BITMAP

description

Syntax

TO_BITMAP(expr) : Convert TINYINT,SMALLINT,INT type column to Bitmap.

BITMAP_UNION(expr) : Calculate the union of Bitmap, return the serialized Bitmap value.

BITMAP_COUNT(expr) : Calculate the distinct value number of a Bitmap.

BITMAP_UNION_INT(expr) : Calculate the distinct value number of TINYINT,SMALLINT and INT type column. Same as COUNT(DISTINCT expr)

Notice：

  1. 1. TO_BITMAP function only receives TINYINT,SMALLINT,INT.
  2. 2. BITMAP_UNION only receives following types of parameter:
  3.     - Column with BITMAP_UNION aggregate type in AGGREGATE KEY mode.
  4.     - TO_BITMAP function.

example

  1. CREATE TABLE `bitmap_udaf` (
  2.   `id` int(11) NULL COMMENT "",
  3.   `id2` int(11)
  4. ) ENGINE=OLAP
  5. DUPLICATE KEY(`id`)
  6. DISTRIBUTED BY HASH(`id`) BUCKETS 10;
  8. mysql> select bitmap_count(bitmap_union(to_bitmap(id2))) from bitmap_udaf;
  9. +----------------------------------------------+
  10. | bitmap_count(bitmap_union(to_bitmap(`id2`))) |
  11. +----------------------------------------------+
  12. |                                            6 |
  13. +----------------------------------------------+
  15. mysql> select bitmap_union_int (id2) from bitmap_udaf;
  16. +-------------------------+
  17. | bitmap_union_int(`id2`) |
  18. +-------------------------+
  19. |                       6 |
  20. +-------------------------+
  23. CREATE TABLE `bitmap_test` (
  24.   `id` int(11) NULL COMMENT "",
  25.   `id2` varchar(0) bitmap_union NULL  // NOTICE: bitmap_union's varchar length must be 0.
  26. ) ENGINE=OLAP
  27. AGGREGATE KEY(`id`)
  28. DISTRIBUTED BY HASH(`id`) BUCKETS 10;
  30. mysql> select bitmap_count(bitmap_union(id2)) from bitmap_test;
  31. +-----------------------------------+
  32. | bitmap_count(bitmap_union(`id2`)) |
  33. +-----------------------------------+
  34. |                                 8 |
  35. +-----------------------------------+

keyword

  1. BITMAP,BITMAP_COUNT,BITMAP_UNION,BITMAP_UNION_INT,TO_BITMAP