dcount_hll()

Learn how to use the dcount_hll() function to calculate the distinct count from hyper log log (hll) intermediate calculation results.

Calculates the distinct count from results generated by hll or hll_merge.

Read about the underlying algorithm (HyperLogLog) and estimation accuracy.

Syntax

dcount_hll(hll)

Parameters

NameTypeRequiredDescription
hllstring✔️An expression generated by hll or hll-merge to be used to find the distinct count.

Returns

Returns the distinct count of each value in hll.

Example

The following example shows the distinct count hll merged results.

StormEvents
| summarize hllRes = hll(DamageProperty) by bin(StartTime,10m)
| summarize hllMerged = hll_merge(hllRes)
| project dcount_hll(hllMerged)

Output

dcount_hll_hllMerged
315

Estimation accuracy