zhjwpku commented on code in PR #754:
URL: https://github.com/apache/iceberg-cpp/pull/754#discussion_r3435543513
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src/iceberg/expression/inclusive_metrics_evaluator.cc:
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@@ -416,6 +429,34 @@ class InclusiveMetricsVisitor : public BoundVisitor<bool> {
// TODO(xiao.dong) handle extract lower and upper bounds
}
+ /// Returns the column's single value if all rows contain the same value.
Defined as a
+ /// column with no nulls, no NaNs, and lower bound equals upper bound.
Returns
+ /// std::nullopt otherwise.
+ Result<std::optional<Literal>> UniqueValue(const std::shared_ptr<Bound>&
expr) {
+ int32_t id = expr->reference()->field().field_id();
+ if (MayContainNull(id)) {
+ return std::nullopt;
+ }
+
+ ICEBERG_ASSIGN_OR_RAISE(auto lower, LowerBound(expr));
+ ICEBERG_ASSIGN_OR_RAISE(auto upper, UpperBound(expr));
+ if (!lower.has_value() || !upper.has_value() || lower->IsNull() ||
upper->IsNull() ||
+ lower->IsNaN() || upper->IsNaN()) {
+ return std::nullopt;
+ }
+
+ auto nan_it = data_file_.nan_value_counts.find(id);
+ if (nan_it != data_file_.nan_value_counts.cend() && nan_it->second != 0) {
+ return std::nullopt;
+ }
+
+ if (!(lower.value() == upper.value())) {
Review Comment:
nit: can we simplify this?
```suggestion
if (lower.value() != upper.value()) {
```
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