topk

Type of operation: Filter

Description

Selects all data for each of top k ranked groups. If no rank method is provided, a default one will be used. Default ranking method sorts groups by the first found numeric column which is not part of the grouping. Groups are sorted by all grouping keys if no such column is found. If no grouping is specified, the set of primary key columns will be used as the grouping.

Usage

topk k [ , rank ] [ , groupby ]

Argument	Type	Required	Multiple
k	int64	Required	Only one
rank	expression	Optional	Only one
groupby	fieldref	Optional	Only one

Accelerable

topk is never accelerable. A dataset that only uses accelerable verbs can be accelerated, making queries on the dataset respond faster.

Examples

topk 100

Select the top 100 groups using the default rank method: sorting by the first suitable numeric field, or by all the group identifiers when no suitable numeric field is found. Primary key columns are used here as default group identifiers.

topk 100, group_by(clusterUid, namespace)

Similar to the first example, but explicitly specifying the grouping

topk 100, max(memory_used)

Select the 100 groups with the highest memory usage in the query window.

topk 1, group_by()

This topk operates on empty grouping, where all rows belong to the same group, and hence all rows will be selected

topk 100, max(memory_used), group_by(clusterUid, namespace)

Rank the maximum memory_used during the query window for each Kubernetes namespace, and select the highest 100 namespaces.