method

prepare_update_statement

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What's this?

prepare_update_statement(o) private

The default strategy for an UPDATE with joins is to use a subquery. This doesn’t work on MySQL (even when aliasing the tables), but MySQL allows using JOIN directly in an UPDATE statement, so in the MySQL visitor we redefine this to do that.

Show source

# File activerecord/lib/arel/visitors/to_sql.rb, line 851
        def prepare_update_statement(o)
          if o.key && (has_limit_or_offset_or_orders?(o) || has_join_sources?(o))
            stmt = o.clone
            stmt.limit = nil
            stmt.offset = nil
            stmt.orders = []
            stmt.wheres = [Nodes::In.new(o.key, [build_subselect(o.key, o)])]
            stmt.relation = o.relation.left if has_join_sources?(o)
            stmt.groups = o.groups unless o.groups.empty?
            stmt.havings = o.havings unless o.havings.empty?
            stmt
          else
            o
          end
        end

prepare_update_statement

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