hll_to_base64

description

Syntax

VARCHAR HLL_TO_BASE64(HLL input)

将一个hll转化成一个base64字符串。输入是NULL的话返回NULL。

example

  1. mysql> select hll_to_base64(NULL);
  2. +---------------------+
  3. | hll_to_base64(NULL) |
  4. +---------------------+
  5. | NULL                |
  6. +---------------------+
  7. 1 row in set (0.00 sec)
  9. mysql> select hll_to_base64(hll_empty());
  10. +----------------------------+
  11. | hll_to_base64(hll_empty()) |
  12. +----------------------------+
  13. | AA==                       |
  14. +----------------------------+
  15. 1 row in set (0.02 sec)
  17. mysql> select hll_to_base64(hll_hash('abc'));
  18. +--------------------------------+
  19. | hll_to_base64(hll_hash('abc')) |
  20. +--------------------------------+
  21. | AQEC5XSzrpDsdw==               |
  22. +--------------------------------+
  23. 1 row in set (0.03 sec)
  25. mysql> select hll_union_agg(hll_from_base64(hll_to_base64(pv))), hll_union_agg(pv) from test_hll;
  26. +---------------------------------------------------+-------------------+
  27. | hll_union_agg(hll_from_base64(hll_to_base64(pv))) | hll_union_agg(pv) |
  28. +---------------------------------------------------+-------------------+
  29. |                                                 3 |                 3 |
  30. +---------------------------------------------------+-------------------+
  31. 1 row in set (0.04 sec)
  33. mysql>  select hll_cardinality(hll_from_base64(hll_to_base64(hll_hash('abc'))));
  34. +------------------------------------------------------------------+
  35. | hll_cardinality(hll_from_base64(hll_to_base64(hll_hash('abc')))) |
  36. +------------------------------------------------------------------+
  37. |                                                                1 |
  38. +------------------------------------------------------------------+
  39. 1 row in set (0.04 sec)

keywords

HLL_TO_BASE64, HLL