Hi, all:
 I want to know which virtual column is in use. For example,
 ```
 CREATE TABLE peoples(age int, virtual_age int as (age + 1) virtual);
 SELECT virtual_age from peoples;
 ```
 After converting, the virtual column is expanded to expression.
 ```
 LogicalProject(virtual_age=[+($0, 1)])
  LogicalTableScan(table=[[default_ns, default, peoples]])
 ```
So `RelMetadataQuery#getColumnOrigins` return RelColumnOrigin that is
age(not is virtual_age).

I try to rewrite code in the implementation class of
`InitializerExpressionFactory`, but I can't know which column is in use.
When I confirm which column is in use, I can't know if the expression is
from a virtual column.

Does anyone have relevant experience?  Thanks~

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