|CREATE CONVERSION(7)||PostgreSQL 15.3 Documentation||CREATE CONVERSION(7)|
CREATE_CONVERSION - define a new encoding conversion
CREATE [ DEFAULT ] CONVERSION name
FOR source_encoding TO dest_encoding FROM function_name
CREATE CONVERSION defines a new conversion between two character set encodings.
Conversions that are marked DEFAULT can be used for automatic encoding conversion between client and server. To support that usage, two conversions, from encoding A to B and from encoding B to A, must be defined.
To be able to create a conversion, you must have EXECUTE privilege on the function and CREATE privilege on the destination schema.
The function must have the following signature:
integer, -- source encoding ID
integer, -- destination encoding ID
cstring, -- source string (null terminated C string)
internal, -- destination (fill with a null terminated C string)
integer, -- source string length
boolean -- if true, don't throw an error if conversion fails ) RETURNS integer;
The return value is the number of source bytes that were successfully converted. If the last argument is false, the function must throw an error on invalid input, and the return value is always equal to the source string length.
Neither the source nor the destination encoding can be SQL_ASCII, as the server's behavior for cases involving the SQL_ASCII “encoding” is hard-wired.
Use DROP CONVERSION to remove user-defined conversions.
The privileges required to create a conversion might be changed in a future release.
To create a conversion from encoding UTF8 to LATIN1 using myfunc:
CREATE CONVERSION myconv FOR 'UTF8' TO 'LATIN1' FROM myfunc;
CREATE CONVERSION is a PostgreSQL extension. There is no CREATE CONVERSION statement in the SQL standard, but a CREATE TRANSLATION statement that is very similar in purpose and syntax.
ALTER CONVERSION (ALTER_CONVERSION(7)), CREATE FUNCTION (CREATE_FUNCTION(7)), DROP CONVERSION (DROP_CONVERSION(7))