try 在rails的模式下执行distinct.
2.1.1 :450 > u.profiles.select("profiles.*").distinct
Profile Load (0.9ms) SELECT DISTINCT profiles.* FROM "profiles" INNER JOIN "integration_profiles" ON "profiles"."id" = "integration_profiles"."profile_id" INNER JOIN "integrations" ON "integration_profiles"."integration_id" = "integrations"."id" WHERE "integrations"."user_id" = $1 [["user_id", 2]]
PG::UndefinedFunction: ERROR: could not identify an equality operator for type json
LINE 1: SELECT DISTINCT profiles.* FROM "profiles" INNER JOIN "integ...
^
: SELECT DISTINCT profiles.* FROM "profiles" INNER JOIN "integration_profiles" ON "profiles"."id" = "integration_profiles"."profile_id" INNER JOIN "integrations" ON "integration_profiles"."integration_id" = "integrations"."id" WHERE "integrations"."user_id" = $1
ActiveRecord::StatementInvalid: PG::UndefinedFunction: ERROR: could not identify an equality operator for type json
LINE 1: SELECT DISTINCT profiles.* FROM "profiles" INNER JOIN "integ...
^
: SELECT DISTINCT profiles.* FROM "profiles" INNER JOIN "integration_profiles" ON "profiles"."id" = "integration_profiles"."profile_id" INNER JOIN "integrations" ON "integration_profiles"."integration_id" = "integrations"."id" WHERE "integrations"."user_id" = $1
from /Users/mmahalwy/.rvm/gems/ruby-2.1.1/gems/rack-mini-profiler-0.9.1/lib/patches/sql_patches.rb:109:in `prepare'
from /Users/mmahalwy/.rvm/gems/ruby-2.1.1/gems/rack-mini-profiler-0.9.1/lib/patches/sql_patches.rb:109:in `prepare'
from /Users/mmahalwy/.rvm/gems/ruby-2.1.1/gems/activerecord-4.0.4/lib/active_record/connection_adapters/postgresql_adapter.rb:834:in `prepare_statement'
from /Users/mmahalwy/.rvm/gems/ruby-2.1.1/gems/activerecord-4.0.4/lib/active_record/connection_adapters/postgresql_adapter.rb:795:in `exec_cache'
from /Users/mmahalwy/.rvm/gems/ruby-2.1.1/gems/activerecord-4.0.4/lib/active_record/connection_adapters/postgresql/database_statements.rb:139:in `block in exec_query'
from /Users/mmahalwy/.rvm/gems/ruby-2.1.1/gems/activerecord-4.0.4/lib/active_record/connection_adapters/abstract_adapter.rb:442:in `block in log'
from /Users/mmahalwy/.rvm/gems/ruby-2.1.1/gems/activesupport-4.0.4/lib/active_support/notifications/instrumenter.rb:20:in `instrument'
from /Users/mmahalwy/.rvm/gems/ruby-2.1.1/gems/activerecord-4.0.4/lib/active_record/connection_adapters/abstract_adapter.rb:437:in `log'
from /Users/mmahalwy/.rvm/gems/ruby-2.1.1/gems/activerecord-4.0.4/lib/active_record/connection_adapters/postgresql/database_statements.rb:137:in `exec_query'
from /Users/mmahalwy/.rvm/gems/ruby-2.1.1/gems/activerecord-4.0.4/lib/active_record/connection_adapters/postgresql_adapter.rb:908:in `select'
from /Users/mmahalwy/.rvm/gems/ruby-2.1.1/gems/activerecord-4.0.4/lib/active_record/connection_adapters/abstract/database_statements.rb:32:in `select_all'
from /Users/mmahalwy/.rvm/gems/ruby-2.1.1/gems/activerecord-4.0.4/lib/active_record/connection_adapters/abstract/query_cache.rb:63:in `select_all'
from /Users/mmahalwy/.rvm/gems/ruby-2.1.1/gems/activerecord-4.0.4/lib/active_record/querying.rb:36:in `find_by_sql'
from /Users/mmahalwy/.rvm/gems/ruby-2.1.1/gems/activerecord-4.0.4/lib/active_record/relation.rb:585:in `exec_queries'
from /Users/mmahalwy/.rvm/gems/ruby-2.1.1/gems/activerecord-4.0.4/lib/active_record/association_relation.rb:15:in `exec_queries'
from /Users/mmahalwy/.rvm/gems/ruby-2.1.1/gems/activerecord-4.0.4/lib/active_record/relation.rb:471:in `load'
from /Users/mmahalwy/.rvm/gems/ruby-2.1.1/gems/activerecord-4.0.4/lib/active_record/relation.rb:220:in `to_a'
from /Users/mmahalwy/.rvm/gems/ruby-2.1.1/gems/activerecord-4.0.4/lib/active_record/relation.rb:573:in `inspect'
from /Users/mmahalwy/.rvm/gems/ruby-2.1.1/gems/railties-4.0.4/lib/rails/commands/console.rb:90:in `start'
from /Users/mmahalwy/.rvm/gems/ruby-2.1.1/gems/railties-4.0.4/lib/rails/commands/console.rb:9:in `start'
from /Users/mmahalwy/.rvm/gems/ruby-2.1.1/gems/railties-4.0.4/lib/rails/commands.rb:62:in `<top (required)>'
from bin/rails:4:in `require'
from bin/rails:4:in `<main>'2.1.1 :451 >
得到一个错误PG::UndefinedFunction: ERROR: could not identify an equality operator for type json
在这种情况下，转换为Hstore不是我的 Select .有什么解决办法吗？