redis dictFind when rehash

[erpeng zhang]

when find a key ,if redis is rehashing, now we should lookup both tables (ht[0] and ht[1]).
why don't we use the key's index comparing to the rehashidx,if index < rehashidx,then we don't need to lookup ht[0].

blow is the code :
for (table = 0; table <= 1; table++) {
idx = h & d->ht[table].sizemask;
he = d->ht[table].table[idx];
while(he) {
if (key==he->key || dictCompareKeys(d, key, he->key))
return he;
he = he->next;
}
if (!dictIsRehashing(d)) return NULL;
}

we can change it :
for (table = 0; table <= 1; table++) {
idx = h & d->ht[table].sizemask;
if (idx < d->rehashidx) continue;
he = d->ht[table].table[idx];
while(he) {
if (key==he->key || dictCompareKeys(d, key, he->key))
return he;
he = he->next;
}
if (!dictIsRehashing(d)) return NULL;
}

if idx < d->rehashidx,we can conclude:
1.it is rehashing(rehashidx is -1 if it is not rehashing)
2.we can't find key in ht[0]

so continue

[Itamar Haber]

Hello Erpeng

This may be an interesting optimization - I suggest that you resubmit it for discussion as a pull request at https://github.com/antirez/redis/pulls for the developers.

Cheers,

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Itamar Haber Technicalist Evangely Phone: +972.54.567.9692

[erpeng zhang]

Ok. Thank you for reply

[erpeng zhang]

Hi,Itamar!

I have commited a pull request:

  https://github.com/antirez/redis/pull/5692/files

welcome a review

在 2018年12月12日星期三 UTC+8下午8:08:02，Itamar Haber写道：