Bitmap decision functions

Bitmap decision functions perform some operations on the input bitmap data and return a Boolean value. The rb_is_empty() and rb_contains() functions are the bitmap decision functions supported by seekdb.

rb_is_empty

The rb_is_empty() function determines whether the input bitmap data is empty. The syntax is as follows:

rb_is_empty(rb)

If the function returns 1, the input bitmap data is empty. If the function returns 0, the input bitmap data is not empty.

Here are some examples:

SELECT rb_is_empty(rb_from_string(''));
+---------------------------------+
| rb_is_empty(rb_from_string('')) |
+---------------------------------+
|                               1 |
+---------------------------------+
1 row in set (0.001 sec)

SELECT rb_is_empty(rb_from_string('1,2,3'));
+--------------------------------------+
| rb_is_empty(rb_from_string('1,2,3')) |
+--------------------------------------+
|                                    0 |
+--------------------------------------+
1 row in set (0.001 sec)

rb_contains

The rb_contains() function has two usage scenarios:

• It determines whether the first input bitmap data (rb1) completely contains the second input bitmap data (rb2).
• It determines whether the input bitmap data contains a specific offset (offset).

The two scenarios are implemented using different syntaxes. The following sections describe the two scenarios.

Scenario 1

The rb_contains() function can be used to determine whether the first input bitmap data (rb1) completely contains the second input bitmap data (rb2). The syntax is as follows:

rb_contains(rb1, rb2)

The following points apply to this scenario:

• The input parameter rb1 serves as the basis for the calculation, and the input parameter rb2 is the bitmap data to be calculated. That is, whether each element in rb2 exists in rb1.
• The order of the rb1 and rb2 parameters affects the result.
• If the function returns 1, rb1 completely contains rb2. If the function returns 0, rb1 does not completely contain rb2.

Here are some examples:

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 (0.001 sec)

Scenario 2

The rb_contains() function can be used to determine whether the input bitmap data contains a specific offset (offset). The syntax is as follows:

rb_contains(rb, offset)

The following points apply to this scenario:

• The input parameter rb serves as the basis for the calculation, and it is a bitmap data.
• offset must be an integer, which is used to determine whether the integer exists in the bitmap data rb.
• If the function returns 1, the input bitmap data contains the offset. If the function returns 0, the input bitmap data does not contain the offset.

Here are some 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 (0.001 sec)

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 (0.001 sec)