Redis how to store associative array? Set or Hash or List?

Question

I'm a bit confused with all the available storing options of Redis. I want to do something simple and I don't want to over engineer it. I'm working with phpredis and Redis v2.8.6.

I have this simple associative array that I need to store. I also need to be able to retrieve an item by its key and loop over all the items.

$a = array(     '12345' => array(         'name' => 'Post A',         'val2' => 'blah blah',         'val3' => 'blah blah blah',     ),     '54321' => array(         'name' => 'Post B',         'val2' => 'blah blah',         'val3' => 'blah blah blah',     ),     '998877' => array(         'name' => 'Post C',         'val2' => 'blah blah',         'val3' => 'blah blah blah',     ) ); 

So what I was doing till now was using hash type. storing my array like this:

foreach ($a as $key => $value) {     $this->redis->hSet('posts', $key, json_encode($value)); } 

Like that I could access the key easily like this:

public function getPost($postId) {     return json_decode($this->redis->hGet('posts', $postId), true); }  // This is returning the information of Post A $post = getPost(12345); 

But now I need to loop over all the posts I don't know how to do it and if I can do it with my current structure. I don't know if I need to store all the post_id in another list to be able to loop over all the posts?

So my question is which data type(s) should I use to store my list of posts, allowing me to fetch a single post by its id and looping over all the posts?

Thanks, Maxime

Answer 1

You can use SET and Hash and SORT in combination

redis 127.0.0.1:6379> HMSET TEST_12345 name "Post A" val2 "Blah Blah" val3 "Blah Blah Blah" OK redis 127.0.0.1:6379> HMSET TEST_54321 name "Post B" val2 "Blah Blah" val3 "Blah Blah Blah" OK redis 127.0.0.1:6379> HMSET TEST_998877 name "Post C" val2 "Blah Blah" val3 "Blah Blah Blah" OK redis 127.0.0.1:6379> SADD All_keys TEST_12345 TEST_54321 TEST_998877 (integer) 3 redis 127.0.0.1:6379> HGETALL TEST_12345 

To GET one HASH:

redis 127.0.0.1:6379> HGETALL TEST_12345 1) "name" 2) "Post A" 3) "val2" 4) "Blah Blah" 5) "val3" 6) "Blah Blah Blah" 

TO GET All HASH

redis 127.0.0.1:6379> SORT All_keys BY nosort GET *->name GET *->val2 GET *->val3 1) "Post A" 2) "Blah Blah" 3) "Blah Blah Blah" 4) "Post B" 5) "Blah Blah" 6) "Blah Blah Blah" 7) "Post C" 8) "Blah Blah" 9) "Blah Blah Blah" 

If you don't want to use sort you can use Fetch All the key names from SET using SMEMBERS and then use Redis Pipeline to fetch all the keys

Answer 2

Just for the folks looking for the PHP code, here is what I've ended up using:

// Create a post hash $key = 'post:'.$post->getId(); $this->redis->hSet($key, 'data', serialize($post->toArray()));  // Add a post in the account posts SET $this->redis->sAdd($account->getId().':posts', $post->getId());  // You can execute the above code as many time as you need  // to add an object in a SET  // Fetch the first $limit posts for this account // SORT <account_id>:posts BY nosort GET <account_id>:post:*->data $key = $account->getId().':posts'; $keys = $this->redis->sort($key, array(     'by' => 'nosort',     'limit' => array($offset, $limit),     'get' => 'post:*->data' ));  // All Good ! var_dump($keys); 

I hope this will help some of you ;)