Built-in Functions
HyperLogLog (HLL) has a series of built-in functions for internal data processing. Generally, users do not need to know how to use these functions. For details, see Table 1.
Function |
Function |
---|---|
hll_in |
Receives hll data in string format. |
hll_out |
Sends hll data in string format. |
hll_recv |
Receives hll data in bytea format. |
hll_send |
Sends hll data in bytea format. |
hll_trans_in |
Receives hll_trans_type data in string format. |
hll_trans_out |
Sends hll_trans_type data in string format. |
hll_trans_recv |
Receives hll_trans_type data in bytea format. |
hll_trans_send |
Sends hll_trans_type data in bytea format. |
hll_typmod_in |
Receives typmod data. |
hll_typmod_out |
Sends typmod data. |
hll_hashval_in |
Receives hll_hashval data. |
hll_hashval_out |
Sends hll_hashval data. |
hll_add_trans0 |
Works similar to hll_add, and is used on the first phase of DNs in distributed aggregation operations. |
hll_union_trans |
Works similar to hll_union, and is used on the first phase of DNs in distributed aggregation operations. |
hll_union_collect |
Works similar to hll_union, and is used on the second phase of CNs in distributed aggregation operations to summarize the results of each DN. |
hll_pack |
Is used on the third phase of CNs in distributed aggregation operations to convert a user-defined type hll_trans_type to the hll type. |
hll |
Converts a hll type to another hll type. Input parameters can be specified. |
hll_hashval |
Converts the bigint type to the hll_hashval type. |
hll_hashval_int4 |
Converts the int4 type to the hll_hashval type. |
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