VECTOR_SUBVECTOR

Syntax

VECTOR_SUBVECTOR(vector_expression, start_position, length)

Arguments

• vector_expression: An expression that evaluates to a vector. The vector must be encoded as a blob containing packed single-precision or double-precision floating-point numbers in little-endian byte order.

• start_position: A 0-indexed number to determine where to start count. A positive index counts from the beginning of the vector. A negative index counts from the end of the vector.

• length: Length of required subvector

Return Type

A blob containing packed single-precision floating-point numbers in little-endian byte order.

Remarks

If the input is NULL, NULL will be returned.

You can specify the data type of the vector elements in which this operation is performed on the vector by adding a suffix to the function. Omitting the suffix from the function is equivalent to suffixing it with _F32. All operations are done using the specified data type. The following table lists the suffixes and their data type.

Examples

CREATE TABLE vsv_t (x BLOB);
INSERT INTO vsv_t VALUES (JSON_ARRAY_PACK('[1,2,3,4,5]'));

SELECT JSON_ARRAY_UNPACK (VECTOR_SUBVECTOR(x,2,2)) AS x from vsv_t;

+-------+
| x     |
+-------+
| [3,4] |
+-------+

SELECT JSON_ARRAY_UNPACK (VECTOR_SUBVECTOR(x,-2,2)) AS x from vsv_t;

+-------+
| x     |
+-------+
| [4,5] |
+-------+

How to Use the Vector Data Type

Currently, VECTOR_SUBVECTOR is not supported with the vector data type. A workaround is provided until support for the vector data type is implemented.

Using VECTOR_SUBVECTOR with the vector data type will result in an error.

SELECT vector_subvector(position, 1, 2) FROM vector_exps;

ERROR 1940 ER_VECTOR_FUNCTION_ERROR: Error with a vector function: 
Function `vector_subvector` is not supported with VECTOR datatype.

There is a way to use VECTOR_SUBVECTOR with a vector data type. First cast to a blob data type and then cast back to a vector data type. The example below shows how to do this:

SET @pos = '[1,2,3,4]':>vector(4);

SELECT vector_subvector(@pos:>blob, 1,2);

+------------------------------------+
| vector_subvector(@pos:>blob, 1, 2) |
+------------------------------------+
|    @@@                             |
+------------------------------------+

SELECT vector_subvector(@pos:>blob, 1, 2):>vector(2);

+-----------------------------------------------+
| vector_subvector(@pos:>blob, 1, 2):>vector(2) |
+-----------------------------------------------+
| [2,3]                                         |
+-----------------------------------------------+