Hive 横向视图分解内部机制

Question

我在单个 table（大小约为 12GB）的单个查询中多次使用横向视图爆炸（大约 9 次）。这产生了大量的地图侧数据（100Pb+）。我不明白它是如何从 12GB 生成这么多数据的。

谁能解释一下横向爆炸的工作原理（内部）？

提前致谢

Answer 1

演示

create table mytable (a1 array<int>,a2 array<int>,a3 array<int>);
insert into mytable select array(1,2),array(3,4,5),array(6,7,8,9);

select  *

from    mytable
        lateral view explode (a1) e1 as a1_val
        lateral view explode (a2) e2 as a2_val
        lateral view explode (a3) e3 as a3_val
;

+-------+---------+-----------+--------+--------+--------+
|  a1   |   a2    |    a3     | a1_val | a2_val | a3_val |
+-------+---------+-----------+--------+--------+--------+
| [1,2] | [3,4,5] | [6,7,8,9] |      1 |      3 |      6 |
| [1,2] | [3,4,5] | [6,7,8,9] |      1 |      3 |      7 |
| [1,2] | [3,4,5] | [6,7,8,9] |      1 |      3 |      8 |
| [1,2] | [3,4,5] | [6,7,8,9] |      1 |      3 |      9 |
| [1,2] | [3,4,5] | [6,7,8,9] |      1 |      4 |      6 |
| [1,2] | [3,4,5] | [6,7,8,9] |      1 |      4 |      7 |
| [1,2] | [3,4,5] | [6,7,8,9] |      1 |      4 |      8 |
| [1,2] | [3,4,5] | [6,7,8,9] |      1 |      4 |      9 |
| [1,2] | [3,4,5] | [6,7,8,9] |      1 |      5 |      6 |
| [1,2] | [3,4,5] | [6,7,8,9] |      1 |      5 |      7 |
| [1,2] | [3,4,5] | [6,7,8,9] |      1 |      5 |      8 |
| [1,2] | [3,4,5] | [6,7,8,9] |      1 |      5 |      9 |
| [1,2] | [3,4,5] | [6,7,8,9] |      2 |      3 |      6 |
| [1,2] | [3,4,5] | [6,7,8,9] |      2 |      3 |      7 |
| [1,2] | [3,4,5] | [6,7,8,9] |      2 |      3 |      8 |
| [1,2] | [3,4,5] | [6,7,8,9] |      2 |      3 |      9 |
| [1,2] | [3,4,5] | [6,7,8,9] |      2 |      4 |      6 |
| [1,2] | [3,4,5] | [6,7,8,9] |      2 |      4 |      7 |
| [1,2] | [3,4,5] | [6,7,8,9] |      2 |      4 |      8 |
| [1,2] | [3,4,5] | [6,7,8,9] |      2 |      4 |      9 |
| [1,2] | [3,4,5] | [6,7,8,9] |      2 |      5 |      6 |
| [1,2] | [3,4,5] | [6,7,8,9] |      2 |      5 |      7 |
| [1,2] | [3,4,5] | [6,7,8,9] |      2 |      5 |      8 |
| [1,2] | [3,4,5] | [6,7,8,9] |      2 |      5 |      9 |
+-------+---------+-----------+--------+--------+--------+

Hive 横向视图分解内部机制

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