CREATE CONVERSION
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## CREATE CONVERSION

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
      ) RETURNS void;

## 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, CREATE FUNCTION, DROP CONVERSION

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