Changing Physical Schema

In addition to your initial superprojections, you can create new projections using the CREATE PROJECTION command. A single table can have multiple projections, if necessary.

If you want to replace a superprojection, a new superprojection must be created before the old one is removed.

Steps:

1. Review the existing projections in your Data Warehouse instance:

   SELECT * FROM projections p WHERE p.projection_schema = '[DW_ID]'
   

2. Run the CREATE PROJECTION commands to create new projections. The projection is automatically populated with data after creation.

   Projection refresh must finish in 2 hours, otherwise the JDBC driver cancels the operation and the projection stays unrefreshed.

3. Drop projections that are no longer necessary using the DROP PROJECTION command.

   You cannot drop a projection if it’s the only superprojection.

Troubleshooting

Occasionally, the following error may occur when dropping a projection:

ROLLBACK: Projection cannot be dropped because history after AHM would be lost

In this case, try again later. If the problem persists, contact GoodData Customer Support.