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stderror() ToolkitTimescaleDB Toolkit functions are available under Timescale Community Edition. They are automatically included with Timescale Cloud. Click to learn more.
Toolkit
TimescaleDB Toolkit functions are available under Timescale Community Edition. They are automatically included with Timescale Cloud. Click to learn more.
The stderror function returns an estimate of the relative standard error of the hyperloglog, based on the hyperloglog error formula. Approximate results are:
| precision | registers | error | bytes |
|---|---|---|---|
| 4 | 16 | 0.2600 | 12 |
| 5 | 32 | 0.1838 | 24 |
| 6 | 64 | 0.1300 | 48 |
| 7 | 128 | 0.0919 | 96 |
| 8 | 256 | 0.0650 | 192 |
| 9 | 512 | 0.0460 | 384 |
| 10 | 1024 | 0.0325 | 768 |
| 11 | 2048 | 0.0230 | |
| 12 | 4096 | 0.0163 | 3072 |
| 13 | 8192 | 0.0115 | 6144 |
| 14 | 16384 | 0.0081 | 12288 |
| 15 | 32768 | 0.0057 | 24576 |
| 16 | 65536 | 0.0041 | 49152 |
| 17 | 131072 | 0.0029 | 98304 |
| 18 | 262144 | 0.0020 | 196608 |
For more information about approximate count distinct functions, see the hyperfunctions documentation.
Required arguments
| Name | Type | Description |
|---|---|---|
| hyperloglog | Hyperloglog | The hyperloglog to extract the count from. |
Returns
| Column | Type | Description |
|---|---|---|
| stderror | BIGINT | The number of distinct elements counted by the hyperloglog. |
Sample usage
This examples retrieves the standard error from a hyperloglog called hyperloglog:
SELECT stderror(hyperloglog(64, data))
FROM generate_series(1, 100) data
stderror
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