Help Center/ GaussDB/ Developer Guide(Distributed_V2.0-8.x)/ SQL Reference/ Functions and Operators/ HLL Functions and Operators/ Built-in Functions
Updated on 2025-08-19 GMT+08:00
View PDF

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.

Table 1 Built-in functions

Function

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 in the first phase of DNs in distributed aggregation operations.

hll_add_trans1

Works similar to hll_add. An input parameter is specified during initialization. It is usually used in the first phase of DNs in distributed aggregation operations.

hll_add_trans2

Works similar to hll_add. Two input parameters are specified during initialization. It is usually used in the first phase of DNs in distributed aggregation operations.

hll_add_trans3

Works similar to hll_add. Three input parameters are specified during initialization. It is usually used in the first phase of DNs in distributed aggregation operations.

hll_add_trans4

Works similar to hll_add. Four input parameters are specified during initialization. It is usually used in 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 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.