KlustronDB

KlustronDB大约 1 分钟

CREATE CONVERSION

CREATE CONVERSION — define a new encoding conversion

Synopsis

CREATE [ DEFAULT ] CONVERSION name
    FOR source_encoding TO dest_encoding FROM function_name

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.

Parameters

DEFAULT : 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.

name : 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.

source_encoding : The source encoding name.

dest_encoding : The destination encoding name.

function_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:

```programlisting
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 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:

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.