ruby - Rails Caching in Agile Web Development w/ Rails4 -

i'm working way through book agile web development rails4, , read (first) part caching parts of view avoid overwhelming database. i've of course set caching option true in config development environment.

the problem caching doesn't seem working. here app/views/store/index.html.erb file, 1 given in book, enable caching :

<% if notice %>   <p id="notice"><%= notice %></p> <% end %>  <h1>your pragmatic catalog</h1>  <% cache ['store', product.latest] %>   <% @products.each |product| %>     <% cache ['entry', product] %>       <div class="entry">         <%= image_tag(product.image_url) %>         <h3><%= product.title %></h3>         <%= sanitize(product.description) %>         <div class="price_line">           <span class="price"><%= number_to_currency(product.price) %></span>         </div>       </div>     <% end %>   <% end %> <% end %> 

and here rails server log, showing databse accessed multiple times (although line mentions caching) : http://pastebin.com/v2jgihkl

here app/views/store/index.html.erb file, tried else caching :

<% if notice %>   <p id="notice"><%= notice %></p> <% end %>  <h1>your pragmatic catalog</h1>  <% cache('caching') %>   <% @products.each |product| %>       <div class="entry">         <%= image_tag(product.image_url) %>         <h3><%= product.title %></h3>         <%= sanitize(product.description) %>         <div class="price_line">           <span class="price"><%= number_to_currency(product.price) %></span>         </div>       </div>   <% end %> <% end %> 

and here corresponding log, showing caching successful (as database not queried) : http://pastebin.com/ztk9a9ra

can explain why 1 seems work , not other, or how first 1 should work ? thank :)

note in book, says caching enabled, reloading store page shouldn't show new parts of store/index.html.erb if changes made inside cached block ; yet in both case. idea ?

the parameter pass cache api caching key. hashing function of key cached fragment stored, , looked for.

in code (cache('caching')) caching key hard-coded, , never changes, so, unless cache invalidated (either manually in code, or when ttl has passed) - same fragment sent client.

in code book (cache ['store', product.latest]) key depends on latest product. means if latest product changes (another product added, or updated) - next call automatically 'know' not take page cache, recreate cache.

what shown in logs:

[1m[35mproduct load (0.3ms)[0m  select  "products".* "products"   order "products"."updated_at" desc limit 1 

is result of product.latest, not of product.all.

to sum - both code fragments cached, in example code, there is (small) hit database verify validity of cache, whether page cached or not.

if invalidating cache yourself, can keep hard-coded version of code, if not, better think of invalidation scheme, whether example code suggests or else.