css - Rails images and assets not being loaded properly -

for example, in rails application have like:

.wax_seal {   background: url("wax-seal-small.png");   display: block;   height: 100px;   margin: 0 auto;   width: 92px; }  .wax_seal:active {   background: url('wax-seal-small-broken.png'); } 

and in config/environments/production.rb file:

# disable rails's static asset server (apache or nginx this). config.serve_static_assets = true 

i manually invoke compiling of assets:

bundle exec rake assets:precompile 

and files created hashes @ end of name:

wax-seal-small-uuhqwduhqwdoi234983jewf.png 

---

so doesn't work:

background: url("wax-seal-small.png"); 

but works fine (when manually type in chrome):

background: url("wax-seal-small-uuhqwduhqwdoi234983jewf.png"); 

---

what step missing here? how can make css rules add in little hash?

adding config.assets.compile = true in config/environments/production.rb makes work, read in rails guide it's bad practice due significant performance hits.

i found in edgerails documentation: http://edgeguides.rubyonrails.org/asset_pipeline.html#css-and-sass

2.3.2 css , sass

when using asset pipeline, paths assets must re-written , sass-rails provides -url , -path helpers (hyphenated in sass, underscored in ruby) following asset classes: image, font, video, audio, javascript , stylesheet.

• image-url("rails.png") becomes url(/assets/rails.png)
• image-path("rails.png") becomes "/assets/rails.png"

the more generic form can used asset path , class must both specified:

• asset-url("rails.png", image) becomes url(/assets/rails.png)
• asset-path("rails.png", image) becomes "/assets/rails.png"