Question

翻译一篇文章中的一段

However, joins can alternatively receive as input only
the columns needed to evaluate the join predicate. The out-
put of the join is then set of pairs of positions in the input
columns for which the predicate succeeded. For example,
the figure below shows the results of a join of a column of
size 5 with a column of size 3. The positions that are output
can then be sent to other columns from the input relations
(since only the columns in the join predicate were sent to
the join) to extract the values at these positions.

Answer 1

加入也可以为输入才来评价的联接谓词所需的列。
外把的连接，然后设置为对这些谓词成功地输入列位置的。
例如，下图显示了一个连接尺寸5列的大小为3列中的结果。
 该输出的位置可以被发送到其他列从输入关系来提取在这些位置中的值。
（因为只有在连接谓词中的列被送往
联接）