create_conversion(7)

—

NAME

CREATE_CONVERSION - define a new encoding conversion

SYNOPSIS

bash

CREATE [ DEFAULT ] CONVERSION \nname\n
\n
    FOR \nsource_encoding\n TO \ndest_encoding\n FROM \nfunction_name

DESCRIPTION

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.

PARAMETERS

DEFAULT

name

source_encoding

dest_encoding

function_name

The function must have the following signature:

bash

conv_proc(
\n
    integer,  -- source encoding ID
\n
    integer,  -- destination encoding ID
\n
    cstring,  -- source string (null terminated C string)
\n
    internal, -- destination (fill with a null terminated C string)
\n
    integer,  -- source string length
\n
    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.

NOTES

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.

EXAMPLES

To create a conversion from encoding UTF8 to LATIN1 using myfunc:

bash

CREATE CONVERSION myconv FOR 'UTF8' TO 'LATIN1' FROM myfunc;

COMPATIBILITY

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.