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CREATE CONVERSION
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CREATE CONVERSION

CREATE CONVERSION — define a new encoding conversion

Synopsis

CREATE [ DEFAULT ] CONVERSIONname    FORsource_encoding TOdest_encoding FROMfunction_name

Description

CREATE CONVERSION defines a new conversion between two character set encodings.

Conversions that are markedDEFAULT can be used for automatic encoding conversion between client and server. To support that usage, two conversions, from encoding A to Band from encoding B to A, must be defined.

To be able to create a conversion, you must haveEXECUTE privilege on the function andCREATE privilege on the destination schema.

Parameters

DEFAULT

TheDEFAULT 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 beSQL_ASCII, as the server's behavior for cases involving theSQL_ASCII“encoding” is hard-wired.

UseDROP 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 encodingUTF8 toLATIN1 usingmyfunc:

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

Compatibility

CREATE CONVERSION is aPostgreSQL extension. There is noCREATE CONVERSION statement in the SQL standard, but aCREATE TRANSLATION statement that is very similar in purpose and syntax.