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Weston Pace commented on ARROW-18334: ------------------------------------- Example output type resolver (from [~bkietz]): {noformat} Result<TypeHolder> FirstTimestampType(KernelContext*, const std::vector<TypeHolder>& types) { for (const auto& type : types) { if (type.id() == Type::TIMESTAMP) return type; } return Status::Invalid("no timestamp type found"); } {noformat} > add function for timestamp/duration is not commutative > ------------------------------------------------------ > > Key: ARROW-18334 > URL: https://issues.apache.org/jira/browse/ARROW-18334 > Project: Apache Arrow > Issue Type: Bug > Components: C++ > Reporter: Weston Pace > Priority: Major > > The expression simplification currently has a small set of functions which it > knows are commutative (IsBinaryAssociativeCommutative). "add" (and > "add_checked" are in this list. This should be ok for > add(timestamp,duration) since this boils down to add(int64,int64) which is > commutative. However, the way the kernels are currently implemented, we are > getting the incorrect output type. > Concretely, we have kernels: > {noformat} > add_checked<Timestamp,Duration>() -> types[0] > add_checked<Duration,Timestamp>() -> types[1] > {noformat} > A call is made with expression {{field_ref("x") + duration_literal}}. This > call is bound to {{add_checked<Timestamp, Duration>}}. However, the > expression is then simplified to {{duration_literal + field_ref("x")}}. > Oddly enough, the math in this case is correct, since it is just addition, > but the output type is not. It assigns an output type of duration instead of > timestamp. -- This message was sent by Atlassian Jira (v8.20.10#820010)