1#include "duckdb/optimizer/rule/case_simplification.hpp"
2
3#include "duckdb/execution/expression_executor.hpp"
4#include "duckdb/planner/expression/bound_case_expression.hpp"
5
6using namespace duckdb;
7using namespace std;
8
9CaseSimplificationRule::CaseSimplificationRule(ExpressionRewriter &rewriter) : Rule(rewriter) {
10 // match on a CaseExpression that has a ConstantExpression as a check
11 auto op = make_unique<CaseExpressionMatcher>();
12 op->check = make_unique<FoldableConstantMatcher>();
13 root = move(op);
14}
15
16unique_ptr<Expression> CaseSimplificationRule::Apply(LogicalOperator &op, vector<Expression *> &bindings,
17 bool &changes_made) {
18 auto root = (BoundCaseExpression *)bindings[0];
19 auto constant_expr = bindings[1];
20 // the constant_expr is a scalar expression that we have to fold
21 assert(constant_expr->IsFoldable());
22
23 // use an ExpressionExecutor to execute the expression
24 auto constant_value = ExpressionExecutor::EvaluateScalar(*constant_expr);
25
26 // fold based on the constant condition
27 auto condition = constant_value.CastAs(TypeId::BOOL);
28 if (condition.is_null || !condition.value_.boolean) {
29 return move(root->result_if_false);
30 } else {
31 return move(root->result_if_true);
32 }
33}
34