ruby on rails - Using crc32 tweak on has_many relations in Thinking Sphinx -

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it's weird actually. have 2 models have has_many relation each other, here models

#model city class city < activerecord::base belong_to :state end  #model state class state < activerecord::base has_many :city end

and have state index

thinkingsphinx::index.define 'state', :with => :active_record   indexes state_name, :sortable => true    #here problem   has "crc32(cities.city_name)", :as => :city_name, :type => :integer end

i want use city_name filter. code above doesn't work , got error message when run 

rake ts:index

here error message

error: index 'state_core': sql_range_query: unknown column 'cities.city_name' in 'field list'

but, when put city_name in indexes block below, indexer runs well!

thinkingsphinx::index.define 'state', :with => :active_record   indexes state_name, :sortable => true   indexes cities.city_name   has "crc32(cities.city_name)", :as => :city_name, :type => :integer end

any suggestions ?

thinking sphinx can't tell if you're referring association tables within sql snippets - in first example, there's nothing indicating needs join on cities.

the join method within index definition exists purpose - so, try following:

thinkingsphinx::index.define 'state', :with => :active_record   indexes state_name, :sortable => true    has "crc32(cities.city_name)", :as => :city_name, :type => :integer    join cities end

however, it's worth noting few things: firstly, may need add cities.city_name group by clause, since it's not part of aggregate values:

# within index definition group_by 'cities.city_name

but also: state model has many cities, not one, should aggregated set of integer values, not one. means don't need group_by call, need add aggregate behaviour yourself. done differently depending on whether you're using postgresql or mysql:

# postgresql has "array_to_string(array_agg(crc32(cities.name)), ',')",   :as => :city_names, :type => :integer, :multi => true  # mysql has "group_concat(crc32(cities.name) separator ',')",   :as => :city_names, :type => :integer, :multi => true

crc32 not native function in postgresql, , may need add yourself. thinking sphinx prior v3 did you, i've rewritten crc32 function no longer required. largely due fact crc32 can result in collisions, , can't reversed, , it's inelegant , imperfect solution. hence, think using fields string comparison better, it's whether preferred in app.

i recommend approach instead:

thinkingsphinx::index.define :state, :with => :active_record   indexes state_name, :sortable => true    has cities.id, :as => :city_ids end  city = city.find_by_name('melbourne') state.search :with => {:city_ids => city.id}

it's accurate , elegant.


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