Importing and Exporting Fixed Width Data

Specify custom formats for fixed-width data with the HAWQ 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.

  name varchar(20), address varchar(30), age int)
LOCATION ('gpfdist://mdw:8081/students.txt')
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, HAWQ writes a null to the table. If null is defined, HAWQ 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.