Expressions

Expressions may also be used instead of mapping rules, and this technique also helps improve performance. To replace the * to * "like" mapping rules, the CopySource expression may be used, and looks like the following:

This expression does the same thing as the * to * mapping, and it is applied during import, rather than via a scan of the table with a SQL statement. The performance of expressions is roughly the same as using a single SQL mapping rule, but it is recommended to use expressions when data volume is large so mapping does not fail because of database governor limits. (Expressions are processed during the import step of the load process.)