Increase sql queries

Brian Moon brianm at
Wed Oct 24 13:22:42 UTC 2007

> I find that coding with a cache in mind results in different code - for 
> example where you would normally do a 'select *' to get a whole bunch of 
> complete records from a DB, you might instead do a 'select id' followed 
> by a string of sub-requests in order to play to the strengths of the 
> cache (i.e. to get cache hits for those individual records as parts of 
> unrelated queries on the same tables). That would normally be a really 
> bad way of talking to the DB, but when you have a cache in the picture 
> it changes things. The downside is that it can also mean that should the 
> cache disappear, you hit the DB harder than you might otherwise.

We used to use this type of thing a lot.  This is some code I just 
hacked up.  It may not even parse.  It could be better like using a 
multi get.  You would need an additional loop though.  Also, order is 
not preserved in this function.

function get_stuff($id_array){

     $data_array = array();
     $fetch_array = array();

     foreach($id_array as $id){
         $data_array[$id] = $memcache->get("some_prefix_".$id);
             $fetch_array[] = $id

     $sql = "select * from table where id in (".implode(",", 
     $res = mysql_query($sql);
     while($rec = mysql_fetch_assoc($res)){
         $data_array[$rec["id"]] = $rec;
         $memcache("some_prefix_".$rec["id"], $rec);

     return $data_array;


Or used to when we used memcached on forward facing servers to cache 
code/queries.  We don't do that anymore due to cache stampedes that you 
mention.  We pregenerate our cache now into MySQL replicated servers.


Brian Moon
Senior Developer
It's good to be cheap =)

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