HLL_FROM_BASE64

描述

将一个 base64 编码的字符串（通常由 HLL_TO_BASE64 函数生成）转换为 HLL 类型。如果输入字符串不合法或为 NULL，则返回 NULL。

语法

HLL_FROM_BASE64(<input>)

参数

参数	说明
`<input>`	base64 编码的字符串，通常由 `HLL_TO_BASE64` 函数生成。如果字符串不合法，则返回 NULL。

示例

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

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

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

select hll_cardinality(hll_from_base64(hll_to_base64(hll_hash(NULL))));

+-----------------------------------------------------------------+
| hll_cardinality(hll_from_base64(hll_to_base64(hll_hash(NULL)))) |
+-----------------------------------------------------------------+
|                                                               0 |
+-----------------------------------------------------------------+

HLL_EMPTY HLL_HASH