Resolve the conflict between the CTE name and the referring table name.

[douenergy]

Fix #5673 and #4987

Provide a clear error message and guide for the case of CTE name and table name shadowing.

❌

with
orders as (
    select * from stg_orders
    where ordered_at >= (select max(ordered_at) from orders)
),
some_more_logic as (
    select *
    from orders
)
select * from some_more_logic;

Error: Binder Error: Circular reference to CTE "orders", There are two possible solutions.

1. use WITH RECURSIVE to use recursive CTEs.
2. If you want to use the TABLE name "orders" the same as the CTE name, please explicitly add "SCHEMA" before table name. You can try "main.orders" (main is the duckdb default schema)

✅

with
orders as (
    select * from stg_orders
    where ordered_at >= (select max(ordered_at) from main.orders) # add schema here 
),
some_more_logic as (
    select *
    from orders
)
select * from some_more_logic;

So user can explicitly add "SCHEMA" to the CTE tableref.

We can pass the schema_name + table_name to FindCTE, as @aarashy says in (#4987 ) "CTE names are never allowed to be qualified" (Postgres also not allow qualified CTE name).

If a tableref is qualified, we can confirm that it should not be a CTE name.

[Mytherin]

Thanks for the PR! LGTM.

One comment:

[douenergy]

Code coverage test pass on my fork !
https://github.com/douenergy/duckdb/actions/runs/5599354959

@Mytherin Please take a look.

[Mytherin]

Thanks!