jonasdedden commented on code in PR #50989:
URL: https://github.com/apache/arrow/pull/50989#discussion_r4118883731
##########
cpp/src/arrow/engine/substrait/extension_set.cc:
##########
@@ -961,6 +975,60 @@ ExtensionIdRegistry::SubstraitCallToArrow
DecodeConcatMapping() {
};
}
+// Substrait's starts_with / ends_with / contains take the pattern as a second
+// value argument. The matching Arrow kernels (starts_with / ends_with /
+// match_substring) are unary and carry the pattern in MatchSubstringOptions,
so
+// the second argument must be a string literal.
+ExtensionIdRegistry::SubstraitCallToArrow DecodeMatchSubstringMapping(
+ const std::string& function_name) {
+ return [function_name](const SubstraitCall& call) ->
Result<compute::Expression> {
+ if (call.size() != 2) {
+ return Status::NotImplemented("Acero does not have a kernel for ",
function_name,
+ " that receives ", call.size(), "
arguments");
+ }
+ ARROW_ASSIGN_OR_RAISE(
+ CaseSensitivity case_sensitivity,
+ ParseOptionOrElse(
+ call, "case_sensitivity", kCaseSensitivityParser,
+ {CaseSensitivity::kCaseSensitive,
CaseSensitivity::kCaseInsensitive},
+ CaseSensitivity::kCaseSensitive));
+ ARROW_ASSIGN_OR_RAISE(compute::Expression input, call.GetValueArg(0));
+ ARROW_ASSIGN_OR_RAISE(compute::Expression substring, call.GetValueArg(1));
+ const Datum* pattern = substring.literal();
+ if (pattern == nullptr || !pattern->is_scalar() ||
+ pattern->type()->id() != Type::STRING || !pattern->scalar()->is_valid)
{
+ return Status::NotImplemented(
+ "The Arrow ", function_name,
+ " kernel requires the substring argument to be a non-null string
literal");
+ }
+ auto options = std::make_shared<compute::MatchSubstringOptions>(
+ std::string(pattern->scalar_as<StringScalar>().view()),
+ /*ignore_case=*/case_sensitivity == CaseSensitivity::kCaseInsensitive);
+ return compute::call(function_name, {std::move(input)},
std::move(options));
+ };
+}
+
+ExtensionIdRegistry::ArrowToSubstraitCall EncodeMatchSubstring(Id
substrait_fn_id) {
+ return
+ [substrait_fn_id](const compute::Expression::Call& call) ->
Result<SubstraitCall> {
+ if (call.options == nullptr) {
+ return Status::Invalid("The call to ", call.function_name,
+ " is missing its MatchSubstringOptions");
+ }
+ auto match_options =
+ checked_pointer_cast<compute::MatchSubstringOptions>(call.options);
+ // nullable=true errs on the side of caution
+ SubstraitCall substrait_call(substrait_fn_id, call.type.GetSharedPtr(),
+ /*nullable=*/true);
+ substrait_call.SetValueArg(0, call.arguments[0]);
+ substrait_call.SetValueArg(1,
compute::literal(match_options->pattern));
Review Comment:
Good point, done. The encoder now requires utf8 input and a valid UTF-8
pattern, and returns `NotImplemented` otherwise. `large_utf8` is rejected too,
because it's serialized as a user-defined type that wouldn't match Substrait's
string/varchar signatures.
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