We are using Teiid via OData and connected to a postgresql database. We found following problem:

If a OData request uses the $orderby=x attribute Teiid generates a SQL query with ORDER BY x NULLS FIRST. This leads to a performance problem if the index of the column is created, as it is the default, wit NULLS LAST. The query runs slow for big tables because the index is not used.

Perhaps this code must be changed but I am not sure:  

https://github.com/teiid/teiid/blob/37780f87c42e9aaa990e09f7a1f3fb0703c2a9d4/connectors/jdbc/translator-jdbc/src/main/java/org/teiid/translator/jdbc/postgresql/PostgreSQLExecutionFactory.java#L453