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Optimize LRANGE to scan the list starting from the head or the tail in order to traverse the minimal number of elements. Thanks to Didier Spezia for noticing the problem and providing a patch.

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antirez 2011-09-14 15:10:28 +02:00
parent 8ac3c86664
commit 9e087a298d
1 changed files with 6 additions and 1 deletions
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7
src/t_list.c
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@ -514,7 +514,12 @@ void lrangeCommand(redisClient *c) {
p = ziplistNext(o->ptr,p); p = ziplistNext(o->ptr,p);
} }
} else if (o->encoding == REDIS_ENCODING_LINKEDLIST) { } else if (o->encoding == REDIS_ENCODING_LINKEDLIST) {
listNode *ln = listIndex(o->ptr,start); listNode *ln;
/* If we are nearest to the end of the list, reach the element
* starting from tail and going backward, as it is faster. */
if (start > llen/2) start -= llen;
ln = listIndex(o->ptr,start);
while(rangelen--) { while(rangelen--) {
addReplyBulk(c,ln->value); addReplyBulk(c,ln->value);