zhjwpku commented on code in PR #289:
URL: https://github.com/apache/iceberg-cpp/pull/289#discussion_r3254097766
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src/iceberg/expression/predicate.cc:
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@@ -286,7 +289,52 @@ Result<std::shared_ptr<Expression>>
UnboundPredicate<B>::BindLiteralOperation(
}
}
- // TODO(gangwu): translate truncate(col) == value to startsWith(value)
+ if (BASE::op() == Expression::Operation::kEq &&
+ bound_term->kind() == Term::Kind::kTransform) {
+ // Safe to cast after kind check confirms it's a transform
+ auto* transform_term = dynamic_cast<BoundTransform*>(bound_term.get());
+ if (!transform_term) {
+ return BoundLiteralPredicate::Make(BASE::op(), std::move(bound_term),
+ std::move(literal));
+ }
+
+ if (transform_term->transform()->transform_type() ==
TransformType::kTruncate &&
+ literal.type()->type_id() == TypeId::kString &&
+ !literal.IsNull()) { // Null safety: skip null literals
+
+ // Apply truncate transform to the literal and check if result matches
+ // This verifies the literal is compatible with the truncate operation
+ auto transformed_result =
transform_term->transform_func()->Transform(literal);
Review Comment:
I'm wondering whether we can simply count the code points in the literal and
compare that with `TruncateTransform.width()`. If they match, we can rewrite it
as a `StartsWith`. We don't need to transform the extended_literal then.
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