width_bucket

Description

构造等宽直方图，其中直方图范围被划分为相同大小的区间，并在计算后返回表达式的值所在的桶号。该函数返回一个整数值或空值（如果任何输入为空值则返回空值）。

Syntax

  1. width_bucket(expr, min_value, max_value, num_buckets)

Arguments

expr - 创建直方图的表达式。此表达式必须计算为数值或可隐式转换为数值的值。

此值的范围必须为 -(2^53 - 1) 到 2^53 - 1 (含).

min_value 和 max_value - 表达式可接受范围的最低值点和最高值点。这两个参数必须为数值并且不相等。

最低值点和最高值点的范围必须为 -(2^53 - 1) to 2^53 - 1 (含)). 此外，最高值点与最低值点的差必须小于 2^53 (例如： abs(max_value - min_value) < 2^53).

num_buckets - 分桶的数量，必须是正整数值。将表达式中的一个值分配给每个存储桶，然后该函数返回相应的存储桶编号。

Returned value

返回表达式值所在的桶号。

当表达式超出范围时，函数返回规则如下：

如果表达式的值小于min_value返回0.

如果表达式的值大于或等于max_value返回num_buckets + 1.

如果任意参数为null返回null.

example

  1. DROP TABLE IF EXISTS width_bucket_test;
  3. CREATE TABLE IF NOT EXISTS width_bucket_test (
  4.               `k1` int NULL COMMENT "",
  5.               `v1` date NULL COMMENT "",
  6.               `v2` double NULL COMMENT "",
  7.               `v3` bigint NULL COMMENT ""
  8.             ) ENGINE=OLAP
  9.             DUPLICATE KEY(`k1`)
  10.             DISTRIBUTED BY HASH(`k1`) BUCKETS 1
  11.             PROPERTIES (
  12.             "replication_allocation" = "tag.location.default: 1",
  13.             "storage_format" = "V2"
  14.             );
  16. INSERT INTO width_bucket_test VALUES (1, "2022-11-18", 290000.00, 290000),
  17.                                       (2, "2023-11-18", 320000.00, 320000),
  18.                                       (3, "2024-11-18", 399999.99, 399999), 
  19.                                       (4, "2025-11-18", 400000.00, 400000), 
  20.                                       (5, "2026-11-18", 470000.00, 470000), 
  21.                                       (6, "2027-11-18", 510000.00, 510000), 
  22.                                       (7, "2028-11-18", 610000.00, 610000), 
  23.                                       (8, null, null, null);
  25. SELECT * FROM width_bucket_test ORDER BY k1;                                      
  27. +------+------------+-----------+--------+
  28. | k1   | v1         | v2        | v3     |
  29. +------+------------+-----------+--------+
  30. |    1 | 2022-11-18 |    290000 | 290000 |
  31. |    2 | 2023-11-18 |    320000 | 320000 |
  32. |    3 | 2024-11-18 | 399999.99 | 399999 |
  33. |    4 | 2025-11-18 |    400000 | 400000 |
  34. |    5 | 2026-11-18 |    470000 | 470000 |
  35. |    6 | 2027-11-18 |    510000 | 510000 |
  36. |    7 | 2028-11-18 |    610000 | 610000 |
  37. |    8 | NULL       |      NULL |   NULL |
  38. +------+------------+-----------+--------+
  40. SELECT k1, v1, v2, v3, width_bucket(v1, date('2023-11-18'), date('2027-11-18'), 4) AS w FROM width_bucket_test ORDER BY k1;
  42. +------+------------+-----------+--------+------+
  43. | k1   | v1         | v2        | v3     | w    |
  44. +------+------------+-----------+--------+------+
  45. |    1 | 2022-11-18 |    290000 | 290000 |    0 |
  46. |    2 | 2023-11-18 |    320000 | 320000 |    1 |
  47. |    3 | 2024-11-18 | 399999.99 | 399999 |    2 |
  48. |    4 | 2025-11-18 |    400000 | 400000 |    3 |
  49. |    5 | 2026-11-18 |    470000 | 470000 |    4 |
  50. |    6 | 2027-11-18 |    510000 | 510000 |    5 |
  51. |    7 | 2028-11-18 |    610000 | 610000 |    5 |
  52. |    8 | NULL       |      NULL |   NULL | NULL |
  53. +------+------------+-----------+--------+------+
  55. SELECT k1, v1, v2, v3, width_bucket(v2, 200000, 600000, 4) AS w FROM width_bucket_test ORDER BY k1;
  57. +------+------------+-----------+--------+------+
  58. | k1   | v1         | v2        | v3     | w    |
  59. +------+------------+-----------+--------+------+
  60. |    1 | 2022-11-18 |    290000 | 290000 |    1 |
  61. |    2 | 2023-11-18 |    320000 | 320000 |    2 |
  62. |    3 | 2024-11-18 | 399999.99 | 399999 |    2 |
  63. |    4 | 2025-11-18 |    400000 | 400000 |    3 |
  64. |    5 | 2026-11-18 |    470000 | 470000 |    3 |
  65. |    6 | 2027-11-18 |    510000 | 510000 |    4 |
  66. |    7 | 2028-11-18 |    610000 | 610000 |    5 |
  67. |    8 | NULL       |      NULL |   NULL | NULL |
  68. +------+------------+-----------+--------+------+
  70. SELECT k1, v1, v2, v3, width_bucket(v3, 200000, 600000, 4) AS w FROM width_bucket_test ORDER BY k1;
  72. +------+------------+-----------+--------+------+
  73. | k1   | v1         | v2        | v3     | w    |
  74. +------+------------+-----------+--------+------+
  75. |    1 | 2022-11-18 |    290000 | 290000 |    1 |
  76. |    2 | 2023-11-18 |    320000 | 320000 |    2 |
  77. |    3 | 2024-11-18 | 399999.99 | 399999 |    2 |
  78. |    4 | 2025-11-18 |    400000 | 400000 |    3 |
  79. |    5 | 2026-11-18 |    470000 | 470000 |    3 |
  80. |    6 | 2027-11-18 |    510000 | 510000 |    4 |
  81. |    7 | 2028-11-18 |    610000 | 610000 |    5 |
  82. |    8 | NULL       |      NULL |   NULL | NULL |
  83. +------+------------+-----------+--------+------+

keywords

WIDTH_BUCKET