[CALCITE-3096] In RelBuilder, make alias method idempotent

• Type: Bug
• Status: Closed
• Priority: Major
• Resolution: Fixed
• Fix Version/s: 1.20.0
• Assignee: Unassigned
• Reporter: Julian Hyde
• Created: 28/May/19 20:29
• Updated: 24/Jun/19 15:02
• Resolved: 29/May/19 20:08

Description

In RelBuilder, make the alias method idempotent. If an expression's alias is already 'foo', then calling alias(e, "foo") will return the expression unchanged.

The intent of this change is to reduce the number of if statements that are required in client code that is trying to produce a concise RelNode tree.