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GH-39603: [R] Error: Cannot convert Dictionary Array of type dictionary<values=large_string, indices=uint32, ordered=0> to R #49710

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Merged
thisisnic merged 7 commits into from
Jun 10, 2026
Merged

GH-39603: [R] Error: Cannot convert Dictionary Array of type dictionary<values=large_string, indices=uint32, ordered=0> to R #49710

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a0fb656
Allow dictionaries from a wider range of types for indices
thisisnic Apr 11, 2026
80788ae
Apply suggestion from @thisisnic
thisisnic Jun 8, 2026
1e02dcb
add coilot suggested test
thisisnic Jun 8, 2026
bfcc9c6
Combine tests
thisisnic Jun 8, 2026
3f57394
Account for large strings
thisisnic Jun 10, 2026
0661910
don't forget the large ones
thisisnic Jun 10, 2026
bc33f7c
don't hardcode levels
thisisnic Jun 10, 2026
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23 changes: 22 additions & 1 deletion r/src/array_to_vector.cpp
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Original file line number Diff line number Diff line change
Expand Up @@ -595,7 +595,9 @@ class Converter_Dictionary : public Converter {
case Type::UINT16:
case Type::INT16:
case Type::INT32:
// TODO: also add int64, uint32, uint64 downcasts, if possible
case Type::UINT32:
case Type::INT64:
case Type::UINT64:
break;
default:
cpp11::stop("Cannot convert Dictionary Array of type `%s` to R",
Expand All @@ -612,6 +614,16 @@ class Converter_Dictionary : public Converter {
dictionary_ = CreateEmptyArray(dict_type.value_type());
}
}

// R factors store their codes in 32-bit integers, so dictionary arrays with
// more levels than that cannot be represented safely.
if (dictionary_->length() > std::numeric_limits<int>::max()) {
const auto& dict_type = checked_cast<const DictionaryType&>(*chunked_array->type());
cpp11::stop(
"Cannot convert Dictionary Array of type `%s` to R: dictionary has "
"more levels than an R factor can represent",
dict_type.ToString().c_str());
}
}

SEXP Allocate(R_xlen_t n) const {
Expand Down Expand Up @@ -653,6 +665,15 @@ class Converter_Dictionary : public Converter {
case Type::INT32:
return Ingest_some_nulls_Impl<arrow::Int32Type>(data, array, start, n,
chunk_index);
case Type::UINT32:
return Ingest_some_nulls_Impl<arrow::UInt32Type>(data, array, start, n,
chunk_index);
case Type::INT64:
return Ingest_some_nulls_Impl<arrow::Int64Type>(data, array, start, n,
chunk_index);
case Type::UINT64:
return Ingest_some_nulls_Impl<arrow::UInt64Type>(data, array, start, n,
chunk_index);
default:
break;
}
Expand Down
16 changes: 16 additions & 0 deletions r/tests/testthat/test-Table.R
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Expand Up @@ -371,6 +371,22 @@ test_that("Can create table with specific dictionary types", {
}
})

test_that("Table converts dictionary arrays with wider index types back to R", {

@jonkeane jonkeane Jun 3, 2026

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with wider index types

I finally got what this was saying, but it took a few clicks. Maybe we say something about uint64 / uint32 here?

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fact <- example_data[, "fct"]

tab_uint32 <- Table$create(fact, schema = schema(fct = dictionary(uint32(), utf8())))
expect_equal(tab_uint32$schema, schema(fct = dictionary(uint32(), utf8())))
expect_equal_data_frame(tab_uint32, fact)

tab_int64 <- Table$create(fact, schema = schema(fct = dictionary(int64(), utf8())))
expect_equal(tab_int64$schema, schema(fct = dictionary(int64(), utf8())))
expect_equal_data_frame(tab_int64, fact)

tab_uint64 <- Table$create(fact, schema = schema(fct = dictionary(uint64(), utf8())))
expect_equal(tab_uint64$schema, schema(fct = dictionary(uint64(), utf8())))
expect_equal_data_frame(tab_uint64, fact)
})

test_that("Table unifies dictionary on conversion back to R (ARROW-8374)", {
b1 <- record_batch(f = factor(c("a"), levels = c("a", "b")))
b2 <- record_batch(f = factor(c("c"), levels = c("c", "d")))
Expand Down
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