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Use flexible array in zskiplistNode to reduce memory usage

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This commit is contained in:
Pieter Noordhuis 2010-08-03 19:21:16 +02:00
parent 6825491928
commit 2159782b51
2 changed files with 64 additions and 83 deletions
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11
src/redis.h
View File

@ -480,13 +480,14 @@ typedef struct _redisSortOperation {
} redisSortOperation;
/* ZSETs use a specialized version of Skiplists */
typedef struct zskiplistNode {
struct zskiplistNode **forward;
struct zskiplistNode *backward;
unsigned int *span;
double score;
robj *obj;
double score;
struct zskiplistNode *backward;
struct zskiplistLevel {
struct zskiplistNode *forward;
unsigned int span;
} level[];
} zskiplistNode;
typedef struct zskiplist {

136
src/t_zset.c
View File

@ -24,13 +24,7 @@
* from tail to head, useful for ZREVRANGE. */
zskiplistNode *zslCreateNode(int level, double score, robj *obj) {
zskiplistNode *zn = zmalloc(sizeof(*zn));
zn->forward = zmalloc(sizeof(zskiplistNode*) * level);
if (level > 1)
zn->span = zmalloc(sizeof(unsigned int) * (level - 1));
else
zn->span = NULL;
zskiplistNode *zn = zmalloc(sizeof(*zn)+level*sizeof(struct zskiplistLevel));
zn->score = score;
zn->obj = obj;
return zn;
@ -45,11 +39,8 @@ zskiplist *zslCreate(void) {
zsl->length = 0;
zsl->header = zslCreateNode(ZSKIPLIST_MAXLEVEL,0,NULL);
for (j = 0; j < ZSKIPLIST_MAXLEVEL; j++) {
zsl->header->forward[j] = NULL;
/* span has space for ZSKIPLIST_MAXLEVEL-1 elements */
if (j < ZSKIPLIST_MAXLEVEL-1)
zsl->header->span[j] = 0;
zsl->header->level[j].forward = NULL;
zsl->header->level[j].span = 0;
}
zsl->header->backward = NULL;
zsl->tail = NULL;
@ -58,19 +49,15 @@ zskiplist *zslCreate(void) {
void zslFreeNode(zskiplistNode *node) {
decrRefCount(node->obj);
zfree(node->forward);
zfree(node->span);
zfree(node);
}
void zslFree(zskiplist *zsl) {
zskiplistNode *node = zsl->header->forward[0], *next;
zskiplistNode *node = zsl->header->level[0].forward, *next;
zfree(zsl->header->forward);
zfree(zsl->header->span);
zfree(zsl->header);
while(node) {
next = node->forward[0];
next = node->level[0].forward;
zslFreeNode(node);
node = next;
}
@ -93,13 +80,12 @@ void zslInsert(zskiplist *zsl, double score, robj *obj) {
for (i = zsl->level-1; i >= 0; i--) {
/* store rank that is crossed to reach the insert position */
rank[i] = i == (zsl->level-1) ? 0 : rank[i+1];
while (x->forward[i] &&
(x->forward[i]->score < score ||
(x->forward[i]->score == score &&
compareStringObjects(x->forward[i]->obj,obj) < 0))) {
rank[i] += i > 0 ? x->span[i-1] : 1;
x = x->forward[i];
while (x->level[i].forward &&
(x->level[i].forward->score < score ||
(x->level[i].forward->score == score &&
compareStringObjects(x->level[i].forward->obj,obj) < 0))) {
rank[i] += x->level[i].span;
x = x->level[i].forward;
}
update[i] = x;
}
@ -112,30 +98,28 @@ void zslInsert(zskiplist *zsl, double score, robj *obj) {
for (i = zsl->level; i < level; i++) {
rank[i] = 0;
update[i] = zsl->header;
update[i]->span[i-1] = zsl->length;
update[i]->level[i].span = zsl->length;
}
zsl->level = level;
}
x = zslCreateNode(level,score,obj);
for (i = 0; i < level; i++) {
x->forward[i] = update[i]->forward[i];
update[i]->forward[i] = x;
x->level[i].forward = update[i]->level[i].forward;
update[i]->level[i].forward = x;
/* update span covered by update[i] as x is inserted here */
if (i > 0) {
x->span[i-1] = update[i]->span[i-1] - (rank[0] - rank[i]);
update[i]->span[i-1] = (rank[0] - rank[i]) + 1;
}
x->level[i].span = update[i]->level[i].span - (rank[0] - rank[i]);
update[i]->level[i].span = (rank[0] - rank[i]) + 1;
