How to return argument data type from sql function

Andrus <kobruleht2@xxxxxx> · Thu, 13 Oct 2022 23:16:09 +0300



    PostgreSQL 12.2+ function is defined as

      
          create FUNCTION torus(eevarus text) returns text immutable AS
      $f$ 

           select translate( $1, U&'\00f8\00e9', U&'\0451\0439'
      );

          $f$ LANGUAGE SQL ; 

      
      This function is called as CHAR(n) or text columns like 

      
          create temp table test (

          charcol char(10),

          textcol text );

          
          insert into test values ('test', 'test');

          
          select torus(charcol), torus(textcol), charcol

      
      torus(charcol) returns text column and loses original column
      width. How to force torus() to return argument type:

      
      if char(n) column is passed as argument, torus() should also
      return char(n) data type.

      I tried to use bpchar instead on text

      
          create or replace FUNCTION torusbpchar(eevarus bpchar) returns
      bpchar immutable AS $f$ 

           select translate( $1, U&'\00f8\00e9', U&'\0451\0439'
      );

          $f$ LANGUAGE SQL ; 

      
      torusbpchar(charcol) still returns text data type.

      
      npgsql DataReader is used to get data.
    Andrus.