From 9d60e6e466bd8f61c23d4664eba05200376cc1b9 Mon Sep 17 00:00:00 2001
From: antirez <antirez@gmail.com>
Date: Mon, 26 Oct 2009 20:47:23 +0100
Subject: [PATCH] A trivial change makes the new implementation O(log(N))
instead of O(log(N))+O(M) when there are M repeated scores!
---
redis.c | 47 +++++++++++++++++++++++++----------------------
1 file changed, 25 insertions(+), 22 deletions(-)
diff --git a/redis.c b/redis.c
index 0fb6b1e8..1c07dbc2 100644
--- a/redis.c
+++ b/redis.c
@@ -3855,7 +3855,10 @@ static void zslInsert(zskiplist *zsl, double score, robj *obj) {
x = zsl->header;
for (i = zsl->level-1; i >= 0; i--) {
- while (x->forward[i] && x->forward[i]->score < score)
+ while (x->forward[i] &&
+ (x->forward[i]->score < score ||
+ (x->forward[i]->score == score &&
+ compareStringObjects(x->forward[i]->obj,obj) < 0)))
x = x->forward[i];
update[i] = x;
}
@@ -3888,34 +3891,34 @@ static int zslDelete(zskiplist *zsl, double score, robj *obj) {
x = zsl->header;
for (i = zsl->level-1; i >= 0; i--) {
- while (x->forward[i] && x->forward[i]->score < score)
+ while (x->forward[i] &&
+ (x->forward[i]->score < score ||
+ (x->forward[i]->score == score &&
+ compareStringObjects(x->forward[i]->obj,obj) < 0)))
x = x->forward[i];
update[i] = x;
}
/* We may have multiple elements with the same score, what we need
* is to find the element with both the right score and object. */
x = x->forward[0];
- while(x->score == score) {
- if (compareStringObjects(x->obj,obj) == 0) {
- for (i = 0; i < zsl->level; i++) {
- if (update[i]->forward[i] != x) break;
- update[i]->forward[i] = x->forward[i];
- }
- if (x->forward[0]) {
- x->forward[0]->backward = (x->backward == zsl->header) ?
- NULL : x->backward;
- } else {
- zsl->tail = x->backward;
- }
- zslFreeNode(x);
- while(zsl->level > 1 && zsl->header->forward[zsl->level-1] == NULL)
- zsl->level--;
- zsl->length--;
- return 1;
- } else {
- x = x->forward[0];
- if (!x) return 0; /* end of the list reached, not found */
+ if (compareStringObjects(x->obj,obj) == 0) {
+ for (i = 0; i < zsl->level; i++) {
+ if (update[i]->forward[i] != x) break;
+ update[i]->forward[i] = x->forward[i];
}
+ if (x->forward[0]) {
+ x->forward[0]->backward = (x->backward == zsl->header) ?
+ NULL : x->backward;
+ } else {
+ zsl->tail = x->backward;
+ }
+ zslFreeNode(x);
+ while(zsl->level > 1 && zsl->header->forward[zsl->level-1] == NULL)
+ zsl->level--;
+ zsl->length--;
+ return 1;
+ } else {
+ return 0; /* not found */
}
return 0; /* not found */
}