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move_ctes_to_top_level

polyglot_sql::transforms

Function move_ctes_to_top_level 

Source 
pub fn move_ctes_to_top_level(expr: Expression) -> Result<Expression>
Expand description

Move CTEs to the top level of the query.

Some dialects (e.g., Hive, T-SQL, Spark prior to version 3) only allow CTEs to be defined at the top-level, so for example queries like:

SELECT * FROM (WITH t(c) AS (SELECT 1) SELECT * FROM t) AS subq

are invalid in those dialects. This transformation moves all CTEs to the top level.

Reference: transforms.py:664-700