hll_merge()
Learn how to use the hll_merge() function toe merge HLL results.
Merges HLL results. This is the scalar version of the aggregate version hll_merge().
Read about the underlying algorithm (HyperLogLog) and estimation accuracy.
Syntax
hll_merge( hll, hll2, [ hll3, … ])
Parameters
| Name | Type | Required | Description |
|---|---|---|---|
| hll, hll2, … | string | ✔️ | The column names containing HLL values to merge. The function expects between 2-64 arguments. |
Returns
Returns one HLL value. The value is the result of merging the columns hll, hll2, … hllN.
Examples
This example shows the value of the merged columns.
range x from 1 to 10 step 1
| extend y = x + 10
| summarize hll_x = hll(x), hll_y = hll(y)
| project merged = hll_merge(hll_x, hll_y)
| project dcount_hll(merged)
Output
dcount_hll_merged |
|---|
| 20 |
Estimation accuracy
Related content
- Using hll() and tdigest()
- hll() (aggregation function)
- hll_if() (aggregation function)
- hll_merge() (aggregation function)
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