PERCENTILE_APPROX

Description

Syntax:

PERCENTILE_APPROX(expr, DOUBLE p[, DOUBLE compression])

This function returns the approximation of th p percentile. The value of P is between 0 and 1.

The compression parameter is optional. Its range is [2048, 10000]. Larger compression values brings more precise results, but also, more time and memory costs. If the compression parameter is not specified or set beyond [2048, 10000], the system will consider it to be 10000.

This function uses fixed-size memory, so it can reduce memory usage of high-cardinality columns. It can be used to calculate statistics such as tp99.

Example

MySQL > select `table`, percentile_approx(cost_time,0.99) from log_statis group by `table`;
+---------------------+---------------------------+
| table    | percentile_approx(`cost_time`, 0.99) |
+----------+--------------------------------------+
| test     |                                54.22 |
+----------+--------------------------------------+

MySQL > select `table`, percentile_approx(cost_time,0.99, 4096) from log_statis group by `table`;
+---------------------+---------------------------+
| table    | percentile_approx(`cost_time`, 0.99, 4096.0) |
+----------+--------------------------------------+
| test     |                                54.21 |
+----------+--------------------------------------+

Keywords

PERCENTILE_APPROX,PERCENTILE,APPROX

PERCENTILE RETENTION