WIDTH_BUCKET
Description
Construct an equal-width histogram, where the histogram range is divided into equal-sized intervals, and after calculation, return the bucket number where the value of the expression falls. Special cases:
- The function returns an integer value or NULL (if any input is NULL, it will return NULL)
Syntax
WIDTH_BUCKET(<expr>, <min_value>, <max_value>, <num_buckets>)
Parameters
| Parameter | Description |
|---|---|
<expr> | The expression for creating the histogram. This expression must evaluate to a numeric value or a value that can be implicitly converted to a numeric value. The value's range must be from -(2^53 - 1) to 2^53 - 1 (inclusive) |
<min_value> | The lowest value point of the acceptable range for the expression. The parameter must be numeric and not equal to <max_value>. The range must be from -(2^53 - 1) to 2^53 - 1 (inclusive). Additionally, the difference between the highest and lowest value points must be less than 2^53 (for example: abs(max_value - min_value) < 2^53) |
<max_value> | The highest value point of the acceptable range for the expression. The parameter must be numeric and not equal to <min_value>. The range must be from -(2^53 - 1) to 2^53 - 1 (inclusive). Additionally, the difference between the highest and lowest value points must be less than 2^53 (for example: abs(max_value - min_value) < 2^53) |
<num_buckets> | The number of buckets. It must be a positive integer. The function assigns a value from the expression to each bucket and returns the corresponding bucket number |
Return Value
Return the bucket number where the expression value falls. The function returns the following rules when the expression is out of range:
- If the value of the expression is less than
min_value, return 0. - If the value of the expression is greater than or equal to max_value, return
num_buckets + 1. - If any parameter is
null, returnnull
Example
DROP TABLE IF EXISTS width_bucket_test;
CREATE TABLE IF NOT EXISTS width_bucket_test (
`k1` int NULL COMMENT "",
`v1` date NULL COMMENT "",
`v2` double NULL COMMENT "",
`v3` bigint NULL COMMENT ""
) ENGINE=OLAP
DUPLICATE KEY(`k1`)
DISTRIBUTED BY HASH(`k1`) BUCKETS 1
PROPERTIES (
"replication_allocation" = "tag.location.default: 1",
"storage_format" = "V2"
);
INSERT INTO width_bucket_test VALUES
(1, "2022-11-18", 290000.00, 290000),
(2, "2023-11-18", 320000.00, 320000),
(3, "2024-11-18", 399999.99, 399999),
(4, "2025-11-18", 400000.00, 400000),
(5, "2026-11-18", 470000.00, 470000),
(6, "2027-11-18", 510000.00, 510000),
(7, "2028-11-18", 610000.00, 610000),
(8, null, null, null);
SELECT * FROM width_bucket_test ORDER BY k1;
+------+------------+-----------+--------+
| k1 | v1 | v2 | v3 |
+------+------------+-----------+--------+
| 1 | 2022-11-18 | 290000 | 290000 |
| 2 | 2023-11-18 | 320000 | 320000 |
| 3 | 2024-11-18 | 399999.99 | 399999 |
| 4 | 2025-11-18 | 400000 | 400000 |
| 5 | 2026-11-18 | 470000 | 470000 |
| 6 | 2027-11-18 | 510000 | 510000 |
| 7 | 2028-11-18 | 610000 | 610000 |
| 8 | NULL | NULL | NULL |
+------+------------+-----------+--------+
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;
+------+------------+-----------+--------+------+
| k1 | v1 | v2 | v3 | w |
+------+------------+-----------+--------+------+
| 1 | 2022-11-18 | 290000 | 290000 | 0 |
| 2 | 2023-11-18 | 320000 | 320000 | 1 |
| 3 | 2024-11-18 | 399999.99 | 399999 | 2 |
| 4 | 2025-11-18 | 400000 | 400000 | 3 |
| 5 | 2026-11-18 | 470000 | 470000 | 4 |
| 6 | 2027-11-18 | 510000 | 510000 | 5 |
| 7 | 2028-11-18 | 610000 | 610000 | 5 |
| 8 | NULL | NULL | NULL | NULL |
+------+------------+-----------+--------+------+
SELECT k1, v1, v2, v3, width_bucket(v2, 200000, 600000, 4) AS w FROM width_bucket_test ORDER BY k1;
+------+------------+-----------+--------+------+
| k1 | v1 | v2 | v3 | w |
+------+------------+-----------+--------+------+
| 1 | 2022-11-18 | 290000 | 290000 | 1 |
| 2 | 2023-11-18 | 320000 | 320000 | 2 |
| 3 | 2024-11-18 | 399999.99 | 399999 | 2 |
| 4 | 2025-11-18 | 400000 | 400000 | 3 |
| 5 | 2026-11-18 | 470000 | 470000 | 3 |
| 6 | 2027-11-18 | 510000 | 510000 | 4 |
| 7 | 2028-11-18 | 610000 | 610000 | 5 |
| 8 | NULL | NULL | NULL | NULL |
+------+------------+-----------+--------+------+
SELECT k1, v1, v2, v3, width_bucket(v3, 200000, 600000, 4) AS w FROM width_bucket_test ORDER BY k1;
+------+------------+-----------+--------+------+
| k1 | v1 | v2 | v3 | w |
+------+------------+-----------+--------+------+
| 1 | 2022-11-18 | 290000 | 290000 | 1 |
| 2 | 2023-11-18 | 320000 | 320000 | 2 |
| 3 | 2024-11-18 | 399999.99 | 399999 | 2 |
| 4 | 2025-11-18 | 400000 | 400000 | 3 |
| 5 | 2026-11-18 | 470000 | 470000 | 3 |
| 6 | 2027-11-18 | 510000 | 510000 | 4 |
| 7 | 2028-11-18 | 610000 | 610000 | 5 |
| 8 | NULL | NULL | NULL | NULL |
+------+------------+-----------+--------+------+
