HyperLogLog
hll_default_log2m
Parameter description: Specifies the number of buckets for HLL data. The number of buckets affects the precision of distinct values calculated by HLL. More buckets indicate a smaller deviation. The deviation range is as follows: [–1.04/2log2m*1/2, +1.04/2log2m*1/2] This parameter can be set at the PDB level.
Parameter type: integer
Unit: none
Value range: 10 to 16
Default value: 14. In the PDB scenario, if this parameter is not set, the global setting is inherited.
Setting method: This is a USERSET parameter. Set it based on instructions provided in Table 1.
Setting suggestion: Retain the default value or adjust the value based on service requirements.
Risks and impacts of improper settings: If the value is too small, the required precision cannot be met. If the value is too large, resources may be wasted.
hll_default_log2explicit
Parameter description: Specifies the default threshold for switching from the explicit mode to the sparse mode. This parameter can be set at the PDB level.
Parameter type: integer
Unit: none
Value range: 0 to 12
- 0: The explicit mode is skipped.
- 1 to 12: The mode is switched when the base value reaches 2hll_default_log2explicit.
Default value: 10. In the PDB scenario, if this parameter is not set, the global setting is inherited.
Setting method: This is a USERSET parameter. Set it based on instructions provided in Table 1.
Setting suggestion: Retain the default value or adjust the value based on service requirements.
Risks and impacts of improper settings: If the value is too small, the required precision cannot be met. If the value is too large, resources may be wasted.
hll_default_log2sparse
Parameter description: Specifies the default threshold for switching from the sparse mode to the full mode. This parameter can be set at the PDB level.
Parameter type: integer
Unit: none
Value range: 0 to 14
- 0: The explicit mode is skipped.
- 1 to 14: The mode is switched when the base value reaches 2hll_default_log2sparse.
Default value: 12. In the PDB scenario, if this parameter is not set, the global setting is inherited.
Setting method: This is a USERSET parameter. Set it based on instructions provided in Table 1.
Setting suggestion: Retain the default value or adjust the value based on service requirements.
Risks and impacts of improper settings: If the value is too small, the required precision cannot be met. If the value is too large, resources may be wasted.
hll_duplicate_check
Parameter description: Specifies whether duplicatecheck is enabled by default.
Parameter type: integer
Unit: none
Value range: 0 to 1
- 0: The function is disabled by default.
- 1: The function is enabled by default.
Default value: 0
Setting method: This is a USERSET parameter. Set it based on instructions provided in Table 1.
Setting suggestion: Retain the default value or adjust the value based on service requirements.
Risks and impacts of improper settings: If this parameter is enabled, more resources may be consumed for duplicate check, but the accuracy of distinct value calculation is improved.
