Module filter_pushdown

Filter Pushdown Optimization Process

The filter pushdown mechanism involves four key steps:

1. Optimizer Asks Parent for a Filter Pushdown Plan: The optimizer calls ExecutionPlan::gather_filters_for_pushdown on the parent node, passing in parent predicates and phase. The parent node creates a FilterDescription by inspecting its logic and children’s schemas, determining which filters can be pushed to each child.
2. Optimizer Executes Pushdown: The optimizer recursively calls push_down_filters in this module on each child, passing the appropriate filters (Vec<Arc<dyn PhysicalExpr>>) for that child.
3. Optimizer Gathers Results: The optimizer collects FilterPushdownPropagation results from children, containing information about which filters were successfully pushed down vs. unsupported.
4. Parent Responds: The optimizer calls ExecutionPlan::handle_child_pushdown_result on the parent, passing a ChildPushdownResult containing the aggregated pushdown outcomes. The parent decides how to handle filters that couldn’t be pushed down (e.g., keep them as FilterExec nodes).

Structs

FilterPushdown

Attempts to recursively push given filters from the top of the tree into leafs.