feat: Support fetching MAP type

src/transform.cpp

@@ -48,6 +48,7 @@ SEXP duckdb_r_allocate(const LogicalType &type, idx_t nrows) {
 	case LogicalTypeId::INTERVAL:
 		return NEW_NUMERIC(nrows);
 	case LogicalTypeId::LIST:
+	case LogicalTypeId::MAP:
 		return NEW_LIST(nrows);
 	case LogicalTypeId::STRUCT: {
 		cpp11::writable::list dest_list;
@@ -147,6 +148,7 @@ void duckdb_r_decorate(const LogicalType &type, const SEXP dest, bool integer64)
 	case LogicalTypeId::BLOB:
 	case LogicalTypeId::UUID:
 	case LogicalTypeId::LIST:
+	case LogicalTypeId::MAP:
 		break; // no extra decoration required, do nothing
 	case LogicalTypeId::TIMESTAMP_SEC:
 	case LogicalTypeId::TIMESTAMP_MS:
@@ -432,6 +434,56 @@ void duckdb_r_transform(Vector &src_vec, const SEXP dest, idx_t dest_offset, idx
 
 		break;
 	}
+
+	case LogicalTypeId::MAP: {
+		auto src_data = ListVector::GetData(src_vec);
+
+		auto &key_type = MapType::KeyType(src_vec.GetType());
+		auto &value_type = MapType::ValueType(src_vec.GetType());
+
+		Vector key_child(key_type, nullptr);
+		Vector value_child(value_type, nullptr);
+
+		for (size_t row_idx = 0; row_idx < n; row_idx++) {
+			if (!FlatVector::Validity(src_vec).RowIsValid(row_idx)) {
+				SET_ELEMENT(dest, dest_offset + row_idx, R_NilValue);
+			} else {
+				auto offset = src_data[row_idx].offset;
+				auto length = src_data[row_idx].length;
+				const auto end = offset + length;
+
+				key_child.Slice(MapVector::GetKeys(src_vec), offset, end);
+				value_child.Slice(MapVector::GetValues(src_vec), offset, end);
+
+				cpp11::sexp key_sexp = duckdb_r_allocate(key_type, length);
+				cpp11::sexp value_sexp = duckdb_r_allocate(value_type, length);
+
+				duckdb_r_decorate(key_type, key_sexp, integer64);
+				duckdb_r_decorate(value_type, value_sexp, integer64);
+
+				duckdb_r_transform(key_child, key_sexp, 0, length, integer64);
+				duckdb_r_transform(value_child, value_sexp, 0, length, integer64);
+
+				cpp11::writable::list dest_list;
+				dest_list.reserve(2);
+
+				dest_list.push_back(cpp11::named_arg("key") = std::move(key_sexp));
+				dest_list.push_back(cpp11::named_arg("value") = std::move(value_sexp));
+
+				// convert to SEXP, with potential side effect of truncation
+				(void)(SEXP)dest_list;
+
+				// Note we cannot use cpp11's data frame here as it tries to calculate the number of rows itself,
+				// but gives the wrong answer if the first column is another data frame or the struct is empty.
+				dest_list.attr(R_ClassSymbol) = RStrings::get().dataframe_str;
+				dest_list.attr(R_RowNamesSymbol) = {NA_INTEGER, -static_cast<int>(length)};
+				// call R's own extract subset method
+				SET_ELEMENT(dest, dest_offset + row_idx, dest_list);
+			}
+		}
+		break;
+	}
+
 	case LogicalTypeId::BLOB: {
 		auto src_ptr = FlatVector::GetData<string_t>(src_vec);
 		auto &mask = FlatVector::Validity(src_vec);

src/types.cpp

@@ -303,12 +303,15 @@ string RApiTypes::DetectLogicalType(const LogicalType &stype, const char *caller
 	case LogicalTypeId::LIST:
 		return "list";
 	case LogicalTypeId::STRUCT:
+	case LogicalTypeId::MAP:
+		return "data.frame";
 		return "data.frame";
 	case LogicalTypeId::ENUM:
 		return "factor";
 	case LogicalTypeId::UNKNOWN:
 	case LogicalTypeId::SQLNULL:
 		return "unknown";
+
 	default:
 		cpp11::stop("%s: Unknown column type for prepare: %s", caller, stype.ToString().c_str());
 		break;

tests/testthat/_snaps/types.md

@@ -2,7 +2,7 @@
 
     Code
       as.list(dbGetQuery(con,
-        "SELECT * EXCLUDE (timestamp_tz, time_tz, timestamp_ns, timestamp_array, timestamptz_array, map, bit, \"union\", fixed_int_array, fixed_varchar_array, fixed_nested_int_array, fixed_nested_varchar_array, fixed_struct_array, struct_of_fixed_array, fixed_array_of_int_list, list_of_fixed_int_array) REPLACE(replace(varchar, chr(0), '') AS varchar) FROM test_all_types(use_large_enum=true)"))
+        "SELECT * EXCLUDE (timestamp_tz, time_tz, timestamp_ns, timestamp_array, timestamptz_array, bit, \"union\", fixed_int_array, fixed_varchar_array, fixed_nested_int_array, fixed_nested_varchar_array, fixed_struct_array, struct_of_fixed_array, fixed_array_of_int_list, list_of_fixed_int_array) REPLACE(replace(varchar, chr(0), '') AS varchar) FROM test_all_types(use_large_enum=true)"))
     Output
       $bool
       [1] FALSE  TRUE    NA
@@ -207,4 +207,18 @@
       NULL
       
