1#include "duckdb/optimizer/filter_pushdown.hpp"
2#include "duckdb/planner/expression/bound_columnref_expression.hpp"
3#include "duckdb/planner/expression_iterator.hpp"
4#include "duckdb/planner/operator/logical_empty_result.hpp"
5#include "duckdb/planner/operator/logical_projection.hpp"
6
7namespace duckdb {
8
9static unique_ptr<Expression> ReplaceProjectionBindings(LogicalProjection &proj, unique_ptr<Expression> expr) {
10 if (expr->type == ExpressionType::BOUND_COLUMN_REF) {
11 auto &colref = expr->Cast<BoundColumnRefExpression>();
12 D_ASSERT(colref.binding.table_index == proj.table_index);
13 D_ASSERT(colref.binding.column_index < proj.expressions.size());
14 D_ASSERT(colref.depth == 0);
15 // replace the binding with a copy to the expression at the referenced index
16 return proj.expressions[colref.binding.column_index]->Copy();
17 }
18 ExpressionIterator::EnumerateChildren(
19 expression&: *expr, callback: [&](unique_ptr<Expression> &child) { child = ReplaceProjectionBindings(proj, expr: std::move(child)); });
20 return expr;
21}
22
23unique_ptr<LogicalOperator> FilterPushdown::PushdownProjection(unique_ptr<LogicalOperator> op) {
24 D_ASSERT(op->type == LogicalOperatorType::LOGICAL_PROJECTION);
25 auto &proj = op->Cast<LogicalProjection>();
26 // push filter through logical projection
27 // all the BoundColumnRefExpressions in the filter should refer to the LogicalProjection
28 // we can rewrite them by replacing those references with the expression of the LogicalProjection node
29 FilterPushdown child_pushdown(optimizer);
30 for (auto &filter : filters) {
31 auto &f = *filter;
32 D_ASSERT(f.bindings.size() <= 1);
33 // rewrite the bindings within this subquery
34 f.filter = ReplaceProjectionBindings(proj, expr: std::move(f.filter));
35 // add the filter to the child pushdown
36 if (child_pushdown.AddFilter(expr: std::move(f.filter)) == FilterResult::UNSATISFIABLE) {
37 // filter statically evaluates to false, strip tree
38 return make_uniq<LogicalEmptyResult>(args: std::move(op));
39 }
40 }
41 child_pushdown.GenerateFilters();
42 // now push into children
43 op->children[0] = child_pushdown.Rewrite(op: std::move(op->children[0]));
44 if (op->children[0]->type == LogicalOperatorType::LOGICAL_EMPTY_RESULT) {
45 // child returns an empty result: generate an empty result here too
46 return make_uniq<LogicalEmptyResult>(args: std::move(op));
47 }
48 return op;
49}
50
51} // namespace duckdb
52