Bitmap decision functions

Bitmap decision functions judge the input bitmap data and return Boolean values. OceanBase Database supports the rb_is_empty() and rb_contains() functions.

rb_is_empty

The rb_is_empty() function judges whether the input bitmap data is empty. Syntax:

rb_is_empty(rb)

When the result is 1, it indicates that the bitmap data is empty. When it is 0, it indicates that the bitmap data is not empty.

Example:

SELECT rb_is_empty(rb_from_string(''));
+---------------------------------+
| rb_is_empty(rb_from_string('')) |
+---------------------------------+
|                               1 |
+---------------------------------+
1 row in set

SELECT rb_is_empty(rb_from_string('1,2,3'));
+--------------------------------------+
| rb_is_empty(rb_from_string('1,2,3')) |
+--------------------------------------+
|                                    0 |
+--------------------------------------+
1 row in set

rb_contains

The rb_contains() function is used in the following two ways:

• To judge whether the input first bitmap data (rb1) contains the input second bitmap data (rb2) completely.
• To judge whether the input bitmap data contains a specified offset (offset).

The two usages are implemented through different syntaxes. Details are as follows.

Usage 1

The rb_contains() function can be used to judge whether the input first bitmap data (rb1) contains the input second bitmap data (rb2) completely. Syntax:

rb_contains(rb1, rb2)

Details:

• The input parameter rb1 serves as the basis for calculation, and the input parameter rb2 serves as the bitmap data to be calculated. It checks whether each element in rb2 is present in rb1.
• The order of parameters rb1 and rb2 affects the result.
• When the result is 1, it indicates that the first bitmap data is completely contained in the second. When it is 0, it indicates that the first is not completely contained in the second.

Example:

SELECT rb_contains(rb_from_string('1,2,3,4,5'), rb_from_string('1,2,3,4'));
+---------------------------------------------------------------------+
| rb_contains(rb_from_string('1,2,3,4,5'), rb_from_string('1,2,3,4')) |
+---------------------------------------------------------------------+
|                                                                   1 |
+---------------------------------------------------------------------+
1 row in set

Usage 2

The rb_contains() function can be used to judge whether the input bitmap data contains a specified offset (offset). Syntax:

rb_contains(rb, offset)

Details:

• The input parameter rb serves as the basis for calculation, representing a bitmap data.
• The offset must be an integer, which is to be checked for existence within the bitmap data rb.
• When the result is 1, it indicates that the offset exists in the bitmap data. When it is 0, it indicates the opposite.

Examples:

SELECT rb_contains(rb_from_string('1,2,3,4,5'), 1);
+---------------------------------------------+
| rb_contains(rb_from_string('1,2,3,4,5'), 1) |
+---------------------------------------------+
|                                           1 |
+---------------------------------------------+
1 row in set

SELECT rb_contains(rb_from_string('1,2,3,4,6'), 5);
+---------------------------------------------+
| rb_contains(rb_from_string('1,2,3,4,6'), 5) |
+---------------------------------------------+
|                                           0 |
+---------------------------------------------+
1 row in set