feat: Initial ALTREP support for LIST logical type

src/include/rapi.hpp

@@ -4,13 +4,18 @@
 
 #include <Rdefines.h>
 #include <R_ext/Altrep.h>
+#include <Rversion.h>
 
 #include "duckdb.hpp"
 #include "duckdb/function/table_function.hpp"
 #include "duckdb/common/unordered_map.hpp"
 #include "duckdb/parser/tableref/table_function_ref.hpp"
 #include "duckdb/common/mutex.hpp"
 
+#if defined(R_VERSION) && R_VERSION >= R_Version(4, 3, 0)
+#define R_HAS_ALTLIST
+#endif
+
 namespace duckdb {
 
 typedef unordered_map<std::string, SEXP> arrow_scans_t;

src/include/reltoaltrep.hpp

@@ -21,4 +21,10 @@ struct RelToAltrep {
 	static R_altrep_class_t int_class;
 	static R_altrep_class_t real_class;
 	static R_altrep_class_t string_class;
+
+#if defined(R_HAS_ALTLIST)
+	static SEXP VectorListElt(SEXP x, R_xlen_t i);
+	static R_altrep_class_t list_class;
+#endif
+
 };

src/reltoaltrep.cpp

@@ -11,6 +11,10 @@ R_altrep_class_t RelToAltrep::int_class;
 R_altrep_class_t RelToAltrep::real_class;
 R_altrep_class_t RelToAltrep::string_class;
 
+#if defined(R_HAS_ALTLIST)
+R_altrep_class_t RelToAltrep::list_class;
+#endif
+
 void RelToAltrep::Initialize(DllInfo *dll) {
 	// this is a string so setting row names will not lead to materialization
 	rownames_class = R_make_altinteger_class("reltoaltrep_rownames_class", "duckdb", dll);
@@ -40,6 +44,15 @@ void RelToAltrep::Initialize(DllInfo *dll) {
 	R_set_altvec_Dataptr_or_null_method(rownames_class, RownamesDataptrOrNull);
 
 	R_set_altstring_Elt_method(string_class, VectorStringElt);
+
+#if defined(R_HAS_ALTLIST)
+	list_class = R_make_altlist_class("reltoaltrep_list_class", "duckdb", dll);
+	R_set_altrep_Inspect_method(list_class, RelInspect);
+	R_set_altrep_Length_method(list_class, VectorLength);
+	R_set_altvec_Dataptr_method(list_class, VectorDataptr);
+	R_set_altlist_Elt_method(list_class, VectorListElt);
+#endif
+
 }
 
 template <class T>
@@ -231,6 +244,14 @@ SEXP RelToAltrep::VectorStringElt(SEXP x, R_xlen_t i) {
 	END_CPP11
 }
 
+#if defined(R_HAS_ALTLIST)
+SEXP RelToAltrep::VectorListElt(SEXP x, R_xlen_t i) {
+	BEGIN_CPP11
+	return VECTOR_ELT(AltrepVectorWrapper::Get(x)->Vector(), i);
+	END_CPP11
+}
+#endif
+
 static R_altrep_class_t LogicalTypeToAltrepType(const LogicalType &type) {
 	switch (type.id()) {
 	case LogicalTypeId::BOOLEAN:
@@ -261,6 +282,12 @@ static R_altrep_class_t LogicalTypeToAltrepType(const LogicalType &type) {
 	case LogicalTypeId::VARCHAR:
 	case LogicalTypeId::UUID:
 		return RelToAltrep::string_class;
+
+#if defined(R_HAS_ALTLIST)
+	case LogicalTypeId::LIST:
+		return RelToAltrep::list_class;
+#endif
+
 	default:
 		cpp11::stop("rel_to_altrep: Unknown column type for altrep: %s", type.ToString().c_str());
 	}

tests/testthat/test_list.R

@@ -26,3 +26,18 @@ test_that("one-level lists can be read", {
   res <- dbGetQuery(con, "SELECT ['Hello', 'World'] a union all select ['There']")$a
   expect_equal(res, list(c("Hello", "World"), c("There")))
 })
+
+test_that("rel_filter() handles LIST logical type", {
+  skip_if_not(getRversion() >= "4.3.0")
+
+  con <- dbConnect(duckdb())
+  on.exit(dbDisconnect(con, shutdown = TRUE))
+
+  df1 <- tibble::tibble(a = list(1, c(1,2)))
+
+  rel1 <- rel_from_df(con, df1)
+  rel2 <- rel_filter(rel1, list(expr_constant(TRUE)))
+
+  df2 <- rel_to_altrep(rel2)
+  expect_equal(df1$a, df2$a)
+})