object, we can get away with just looking in the pack index. For a loose object, we only need to inflate the first couple of header bytes. This is a bit of a gamble; if we do find a tag object, then we will end up loading the content anyway, and the extra lookup will have been wasteful. However, if it is not a tag object, then we save loading the object entirely. Depending on the ratio of non-tags to tags in the input, this can be a minor win or minor loss. However, it does give us one potential major win: if a ref points to a large blob (e.g., via an unannotated tag), then we can avoid looking at it entirely. Signed-off-by: Jeff King <peff@peff.net> Signed-off-by: Junio C Hamano <gitster@pobox.com>

Jeff King committed Oct 4, 2012 at 04:02 UTC 6c4a060d7d895c90610eb442cb4f910fe43ef13a

1 file changed +9 -2

refs.c

+9 -2

@@ -1225,8 +1225,15 @@ int peel_ref(const char *refname, unsigned char *sha1)

1225 }

1226

1227 fallback:

1228 - o = parse_object(base);

1229 - if (o && o->type == OBJ_TAG) {

1228 + o = lookup_unknown_object(base);

1229 + if (o->type == OBJ_NONE) {

1230 + int type = sha1_object_info(base, NULL);

1231 + if (type < 0)

1232 + return -1;

1233 + o->type = type;

1234 + }

1235 +

1236 + if (o->type == OBJ_TAG) {

1237 o = deref_tag_noverify(o);

1238 if (o) {

1239 hashcpy(sha1, o->sha1);