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Less blocking dictGetRandomKeys().

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Related to issue #2306.
This commit is contained in:
antirez 2015-02-04 22:12:46 +01:00
parent 5e3dcc522b
commit 170e41464d
1 changed files with 31 additions and 23 deletions
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54
src/dict.c
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@ -666,34 +666,42 @@ dictEntry *dictGetRandomKey(dict *d)
* at producing N elements, and the elements are guaranteed to be non
* repeating. */
unsigned int dictGetRandomKeys(dict *d, dictEntry **des, unsigned int count) {
int j; /* internal hash table id, 0 or 1. */
unsigned int stored = 0;
unsigned int j; /* internal hash table id, 0 or 1. */
unsigned int tables; /* 1 or 2 tables? */
unsigned int stored = 0, maxsizemask;
if (dictSize(d) < count) count = dictSize(d);
while(stored < count) {
for (j = 0; j < 2; j++) {
/* Pick a random point inside the hash table 0 or 1. */
unsigned int i = random() & d->ht[j].sizemask;
int size = d->ht[j].size;
/* Make sure to visit every bucket by iterating 'size' times. */
while(size--) {
dictEntry *he = d->ht[j].table[i];
while (he) {
/* Collect all the elements of the buckets found non
* empty while iterating. */
*des = he;
des++;
he = he->next;
stored++;
if (stored == count) return stored;
}
i = (i+1) & d->ht[j].sizemask;
/* Try to do a rehashing work proportional to 'count'. */
for (j = 0; j < count; j++) {
if (dictIsRehashing(d))
_dictRehashStep(d);
else
break;
}
tables = dictIsRehashing(d) ? 2 : 1;
maxsizemask = d->ht[0].sizemask;
if (tables > 1 && maxsizemask < d->ht[1].sizemask)
maxsizemask = d->ht[1].sizemask;
/* Pick a random point inside the larger table. */
unsigned int i = random() & maxsizemask;
while(stored < count) {
for (j = 0; j < tables; j++) {
if (i >= d->ht[j].size) continue; /* Out of range for this table. */
dictEntry *he = d->ht[j].table[i];
while (he) {
/* Collect all the elements of the buckets found non
* empty while iterating. */
*des = he;
des++;
he = he->next;
stored++;
if (stored == count) return stored;
}
/* If there is only one table and we iterated it all, we should
* already have 'count' elements. Assert this condition. */
assert(dictIsRehashing(d) != 0);
}
i = (i+1) & maxsizemask;
}
return stored; /* Never reached. */
}