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pushdown_projections

polyglot_sql::optimizer::pushdown_projections

Function pushdown_projections 

Source 
pub fn pushdown_projections(
    expression: Expression,
    _dialect: Option<DialectType>,
    remove_unused_selections: bool,
) -> Expression
Expand description

Rewrite SQL AST to remove unused column projections.

§Example

-- Before:
SELECT y.a AS a FROM (SELECT x.a AS a, x.b AS b FROM x) AS y
-- After:
SELECT y.a AS a FROM (SELECT x.a AS a FROM x) AS y

§Arguments

  • expression - The expression to optimize
  • dialect - Optional dialect for dialect-specific behavior
  • remove_unused_selections - Whether to actually remove unused selections

§Returns

The optimized expression with unused projections removed