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Diffstat (limited to 'lib/arel/relations/join.rb')
| -rw-r--r-- | lib/arel/relations/join.rb | 92 |
1 files changed, 92 insertions, 0 deletions
diff --git a/lib/arel/relations/join.rb b/lib/arel/relations/join.rb new file mode 100644 index 0000000000..fb51ea0260 --- /dev/null +++ b/lib/arel/relations/join.rb @@ -0,0 +1,92 @@ +module Arel + class Join < Relation + attr_reader :join_sql, :relation1, :relation2, :predicates + + delegate :engine, :to => :relation1 + + hash_on :relation1 + + def initialize(join_sql, relation1, relation2 = Nil.new, *predicates) + @join_sql, @relation1, @relation2, @predicates = join_sql, relation1, relation2, predicates + end + + def ==(other) + self.class == other.class and + predicates == other.predicates and ( + (relation1 == other.relation1 and relation2 == other.relation2) or + (relation2 == other.relation1 and relation1 == other.relation2) + ) + end + + def attributes + (externalize(relation1).attributes + + externalize(relation2).attributes).collect { |a| a.bind(self) } + end + + def prefix_for(attribute) + if relation1[attribute] && !relation2[attribute] + externalize(relation1).prefix_for(attribute) + elsif relation2[attribute] && !relation1[attribute] + externalize(relation2).prefix_for(attribute) + else + if (attribute % relation1[attribute]).size < (attribute % relation2[attribute]).size + externalize(relation1).prefix_for(attribute) + else + externalize(relation2).prefix_for(attribute) + end + end + end + + def joins + this_join = [ + join_sql, + externalize(relation2).table_sql, + ("ON" unless predicates.blank?), + predicates.collect { |p| p.bind(self).to_sql }.join(' AND ') + ].compact.join(" ") + [relation1.joins, relation2.joins, this_join].compact.join(" ") + end + + def selects + externalize(relation1).selects + externalize(relation2).selects + end + + def table_sql + externalize(relation1).table_sql + end + + private + def externalize(relation) + Externalizer.new(relation) + end + + Externalizer = Struct.new(:relation) do + delegate :engine, :to => :relation + + def table_sql + case + when relation.aggregation? + relation.to_sql(Sql::TableReference.new(engine)) + when relation.alias? + relation.table_sql + ' AS ' + engine.quote_table_name(relation.alias.to_s) + else + relation.table_sql + end + end + + def selects + relation.aggregation?? [] : relation.selects + end + + def attributes + relation.aggregation?? relation.attributes.collect(&:to_attribute) : relation.attributes + end + + def prefix_for(attribute) + if relation[attribute] + relation.alias?? relation.alias : relation.prefix_for(attribute) + end + end + end + end +end
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