hll-to-base64

根据您提供的规范，我将重新整理文档：

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{ "title": "HLL_TO_BASE64", "language": "en" }

---

Description

Converts an input HLL to a base64-encoded string. If the input is <null>, the function returns <null>.

Syntax

HLL_TO_BASE64(<hll_input>)

Parameters

Parameter	Description
<hll_input>	The HyperLogLog (HLL) data to be converted to a base64-encoded string. If the input is <null>, the function returns <null>.

Examples

select hll_to_base64(NULL);

+---------------------+
| hll_to_base64(NULL) |
+---------------------+
| NULL                |
+---------------------+

select hll_to_base64(hll_empty());

+----------------------------+
| hll_to_base64(hll_empty()) |
+----------------------------+
| AA==                       |
+----------------------------+

select hll_to_base64(hll_hash('abc'));

+--------------------------------+
| hll_to_base64(hll_hash('abc')) |
+--------------------------------+
| AQEC5XSzrpDsdw==               |
+--------------------------------+

select hll_union_agg(hll_from_base64(hll_to_base64(pv))), hll_union_agg(pv) from test_hll;

+---------------------------------------------------+-------------------+
| hll_union_agg(hll_from_base64(hll_to_base64(pv))) | hll_union_agg(pv) |
+---------------------------------------------------+-------------------+
|                                                 3 |                 3 |
+---------------------------------------------------+-------------------+

select hll_cardinality(hll_from_base64(hll_to_base64(hll_hash('abc'))));

+------------------------------------------------------------------+
| hll_cardinality(hll_from_base64(hll_to_base64(hll_hash('abc')))) |
+------------------------------------------------------------------+
|                                                                1 |
+------------------------------------------------------------------+