CREATE [ DEFAULT ] CONVERSION name
FOR source_encoding TO dest_encoding FROM function_name
The following description applies both to Postgres-XC and PostgreSQL if not described explicitly.
CREATE CONVERSION defines a new conversion between character set encodings. Also, conversions that are marked DEFAULT can be used for automatic encoding conversion between client and server. For this purpose, 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 DEFAULT clause indicates that this conversion is the default for this particular source to destination encoding. There should be only one default encoding in a schema for the encoding pair.
- The name of the conversion. The conversion name can be schema-qualified. If it is not, the conversion is defined in the current schema. The conversion name must be unique within a schema.
- The source encoding name.
- The destination encoding name.
The function used to perform the conversion. The function name can be schema-qualified. If it is not, the function will be looked up in the path.
The function must have the following signature:
conv_proc( 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 ) RETURNS void;
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 Postgres-XC extension. There is no CREATE CONVERSION statement in the SQL standard, but a CREATE TRANSLATION statement that is very similar in purpose and syntax.