Module | Sequel::Plugins::IdentityMap::ClassMethods |
In: |
lib/sequel/plugins/identity_map.rb
|
Returns the current thread-local identity map. Should be a hash if there is an active identity map, and nil otherwise.
# File lib/sequel/plugins/identity_map.rb, line 42 42: def identity_map 43: Thread.current[:sequel_identity_map] 44: end
The identity map key for an object of the current class with the given pk. May not always be correct for a class which uses STI.
# File lib/sequel/plugins/identity_map.rb, line 48 48: def identity_map_key(pk) 49: "#{self}:#{pk ? Array(pk).join(',') : "nil:#{rand}"}" 50: end
If the identity map is in use, check it for a current copy of the object. If a copy does not exist, create a new object and add it to the identity map. If a copy exists, add any values in the given row that aren‘t currently in the object to the object‘s values. This allows you to only request certain fields in an initial query, make modifications to some of those fields and request other, potentially overlapping fields in a new query, and not have the second query override fields you modified.
# File lib/sequel/plugins/identity_map.rb, line 59 59: def load(row) 60: return super unless idm = identity_map 61: if o = idm[identity_map_key(Array(primary_key).map{|x| row[x]})] 62: o.merge_db_update(row) 63: else 64: o = super 65: idm[identity_map_key(o.pk)] = o 66: end 67: o 68: end
Take a block and inside that block use an identity map to ensure a 1-1 correspondence of objects to the database row they represent.
# File lib/sequel/plugins/identity_map.rb, line 72 72: def with_identity_map 73: return yield if identity_map 74: begin 75: self.identity_map = {} 76: yield 77: ensure 78: self.identity_map = nil 79: end 80: end