}
/* increment span for untouched levels */
for (i = level; i < zsl->level; i++) {
update[i]->span[i-1]++;
update[i]->level[i].span++;
}
x->backward = (update[0] == zsl->header) ? NULL : update[0];
if (x->forward[0])
x->forward[0]->backward = x;
if (x->level[0].forward)
x->level[0].forward->backward = x;
else
zsl->tail = x;
zsl->length++;
@ -145,23 +129,19 @@ void zslInsert(zskiplist *zsl, double score, robj *obj) {
void zslDeleteNode(zskiplist *zsl, zskiplistNode *x, zskiplistNode **update) {
int i;
for (i = 0; i < zsl->level; i++) {
if (update[i]->forward[i] == x) {
if (i > 0) {
update[i]->span[i-1] += x->span[i-1] - 1;
}
update[i]->forward[i] = x->forward[i];
if (update[i]->level[i].forward == x) {
update[i]->level[i].span += x->level[i].span - 1;
update[i]->level[i].forward = x->level[i].forward;
} else {
/* invariant: i > 0, because update[0]->forward[0]
* is always equal to x */
update[i]->span[i-1] -= 1;
update[i]->level[i].span -= 1;
}
}
if (x->forward[0]) {
x->forward[0]->backward = x->backward;
if (x->level[0].forward) {
x->level[0].forward->backward = x->backward;
} else {
zsl->tail = x->backward;
}
while(zsl->level > 1 && zsl->header->forward[zsl->level-1] == NULL)
while(zsl->level > 1 && zsl->header->level[zsl->level-1].forward == NULL)
zsl->level--;
zsl->length--;
}
@ -173,16 +153,16 @@ 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 ||
(x->forward[i]->score == score &&
compareStringObjects(x->forward[i]->obj,obj) < 0)))
x = x->forward[i];
while (x->level[i].forward &&
(x->level[i].forward->score < score ||
(x->level[i].forward->score == score &&
compareStringObjects(x->level[i].forward->obj,obj) < 0)))
x = x->level[i].forward;
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];
x = x->level[0].forward;
if (x && score == x->score && equalStringObjects(x->obj,obj)) {
zslDeleteNode(zsl, x, update);
zslFreeNode(x);
@ -204,15 +184,15 @@ unsigned long zslDeleteRangeByScore(zskiplist *zsl, double min, double max, dict
x = zsl->header;
for (i = zsl->level-1; i >= 0; i--) {
while (x->forward[i] && x->forward[i]->score < min)
x = x->forward[i];
while (x->level[i].forward && x->level[i].forward->score < min)
x = x->level[i].forward;
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];
x = x->level[0].forward;
while (x && x->score <= max) {
zskiplistNode *next = x->forward[0];
zskiplistNode *next = x->level[0].forward;
zslDeleteNode(zsl, x, update);
dictDelete(dict,x->obj);
zslFreeNode(x);
@ -231,17 +211,17 @@ unsigned long zslDeleteRangeByRank(zskiplist *zsl, unsigned int start, unsigned
x = zsl->header;
for (i = zsl->level-1; i >= 0; i--) {
while (x->forward[i] && (traversed + (i > 0 ? x->span[i-1] : 1)) < start) {
traversed += i > 0 ? x->span[i-1] : 1;
x = x->forward[i];
while (x->level[i].forward && (traversed + x->level[i].span) < start) {
traversed += x->level[i].span;
x = x->level[i].forward;
}
update[i] = x;
}
traversed++;
x = x->forward[0];
x = x->level[0].forward;
while (x && traversed <= end) {
zskiplistNode *next = x->forward[0];
zskiplistNode *next = x->level[0].forward;
zslDeleteNode(zsl, x, update);
dictDelete(dict,x->obj);
zslFreeNode(x);
@ -260,12 +240,12 @@ zskiplistNode *zslFirstWithScore(zskiplist *zsl, double score) {
x = zsl->header;
for (i = zsl->level-1; i >= 0; i--) {
while (x->forward[i] && x->forward[i]->score < score)
x = x->forward[i];
while (x->level[i].forward && x->level[i].forward->score < score)
x = x->level[i].forward;
}
/* We may have multiple elements with the same score, what we need
* is to find the element with both the right score and object. */
return x->forward[0];
return x->level[0].forward;
}
/* Find the rank for an element by both score and key.
