orafce

The orafce module provides Oracle Compatibility SQL functions in LightDB-A Database. These functions target PostgreSQL but can also be used in LightDB-A.

The LightDB-A Database orafce module is a modified version of the open source Orafce PostgreSQL module extension. The modified orafce source files for LightDB-A Database can be found in the gpcontrib/orafce directory in the LightDB-A Database open source project. The source reflects the Orafce 3.6.1 release and additional commits to 3af70a28f6.

There are some restrictions and limitations when you use the module in LightDB-A Database.

Installing and Registering the Module

Note Always use the Oracle Compatibility Functions module included with your LightDB-A Database version. Before upgrading to a new LightDB-A Database version, uninstall the compatibility functions from each of your databases, and then, when the upgrade is complete, reinstall the compatibility functions from the new LightDB-A Database release. See the LightDB-A Database release notes for upgrade prerequisites and procedures.

The orafce module is installed when you install LightDB-A Database. Before you can use any of the functions defined in the module, you must register the orafce extension in each database in which you want to use the functions. Refer to Installing Additional Supplied Modules for more information.

LightDB-A Database Considerations

The following functions are available by default in LightDB-A Database and do not require installing the Oracle Compatibility Functions:

LightDB-A Implementation Differences

There are differences in the implementation of the compatibility functions in LightDB-A Database from the original PostgreSQL orafce module extension implementation. Some of the differences are as follows:

  • The original orafce module implementation performs a decimal round off, the LightDB-A Database implementation does not:
    • 2.00 becomes 2 in the original module implementation
    • 2.00 remains 2.00 in the LightDB-A Database implementation

  • The provided Oracle compatibility functions handle implicit type conversions differently. For example, using the decode function:

    decode(<expression>, <value>, <return> [,<value>, <return>]...
            [, default])

    The original orafce module implementation automatically converts expression and each value to the data type of the first value before comparing. It automatically converts return to the same data type as the first result.

    The LightDB-A Database implementation restricts return and default to be of the same data type. The expression and value can be different types if the data type of value can be converted into the data type of the expression. This is done implicitly. Otherwise, decode fails with an invalid input syntax error. For example:

    SELECT decode('a','M',true,false);
CASE
------
 f
(1 row)
SELECT decode(1,'M',true,false);
ERROR: Invalid input syntax for integer:*"M" 
*LINE 1: SELECT decode(1,'M',true,false);

  • Numbers in bigint format are displayed in scientific notation in the original orafce module implementation but not in the LightDB-A Database implementation:

    • 9223372036854775 displays as 9.2234E+15 in the original implementation
    • 9223372036854775 remains 9223372036854775 in the LightDB-A Database implementation

  • The default date and timestamp format in the original orafce module implementation is different than the default format in the LightDB-A Database implementation. If the following code is run:

    CREATE TABLE TEST(date1 date, time1 timestamp, time2 
                  timestamp with time zone);
INSERT INTO TEST VALUES ('2001-11-11','2001-12-13 
                 01:51:15','2001-12-13 01:51:15 -08:00');
SELECT DECODE(date1, '2001-11-11', '2001-01-01') FROM TEST;

    The LightDB-A Database implementation returns the row, but the original implementation returns no rows.

    Note The correct syntax when using the original orafce implementation to return the row is:

    SELECT DECODE(to_char(date1, 'YYYY-MM-DD'), '2001-11-11', 
              '2001-01-01') FROM TEST

  • The functions in the Oracle Compatibility Functions dbms_alert package are not implemented for LightDB-A Database.

  • The decode() function is removed from the LightDB-A Database Oracle Compatibility Functions. The LightDB-A Database parser internally converts a decode() function call to a CASE statement.

Using orafce

Some Oracle Compatibility Functions reside in the oracle schema. To access them, set the search path for the database to include the oracle schema name. For example, this command sets the default search path for a database to include the oracle schema:

ALTER DATABASE <db_name> SET <search_path> = "$user", public, oracle;

Note the following differences when using the Oracle Compatibility Functions with PostgreSQL vs. using them with LightDB-A Database:

  • If you use validation scripts, the output may not be exactly the same as with the original orafce module implementation.
  • The functions in the Oracle Compatibility Functions dbms_pipe package run only on the LightDB-A Database coordinator host.
  • The upgrade scripts in the Orafce project do not work with LightDB-A Database.

Additional Module Documentation

Refer to the README and LightDB-A Database orafce documentation in the LightDB-A Database github repository for detailed information about the individual functions and supporting objects provided in this module.