explode_map

description

表函数，需配合 Lateral View 使用, 可以支持多个 Lateral view, 仅仅支持新优化器。

将 map 列展开成多行。当 map 为NULL或者为空时，explode_map_outer 返回NULL。 explode_map 和 explode_map_outer 均会返回 map 内部的NULL元素。

syntax

1. explode_map(expr)
2. explode_map_outer(expr)

example

1. mysql> set enable_vectorized_engine = true
2. mysql> SET enable_nereids_planner=true
3. mysql> SET enable_fallback_to_original_planner=false

5. mysql> CREATE TABLE IF NOT EXISTS `sdu`(
6. `id` INT NULL,
7. `name` TEXT NULL,
8. `score` MAP<TEXT,INT> NULL
9. ) ENGINE=OLAP
10. DUPLICATE KEY(`id`)
11. COMMENT 'OLAP'
12. DISTRIBUTED BY HASH(`id`) BUCKETS 1
13. PROPERTIES ("replication_allocation" = "tag.location.default: 1");
14. Query OK, 0 rows affected (0.15 sec)

16. mysql> insert into sdu values (0, "zhangsan", {"Chinese":"80","Math":"60","English":"90"}), (1, "lisi", {"null":null}), (2, "wangwu", {"Chinese":"88","Math":"90","English":"96"}), (3, "lisi2", {null:null}), (4, "amory", NULL);
17. Query OK, 5 rows affected (0.23 sec)
18. {'label':'label_9b35d9d9d59147f5_bffb974881ed2133', 'status':'VISIBLE', 'txnId':'4005'}

20. mysql> select * from sdu order by id;
21. +------+----------+-----------------------------------------+
22. | id   | name     | score                                   |
23. +------+----------+-----------------------------------------+
24. |    0 | zhangsan | {"Chinese":80, "Math":60, "English":90} |
25. |    1 | lisi     | {"null":null}                           |
26. |    2 | wangwu   | {"Chinese":88, "Math":90, "English":96} |
27. |    3 | lisi2    | {null:null}                             |
28. |    4 | amory    | NULL                                    |
29. +------+----------+-----------------------------------------+

31. mysql> select name, k,v from sdu lateral view explode_map(score) tmp as k,v;
32. +----------+---------+------+
33. | name     | k       | v    |
34. +----------+---------+------+
35. | zhangsan | Chinese |   80 |
36. | zhangsan | Math    |   60 |
37. | zhangsan | English |   90 |
38. | lisi     | null    | NULL |
39. | wangwu   | Chinese |   88 |
40. | wangwu   | Math    |   90 |
41. | wangwu   | English |   96 |
42. | lisi2    | NULL    | NULL |
43. +----------+---------+------+

45. mysql> select name, k,v from sdu lateral view explode_map_outer(score) tmp as k,v;
46. +----------+---------+------+
47. | name     | k       | v    |
48. +----------+---------+------+
49. | zhangsan | Chinese |   80 |
50. | zhangsan | Math    |   60 |
51. | zhangsan | English |   90 |
52. | lisi     | null    | NULL |
53. | wangwu   | Chinese |   88 |
54. | wangwu   | Math    |   90 |
55. | wangwu   | English |   96 |
56. | lisi2    | NULL    | NULL |
57. | amory    | NULL    | NULL |
58. +----------+---------+------+

60. mysql> select name, k,v,k1,v1 from sdu lateral view explode_map_outer(score) tmp as k,v lateral view explode_map(score) tmp2 as k1,v1;
61. +----------+---------+------+---------+------+
62. | name     | k       | v    | k1      | v1   |
63. +----------+---------+------+---------+------+
64. | zhangsan | Chinese |   80 | Chinese |   80 |
65. | zhangsan | Chinese |   80 | Math    |   60 |
66. | zhangsan | Chinese |   80 | English |   90 |
67. | zhangsan | Math    |   60 | Chinese |   80 |
68. | zhangsan | Math    |   60 | Math    |   60 |
69. | zhangsan | Math    |   60 | English |   90 |
70. | zhangsan | English |   90 | Chinese |   80 |
71. | zhangsan | English |   90 | Math    |   60 |
72. | zhangsan | English |   90 | English |   90 |
73. | lisi     | null    | NULL | null    | NULL |
74. | wangwu   | Chinese |   88 | Chinese |   88 |
75. | wangwu   | Chinese |   88 | Math    |   90 |
76. | wangwu   | Chinese |   88 | English |   96 |
77. | wangwu   | Math    |   90 | Chinese |   88 |
78. | wangwu   | Math    |   90 | Math    |   90 |
79. | wangwu   | Math    |   90 | English |   96 |
80. | wangwu   | English |   96 | Chinese |   88 |
81. | wangwu   | English |   96 | Math    |   90 |
82. | wangwu   | English |   96 | English |   96 |
83. | lisi2    | NULL    | NULL | NULL    | NULL |
84. +----------+---------+------+---------+------+

keywords

EXPLODE_MAP,EXPLODE_MAP_OUTER,MAP