@ -279,12 +259,12 @@ unsigned long zslistTypeGetRank(zskiplist *zsl, double score, robj *o) {
x = zsl->header;
for (i = zsl->level-1; i >= 0; i--) {
while (x->forward[i] &&
(x->forward[i]->score < score ||
(x->forward[i]->score == score &&
compareStringObjects(x->forward[i]->obj,o) <= 0))) {
rank += i > 0 ? x->span[i-1] : 1;
x = x->forward[i];
while (x->level[i].forward &&
(x->level[i].forward->score < score ||
(x->level[i].forward->score == score &&
compareStringObjects(x->level[i].forward->obj,o) <= 0))) {
rank += x->level[i].span;
x = x->level[i].forward;
}
/* x might be equal to zsl->header, so test if obj is non-NULL */
@ -303,10 +283,10 @@ zskiplistNode* zslistTypeGetElementByRank(zskiplist *zsl, unsigned long rank) {
x = zsl->header;
for (i = zsl->level-1; i >= 0; i--) {
while (x->forward[i] && (traversed + (i>0 ? x->span[i-1] : 1)) <= rank)
while (x->level[i].forward && (traversed + x->level[i].span) <= rank)
{
traversed += i > 0 ? x->span[i-1] : 1;
x = x->forward[i];
traversed += x->level[i].span;
x = x->level[i].forward;
}
if (traversed == rank) {
return x;
@ -778,7 +758,7 @@ void zrangeGenericCommand(redisClient *c, int reverse) {
ln = start == 0 ? zsl->tail : zslistTypeGetElementByRank(zsl, llen-start);
} else {
ln = start == 0 ?
zsl->header->forward[0] : zslistTypeGetElementByRank(zsl, start+1);
zsl->header->level[0].forward : zslistTypeGetElementByRank(zsl, start+1);
}
/* Return the result in form of a multi-bulk reply */
@ -789,7 +769,7 @@ void zrangeGenericCommand(redisClient *c, int reverse) {
addReplyBulk(c,ele);
if (withscores)
addReplyDouble(c,ln->score);
ln = reverse ? ln->backward : ln->forward[0];
ln = reverse ? ln->backward : ln->level[0].forward;
}
}
@ -872,7 +852,7 @@ void genericZrangebyscoreCommand(redisClient *c, int justcount) {
/* Get the first node with the score >= min, or with
* score > min if 'minex' is true. */
ln = zslFirstWithScore(zsl,min);
while (minex && ln && ln->score == min) ln = ln->forward[0];
while (minex && ln && ln->score == min) ln = ln->level[0].forward;
if (ln == NULL) {
/* No element matching the speciifed interval */
@ -893,7 +873,7 @@ void genericZrangebyscoreCommand(redisClient *c, int justcount) {
while(ln && (maxex ? (ln->score < max) : (ln->score <= max))) {
if (offset) {
offset--;
ln = ln->forward[0];
ln = ln->level[0].forward;
continue;
}
if (limit == 0) break;
@ -903,7 +883,7 @@ void genericZrangebyscoreCommand(redisClient *c, int justcount) {
if (withscores)
addReplyDouble(c,ln->score);
}
ln = ln->forward[0];
ln = ln->level[0].forward;
rangelen++;
if (limit > 0) limit--;
}