Updated on 2025-02-27 GMT+08:00

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. The more buckets there are, the smaller the deviation is. The deviation range is as follows: [–1.04/2log2m*1/2, +1.04/2log2m*1/2]

This is a USERSET parameter. Set it based on instructions in Table 1.

Value range: an integer ranging from 10 to 16

Default value: 14

hll_default_log2explicit

Parameter description: Specifies the default threshold for switching from the explicit mode to the sparse mode.

This is a USERSET parameter. Set it based on instructions in Table 1.

Value range: an integer ranging from 0 to 12 The value 0 indicates that the explicit mode is skipped. The value 1 to 12 indicates that the mode is switched when the number of distinct values reaches 2hll_default_log2explicit.

Default value: 10

hll_default_log2sparse

Parameter description: Specifies the default threshold for switching from the sparse mode to the full mode.

This is a USERSET parameter. Set it based on instructions in Table 1.

Value range: an integer ranging from 0 to 14 The value 0 indicates that the explicit mode is skipped. The value 1 to 14 indicates that the mode is switched when the number of distinct values reaches 2hll_default_log2sparse.

Default value: 12

hll_duplicate_check

Parameter description: Specifies whether duplicatecheck is enabled by default.

This is a USERSET parameter. Set it based on instructions in Table 1.

Value range: 0 or 1 0: disabled; 1: enabled

Default value: 0