VECTOR_SUBVECTOR

Derives a vector expression from another vector expression.

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

A vector can be of any length, but the input blob length must be divisible by the packed vector element size (1, 2, 4 or 8 bytes, depending on the vector element).

You can specify the datatype 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 datatype. The following table lists the suffixes and their datatype.

Suffix

Datatype

_I8

8-bit signed integer

_I16

16-bit signed integer

_I32

32-bit signed integer

_I64

64-bit signed integer

_F32

32-bit floating-point number (IEEE standard format)

_F64

64-bit floating-point number (IEEE standard format)

Examples

CREATE TABLE t (x BLOB);
INSERT INTO t VALUES (JSON_ARRAY_PACK('[1,2,3,4,5]'));
SELECT JSON_ARRAY_UNPACK (VECTOR_SUBVECTOR(x,2,2)) AS x from t;
+-------+
| x     |
+-------+
| [3,4] |
+-------+
   
****

SELECT JSON_ARRAY_UNPACK (VECTOR_SUBVECTOR(x,-2,2)) AS x from t;
+-------+
| x     |
+-------+
| [4,5] |
+-------+