HLL_TO_BASE64

描述

将一个 HLL 类型转换为一个 base64 编码的字符串。如果输入为 NULL，则返回 NULL。

语法

HLL_TO_BASE64(<hll_input>)

参数

参数	说明
<hll_input>	HLL 类型数据，如果输入为 NULL，则返回 NULL。

示例

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 |
+------------------------------------------------------------------+