Module optimize_projections 

OptimizeProjections identifies and eliminates unused columns

Modules

required_indices 🔒

RequiredIndices helper for OptimizeProjection

Structs

OptimizeProjections

Optimizer rule to prune unnecessary columns from intermediate schemas inside the LogicalPlan. This rule:

Functions

add_projection_on_top_if_helpful 🔒

Adds a projection on top of a logical plan if doing so reduces the number of columns for the parent operator.

expr_contains_subquery 🔒

is_expr_trivial 🔒

is_projection_unnecessary

Projection is unnecessary, when

merge_consecutive_projections 🔒

Merges consecutive projections.

optimize_projections 🔒

Removes unnecessary columns (e.g. columns that do not appear in the output schema and/or are not used during any computation step such as expression evaluation) from the logical plan and its inputs.

outer_columns 🔒

Accumulates outer-referenced columns by the given expression, expr.

outer_columns_helper_multi 🔒

A recursive subroutine that accumulates outer-referenced columns by the given expressions (exprs).

plan_contains_other_subqueries 🔒

Returns true if the plan subtree contains any subqueries that are not the CTE reference itself. This treats any non-CTE LogicalPlan::SubqueryAlias node (including aliased relations) as a blocker, along with expression-level subqueries like scalar, EXISTS, or IN. These cases prevent projection pushdown for now because we cannot safely reason about their column usage.

rewrite_expr 🔒

Rewrites a projection expression using the projection before it (i.e. its input) This is a subroutine to the merge_consecutive_projections function.

rewrite_projection_given_requirements 🔒

Rewrite the given projection according to the fields required by its ancestors.

split_join_requirements 🔒

Splits requirement indices for a join into left and right children based on the join type.

subquery_alias_targets_recursive_cte 🔒