PHP：如何在redis中缓存一个大表？

Question

Assume, that I have a big (MySQL-)table (>10k rows) with id -> string. I can put them all in an array and cache this array. But the question ist: How to cache it efficiently?

a) Cache it as one big item. So I will execute

$redis->set("array", $array);

Quite short and easy. But for every entry I need, I have to fetch the whole thing. Absolutely inefficient.

b) Cache every entry itself:

foreach( $array as $id => $str )
  $redis->set( "array:$id", $str );

Using this way, I will have >10k entries in Redis. That doesn't feel good. If I have 10 of these tables, i will have 100k entries....

So what's your proposal? How to cache a big array?

Answer 1

Caching the big array only makes helpful if you're planning to retrieve it always as a whole. However cache invalidation will be a very "heavy" operation as anytime when you change something you have to invalidate the whole array and reread it from the DB.

10k in redis is not much at all. You can have millions of entries without problem.

I would go with the b) version. Cache every entry individually. Easier to maintain, simpler application code and smaller memory footprint from application side which gets more and more important when you want to scale your application.