Compatibility

Collaboration diagram for Compatibility:

About:

The compatibility module replicates standard SQL functionality that cannot be used on all platforms supported by MADlib -- be it due to incomplete implementation of the SQL standard or bugs.

This module contains workarounds for the following issues:

• CREATE TABLE table_name AS query statements where query contains certain MADlib functions fails with the error “function cannot execute on segment because it issues a non-SELECT statement” (Greenplum versions before version 4.2, and in rare special cases also later versions). The workaround is:

  SELECT create_table_as('table_name', $$
      query
  $$, 'BY (column, [...]) | RANDOMLY');

• INSERT INTO table_name query where query contains certain MADlib functions fails with the error “function cannot execute on segment because it issues a non-SELECT statement” (Greenplum versions before version 4.2, and in rare special cases also later versions). The workaround is:

  SELECT insert_into('table_name', $$
      query
  $$);

Note:

These functions are not needed on PostgreSQL and are usually not needed on Greenplum 4.2 and later. However, they are always installed for compatibility with other platforms. Workarounds should be used only when necessary. For portability and best performance, standard SQL should be prefered whenever possible.

Literature:

[1] Greenplum Admin Guide

See also:

File compatibility.sql_in (documenting the SQL functions)