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ref-filter: use generation number for --contains

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A commit A can reach a commit B only if the generation number of A
is strictly larger than the generation number of B. This condition
allows significantly short-circuiting commit-graph walks.

Use generation number for '--contains' type queries.

On a copy of the Linux repository where HEAD is contained in v4.13
but no earlier tag, the command 'git tag --contains HEAD' had the
following peformance improvement:

Before: 0.81s
After:  0.04s
Rel %:  -95%

Helped-by: Jeff King <peff@peff.net>
Signed-off-by: Derrick Stolee <dstolee@microsoft.com>
Signed-off-by: Junio C Hamano <gitster@pobox.com>
This commit is contained in:
Derrick Stolee 2018-05-01 12:47:15 +00:00 committed by Junio C Hamano
parent e2838d85b6
commit 819807b33f
1 changed files with 20 additions and 4 deletions
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24
ref-filter.c
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@ -16,6 +16,7 @@
#include "trailer.h"
#include "wt-status.h"
#include "commit-slab.h"
#include "commit-graph.h"
static struct ref_msg {
const char *gone;
@ -1587,7 +1588,8 @@ static int in_commit_list(const struct commit_list *want, struct commit *c)
*/
static enum contains_result contains_test(struct commit *candidate,
const struct commit_list *want,
struct contains_cache *cache)
struct contains_cache *cache,
uint32_t cutoff)
{
enum contains_result *cached = contains_cache_at(cache, candidate);
@ -1603,6 +1605,10 @@ static enum contains_result contains_test(struct commit *candidate,
/* Otherwise, we don't know; prepare to recurse */
parse_commit_or_die(candidate);
if (candidate->generation < cutoff)
return CONTAINS_NO;
return CONTAINS_UNKNOWN;
}
@ -1618,8 +1624,18 @@ static enum contains_result contains_tag_algo(struct commit *candidate,
struct contains_cache *cache)
{
struct contains_stack contains_stack = { 0, 0, NULL };
enum contains_result result = contains_test(candidate, want, cache);
enum contains_result result;
uint32_t cutoff = GENERATION_NUMBER_INFINITY;
const struct commit_list *p;
for (p = want; p; p = p->next) {
struct commit *c = p->item;
load_commit_graph_info(c);
if (c->generation < cutoff)
cutoff = c->generation;
}
result = contains_test(candidate, want, cache, cutoff);
if (result != CONTAINS_UNKNOWN)
return result;
@ -1637,7 +1653,7 @@ static enum contains_result contains_tag_algo(struct commit *candidate,
* If we just popped the stack, parents->item has been marked,
* therefore contains_test will return a meaningful yes/no.
*/
else switch (contains_test(parents->item, want, cache)) {
else switch (contains_test(parents->item, want, cache, cutoff)) {
case CONTAINS_YES:
*contains_cache_at(cache, commit) = CONTAINS_YES;
contains_stack.nr--;
@ -1651,7 +1667,7 @@ static enum contains_result contains_tag_algo(struct commit *candidate,
}
}
free(contains_stack.contains_stack);
return contains_test(candidate, want, cache);
return contains_test(candidate, want, cache, cutoff);
}
static int commit_contains(struct ref_filter *filter, struct commit *commit,