CREATE CONVERSION
Defines a new encoding conversion.
Synopsis
CREATE [DEFAULT] CONVERSION <name>
FOR <source_encoding> TO <dest_encoding> FROM <function_name>
Description
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 create a conversion, you must have EXECUTE privilege on the function and CREATE privilege on the destination schema.
Parameters
DEFAULT
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.
name
The name of the conversion. The conversion name may be schema-qualified. If it is not, the conversion is defined in the current schema. The conversion name must be unique within a schema.
source_encoding
The source encoding name.
dest_encoding
The destination encoding name.
function_name
The function used to perform the conversion. The function name may 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;
Notes
Use DROP CONVERSION to remove a user-defined conversion.
The privileges required to create a conversion might change in a feature release.
Note that in this release of Cloudberry Database, user-defined functions used in a user-defined conversion must be defined as IMMUTABLE. Any compiled code (shared library files) for custom functions must be placed in the same location on every host in your Cloudberry Database array (coordinator and all segments). This location must also be in the LD_LIBRARY_PATH so that the server can locate the files.
Examples
To create a conversion from encoding UTF8 to LATIN1 using myfunc:
CREATE CONVERSION myconv FOR 'UTF8' TO 'LATIN1' FROM myfunc;
Compatibility
CREATE CONVERSION is a Cloudberry Database extension. There is no CREATE CONVERSION statement in the SQL standard, but there is a CREATE TRANSLATION statement that is very similar in purpose and syntax.
