Importing and Exporting Fixed Width Data

Specify custom formats for fixed-width data with the LightDB-A Database functions fixedwith_in and fixedwidth_out. These functions already exist in the file $GPHOME/share/postgresql/cdb_external_extensions.sql. The following example declares a custom format, then calls the fixedwidth_in function to format the data.

CREATE READABLE EXTERNAL TABLE students (
name varchar(20), address varchar(30), age int)
LOCATION ('file://<host>/file/path/')
FORMAT 'CUSTOM' (formatter=fixedwidth_in, 
         name='20', address='30', age='4');

The following options specify how to import fixed width data.

• Read all the data.

  To load all the fields on a line of fixed with data, you must load them in their physical order. You must specify the field length, but cannot specify a starting and ending position. The fields names in the fixed width arguments must match the order in the field list at the beginning of the CREATE TABLE command.

• Set options for blank and null characters.

  Trailing blanks are trimmed by default. To keep trailing blanks, use the preserve_blanks=on option. You can reset the trailing blanks option to the default with the preserve_blanks=off option.

  Use the null='null_string_value' option to specify a value for null characters.

• If you specify preserve_blanks=on, you must also define a value for null characters.

• If you specify preserve_blanks=off, null is not defined, and the field contains only blanks, LightDB-A writes a null to the table. If null is defined, LightDB-A writes an empty string to the table.

  Use the line_delim='line_ending' parameter to specify the line ending character. The following examples cover most cases. The E specifies an escape string constant.

  line_delim=E'\n'
  line_delim=E'\r'
  line_delim=E'\r\n'
  line_delim='abc'
  

Parent topic: Using a Custom Format