Module transform 

Op Tree Transformations

Visitor and transformer patterns for query algebra trees.

Patterns

• OpVisitor: Read-only traversal for analysis
• OpTransform: Transform tree nodes (returns new tree)
• TransformCopy: Default copy transform (base for custom transforms)
• TransformPushFilter: Push filters down for early evaluation

Structs

OpPrinter

Op tree printer visitor

OpStats

Op statistics visitor

TransformCopy

Default copy transform (identity transformation)

TransformPushFilter

Filter pushdown transform

VarCollector

Variable collector visitor

Traits

OpTransform

Transformer trait for transforming Op trees

OpVisitor

Visitor trait for walking Op trees (read-only)

Functions

transform_op

Apply a transform to an Op tree (bottom-up)

walk_op

Walk an Op tree with a visitor