From: Jeff Hostetler <jeffhost@xxxxxxxxxxxxx>
Teach has_dir_name() to see if the path of the new item
is greater than the last path in the index array before
attempting to search for it.
has_dir_name() is looking for file/directory collisions
in the index and has to consider each sub-directory
prefix in turn. This can cause multiple binary searches
for each path.
During operations like checkout, merge_working_tree()
populates the new index in sorted order, so we expect
to be able to append in many cases.
This commit is part 1 of 2. This commit handles the top
of has_dir_name() and the trivial optimization.
Signed-off-by: Jeff Hostetler <jeffhost@xxxxxxxxxxxxx>
---
read-cache.c | 45 +++++++++++++++++++++++++++++++++++++++++++++
1 file changed, 45 insertions(+)
diff --git a/read-cache.c b/read-cache.c
index 6a27688..9af0bd4 100644
--- a/read-cache.c
+++ b/read-cache.c
@@ -910,6 +910,9 @@ int strcmp_offset(const char *s1, const char *s2, size_t *first_change)
/*
* Do we have another file with a pathname that is a proper
* subset of the name we're trying to add?
+ *
+ * That is, is there another file in the index with a path
+ * that matches a sub-directory in the given entry?
*/
static int has_dir_name(struct index_state *istate,
const struct cache_entry *ce, int pos, int ok_to_replace)
@@ -918,6 +921,48 @@ static int has_dir_name(struct index_state *istate,
int stage = ce_stage(ce);
const char *name = ce->name;
const char *slash = name + ce_namelen(ce);
+ size_t len_eq_last;
+ int cmp_last = 0;
+
+ /*
+ * We are frequently called during an iteration on a sorted
+ * list of pathnames and while building a new index. Therefore,
+ * there is a high probability that this entry will eventually
+ * be appended to the index, rather than inserted in the middle.
+ * If we can confirm that, we can avoid binary searches on the
+ * components of the pathname.
+ *
+ * Compare the entry's full path with the last path in the index.
+ */
+ if (istate->cache_nr > 0) {
+ cmp_last = strcmp_offset(name,
+ istate->cache[istate->cache_nr - 1]->name,
+ &len_eq_last);
+ if (cmp_last > 0) {
+ if (len_eq_last == 0) {
+ /*
+ * The entry sorts AFTER the last one in the
+ * index and their paths have no common prefix,
+ * so there cannot be a F/D conflict.
+ */
+ return retval;
+ } else {
+ /*
+ * The entry sorts AFTER the last one in the
+ * index, but has a common prefix. Fall through
+ * to the loop below to disect the entry's path
+ * and see where the difference is.
+ */
+ }
+ } else if (cmp_last == 0) {
+ /*
+ * The entry exactly matches the last one in the
+ * index, but because of multiple stage and CE_REMOVE
+ * items, we fall through and let the regular search
+ * code handle it.
+ */
+ }
+ }
for (;;) {
int len;
--
2.9.3
