VECTOR_SUB

Returns a vector blob from two input vectors by subtracting the second vector from the first vector.

Syntax

VECTOR_SUB(vector_expression, vector_expression)

vector_expression

An expression that evaluates to a vector. The vector must be encoded as a blob containing packed single-precision floating-point numbers in little-endian byte order. A vector can be of any length, but both input vectors must be the same length and the blob lengths must be divisible by 4 bytes.

Return Value

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

Remarks

To execute this function, the host processor must support AVX2 instruction set extensions. If AVX2 is not supported, an error will occur during execution.

Examples

Example: SELECT Using VECTOR_SUB() on Existing Rows

The following example executes VECTOR_SUB() on a row containing two vectors. The HEX() built-in function is also used to return a readable form of the binary output.

Create a table with two BLOB-typed columns:

memsql> CREATE TABLE t (a BLOB, b BLOB);
Query OK, 0 rows affected (0.26 sec)

Using the JSON_ARRAY_PACK() built-in function to easily insert properly formatted vectors, insert a row with each vector in a different column:

memsql> INSERT INTO t VALUES (JSON_ARRAY_PACK('[0.7, 0.2, 1.7]'), JSON_ARRAY_PACK('[1.0, 0.5, 2.0]'));
Query OK, 1 row affected (0.22 sec)

To demonstrate the contents of the table, use the HEX() built-in function to return a readable form of the binary data:

memsql> SELECT HEX(t.a), HEX(t.b) FROM t;
+--------------------------+--------------------------+
| HEX(t.a)                 | HEX(t.b)                 |
+--------------------------+--------------------------+
| 3333333FCDCC4C3E9A99D93F | 0000803F0000003F00000040 |
+--------------------------+--------------------------+
1 row in set (0.15 sec)

Query the table using the VECTOR_SUB() function in a SELECT statement:

memsql> SELECT HEX(VECTOR_SUB(t.a, t.b)) FROM t;
+---------------------------+
| HEX(VECTOR_SUB(t.a, t.b)) |
+---------------------------+
| 9A9999BE9A9999BE989999BE  |
+---------------------------+
1 row in set (0.16 sec)

Example: VECTOR_SUB() with JSON_ARRAY_PACK()

The following example uses JSON_ARRAY_PACK() as input parameters to the VECTOR_SUB() built-in function. The HEX() built-in function is also used to return a readable form of the binary output:

memsql> SELECT HEX(VECTOR_SUB(JSON_ARRAY_PACK('[1.0, 0.5, 2.0]'), JSON_ARRAY_PACK('[0.7, 0.2, 1.7]')));
+-----------------------------------------------------------------------------------------+
| HEX(VECTOR_SUB(JSON_ARRAY_PACK('[1.0, 0.5, 2.0]'), JSON_ARRAY_PACK('[0.7, 0.2, 1.7]'))) |
+-----------------------------------------------------------------------------------------+
| 9A99993E9A99993E9899993E                                                                |
+-----------------------------------------------------------------------------------------+
1 row in set (0.11 sec)

Related Topics

Was this article useful?