top() function

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top() sorts each input table by specified columns and keeps the top n records in each table.

Note: top() drops empty tables.

Function type signature

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Parameters

n

({{< req >}}) Number of rows to return from each input table.

columns

List of columns to sort by. Default is ["_value"].

Sort precedence is determined by list order (left to right).

tables

Input data. Default is piped-forward data (<-).

Examples

Return rows with the three highest values in each input table

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Input data

_time	_value	*tag
2021-01-01T00:00:00Z	-2	t1
2021-01-01T00:00:10Z	10	t1
2021-01-01T00:00:20Z	7	t1
2021-01-01T00:00:30Z	17	t1
2021-01-01T00:00:40Z	15	t1
2021-01-01T00:00:50Z	4	t1

_time	_value	*tag
2021-01-01T00:00:00Z	19	t2
2021-01-01T00:00:10Z	4	t2
2021-01-01T00:00:20Z	-3	t2
2021-01-01T00:00:30Z	19	t2
2021-01-01T00:00:40Z	13	t2
2021-01-01T00:00:50Z	1	t2

Output data

_time	_value	*tag
2021-01-01T00:00:30Z	17	t1
2021-01-01T00:00:40Z	15	t1
2021-01-01T00:00:10Z	10	t1

_time	_value	*tag
2021-01-01T00:00:00Z	19	t2
2021-01-01T00:00:30Z	19	t2
2021-01-01T00:00:40Z	13	t2

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