CREATE_CONVERSION(7) - Man pages

CREATE CONVERSION(7)     PostgreSQL 15.7 Documentation    CREATE CONVERSION(7)

NAME
       CREATE_CONVERSION - define 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 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
           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:

               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
                   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:

           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.

SEE ALSO
       ALTER CONVERSION (ALTER_CONVERSION(7)), CREATE FUNCTION
       (CREATE_FUNCTION(7)), DROP CONVERSION (DROP_CONVERSION(7))

PostgreSQL 15.7                      2024                 CREATE CONVERSION(7)

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