       
+      $map
+      $map[[1]]
+      [1] key   value
+      <0 rows> (or 0-length row.names)
+      
+      $map[[2]]
+         key        value
+      1 key1 🦆🦆🦆🦆🦆🦆
+      2 key2        goose
+      
+      $map[[3]]
+      NULL
+      
+      
 

tests/testthat/test-map.R

@@ -0,0 +1,87 @@
+test_that("maps can be read", {
+  skip_if_not_installed("vctrs")
+
+  con <- dbConnect(duckdb())
+  on.exit(dbDisconnect(con, shutdown = TRUE))
+
+  res <- dbGetQuery(
+    con,
+    "SELECT map([1,2],['a','b']) AS x"
+  )
+  expect_equal(res, vctrs::data_frame(
+    x = list(
+      vctrs::data_frame(key = 1:2, value = letters[1:2])
+    )
+  ))
+
+  res <- dbGetQuery(
+    con,
+    "SELECT 1 as a, map([1,2],[1.5,2.5]) AS x UNION SELECT 2, map([3,4,5],[5.5,4.5,3.5]) ORDER BY a"
+  )
+  expect_equal(res, vctrs::data_frame(
+    a = 1:2,
+    x = list(
+      vctrs::data_frame(key = 1:2, value = 1:2 + 0.5),
+      vctrs::data_frame(key = 3:5, value = 5:3 + 0.5)
+    )
+  ))
+
+  res <- dbGetQuery(
+    con,
+    "SELECT 1 as a, map([1,2],[TRUE,FALSE]) AS x UNION SELECT 2, NULL ORDER BY a"
+  )
+  expect_equal(res, vctrs::data_frame(
+    a = 1:2,
+    x = list(
+      vctrs::data_frame(key = 1:2, value = c(TRUE, FALSE)),
+      NULL
+    )
+  ))
+})
+
+test_that("structs give the same results via Arrow", {
+  skip_on_cran()
+  skip_if_not_installed("vctrs")
+  skip_if_not_installed("tibble")
+  skip_if_not_installed("arrow", "13.0.0")
+
+  con <- dbConnect(duckdb())
+  on.exit(dbDisconnect(con, shutdown = TRUE))
+
+  res <- dbGetQuery(
+    con,
+    "SELECT map([1,2],['a','b']) AS x",
+    arrow = TRUE
+  )
+  expect_equal(res, vctrs::data_frame(
+    x = structure(class = c("arrow_list", class(vctrs::list_of(logical()))), vctrs::list_of(
+      tibble::tibble(key = 1:2, value = letters[1:2])
+    ))
+  ))
+
+  res <- dbGetQuery(
+    con,
+    "SELECT 1 as a, map([1,2],[1.5,2.5]) AS x UNION SELECT 2, map([3,4,5],[5.5,4.5,3.5]) ORDER BY a",
+    arrow = TRUE
+  )
+  expect_equal(res, vctrs::data_frame(
+    a = 1:2,
+    x = structure(class = c("arrow_list", class(vctrs::list_of(logical()))), vctrs::list_of(
+      tibble::tibble(key = 1:2, value = 1:2 + 0.5),
+      tibble::tibble(key = 3:5, value = 5:3 + 0.5)
+    ))
+  ))
+
+  res <- dbGetQuery(
+    con,
+    "SELECT 1 as a, map([1,2],[TRUE,FALSE]) AS x UNION SELECT 2, NULL ORDER BY a",
+    arrow = TRUE
+  )
+  expect_equal(res, vctrs::data_frame(
+    a = 1:2,
+    x = structure(class = c("arrow_list", class(vctrs::list_of(logical()))), vctrs::list_of(
+      tibble::tibble(key = 1:2, value = c(TRUE, FALSE)),
+      NULL
+    ))
+  ))
+})

tests/testthat/test-types.R

@@ -9,6 +9,6 @@ test_that("test_all_types() output", {
 
   # Need to omit timestamp columns, likely due to https://bugs.r-project.org/show_bug.cgi?id=16856
   expect_snapshot({
-    as.list(dbGetQuery(con, "SELECT * EXCLUDE (timestamp_tz, time_tz, timestamp_ns, timestamp_array, timestamptz_array, map, bit, \"union\", fixed_int_array, fixed_varchar_array, fixed_nested_int_array, fixed_nested_varchar_array, fixed_struct_array, struct_of_fixed_array, fixed_array_of_int_list, list_of_fixed_int_array) REPLACE(replace(varchar, chr(0), '') AS varchar) FROM test_all_types(use_large_enum=true)"))
+    as.list(dbGetQuery(con, "SELECT * EXCLUDE (timestamp_tz, time_tz, timestamp_ns, timestamp_array, timestamptz_array, bit, \"union\", fixed_int_array, fixed_varchar_array, fixed_nested_int_array, fixed_nested_varchar_array, fixed_struct_array, struct_of_fixed_array, fixed_array_of_int_list, list_of_fixed_int_array) REPLACE(replace(varchar, chr(0), '') AS varchar) FROM test_all_types(use_large_enum=true)"))
   })
 })