distinctcounttuplesketch.md

description
This section contains reference documentation for the DISTINCTCOUNTTUPLESKETCH function.

DISTINCTCOUNTTUPLESKETCH

The Tuple Sketch is an extension of the Theta Sketch. Tuple sketches store an additional summary value with each retained entry which makes the sketch ideal for summarizing attributes such as impressions or clicks. Tuple sketches are interoperable with the Theta Sketch and enable set operations over a stream of data, and can also be used for cardinality estimation.

Signature

distinctCountTupleSketch(<tupleSketchColumn>, <tupleSketchParams>) -> Long

• tupleSketchColumn (required): Name of the column to aggregate on. This must be an existing tuple sketch serialized as bytes.
• tupleSketchParams (required): Semicolon-separated parameter string for constructing the intermediate tuple-sketches.
  • The supported parameters are:
  • nominalEntries: The nominal entries used to create the sketch. (Default 65536)
  • accumulatorThreshold: How many sketches should be kept in memory before merging. (Default 2)

These examples are based on the Batch Quick Start. A new Tuple Sketch metric called playerHomeRuns was created during ingestion by updating the ingestion config as follows:

	"ingestionConfig": {
		"transformConfigs": [
			{
				"columnName": "playerHomeRuns",
				"transformFunction": "toIntegerSumTupleSketch(playerID, homeRuns)"
			}
		]
	}

The distinctCountTupleSketch function can be used to extract an estimate of the number of unique items in a Tuple sketch.

select distinctCountTupleSketch(playerHomeRuns) as value
from baseballStats 

value
17549

select distinctCountTupleSketch(playerHomeRuns, 'nominalEntries=65536;accumulatorThreshold=10) as value
from baseballStats 

value
17549

This function can also be used with the V2 query engine.