With the "weight" assigned to tip of each ref, we can give more
intuitive results from "name-rev" that is more suitable to answer
"what is the oldest tag that contains this commit?" However, this
number is very expensive to compute.
Use the notes-cache mechanism to cache this value. The result
becomes usable again.
(priming the cache from scratch)
$ rm .git/refs/notes/name-rev-weight
$ /usr/bin/time git name-rev --weight --tags 0136db586c
0136db586c tags/v3.5-rc1~83^2~81^2~76
6.06user 0.46system 0:06.54elapsed 99%CPU (0avgtext+0avgdata 1861456maxresident)k
8inputs+16outputs (0major+128576minor)pagefaults 0swaps
(with cache already primed)
$ /usr/bin/time git name-rev --weight --tags 0136db586c
0136db586c tags/v3.5-rc1~83^2~81^2~76
0.50user 0.22system 0:00.72elapsed 100%CPU (0avgtext+0avgdata 244224maxresident)k
0inputs+0outputs (0major+16062minor)pagefaults 0swaps
(the old "shortest path" version)
$ /usr/bin/time git name-rev --tags 0136db586c
0136db586c tags/v3.6-rc1~59^2~56^2~76
0.31user 0.01system 0:00.32elapsed 100%CPU (0avgtext+0avgdata 243488maxresident)k
0inputs+0outputs (0major+16000minor)pagefaults 0swaps
This version does not invalidate the cache in the presense of
modified grafts and object replacement, but in a later version we
can compute a hash of the grafts and replacement data and pass it as
the validity token to automatically invalidate the cache when these
data that affects the perceived topology change.
Signed-off-by: Junio C Hamano <gitster@xxxxxxxxx>
---
builtin/name-rev.c | 56 +++++++++++++++++++++++++++++++++++++++++++++++++-----
1 file changed, 51 insertions(+), 5 deletions(-)
diff --git a/builtin/name-rev.c b/builtin/name-rev.c
index 7cdb758..d78eedd 100644
--- a/builtin/name-rev.c
+++ b/builtin/name-rev.c
@@ -6,6 +6,7 @@
#include "parse-options.h"
#include "diff.h"
#include "revision.h"
+#include "notes-cache.h"
#define CUTOFF_DATE_SLOP 86400 /* one day */
@@ -32,10 +33,6 @@ struct rev_name {
*/
static int use_weight;
-/*
- * NEEDSWORK: the result of this computation must be cached to
- * a dedicated notes tree, keyed by the commit object name.
- */
static int compute_ref_weight(struct commit *commit)
{
struct rev_info revs;
@@ -50,6 +47,32 @@ static int compute_ref_weight(struct commit *commit)
return weight;
}
+static struct notes_cache weight_cache;
+static int weight_cache_updated;
+
+static int get_ref_weight(struct commit *commit)
+{
+ struct strbuf buf = STRBUF_INIT;
+ size_t sz;
+ int weight;
+ char *note;
+
+ note = notes_cache_get(&weight_cache, commit->object.sha1, &sz);
+ if (note && !strtol_i(note, 10, &weight)) {
+ free(note);
+ return weight;
+ }
+ free(note);
+
+ weight = compute_ref_weight(commit);
+ strbuf_addf(&buf, "%d", weight);
+ notes_cache_put(&weight_cache, commit->object.sha1,
+ buf.buf, buf.len);
+ strbuf_release(&buf);
+ weight_cache_updated = 1;
+ return weight;
+}
+
static int ref_weight(const char *refname, size_t reflen)
{
struct strbuf buf = STRBUF_INIT;
@@ -69,7 +92,7 @@ static int ref_weight(const char *refname, size_t reflen)
if (!name)
die("Internal error: a tip without name '%s'", buf.buf);
if (!name->weight)
- name->weight = compute_ref_weight(commit);
+ name->weight = get_ref_weight(commit);
return name->weight;
}
@@ -323,6 +346,22 @@ static void name_rev_line(char *p, struct name_ref_data *data)
fwrite(p_start, p - p_start, 1, stdout);
}
+static const char *get_validity_token(void)
+{
+ /*
+ * In future versions, we may want to automatically invalidate
+ * the cached weight data whenever grafts and replacement
+ * changes. We could do so by (1) reading the contents of the
+ * grafts file, (2) enumerating the replacement data (original
+ * object name and replacement object name) and sorting the
+ * result, and (3) concatenating (1) and (2) and hashing it,
+ * to come up with "dynamic validity: [0-9a-f]{40}" or something.
+ *
+ * In this verison, we simply do not bother ;-).
+ */
+ return "static validity token";
+}
+
int cmd_name_rev(int argc, const char **argv, const char *prefix)
{
struct object_array revs = OBJECT_ARRAY_INIT;
@@ -353,6 +392,10 @@ int cmd_name_rev(int argc, const char **argv, const char *prefix)
if (all || transform_stdin)
cutoff = 0;
+ if (use_weight)
+ notes_cache_init(&weight_cache, "name-rev-weight",
+ get_validity_token());
+
for (; argc; argc--, argv++) {
unsigned char sha1[20];
struct object *o;
@@ -408,5 +451,8 @@ int cmd_name_rev(int argc, const char **argv, const char *prefix)
always, allow_undefined, data.name_only);
}
+ if (use_weight && weight_cache_updated)
+ notes_cache_write(&weight_cache);
+
return 0;
}
--
1.7.12.286.g9df01f7
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