Built-in Functions
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 Built-in functions.
Name |
Description |
---|---|
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. No input parameter is specified during initialization. It is usually used on DNs in the first phase of aggregation operations. |
hll_add_trans1 |
Works similar to hll_add. An input parameter is specified during initialization. It is usually used on DNs in the first phase of aggregation operations. |
hll_add_trans2 |
Works similar to hll_add. Two input parameters are specified during initialization. It is usually used on DNs in the first phase of aggregation operations. |
hll_add_trans3 |
Works similar to hll_add. Three input parameters are specified during initialization. It is usually used on DNs in the first phase of aggregation operations. |
hll_add_trans4 |
Works similar to hll_add. Four input parameters are specified during initialization. It is usually used on DNs in the first phase of aggregation operations. |
hll_union_trans |
Works similar to hll_union and is used on DNs in the first phase of aggregation operations. |
hll_union_collect |
Works similar to hll_union and is used on DNs in the second phase of aggregation operations to summarize the results of each DN. |
hll_pack |
Converts the user-defined hll_trans_type to the HLL type on DNs in the third phase of aggregation operations. |
hll |
Converts an 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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