PolarDB for PostgreSQL (Compatible with Oracle) supports the Oracle-compatible TO_SINGLE_BYTE and TO_MULTI_BYTE functions via the polar_to_single_byte extension. TO_SINGLE_BYTE converts multibyte characters (such as fullwidth digits and letters) to their single-byte equivalents. TO_MULTI_BYTE does the reverse. These functions are not part of standard PostgreSQL; they are provided as an extension to maintain Oracle compatibility.
Prerequisites
Whether the extension is available depends on when your cluster was created:
-
Clusters created on or after March 30, 2020: The extension is created automatically when you create a database. No additional steps are required.
-
Clusters created before March 30, 2020: The extension is not created automatically. After creating a database, run the following statement to install it:
CREATE EXTENSION polar_to_single_byte;
For the original Oracle function specifications, see the TO_SINGLE_BYTE and TO_MULTI_BYTE references in the Oracle documentation.
Supported data types
Both functions accept the following input types and return the same type as the input.
| Function | Input type | Output type |
|---|---|---|
| TO_SINGLE_BYTE | CHAR | CHAR |
| TO_SINGLE_BYTE | CHARACTER VARYING | CHARACTER VARYING |
| TO_SINGLE_BYTE | TEXT | TEXT |
| TO_MULTI_BYTE | CHAR | CHAR |
| TO_MULTI_BYTE | CHARACTER VARYING | CHARACTER VARYING |
| TO_MULTI_BYTE | TEXT | TEXT |
Examples
TO_SINGLE_BYTE
Convert a fullwidth string to ASCII:
SELECT to_single_byte('１２３＄ｔｅｓｔ');
to_single_byte
----------------
123$test
(1 row)TO_MULTI_BYTE
Convert an ASCII string to fullwidth:
SELECT to_multi_byte('123$test');
to_multi_byte
------------------
１２３＄ｔｅｓｔ
(1 row)